1 00:00:00,966 --> 00:00:02,933 ♪ ♪ 2 00:00:05,400 --> 00:00:09,433 ♪ ♪ 3 00:00:09,466 --> 00:00:15,700 NARRATOR: 60 miles west of Bangkok is the Khao Chong Phran cave, 4 00:00:15,733 --> 00:00:18,200 {\an1}famous throughout all of Asia. 5 00:00:18,233 --> 00:00:21,233 ♪ ♪ 6 00:00:21,266 --> 00:00:25,200 For centuries, a sanctuary for the faithful... 7 00:00:25,233 --> 00:00:29,700 {\an1}and now, the curious. 8 00:00:32,300 --> 00:00:34,233 {\an1}Scientists... who come to learn 9 00:00:34,266 --> 00:00:37,566 {\an1}from the most unusual of creatures... 10 00:00:37,600 --> 00:00:44,700 {\an8}♪ ♪ 11 00:00:44,733 --> 00:00:49,300 {\an1}As the sun sets, three million bats begin to stir, 12 00:00:49,333 --> 00:00:53,266 {\an1}preparing for one of nature's greatest spectacles. 13 00:00:53,300 --> 00:00:56,533 {\an1}Rocketing to the skies in a blizzard of flapping wings, 14 00:00:56,566 --> 00:01:00,900 {\an1}they will pass the night gorging on insects. 15 00:01:03,633 --> 00:01:08,800 {\an1}This epic nocturnal excursion is a feast for the eyes. 16 00:01:08,833 --> 00:01:14,900 {\an1}But for science, bats are much more: a biological treasure. 17 00:01:17,200 --> 00:01:19,766 EMMA TEELING: They are by far 18 00:01:19,800 --> 00:01:21,966 {\an1}the most fascinating of all animals. 19 00:01:22,000 --> 00:01:23,500 (squeaking) 20 00:01:23,533 --> 00:01:26,866 SHARON SWARTZ: They are remarkable and extraordinary creatures. 21 00:01:28,400 --> 00:01:31,300 JARED HOLMES: As a biologist, it's my job to really tell people that 22 00:01:31,333 --> 00:01:32,966 {\an1}we, we need the bats. 23 00:01:33,000 --> 00:01:35,533 NARRATOR: There are more than 1,400 24 00:01:35,566 --> 00:01:38,300 {\an1}different species of bats, playing crucial roles 25 00:01:38,333 --> 00:01:42,166 in ecosystems all over the world. 26 00:01:42,200 --> 00:01:46,933 {\an1}But for many people, bats are the stuff of nightmares. 27 00:01:46,966 --> 00:01:49,733 {\an7}Bats have been demonized in the society. 28 00:01:49,766 --> 00:01:52,066 {\an8}♪ ♪ 29 00:01:52,100 --> 00:01:55,233 KENNY BREUER: I thought bats were scary and creepy 30 00:01:55,266 --> 00:01:56,900 and a little bit kind of unpleasant. 31 00:01:58,000 --> 00:01:59,966 (screams) 32 00:02:00,000 --> 00:02:02,933 NARRATOR: Already vilified in pop culture, 33 00:02:02,966 --> 00:02:04,933 {\an1}recent news reports 34 00:02:04,966 --> 00:02:10,066 {\an1}have been giving bats an especially dangerous rep. 35 00:02:10,100 --> 00:02:14,100 {\an7}The ancestor of the virus in humans had to be a bat virus. 36 00:02:14,133 --> 00:02:16,200 {\an8}(translated): There is a virus that is 96% similar 37 00:02:16,233 --> 00:02:17,766 {\an7}to this new coronavirus in bats. 38 00:02:17,800 --> 00:02:20,833 {\an8}REPORTER: Early research suggests human picked up the coronavirus 39 00:02:20,866 --> 00:02:22,700 {\an7}from animals, possibly bats. 40 00:02:22,733 --> 00:02:25,666 {\an8}NARRATOR: Though we still don't know the exact source of the virus 41 00:02:25,700 --> 00:02:30,233 {\an1}that started the COVID pandemic, bats are a prime suspect. 42 00:02:31,566 --> 00:02:34,366 {\an1}But rather than fear these flying creatures, 43 00:02:34,400 --> 00:02:37,933 {\an1}biologists are hailing them as potential saviors. 44 00:02:39,366 --> 00:02:42,500 {\an8}MATAE AHN: They can really get infection without getting sick. 45 00:02:43,400 --> 00:02:44,833 {\an8}LINFA WANG: Bats teach us lesson, 46 00:02:44,866 --> 00:02:46,666 {\an7}not to suffer autoimmune disease, 47 00:02:46,700 --> 00:02:48,233 {\an7}diabetes, arthritis. 48 00:02:48,266 --> 00:02:49,376 {\an1}SÉBASTIEN PUECHMAILLE (translated): Whether you capture a bat 49 00:02:49,400 --> 00:02:51,100 {\an1}that is two years old or 15, 50 00:02:51,133 --> 00:02:52,300 or 20 years old, 51 00:02:52,333 --> 00:02:54,766 {\an1}you don't see any difference. 52 00:02:54,800 --> 00:02:57,500 GARY MCCRACKEN: For the body size of these animals, 53 00:02:57,533 --> 00:03:00,300 {\an1}they are way off scale in terms of their longevity. 54 00:03:00,333 --> 00:03:03,233 TEELING: Bats hold the cure. 55 00:03:03,266 --> 00:03:05,300 {\an1}They hold our treatment. 56 00:03:06,733 --> 00:03:09,866 NARRATOR: Science is beginning to decipher their strange powers. 57 00:03:11,400 --> 00:03:14,300 {\an1}Could these much-maligned creatures hold precious secrets 58 00:03:14,333 --> 00:03:16,100 {\an1}for our own health? 59 00:03:16,133 --> 00:03:18,500 (bats squeaking) 60 00:03:18,533 --> 00:03:20,566 {\an1}"Bat Superpowers." 61 00:03:20,600 --> 00:03:23,866 {\an1}Right now, on "NOVA." 62 00:03:23,900 --> 00:03:28,800 ♪ ♪ 63 00:03:46,033 --> 00:03:52,033 ♪ ♪ 64 00:03:52,066 --> 00:03:54,466 {\an8}NARRATOR: Many experts believe that the coronavirus 65 00:03:54,500 --> 00:03:57,333 {\an7}that tore through the world's population in 2020 66 00:03:57,366 --> 00:03:59,766 {\an8}came from a bat. 67 00:04:02,433 --> 00:04:05,233 {\an1}Virologist Supaporn Wacharapluesadee 68 00:04:05,266 --> 00:04:07,133 {\an1}is world-renowned for her ability 69 00:04:07,166 --> 00:04:10,966 {\an1}to track viruses in the wild. 70 00:04:12,366 --> 00:04:15,833 {\an1}Today, her team has come to test the giant colony 71 00:04:15,866 --> 00:04:18,966 {\an1}at Khao Chong Phran. 72 00:04:19,000 --> 00:04:21,309 {\an1}WACHARAPLUESADEE (translated): There are bats in the caves, and we put this on 73 00:04:21,333 --> 00:04:23,533 {\an7}to be safe while we work. 74 00:04:25,966 --> 00:04:28,166 {\an1}It doesn't mean that there are deadly viruses in there, 75 00:04:28,200 --> 00:04:30,200 {\an1}but we need to protect ourselves 76 00:04:30,233 --> 00:04:32,900 {\an1}to do our work safely. 77 00:04:34,966 --> 00:04:37,766 NARRATOR: Once fully suited up, the scientists descend 78 00:04:37,800 --> 00:04:40,366 {\an1}deep into the cave. 79 00:04:40,400 --> 00:04:42,966 {\an1}Under the gaze of the Buddha statues, the team installs 80 00:04:43,000 --> 00:04:44,233 {\an1}a net in the large chamber 81 00:04:44,266 --> 00:04:45,800 {\an1}that local monks share year-round 82 00:04:45,833 --> 00:04:48,566 {\an1}with its native residents. 83 00:04:52,166 --> 00:04:56,833 {\an1}WACHARAPLUESADEE (translated): We have been doing research work here for more than ten years. 84 00:04:56,866 --> 00:04:59,333 {\an1}Now, for safety reasons, we have come back to test 85 00:04:59,366 --> 00:05:01,466 {\an1}if there is coronavirus, 86 00:05:01,500 --> 00:05:04,700 {\an1}which could be dangerous for the people in the area. 87 00:05:06,600 --> 00:05:09,066 {\an8}NARRATOR: A second team waits at the exit 88 00:05:09,100 --> 00:05:12,166 {\an7}of the cave to catch bats flying outside. 89 00:05:14,166 --> 00:05:17,933 {\an7}Tonight, about 70 bats will miss their nighttime excursion. 90 00:05:20,200 --> 00:05:25,400 {\an8}♪ ♪ 91 00:05:33,133 --> 00:05:37,833 {\an7}Instead, they will spend a few hours in a makeshift lab 92 00:05:37,866 --> 00:05:40,900 {\an1}set up at the base of the hill. 93 00:05:40,933 --> 00:05:43,533 {\an1}Each bat is given a careful medical checkup. 94 00:05:43,566 --> 00:05:46,533 {\an1}Trying to limit stress to the animal, 95 00:05:46,566 --> 00:05:48,933 {\an1}scientists take multiple samples from the skin, 96 00:05:48,966 --> 00:05:52,233 the mouth, and even the intestines... 97 00:05:52,266 --> 00:05:56,400 {\an1}all organs that are susceptible to containing viruses, 98 00:05:56,433 --> 00:05:58,800 {\an1}known or unknown. 99 00:06:03,233 --> 00:06:08,233 {\an1}WACHARAPLUESADEE (translated): We have discovered hundreds of viruses in bats. 100 00:06:08,266 --> 00:06:11,666 {\an1}Actually, there are more than 60 viruses in bats 101 00:06:11,700 --> 00:06:15,366 {\an1}that could eventually be transmitted to human beings. 102 00:06:15,400 --> 00:06:17,266 NARRATOR: In addition to being 103 00:06:17,300 --> 00:06:20,600 {\an1}a key transmitter of the deadly rabies virus, 104 00:06:20,633 --> 00:06:22,266 {\an1}bats are suspected sources 105 00:06:22,300 --> 00:06:25,700 {\an1}for numerous viral outbreaks around the world: 106 00:06:25,733 --> 00:06:29,900 {\an1}the 1967 Marburg virus in Europe; 107 00:06:29,933 --> 00:06:33,333 {\an1}two waves of Ebola in Africa; 108 00:06:33,366 --> 00:06:35,266 {\an1}the Hendra virus in Australia; 109 00:06:35,300 --> 00:06:37,800 {\an1}the Nipah virus in Malaysia. 110 00:06:37,833 --> 00:06:40,500 {\an1}Then a series of coronavirus outbreaks: 111 00:06:40,533 --> 00:06:42,566 {\an1}SARS, that started in China; 112 00:06:42,600 --> 00:06:45,166 {\an1}MERS in the Arabian Peninsula; 113 00:06:45,200 --> 00:06:47,166 {\an1}and now the COVID-19 pandemic 114 00:06:47,200 --> 00:06:50,800 {\an1}that engulfed the planet in just a few months. 115 00:06:50,833 --> 00:06:51,900 {\an1}For some scientists, 116 00:06:51,933 --> 00:06:54,133 {\an1}it is a trend that will no doubt continue 117 00:06:54,166 --> 00:06:56,300 {\an1}as human beings encroach 118 00:06:56,333 --> 00:06:59,700 {\an1}more and more on the bat's natural habitat. 119 00:06:59,733 --> 00:07:01,700 {\an1}Supaporn is hoping to discover 120 00:07:01,733 --> 00:07:04,733 {\an1}why viruses circulate so well within bat colonies 121 00:07:04,766 --> 00:07:06,400 {\an1}and how they might transmit them 122 00:07:06,433 --> 00:07:08,633 {\an1}to other animal species 123 00:07:08,666 --> 00:07:10,600 that in turn could pass them on to humans. 124 00:07:10,633 --> 00:07:14,100 {\an1}But above all, she wants to know why this animal, 125 00:07:14,133 --> 00:07:16,366 infected by so many dangerous viruses, 126 00:07:16,400 --> 00:07:21,400 {\an1}seems totally impervious to their effects. 127 00:07:21,433 --> 00:07:23,809 {\an1}WACHARAPLUESADEE (translated): As far as I know from the research work 128 00:07:23,833 --> 00:07:26,733 overseas and my research work here, 129 00:07:26,766 --> 00:07:29,333 {\an1}bats with viruses aren't getting sick. 130 00:07:29,366 --> 00:07:32,866 {\an1}The bat aren't getting sick while the viruses still 131 00:07:32,900 --> 00:07:35,033 {\an1}live within them. 132 00:07:37,366 --> 00:07:42,333 ♪ ♪ 133 00:07:42,366 --> 00:07:47,633 {\an7}Because of the whole world is so desperately trying 134 00:07:47,666 --> 00:07:50,200 {\an7}to deal with, with COVID-19 and its horrible effects, 135 00:07:50,233 --> 00:07:51,700 {\an8}bats have come into the limelight, 136 00:07:51,733 --> 00:07:53,433 and they've come into the limelight 137 00:07:53,466 --> 00:07:56,533 {\an1}as potential reservoirs for many, many viruses. 138 00:07:56,566 --> 00:07:59,533 {\an1}And the question is, why? 139 00:07:59,566 --> 00:08:01,033 Why can they... 140 00:08:01,066 --> 00:08:02,566 {\an1}Are bats really special? 141 00:08:02,600 --> 00:08:04,766 {\an1}Is there something unique about bats' biology, 142 00:08:04,800 --> 00:08:06,533 {\an1}their physiology, the genetics, 143 00:08:06,566 --> 00:08:08,966 that allows them to tolerate these viruses? 144 00:08:09,000 --> 00:08:10,133 {\an1}What's the reason? 145 00:08:11,833 --> 00:08:13,300 NARRATOR: Will studying bats allow us 146 00:08:13,333 --> 00:08:16,333 {\an1}to avoid the next deadly virus outbreak? 147 00:08:16,366 --> 00:08:18,966 {\an1}Could their disease-defying biology 148 00:08:19,000 --> 00:08:22,500 {\an1}help us to live longer and in better health? 149 00:08:22,533 --> 00:08:25,233 {\an1}Laboratories around the world are mobilizing 150 00:08:25,266 --> 00:08:27,566 {\an1}to find the answers. 151 00:08:27,600 --> 00:08:30,866 {\an1}Because just how this stealthy, nocturnal animal functions 152 00:08:30,900 --> 00:08:33,966 {\an1}remains largely a mystery. 153 00:08:36,566 --> 00:08:41,433 ♪ ♪ 154 00:08:44,266 --> 00:08:47,933 {\an1}New Yorkers may not realize that one of the most unique 155 00:08:47,966 --> 00:08:51,266 {\an1}biological banks in the world is just next door: 156 00:08:51,300 --> 00:08:55,400 {\an1}a huge collection of bat organs and tissues, stored at 157 00:08:55,433 --> 00:08:58,600 {\an1}Stony Brook University. 158 00:08:58,633 --> 00:09:02,266 {\an1}A veritable treasure trove for scientists like Liliana Dávalos. 159 00:09:02,300 --> 00:09:08,066 ♪ ♪ 160 00:09:08,100 --> 00:09:11,400 DÁVALOS: It's a piece of brain from Belize. 161 00:09:11,433 --> 00:09:13,000 This is, um, 162 00:09:13,033 --> 00:09:17,000 {\an1}liver, liver sample, and it's from Colombia. 163 00:09:17,033 --> 00:09:19,933 {\an1}This is from our last expedition. 164 00:09:19,966 --> 00:09:22,733 {\an1}Our collection has 165 00:09:22,766 --> 00:09:24,733 {\an1}everything from the 166 00:09:24,766 --> 00:09:28,166 {\an7}top of the head, the brain, the nose, the eyes, 167 00:09:28,200 --> 00:09:30,200 {\an1}and every organ in the body. 168 00:09:30,233 --> 00:09:32,900 ♪ ♪ 169 00:09:32,933 --> 00:09:34,000 NARRATOR: Mummified bats, 170 00:09:34,033 --> 00:09:36,966 cabinets stuffed with body parts... 171 00:09:37,000 --> 00:09:38,576 {\an1}the Dávalos Lab might feel like something 172 00:09:38,600 --> 00:09:41,233 {\an1}out of a Frankenstein film. 173 00:09:41,266 --> 00:09:44,600 {\an1}(electricity buzzing, machine roaring) 174 00:09:46,600 --> 00:09:48,800 Not to worry... It's not what you think. 175 00:09:48,833 --> 00:09:51,600 And Liliana, rather than being frightened 176 00:09:51,633 --> 00:09:56,133 {\an1}or repelled by bats, is in fact one of their biggest fans. 177 00:09:59,100 --> 00:10:01,933 DÁVALOS: What have we got here? 178 00:10:03,600 --> 00:10:06,266 {\an1}Oh, this is so amazing. 179 00:10:06,300 --> 00:10:10,166 {\an1}This is a horseshoe bat. 180 00:10:10,200 --> 00:10:12,966 {\an1}This collection happened in 1934, 181 00:10:13,000 --> 00:10:16,233 December 27. 182 00:10:16,266 --> 00:10:17,733 {\an1}Somebody was out there, 183 00:10:17,766 --> 00:10:21,733 {\an1}in Chengdu, in China, catching bats. 184 00:10:21,766 --> 00:10:25,633 {\an7}This is the horseshoe down here, you see it? 185 00:10:25,666 --> 00:10:29,233 {\an8}NARRATOR: The horseshoe bat is widespread throughout Asia 186 00:10:29,266 --> 00:10:33,266 {\an1}and suspected to be at the origin of SARS-CoV-2, 187 00:10:33,300 --> 00:10:36,933 {\an1}the virus that causes COVID-19. 188 00:10:38,700 --> 00:10:40,633 {\an1}With this specimen, 189 00:10:40,666 --> 00:10:44,366 {\an1}Liliana will be able to study just how bats become infected. 190 00:10:44,400 --> 00:10:46,733 Since COVID is a respiratory disease, 191 00:10:46,766 --> 00:10:48,433 {\an1}the team concentrates their efforts 192 00:10:48,466 --> 00:10:50,766 {\an7}on the animal's respiratory tract, 193 00:10:50,800 --> 00:10:53,166 {\an7}especially its nose and nasal cavities. 194 00:10:53,200 --> 00:10:55,133 {\an8}♪ ♪ 195 00:10:55,166 --> 00:10:59,300 {\an1}Could it be that the inside of this strange-looking nose 196 00:10:59,333 --> 00:11:02,933 {\an1}contains the key to how bat viruses also infect humans? 197 00:11:06,233 --> 00:11:07,566 {\an7}Thanks to Laurel Yohe, 198 00:11:07,600 --> 00:11:09,966 {\an7}a researcher at nearby Yale University, 199 00:11:10,000 --> 00:11:11,833 {\an1}the team has access to a 3D scanner. 200 00:11:11,866 --> 00:11:15,333 {\an1}It's the first time ever this technique will be used 201 00:11:15,366 --> 00:11:17,600 {\an1}to study the inside of a bat. 202 00:11:17,633 --> 00:11:19,833 (typing) 203 00:11:19,866 --> 00:11:22,033 {\an4}(scanner beeping) YOHE: Here are the teeth. 204 00:11:22,066 --> 00:11:24,366 {\an7}You can see the neurons in the teeth. 205 00:11:24,400 --> 00:11:28,166 {\an7}As we move through, here is the tongue. 206 00:11:28,200 --> 00:11:30,500 {\an7}Here is the nasal cavity. 207 00:11:30,533 --> 00:11:34,733 NARRATOR: The horseshoe bat's nose is of particular interest 208 00:11:34,766 --> 00:11:37,233 {\an1}to Liliana and her spouse and research partner, 209 00:11:37,266 --> 00:11:39,233 {\an1}Angelique Corthals. 210 00:11:39,266 --> 00:11:40,342 {\an1}An expert in human biology, 211 00:11:40,366 --> 00:11:43,133 {\an1}Angelique studied the respiratory tracts 212 00:11:43,166 --> 00:11:47,933 of COVID victims at the height of the pandemic. 213 00:11:47,966 --> 00:11:49,866 {\an1}The bat is very similar to humans, 214 00:11:49,900 --> 00:11:54,566 {\an1}because you can see actually the same structure of the nose. 215 00:11:54,600 --> 00:11:57,133 CORTHALS: Bats that are known to harbor 216 00:11:57,166 --> 00:12:00,433 {\an1}the closest relative to SARS-CoV-2 217 00:12:00,466 --> 00:12:02,666 {\an7}have a nasal cavity 218 00:12:02,700 --> 00:12:04,066 {\an8}that is to, 219 00:12:04,100 --> 00:12:08,166 {\an7}that is actually closely resembling that of human, 220 00:12:08,200 --> 00:12:10,566 {\an1}which is very likely 221 00:12:10,600 --> 00:12:14,666 {\an1}part of the reason why we can be infected 222 00:12:14,700 --> 00:12:19,500 {\an1}so quickly with SARS-CoV-2, because all of a sudden, 223 00:12:19,533 --> 00:12:23,733 {\an1}it's not completely strange territory for coronavirus 224 00:12:23,766 --> 00:12:27,500 {\an1}to enter the nasal cavity of a human. 225 00:12:27,533 --> 00:12:30,900 NARRATOR: But once it has arrived in the nose of a bat or a human, 226 00:12:30,933 --> 00:12:35,200 {\an1}how does the virus infect the rest of the body? 227 00:12:35,233 --> 00:12:37,366 {\an1}Liliana and Angelique focus their research 228 00:12:37,400 --> 00:12:41,200 on the cells that line the nasal cavity. 229 00:12:44,400 --> 00:12:48,966 {\an8}CORTHALS: You see those hollow points in this layer? 230 00:12:49,000 --> 00:12:51,133 {\an7}Those are not holes, they are cells... 231 00:12:51,166 --> 00:12:53,633 {\an8}they are called the goblet cells, 232 00:12:53,666 --> 00:12:55,400 {\an7}which are mucus-producing cells. 233 00:12:55,433 --> 00:12:57,600 {\an1}They are the first barrier 234 00:12:57,633 --> 00:13:00,333 {\an1}against pathogens, against allergens, 235 00:13:00,366 --> 00:13:02,200 against any kind of foreign bodies 236 00:13:02,233 --> 00:13:03,966 {\an1}that enters through the nose. 237 00:13:04,000 --> 00:13:07,633 NARRATOR: Mucus produced by goblet cells 238 00:13:07,666 --> 00:13:11,200 {\an1}usually traps viruses before they can enter the body. 239 00:13:11,233 --> 00:13:15,533 {\an1}But when it comes to COVID-19, goblet cells have a weakness: 240 00:13:15,566 --> 00:13:19,666 {\an1}they are covered by a receptor that the coronavirus recognizes. 241 00:13:19,700 --> 00:13:23,600 {\an1}Like a key entering a lock, the virus attaches to the receptor, 242 00:13:23,633 --> 00:13:25,666 opens a passage, 243 00:13:25,700 --> 00:13:27,366 and injects its genetic material. 244 00:13:27,400 --> 00:13:29,133 {\an1}The cell then starts manufacturing the virus 245 00:13:29,166 --> 00:13:32,433 {\an1}by the hundreds, starting a chain reaction that can spread 246 00:13:32,466 --> 00:13:36,533 {\an1}throughout the whole organism. 247 00:13:38,300 --> 00:13:40,533 {\an1}The coronavirus can enter both bats 248 00:13:40,566 --> 00:13:43,166 {\an1}and humans in the same way, 249 00:13:43,200 --> 00:13:44,766 {\an1}through these goblet cells. 250 00:13:44,800 --> 00:13:47,533 {\an1}So how come humans can become so sick, 251 00:13:47,566 --> 00:13:49,466 {\an1}while bats don't? 252 00:13:49,500 --> 00:13:52,233 ♪ ♪ 253 00:13:52,266 --> 00:13:54,466 DÁVALOS: Our scientific understanding so far 254 00:13:54,500 --> 00:13:56,900 {\an1}is that the viral loads are fairly low, 255 00:13:56,933 --> 00:14:00,266 {\an1}meaning that these infections are circulating, 256 00:14:00,300 --> 00:14:02,533 {\an1}but they do not have the same consequences 257 00:14:02,566 --> 00:14:04,400 {\an1}in the bats that they have in people. 258 00:14:04,433 --> 00:14:06,400 {\an1}We don't understand yet fully why. 259 00:14:06,433 --> 00:14:07,900 ♪ ♪ 260 00:14:07,933 --> 00:14:11,600 NARRATOR: Somehow, the virus is able to enter bats' noses 261 00:14:11,633 --> 00:14:17,033 {\an1}the same way it does in humans, but the similarities end there. 262 00:14:17,066 --> 00:14:22,766 {\an1}In bats, the virus is present, but at a consistently low level. 263 00:14:22,800 --> 00:14:27,466 The question is: how are bats keeping the virus 264 00:14:27,500 --> 00:14:31,766 under control once it has entered? 265 00:14:36,766 --> 00:14:38,833 {\an1}That's what scientists in Singapore 266 00:14:38,866 --> 00:14:42,566 {\an1}are trying to find out at the Duke-N.U.S. Medical School, 267 00:14:42,600 --> 00:14:47,233 {\an1}where the bats' immune system has come under the microscope. 268 00:14:52,133 --> 00:14:56,900 {\an7}Professor Linfa Wang, known to colleagues as "Batman," 269 00:14:56,933 --> 00:15:02,066 {\an7}thinks he has found the secret to bats' super-immunity. 270 00:15:02,100 --> 00:15:03,733 {\an8}WANG: My students, when they first 271 00:15:03,766 --> 00:15:05,166 {\an7}work in my lab, they got it wrong. 272 00:15:05,200 --> 00:15:07,000 {\an7}They say bats has a more efficient 273 00:15:07,033 --> 00:15:08,766 {\an7}immune system to clear the virus. 274 00:15:08,800 --> 00:15:12,566 {\an7}I say. "No, bats have a more efficient immune system 275 00:15:12,600 --> 00:15:13,666 {\an7}not to develop disease." 276 00:15:13,700 --> 00:15:15,900 {\an7}They are more efficient, really, 277 00:15:15,933 --> 00:15:17,666 {\an7}to control the virus. 278 00:15:17,700 --> 00:15:19,660 {\an7}Otherwise, they will not be good reservoir, right? 279 00:15:21,133 --> 00:15:23,266 NARRATOR: Matae Ahn wrote his thesis under 280 00:15:23,300 --> 00:15:25,000 {\an1}Linfa Wang's direction. 281 00:15:25,033 --> 00:15:27,033 {\an1}When he joined the team in 2014, 282 00:15:27,066 --> 00:15:32,400 {\an1}the lab did not yet have a living bat colony to work with. 283 00:15:32,433 --> 00:15:34,200 {\an8}AHN: In the past, we had to 284 00:15:34,233 --> 00:15:37,066 {\an7}fly over to Australia to get all sample 285 00:15:37,100 --> 00:15:38,800 {\an7}for our studies, and now, 286 00:15:38,833 --> 00:15:41,033 {\an7}we have a local bat colony, right here. 287 00:15:41,066 --> 00:15:44,533 {\an7}And this allows us to get the fresh sample easily 288 00:15:44,566 --> 00:15:46,866 {\an7}and study bats really closely. 289 00:15:49,366 --> 00:15:52,333 NARRATOR: The cave nectar bat has a fox-like head 290 00:15:52,366 --> 00:15:55,500 {\an1}and lives principally in Southeast Asia. 291 00:15:55,533 --> 00:15:59,866 {\an1}In the wild, these bats are carriers of many viruses, 292 00:15:59,900 --> 00:16:01,200 {\an1}but don't get sick. 293 00:16:01,233 --> 00:16:03,900 {\an1}But in the lab, conditions are strictly controlled 294 00:16:03,933 --> 00:16:07,333 and the animals remain uncontaminated. 295 00:16:07,366 --> 00:16:09,900 {\an8}AHN: We are using the fresh bat samples 296 00:16:09,933 --> 00:16:12,833 {\an7}to analyze their contents in details, 297 00:16:12,866 --> 00:16:15,266 {\an7}starting from genes, mRNA, 298 00:16:15,300 --> 00:16:18,133 {\an7}protein, cells, to even tissues. 299 00:16:18,166 --> 00:16:19,766 {\an7}And all of these component can be 300 00:16:19,800 --> 00:16:21,466 {\an7}used and utilized to study bats 301 00:16:21,500 --> 00:16:24,400 {\an7}and their immune system. 302 00:16:24,433 --> 00:16:28,466 ♪ ♪ 303 00:16:28,500 --> 00:16:31,633 NARRATOR: Matae's experiment concentrates on 304 00:16:31,666 --> 00:16:34,300 {\an1}proteins involved in the immune response, 305 00:16:34,333 --> 00:16:39,333 {\an1}and on one molecule in particular: interferon alpha. 306 00:16:40,733 --> 00:16:42,733 {\an8}AHN: To be simple, interferon alpha 307 00:16:42,766 --> 00:16:47,166 {\an7}is a key molecule that alerts the body to the intruder. 308 00:16:47,200 --> 00:16:50,666 {\an7}It tells the surrounding cells that an infection is occurring. 309 00:16:52,133 --> 00:16:54,800 NARRATOR: When a cell detects a virus, 310 00:16:54,833 --> 00:16:57,500 {\an1}it unleashes a barrage of interferon molecules 311 00:16:57,533 --> 00:16:59,533 {\an1}which spread through the body, 312 00:16:59,566 --> 00:17:02,033 {\an1}spurring immune cells into action. 313 00:17:02,066 --> 00:17:04,133 Which, in turn, wipe out the intruding pathogens 314 00:17:04,166 --> 00:17:07,233 {\an1}and get rid of the cells already infected. 315 00:17:09,333 --> 00:17:11,600 {\an8}AHN: So we want to examine and compare 316 00:17:11,633 --> 00:17:13,500 {\an7}the level of interferon production 317 00:17:13,533 --> 00:17:15,700 {\an7}between human and bat cells 318 00:17:15,733 --> 00:17:18,733 {\an7}before any infection actually occurs. 319 00:17:18,766 --> 00:17:20,766 {\an8}(whirring) 320 00:17:24,033 --> 00:17:26,300 {\an8}(device beeps) So look, look at this curve. 321 00:17:26,333 --> 00:17:29,700 {\an7}This curve is a human sample, it's flat. 322 00:17:29,733 --> 00:17:31,466 {\an7}It means that interferon alpha 323 00:17:31,500 --> 00:17:33,000 {\an7}is almost undetectable. 324 00:17:33,033 --> 00:17:35,333 {\an8}In contrast, in our bat sample, 325 00:17:35,366 --> 00:17:37,666 {\an8}we have a lot of interferon alpha detected, 326 00:17:37,700 --> 00:17:41,433 {\an7}even though there is no infection occurring right there. 327 00:17:42,733 --> 00:17:45,500 NARRATOR: In other words, bats have adopted 328 00:17:45,533 --> 00:17:48,266 {\an1}a proactive strategy of defense. 329 00:17:48,300 --> 00:17:50,633 (whirring) 330 00:17:50,666 --> 00:17:53,133 {\an1}Thanks to interferon being permanently present, 331 00:17:53,166 --> 00:17:55,333 {\an1}when a virus penetrates the bat's body, 332 00:17:55,366 --> 00:17:58,133 {\an1}their immune system is already active. 333 00:17:58,166 --> 00:18:01,300 {\an1}But in humans, that reaction is much slower. 334 00:18:01,333 --> 00:18:03,866 {\an7}While our body's immune system is ramping up 335 00:18:03,900 --> 00:18:07,100 {\an7}to produce interferon, the virus can be spreading. 336 00:18:07,133 --> 00:18:10,700 {\an7}The risk of getting sick is therefore much greater in us 337 00:18:10,733 --> 00:18:14,666 {\an7}than in bats, where the virus remains under tighter control. 338 00:18:14,700 --> 00:18:16,342 {\an8}WANG: Human, for example, our defense system 339 00:18:16,366 --> 00:18:19,066 {\an8}is switched off most of the time, 340 00:18:19,100 --> 00:18:22,866 {\an7}until we see enemies, and then we switch on. 341 00:18:22,900 --> 00:18:28,633 NARRATOR: Unlike us, the bats' defenses are always on high alert. 342 00:18:28,666 --> 00:18:31,500 {\an1}Their immune system can prevent damaging infection 343 00:18:31,533 --> 00:18:33,766 {\an1}while letting some virus hang around. 344 00:18:33,800 --> 00:18:35,300 {\an1}That's good news for the bat, 345 00:18:35,333 --> 00:18:38,133 {\an1}but it might be really bad news for humans. 346 00:18:38,166 --> 00:18:39,666 {\an8}WANG: One theory is that 347 00:18:39,700 --> 00:18:42,433 {\an7}if the virus live inside a bat body, 348 00:18:42,466 --> 00:18:45,266 {\an7}you know, you already have elevated defense systems. 349 00:18:45,300 --> 00:18:48,100 {\an7}So when they jump to a different host, like human, 350 00:18:48,133 --> 00:18:51,333 {\an7}and that's, it's, like, you know, free playground for them 351 00:18:51,366 --> 00:18:54,033 {\an7}and they just go and rampage in us. 352 00:18:54,066 --> 00:18:56,800 {\an7}So very efficient. 353 00:18:56,833 --> 00:18:58,409 NARRATOR: A virus that battles for survival 354 00:18:58,433 --> 00:19:01,166 inside a bat's super-immune system 355 00:19:01,200 --> 00:19:03,833 {\an1}becomes a formidable enemy. 356 00:19:03,866 --> 00:19:06,933 {\an1}When it jumps to a less defended species, like a human, 357 00:19:06,966 --> 00:19:09,166 {\an1}it's much more dangerous. 358 00:19:09,200 --> 00:19:10,833 {\an1}But why did bats develop 359 00:19:10,866 --> 00:19:13,833 {\an1}such a highly functioning immune system? 360 00:19:13,866 --> 00:19:17,833 {\an1}Why did nature bestow bats with this superpower 361 00:19:17,866 --> 00:19:20,900 {\an1}while our own defense system has proven so weak 362 00:19:20,933 --> 00:19:23,500 in the face of multiple epidemics? 363 00:19:23,533 --> 00:19:27,566 ♪ ♪ 364 00:19:36,866 --> 00:19:41,866 {\an1}It's a question that zoologist and geneticist Emma Teeling 365 00:19:41,900 --> 00:19:45,500 {\an1}has spent decades researching. 366 00:19:47,633 --> 00:19:50,866 {\an1}Nearby her lab at University College Dublin, 367 00:19:50,900 --> 00:19:53,166 {\an1}Emma takes advantage of the last 368 00:19:53,200 --> 00:19:56,066 {\an1}few days of fall to visit a local colony 369 00:19:56,100 --> 00:19:59,533 {\an1}before the bats start their winter hibernation. 370 00:19:59,566 --> 00:20:05,000 ♪ ♪ 371 00:20:05,033 --> 00:20:06,866 TEELING: Some people don't actually like them, 372 00:20:06,900 --> 00:20:09,200 {\an1}and the question is why? 373 00:20:09,233 --> 00:20:11,966 {\an1}As primates, we primarily 374 00:20:12,000 --> 00:20:13,866 {\an1}get the information from our environment 375 00:20:13,900 --> 00:20:15,300 {\an1}through our eyes. 376 00:20:15,333 --> 00:20:17,033 At night, we're a bit frightened... 377 00:20:17,066 --> 00:20:18,700 {\an1}we can't really see them. 378 00:20:18,733 --> 00:20:19,876 {\an1}People think, "Oh, they're gonna get 379 00:20:19,900 --> 00:20:22,100 {\an1}caught in your hair"... They, they don't. 380 00:20:22,133 --> 00:20:23,733 {\an1}What they do is, they're flying, 381 00:20:23,766 --> 00:20:27,733 {\an1}feeding on insects that are trying to bite you. 382 00:20:27,766 --> 00:20:32,733 ♪ ♪ 383 00:20:32,766 --> 00:20:34,633 {\an7}(animal clicking) 384 00:20:34,666 --> 00:20:36,966 {\an7}There you go, there's a bat. 385 00:20:37,000 --> 00:20:39,500 {\an7}More than likely, it's a, it's a... 386 00:20:39,533 --> 00:20:41,633 {\an1}Oh, hello, you beauty. 387 00:20:41,666 --> 00:20:45,000 {\an1}More than likely, this is a soprano pipistrelle. 388 00:20:45,033 --> 00:20:46,733 {\an1}Because you can hear, its peak frequency 389 00:20:46,766 --> 00:20:47,933 {\an1}is about 45 kilohertz. 390 00:20:47,966 --> 00:20:50,133 {\an1}Do you see that little bat fly across? 391 00:20:50,166 --> 00:20:52,900 {\an1}This bat detector is picking up the sound 392 00:20:52,933 --> 00:20:55,300 {\an1}that's been emitted from the bat's mouth. 393 00:20:55,333 --> 00:20:57,966 {\an1}And what's happening is, the bat emits its call 394 00:20:58,000 --> 00:20:59,566 {\an1}and it listens to the echoes, 395 00:20:59,600 --> 00:21:03,166 {\an1}and it uses this to be able to orient in complete darkness. 396 00:21:03,200 --> 00:21:04,900 {\an1}I have a head torch on right now. 397 00:21:04,933 --> 00:21:08,300 {\an1}Right now, this is dusk... You can't see anything, 398 00:21:08,333 --> 00:21:10,500 {\an1}but the bats have woken up and they are flying around, 399 00:21:10,533 --> 00:21:11,600 {\an1}feeding on the insects, 400 00:21:11,633 --> 00:21:14,066 {\an1}and are more than likely flying up and down 401 00:21:14,100 --> 00:21:16,233 {\an1}this small stream here. 402 00:21:16,266 --> 00:21:17,409 (bird squawks, bats clicking) 403 00:21:17,433 --> 00:21:18,533 Hear? 404 00:21:18,566 --> 00:21:21,233 {\an1}Bang-bang-bang-bang-bang? 405 00:21:21,266 --> 00:21:26,133 (bats clicking) 406 00:21:26,166 --> 00:21:28,433 NARRATOR: Aided by their unique capabilities, 407 00:21:28,466 --> 00:21:32,633 {\an1}bats thrive on every continent except Antarctica. 408 00:21:32,666 --> 00:21:35,900 It's a story of extraordinary adaptation, 409 00:21:35,933 --> 00:21:37,633 {\an1}the secrets of which are inscribed 410 00:21:37,666 --> 00:21:40,400 in their DNA. 411 00:21:43,700 --> 00:21:47,500 {\an1}A wing flap away is Emma's center of operations, 412 00:21:47,533 --> 00:21:51,100 {\an1}a laboratory of mammalian molecular evolution. 413 00:21:51,133 --> 00:21:52,766 {\an1}Equipped with the latest tech, 414 00:21:52,800 --> 00:21:55,766 {\an1}it's affectionately called the Batlab. 415 00:21:55,800 --> 00:21:58,666 {\an1}Here, Emma co-pilots 416 00:21:58,700 --> 00:22:01,866 {\an1}one of the largest studies of bats in the world. 417 00:22:01,900 --> 00:22:03,700 {\an1}The project Bat1K 418 00:22:03,733 --> 00:22:06,400 {\an1}connects over a hundred scientists around the globe 419 00:22:06,433 --> 00:22:07,866 {\an1}in a joint effort 420 00:22:07,900 --> 00:22:10,366 {\an1}to sequence the genomes of the approximately 421 00:22:10,400 --> 00:22:12,700 {\an1}1,400 bat species. 422 00:22:12,733 --> 00:22:14,266 TEELING: We wanted to sequence 423 00:22:14,300 --> 00:22:17,800 {\an1}the entire DNA code that's in every single cell 424 00:22:17,833 --> 00:22:19,633 {\an1}of a particular species, 425 00:22:19,666 --> 00:22:23,200 {\an1}but we wanted to do it to the quality of the genomes 426 00:22:23,233 --> 00:22:27,733 {\an1}that we have for humans or mice, so that we could now use this 427 00:22:27,766 --> 00:22:31,600 {\an1}to investigate the likes of, what have bats evolved 428 00:22:31,633 --> 00:22:35,433 {\an1}to allow them live with coronaviruses and not die? 429 00:22:35,466 --> 00:22:38,000 ♪ ♪ 430 00:22:38,033 --> 00:22:42,333 NARRATOR: Bat1K's approach is to compare the billions of letters 431 00:22:42,366 --> 00:22:46,133 {\an1}that make up bats' genetic code with the DNA of other mammals. 432 00:22:46,166 --> 00:22:48,900 {\an1}In theory, finding out what is different 433 00:22:48,933 --> 00:22:53,000 {\an1}will lead researchers to those parts of the bat genome 434 00:22:53,033 --> 00:22:55,666 responsible for its robust health. 435 00:22:55,700 --> 00:22:59,133 TEELING: Darwinian selection... did natural selection act 436 00:22:59,166 --> 00:23:00,966 {\an1}on a particular part of the genome in bats 437 00:23:01,000 --> 00:23:03,000 {\an1}that make it very different 438 00:23:03,033 --> 00:23:05,800 {\an1}at the same region in bats and everything else? 439 00:23:05,833 --> 00:23:08,333 {\an1}And this may indicate that this is the region 440 00:23:08,366 --> 00:23:10,466 that's driving their unique adaptations. 441 00:23:10,500 --> 00:23:13,466 ♪ ♪ 442 00:23:13,500 --> 00:23:18,500 NARRATOR: Bat1K has already fully decoded the genomes of six bat species: 443 00:23:18,533 --> 00:23:21,200 {\an1}the velvety free-tailed bat, 444 00:23:21,233 --> 00:23:23,266 {\an1}the greater horseshoe bat, 445 00:23:23,300 --> 00:23:25,100 {\an1}the Egyptian fruit bat, 446 00:23:25,133 --> 00:23:27,400 {\an1}the pale spear-nosed bat, 447 00:23:27,433 --> 00:23:29,633 {\an1}the greater mouse-eared bat, 448 00:23:29,666 --> 00:23:33,100 {\an1}and Kuhl's pipistrelle. 449 00:23:33,133 --> 00:23:36,233 {\an1}A meticulous comparison of their DNA 450 00:23:36,266 --> 00:23:38,133 {\an1}with that of land-based mammals 451 00:23:38,166 --> 00:23:42,266 {\an1}revealed something totally unexpected. 452 00:23:42,300 --> 00:23:44,533 {\an1}When the bat's ancestor developed wings 453 00:23:44,566 --> 00:23:48,833 {\an1}and evolved the ability to fly... At least 55 million years ago... 454 00:23:48,866 --> 00:23:52,533 {\an1}the genes controlling their immune system also evolved, 455 00:23:52,566 --> 00:23:54,833 {\an1}mutating significantly. 456 00:23:54,866 --> 00:23:57,133 {\an1}It's as if their evolution as flyers 457 00:23:57,166 --> 00:23:58,833 {\an1}somehow provoked or required 458 00:23:58,866 --> 00:24:03,333 {\an1}a similar evolution in their immune system. 459 00:24:03,366 --> 00:24:05,433 TEELING: They can fly. 460 00:24:05,466 --> 00:24:06,833 {\an1}They're able to tolerate all their, 461 00:24:06,866 --> 00:24:08,642 {\an1}these, these unique viruses... Is there a connection? 462 00:24:08,666 --> 00:24:10,100 {\an1}What's the connection? 463 00:24:10,133 --> 00:24:13,266 {\an1}And this is something I've been working on for a very long time. 464 00:24:13,300 --> 00:24:14,800 {\an1}I have written research grants. 465 00:24:14,833 --> 00:24:16,700 {\an1}I've gotten slammed, 466 00:24:16,733 --> 00:24:18,466 {\an1}I've gotten abuse left, right, and center. 467 00:24:18,500 --> 00:24:21,733 {\an1}It's caused such scientific controversy, and it still does. 468 00:24:21,766 --> 00:24:24,633 {\an1}So the idea is, evolving... 469 00:24:24,666 --> 00:24:27,333 {\an1}Could evolving a new form of locomotion 470 00:24:27,366 --> 00:24:31,500 {\an1}drive an immunological and a genetic response? 471 00:24:31,533 --> 00:24:32,600 {\an1}A physiological response? 472 00:24:32,633 --> 00:24:34,433 {\an1}So I'm going to argue that yes. 473 00:24:34,466 --> 00:24:38,733 NARRATOR: For Emma Teeling, bats' extraordinary resistance 474 00:24:38,766 --> 00:24:42,166 to viruses seems to have evolved hand-in-hand 475 00:24:42,200 --> 00:24:44,200 {\an1}with their other superpower: 476 00:24:44,233 --> 00:24:47,166 {\an1}their supreme prowess in the air. 477 00:24:47,200 --> 00:24:50,900 {\an1}But how could flight protect this tiny mammal from sickness? 478 00:24:50,933 --> 00:24:53,933 What is the link between the two? 479 00:24:55,800 --> 00:24:59,800 {\an1}As the only mammals known to have evolved true flight, 480 00:24:59,833 --> 00:25:02,766 {\an1}bats' flying technique is totally unique 481 00:25:02,800 --> 00:25:05,333 {\an1}in the animal kingdom. 482 00:25:05,366 --> 00:25:07,633 {\an1}Every year at the Frio Cave, 483 00:25:07,666 --> 00:25:10,766 {\an1}about 70 miles west of San Antonio, Texas, 484 00:25:10,800 --> 00:25:13,233 newborn bat pups will take to the skies 485 00:25:13,266 --> 00:25:15,466 {\an1}for the very first time. 486 00:25:15,500 --> 00:25:18,700 ♪ ♪ 487 00:25:18,733 --> 00:25:20,866 (chuckling) 488 00:25:20,900 --> 00:25:24,333 {\an1}Millions of female Mexican free-tailed bats migrate here 489 00:25:24,366 --> 00:25:27,433 {\an1}in the spring, and it's the perfect opportunity 490 00:25:27,466 --> 00:25:29,933 {\an1}for biologist Gary McCracken 491 00:25:29,966 --> 00:25:34,700 {\an1}to observe the animals in action. 492 00:25:34,733 --> 00:25:37,900 MCCRACKEN: This is the time of year when mothers are beginning 493 00:25:37,933 --> 00:25:39,600 {\an1}to give birth to their pups. 494 00:25:39,633 --> 00:25:41,833 {\an7}We can't go very deep into the cave 495 00:25:41,866 --> 00:25:44,000 {\an8}with everybody, lights or cameras, 496 00:25:44,033 --> 00:25:46,366 {\an7}because it's just too disruptive at this time of year 497 00:25:46,400 --> 00:25:51,200 {\an1}for, for the bats, so we're respectful for that, yeah. 498 00:25:51,233 --> 00:25:53,000 There you go! 499 00:25:54,866 --> 00:25:57,366 NARRATOR: Gary goes just inside the mouth of the cave 500 00:25:57,400 --> 00:26:00,666 {\an1}so he won't disturb the pups. 501 00:26:02,333 --> 00:26:05,200 MCCRACKEN: I well remember the first time 502 00:26:05,233 --> 00:26:08,800 {\an1}that I went into a Mexican free-tailed bat cave. 503 00:26:08,833 --> 00:26:11,500 {\an1}I thought I was on the surface of the moon. 504 00:26:11,533 --> 00:26:14,866 I mean, really, the dust covering the rocks, 505 00:26:14,900 --> 00:26:17,300 you, you walk and your footprints stay there, 506 00:26:17,333 --> 00:26:20,166 {\an1}and then they get reworked by the beetles. 507 00:26:20,200 --> 00:26:21,400 {\an1}The atmosphere is heavy 508 00:26:21,433 --> 00:26:23,900 {\an1}with simple compounds of carbon and nitrogen, 509 00:26:23,933 --> 00:26:26,366 {\an1}methane and ammonia. 510 00:26:26,400 --> 00:26:29,833 {\an1}I mean, it really does seem like you're on another planet. 511 00:26:31,166 --> 00:26:35,333 (bats squeaking) 512 00:26:35,366 --> 00:26:37,133 {\an1}When I first saw the babies, 513 00:26:37,166 --> 00:26:41,133 {\an1}the dense concentrations of babies, it was just amazing. 514 00:26:41,166 --> 00:26:43,766 Soon, you've got 4,000 to 5,000 babies 515 00:26:43,800 --> 00:26:45,333 {\an1}in an area of about a square meter... 516 00:26:45,366 --> 00:26:48,166 {\an1}4,000 to 5,000 babies. 517 00:26:48,200 --> 00:26:50,666 NARRATOR: After about a month clinging to the walls, 518 00:26:50,700 --> 00:26:55,600 {\an1}the young pups will attempt their very first flight. 519 00:26:55,633 --> 00:26:58,333 {\an1}The slightest error could be fatal. 520 00:26:58,366 --> 00:27:01,200 MCCRACKEN: It's really awesome to imagine 521 00:27:01,233 --> 00:27:03,733 {\an1}what it must be like to take that first flight. 522 00:27:03,766 --> 00:27:06,766 {\an1}Looking down below... (chuckling) 523 00:27:06,800 --> 00:27:08,833 {\an1}Thinking about, what happens if I don't make it? 524 00:27:08,866 --> 00:27:11,700 {\an1}And, and if you don't make it, you're not going to get back. 525 00:27:11,733 --> 00:27:12,742 You're going to, you're going to, 526 00:27:12,766 --> 00:27:14,433 {\an1}you're going to land in the guano 527 00:27:14,466 --> 00:27:17,633 {\an1}and, and be eaten by dermestid beetles. 528 00:27:17,666 --> 00:27:20,400 And, you know, the amazing thing is that 529 00:27:20,433 --> 00:27:23,400 {\an1}it seems that the vast majority of them do make it work. 530 00:27:24,633 --> 00:27:27,900 NARRATOR: Once mature, the Mexican free-tailed bat 531 00:27:27,933 --> 00:27:30,200 {\an1}develops into an extraordinarily powerful 532 00:27:30,233 --> 00:27:33,666 {\an1}flying machine, and it's their outstanding performance 533 00:27:33,700 --> 00:27:37,333 {\an1}in the air that Gary has come here to measure. 534 00:27:37,366 --> 00:27:43,066 {\an1}Helping him is local biologist Jared Holmes. 535 00:27:43,100 --> 00:27:44,442 HOLMES: Yesterday, they started flying 536 00:27:44,466 --> 00:27:46,933 {\an8}about 7:30. MCCRACKEN: Uh-huh, yeah. 537 00:27:46,966 --> 00:27:48,533 {\an8}So we'll be ready by 7:30, for sure. 538 00:27:48,566 --> 00:27:50,666 {\an4}Okay. Yeah, we'll have the plane ready to go. 539 00:27:50,700 --> 00:27:53,233 So I'll tell you when we're taking off, 540 00:27:53,266 --> 00:27:55,200 {\an1}and you get the bat ready 541 00:27:55,233 --> 00:27:58,166 {\an1}and stick the radio on it. Oh, all right! 542 00:27:58,200 --> 00:28:01,800 These bats weigh a half an ounce, 12 grams. 543 00:28:01,833 --> 00:28:06,866 {\an1}They are too small, too light with current technology 544 00:28:06,900 --> 00:28:09,300 {\an1}to carry GPS trackers. 545 00:28:09,333 --> 00:28:12,533 {\an1}But they can carry these little radios 546 00:28:12,566 --> 00:28:15,100 {\an1}that are basically location locators. 547 00:28:15,133 --> 00:28:17,300 {\an1}HOLMES: And we're still looking for a female bat 548 00:28:17,333 --> 00:28:20,500 {\an1}of, of average size... Average size. 549 00:28:20,533 --> 00:28:21,900 Not too pregnant. 550 00:28:21,933 --> 00:28:24,933 {\an4}Gotcha. And, uh, and obviously, good health. 551 00:28:24,966 --> 00:28:26,042 A nice plump one. Yup, yeah. 552 00:28:26,066 --> 00:28:27,966 Yeah, just a nice bat. Okay. 553 00:28:28,000 --> 00:28:31,366 ♪ ♪ 554 00:28:31,400 --> 00:28:34,800 NARRATOR: The next day, on the tarmac at Garner Field airport, 555 00:28:34,833 --> 00:28:36,133 {\an1}not far from Frio Cave, 556 00:28:36,166 --> 00:28:40,066 {\an1}Gary adjusts the settings of his radio telemetry receiver. 557 00:28:40,100 --> 00:28:44,066 {\an1}This device will use radio signals to follow the bat 558 00:28:44,100 --> 00:28:46,600 {\an1}that Jared is about to capture and equip 559 00:28:46,633 --> 00:28:47,766 {\an1}with the transmitter. 560 00:28:48,733 --> 00:28:50,533 {\an1}(plane door shuts) 561 00:28:50,566 --> 00:28:51,933 MCCRACKEN: With the airplane, 562 00:28:51,966 --> 00:28:57,100 {\an1}it is possible to triangulate the location of the bat. 563 00:28:57,133 --> 00:29:01,200 {\an1}And by carefully listening to the signal from the transmitter, 564 00:29:01,233 --> 00:29:05,466 {\an1}we're able to pinpoint the location with some precision. 565 00:29:05,500 --> 00:29:07,142 {\an5}(radio chirps) HOLMES: Gary, the flight has started. 566 00:29:07,166 --> 00:29:09,366 {\an1}Are you in the air? 567 00:29:09,400 --> 00:29:11,576 {\an1}MCCRACKEN (over radio): Jared, we're just taking off right now. 568 00:29:11,600 --> 00:29:13,866 {\an1}We should be there in 15 minutes. 569 00:29:13,900 --> 00:29:15,600 {\an1}HOLMES (over radio): Okay, roger that. 570 00:29:15,633 --> 00:29:17,500 {\an1}I'm gonna go ahead and try to catch a bat. 571 00:29:17,533 --> 00:29:20,533 {\an1}MCCRACKEN (over radio): Be sure to get a nice, young, fluffy-looking one. 572 00:29:20,566 --> 00:29:21,533 (radio chirps) 573 00:29:21,566 --> 00:29:28,100 ♪ ♪ 574 00:29:30,266 --> 00:29:33,066 {\an1}HOLMES (over radio): I got a couple in the net, one looks good. 575 00:29:33,100 --> 00:29:35,633 {\an1}I'm gonna go ahead and tag it, gonna get it released. 576 00:29:35,666 --> 00:29:36,633 Good deal. 577 00:29:36,666 --> 00:29:39,900 {\an1}This is working really well right now. 578 00:29:39,933 --> 00:29:41,466 {\an1}(laughs) 579 00:29:41,500 --> 00:29:43,933 ♪ ♪ 580 00:29:43,966 --> 00:29:46,842 {\an1}MCCRACKEN (over radio): Okay, Jared, we're coming in, we're approaching the zone, 581 00:29:46,866 --> 00:29:48,866 {\an1}we're approaching the zone. 582 00:29:48,900 --> 00:29:51,466 {\an7}I've got the signal. 583 00:29:51,500 --> 00:29:53,266 {\an7}We're right overhead. 584 00:29:53,300 --> 00:29:54,766 {\an8}(over radio): Okay, you can release! 585 00:29:54,800 --> 00:29:56,666 {\an8}(radio chirps) HOLMES: Releasing her now. 586 00:30:02,766 --> 00:30:05,833 {\an1}HOLMES (over radio): Gary, I see the plane, I hope the bat's coming with you. 587 00:30:05,866 --> 00:30:07,500 (radio chirps) 588 00:30:07,533 --> 00:30:10,233 MCCRACKEN: Okay... okay... 589 00:30:10,266 --> 00:30:12,866 {\an1}Okay, okay... got it! Got it, good. 590 00:30:12,900 --> 00:30:17,333 NARRATOR: When the bat flies just underneath the plane, 591 00:30:17,366 --> 00:30:20,100 {\an1}the radio signal gets stronger and the pursuit begins. 592 00:30:20,133 --> 00:30:23,033 {\an1}As soon as the bat veers off, the signal weakens, 593 00:30:23,066 --> 00:30:28,266 {\an1}allowing Gary to guide the pilot to stay on the bat's course. 594 00:30:28,300 --> 00:30:29,976 {\an7}(device beeping at low pitch) Can you speed up just a little bit? 595 00:30:30,000 --> 00:30:31,766 {\an7}We're losing her, we're losing her. 596 00:30:31,800 --> 00:30:33,133 {\an7}A little bit, a little bit. 597 00:30:33,166 --> 00:30:36,633 {\an7}(device beeping at high pitch) Right on top, got it! 598 00:30:38,300 --> 00:30:41,566 NARRATOR: The plane is able to follow the bat for three hours 599 00:30:41,600 --> 00:30:46,033 {\an1}as it circles the area, hunting flying insects. 600 00:30:46,066 --> 00:30:48,466 {\an1}Now she's heading back north, 601 00:30:48,500 --> 00:30:51,266 {\an1}heading back in the direction of the cave. 602 00:30:51,300 --> 00:30:54,633 I think she, our bat went home. 603 00:30:54,666 --> 00:30:57,866 {\an1}This is so cool... wow. 604 00:30:57,900 --> 00:30:59,566 NARRATOR: When radio telemetry was used 605 00:30:59,600 --> 00:31:03,466 a few years ago, it allowed scientists to track 606 00:31:03,500 --> 00:31:06,666 {\an1}the Mexican free-tailed bat for the first time 607 00:31:06,700 --> 00:31:09,666 in mid-flight with jaw-dropping results. 608 00:31:09,700 --> 00:31:12,766 MCCRACKEN: We knew the bats were flying long distances. 609 00:31:12,800 --> 00:31:15,833 {\an1}We knew that this particular type of bat 610 00:31:15,866 --> 00:31:18,633 {\an1}can fly really, really fast. 611 00:31:18,666 --> 00:31:22,733 {\an1}But we, we didn't expect to see this, this sort of performance. 612 00:31:22,766 --> 00:31:26,366 {\an1}We think we've seen a bat going 100 miles an hour. 613 00:31:26,400 --> 00:31:28,766 ♪ ♪ 614 00:31:28,800 --> 00:31:30,333 NARRATOR: After studying the data, 615 00:31:30,366 --> 00:31:33,166 {\an1}initial field observations were confirmed: 616 00:31:33,200 --> 00:31:35,666 {\an1}the Mexican free-tailed bat got up to speeds 617 00:31:35,700 --> 00:31:38,100 {\an1}of about 100 miles per hour, 618 00:31:38,133 --> 00:31:41,566 {\an1}the fastest horizontal flight of any animal 619 00:31:41,600 --> 00:31:43,866 ever recorded. 620 00:31:43,900 --> 00:31:47,633 {\an1}But even if bats have proved to be the fastest flyers, 621 00:31:47,666 --> 00:31:52,266 {\an1}how would that help them to resist diseases? 622 00:31:56,833 --> 00:31:59,433 {\an8}♪ ♪ 623 00:31:59,466 --> 00:32:02,333 {\an1}Back on terra firma, scientists at Brown University 624 00:32:02,366 --> 00:32:05,000 are studying the possible connections 625 00:32:05,033 --> 00:32:07,500 {\an1}between bat flight and bat health. 626 00:32:11,100 --> 00:32:15,166 Kenny Breuer is an aeronautical engineer, 627 00:32:15,200 --> 00:32:16,733 {\an1}and for the past 15 years, 628 00:32:16,766 --> 00:32:18,666 {\an1}he has been creating mechanical wings 629 00:32:18,700 --> 00:32:21,433 {\an1}that imitate the bat's anatomy. 630 00:32:21,466 --> 00:32:23,933 {\an1}His prototypes have improved, 631 00:32:23,966 --> 00:32:26,533 {\an1}but nothing comes close to the real thing. 632 00:32:26,566 --> 00:32:28,300 {\an1}(mechanical whirring) 633 00:32:28,333 --> 00:32:32,266 {\an1}They have, however, helped him understand the physical effort 634 00:32:32,300 --> 00:32:35,966 {\an1}required for bats to navigate the skies. 635 00:32:37,766 --> 00:32:40,100 {\an8}BREUER: Flying is an expensive operation 636 00:32:40,133 --> 00:32:41,909 {\an7}in terms of energy... It takes a lot of energy 637 00:32:41,933 --> 00:32:44,333 {\an7}to get into the air and to propel yourself. 638 00:32:44,366 --> 00:32:47,166 {\an1}And you have to not only generate your own thrust, 639 00:32:47,200 --> 00:32:49,033 {\an1}but you have to overcome 640 00:32:49,066 --> 00:32:51,600 {\an1}the drag that is, that is experienced 641 00:32:51,633 --> 00:32:53,366 {\an1}by your body and by your wings. 642 00:32:53,400 --> 00:32:55,300 ♪ ♪ 643 00:32:55,333 --> 00:32:58,033 NARRATOR: Scientists estimate that the physical effort 644 00:32:58,066 --> 00:33:01,866 {\an1}expended by a bat in flight is about three times more than 645 00:33:01,900 --> 00:33:04,400 {\an1}a terrestrial mammal of the same size 646 00:33:04,433 --> 00:33:06,500 {\an1}running at full speed. 647 00:33:06,533 --> 00:33:09,666 The heartbeat of certain flying bats can reach 648 00:33:09,700 --> 00:33:13,233 {\an1}1,066 beats per minute. 649 00:33:13,266 --> 00:33:15,066 {\an1}(heart beating rapidly) 650 00:33:15,100 --> 00:33:20,733 {\an1}Could this level of activity, unrivaled by any other mammal, 651 00:33:20,766 --> 00:33:23,466 {\an1}somehow explain bats' super-immunity? 652 00:33:23,500 --> 00:33:26,800 ♪ ♪ 653 00:33:26,833 --> 00:33:28,000 SWARTZ: A few measurements 654 00:33:28,033 --> 00:33:31,200 {\an7}have suggested that body temperature in bats 655 00:33:31,233 --> 00:33:33,666 {\an7}might be unusually high. 656 00:33:33,700 --> 00:33:36,766 {\an7}This has led some scientists to suggest 657 00:33:36,800 --> 00:33:40,666 {\an7}that bats' body temperatures might be so high, 658 00:33:40,700 --> 00:33:45,866 {\an7}that it's as if they continually operate 659 00:33:45,900 --> 00:33:48,466 {\an7}at fever-like temperatures 660 00:33:48,500 --> 00:33:51,300 {\an1}during their nightly flights. 661 00:33:51,333 --> 00:33:52,900 ♪ ♪ 662 00:33:52,933 --> 00:33:57,600 NARRATOR: Fever is well-known as a means of fighting infection. 663 00:33:57,633 --> 00:34:00,966 {\an1}High temperatures slow down the replication of the virus 664 00:34:01,000 --> 00:34:03,666 {\an1}and boost the foot soldiers of the immune system 665 00:34:03,700 --> 00:34:05,833 {\an1}to devour intruders. 666 00:34:05,866 --> 00:34:11,233 {\an1}A feverish body is a hostile environment for a virus. 667 00:34:13,100 --> 00:34:15,000 {\an1}So could the extreme energy spent 668 00:34:15,033 --> 00:34:16,633 {\an1}during nightly hunting forays 669 00:34:16,666 --> 00:34:19,000 cause a spike in body temperature 670 00:34:19,033 --> 00:34:21,133 {\an1}that would protect bats from viruses? 671 00:34:21,166 --> 00:34:22,566 {\an1}To know for sure, 672 00:34:22,600 --> 00:34:26,000 {\an1}scientists must collect data in perfectly controlled conditions. 673 00:34:26,033 --> 00:34:31,300 This is where the Egyptian fruit bat comes in. 674 00:34:31,333 --> 00:34:32,666 {\an1}With its two-foot wingspan, 675 00:34:32,700 --> 00:34:35,900 {\an1}it is a remarkable flying machine. 676 00:34:39,066 --> 00:34:43,200 {\an1}Equipped with expertly placed mini-thermometers, 677 00:34:43,233 --> 00:34:47,933 {\an1}the animal takes flight under the team's watchful eye. 678 00:34:47,966 --> 00:34:51,166 ANDREA RUMMEL: Oh, my God, that's not bad! 679 00:34:51,200 --> 00:34:52,966 {\an1}I'm very impressed. 680 00:34:53,000 --> 00:34:55,533 - Great spread! RUMMEL: Yeah. 681 00:34:55,566 --> 00:34:58,900 ♪ ♪ 682 00:35:02,033 --> 00:35:07,566 ♪ ♪ 683 00:35:17,400 --> 00:35:20,566 NARRATOR: The experiment was performed on four different bats, 684 00:35:20,600 --> 00:35:25,000 {\an1}and the result was exactly the same for each one. 685 00:35:27,900 --> 00:35:29,466 {\an8}RUMMEL: We got these temperature traces 686 00:35:29,500 --> 00:35:32,233 {\an7}for three muscles along the bat wing. 687 00:35:32,266 --> 00:35:35,033 {\an7}So the red is a muscle that's in the core, 688 00:35:35,066 --> 00:35:37,966 {\an7}the pectoralis muscle, which is really important for flight. 689 00:35:38,000 --> 00:35:39,866 {\an7}And then we have the biceps and the muscle 690 00:35:39,900 --> 00:35:41,566 {\an7}in the forearm of the bat. 691 00:35:41,600 --> 00:35:42,800 {\an7}So closest to the core, 692 00:35:42,833 --> 00:35:45,366 {\an7}and then the blue curve is furthest from the core. 693 00:35:45,400 --> 00:35:47,133 {\an1}And as time proceeds, 694 00:35:47,166 --> 00:35:49,666 {\an1}the red and the green muscle stay pretty close 695 00:35:49,700 --> 00:35:52,500 {\an1}to the high body temperature that it started with. 696 00:35:52,533 --> 00:35:56,366 {\an1}But as we move through time, the blue muscle, 697 00:35:56,400 --> 00:35:58,766 {\an1}the forearm muscle that's further away from the core, 698 00:35:58,800 --> 00:36:01,900 {\an1}gets really cold and stays cold. 699 00:36:01,933 --> 00:36:03,776 {\an1}As they're flying, they're flapping their wings. 700 00:36:03,800 --> 00:36:05,666 {\an1}And so heat is going to be wicked away 701 00:36:05,700 --> 00:36:06,866 {\an1}from, from the bat wings, 702 00:36:06,900 --> 00:36:09,166 just by virtue of their movement. 703 00:36:09,200 --> 00:36:11,700 {\an1}And so bats are really effective at dumping heat, 704 00:36:11,733 --> 00:36:13,400 {\an1}even if they're generating a lot, 705 00:36:13,433 --> 00:36:17,233 {\an1}and their body temperatures stay fairly normal. 706 00:36:17,266 --> 00:36:19,833 ♪ ♪ 707 00:36:19,866 --> 00:36:22,433 NARRATOR: In other words, the naked wings of bats 708 00:36:22,466 --> 00:36:25,366 {\an1}act as an ultra-efficient cooling system 709 00:36:25,400 --> 00:36:28,166 {\an1}that keeps their temperatures from rising. 710 00:36:32,066 --> 00:36:34,366 ♪ ♪ 711 00:36:34,400 --> 00:36:36,633 {\an1}There's no fever-like temperatures 712 00:36:36,666 --> 00:36:40,266 {\an1}that could explain their super-immunity. 713 00:36:42,933 --> 00:36:46,300 {\an1}But some researchers are still convinced that flight 714 00:36:46,333 --> 00:36:49,766 {\an1}must have somehow helped shape their immune system. 715 00:36:51,600 --> 00:36:58,566 ♪ ♪ 716 00:37:02,933 --> 00:37:06,800 ♪ ♪ 717 00:37:06,833 --> 00:37:08,500 It sounds, like, very promising... 718 00:37:08,533 --> 00:37:09,933 NARRATOR: One believer 719 00:37:09,966 --> 00:37:13,133 {\an1}is Linfa Wang, and he thinks he's found out how. 720 00:37:13,166 --> 00:37:14,833 {\an7}(indistinct chatter) 721 00:37:14,866 --> 00:37:17,733 {\an8}WANG: Especially in the very ancient bats, 722 00:37:17,766 --> 00:37:21,166 {\an7}when they just acquired flight capability, 723 00:37:21,200 --> 00:37:23,800 {\an7}the number-one challenge they have to deal with 724 00:37:23,833 --> 00:37:25,300 {\an7}is this high metabolism. 725 00:37:25,333 --> 00:37:29,233 NARRATOR: The high metabolism required for flight 726 00:37:29,266 --> 00:37:30,600 {\an1}should lead to inflammation: 727 00:37:30,633 --> 00:37:32,600 {\an1}when animals' muscles work really hard, 728 00:37:32,633 --> 00:37:36,533 {\an1}the intense physical activity creates toxic by-products, 729 00:37:36,566 --> 00:37:38,866 {\an1}and these usually trigger inflammation. 730 00:37:38,900 --> 00:37:42,300 {\an1}Inflammation intrigues Linfa, because it is also caused 731 00:37:42,333 --> 00:37:45,166 {\an1}by viral infections, and in humans, 732 00:37:45,200 --> 00:37:49,033 {\an1}too much inflammation can have devastating effects. 733 00:37:49,066 --> 00:37:51,266 {\an8}WANG: For other mammals, human included, 734 00:37:51,300 --> 00:37:54,800 {\an7}when the coordination goes, you know, out a window, 735 00:37:54,833 --> 00:37:56,500 {\an7}and then when you over-defense, 736 00:37:56,533 --> 00:37:59,933 {\an7}that actually cause the pathology. 737 00:37:59,966 --> 00:38:01,900 {\an7}You know, now you get disease. 738 00:38:01,933 --> 00:38:04,300 {\an7}So we have a cliché in our field to say, 739 00:38:04,333 --> 00:38:07,100 {\an7}"Very few virus kills us, we kill ourself." 740 00:38:07,133 --> 00:38:10,600 NARRATOR: This is what happened in some of the most severe 741 00:38:10,633 --> 00:38:13,533 {\an1}cases of COVID-19, when patients' immune systems 742 00:38:13,566 --> 00:38:16,166 {\an1}raged out of control 743 00:38:16,200 --> 00:38:18,500 with so-called cytokine storms. 744 00:38:21,366 --> 00:38:24,433 {\an1}Cytokines, like interferons, 745 00:38:24,466 --> 00:38:26,533 {\an1}are molecules manufactured by the body 746 00:38:26,566 --> 00:38:30,433 {\an1}to regulate an immune response in case of an attack. 747 00:38:30,466 --> 00:38:32,466 {\an1}Sometimes, the system goes berserk 748 00:38:32,500 --> 00:38:34,766 {\an1}and produces too many cytokines. 749 00:38:34,800 --> 00:38:38,300 {\an1}The resulting inflammation doesn't just hurt the virus, 750 00:38:38,333 --> 00:38:42,033 {\an1}but everything in its path, including organs like the lungs, 751 00:38:42,066 --> 00:38:45,400 {\an1}heart, and even the brain. (EKG flatlining) 752 00:38:45,433 --> 00:38:50,933 {\an1}But bats don't seem to experience these symptoms. 753 00:38:50,966 --> 00:38:52,966 {\an1}So, have bats figured out a way 754 00:38:53,000 --> 00:38:55,333 {\an1}to control the inflammation associated with 755 00:38:55,366 --> 00:38:59,033 {\an1}both high metabolism and infection? 756 00:38:59,066 --> 00:39:00,700 To find out, 757 00:39:00,733 --> 00:39:02,866 {\an1}Wang's team is mixing bat immune cells 758 00:39:02,900 --> 00:39:05,066 {\an1}with toxic molecules 759 00:39:05,100 --> 00:39:07,600 that, in humans, would trigger inflammation. 760 00:39:10,833 --> 00:39:13,400 {\an8}AHN: So actually, we have isolated bat immune cells 761 00:39:13,433 --> 00:39:16,633 {\an8}and treated them with the toxic substances 762 00:39:16,666 --> 00:39:18,600 {\an7}that are produced by the body 763 00:39:18,633 --> 00:39:20,433 {\an7}when the metabolism is high. 764 00:39:20,466 --> 00:39:22,433 NARRATOR: In most animals, 765 00:39:22,466 --> 00:39:25,466 like humans, these toxins trigger 766 00:39:25,500 --> 00:39:29,133 {\an1}the production of a protein called NLRP3, 767 00:39:29,166 --> 00:39:30,633 {\an1}which in turn ramps up 768 00:39:30,666 --> 00:39:32,366 {\an1}the immune response and inflammation. 769 00:39:32,400 --> 00:39:37,000 {\an1}This microscope reveals the presence of the protein 770 00:39:37,033 --> 00:39:41,000 {\an1}in the form of a red dot. 771 00:39:41,033 --> 00:39:43,466 {\an8}AHN: We are comparing the inflammatory response 772 00:39:43,500 --> 00:39:45,133 {\an7}between human and bat cells. 773 00:39:45,166 --> 00:39:48,100 NARRATOR: In the human cells, the red dot shows that the protein 774 00:39:48,133 --> 00:39:51,466 {\an1}is being produced, meaning the immune response has begun. 775 00:39:51,500 --> 00:39:53,766 {\an1}But over on the bat side, 776 00:39:53,800 --> 00:39:56,333 {\an1}there are no red dots, meaning no protein 777 00:39:56,366 --> 00:39:58,433 {\an1}and no immune response. 778 00:39:58,466 --> 00:40:00,500 {\an1}Their cells seem to have tolerated the attack 779 00:40:00,533 --> 00:40:01,766 {\an1}of the added toxins 780 00:40:01,800 --> 00:40:05,033 {\an1}without any immune reaction. 781 00:40:05,066 --> 00:40:09,066 AHN: So, the bat have naturally tempered NLRP3 protein, 782 00:40:09,100 --> 00:40:12,600 {\an1}so that the stress-related and the viral-induced inflammation 783 00:40:12,633 --> 00:40:14,400 {\an1}always stay under control. 784 00:40:14,433 --> 00:40:16,000 ♪ ♪ 785 00:40:16,033 --> 00:40:17,966 NARRATOR: To become successful flyers, 786 00:40:18,000 --> 00:40:20,866 {\an1}bats had to tamp down their response to the toxins 787 00:40:20,900 --> 00:40:24,200 {\an1}produced during flight and prevent inflammation. 788 00:40:24,233 --> 00:40:27,966 {\an1}Linfa Wang thinks this same anti-inflammatory chemistry 789 00:40:28,000 --> 00:40:33,100 {\an1}is what's preventing bats from over-reacting to viruses. 790 00:40:33,133 --> 00:40:36,166 {\an8}WANG: Bats are very good virus reservoirs. 791 00:40:36,200 --> 00:40:40,566 {\an7}You know, we believe is that their adaptation to flight. 792 00:40:40,600 --> 00:40:44,900 {\an8}So that created a very different immune system. 793 00:40:44,933 --> 00:40:48,566 {\an7}Of course, that was evolved not to host virus, per se. 794 00:40:48,600 --> 00:40:50,833 {\an8}That's evolved adaptation to flight. 795 00:40:50,866 --> 00:40:53,300 {\an7}So their ability to host virus 796 00:40:53,333 --> 00:40:56,466 {\an7}is almost like a by-product, in my view. 797 00:40:56,500 --> 00:41:01,066 NARRATOR: For the team in Singapore, this unique adaptation isn't just 798 00:41:01,100 --> 00:41:04,100 {\an1}an evolutionary curiosity... It could pave the way 799 00:41:04,133 --> 00:41:06,900 {\an1}to revolutionary new therapies for all sorts of 800 00:41:06,933 --> 00:41:09,566 human diseases that involve inflammation. 801 00:41:09,600 --> 00:41:11,600 {\an8}AHN: In COVID-19 infections 802 00:41:11,633 --> 00:41:15,600 {\an7}and many age-related chronic diseases, 803 00:41:15,633 --> 00:41:20,000 {\an7}such as Alzheimer's or stroke, coronary artery disease, 804 00:41:20,033 --> 00:41:23,533 {\an7}diabetes... in all these diseases, 805 00:41:23,566 --> 00:41:25,933 {\an7}inflammation is over-activated. 806 00:41:25,966 --> 00:41:27,433 {\an7}That cause a lot of problem. 807 00:41:27,466 --> 00:41:33,700 {\an8}♪ ♪ 808 00:41:33,733 --> 00:41:37,166 {\an8}WANG: I'm really excited, from a basic scientist's point of view, 809 00:41:37,200 --> 00:41:40,233 {\an7}is that we are studying a very important mammal 810 00:41:40,266 --> 00:41:43,733 {\an7}as a model for living, you know, 811 00:41:43,766 --> 00:41:45,900 {\an7}a health, you know... I mean, 812 00:41:45,933 --> 00:41:47,600 {\an7}to health living and longevity, yeah. 813 00:41:47,633 --> 00:41:49,400 ♪ ♪ 814 00:41:49,433 --> 00:41:52,200 NARRATOR: This is the paradox of the bat. 815 00:41:52,233 --> 00:41:54,933 {\an1}Held responsible for a pandemic, 816 00:41:54,966 --> 00:41:57,533 {\an1}could the bat also be the source 817 00:41:57,566 --> 00:41:59,500 {\an1}of potential new cures? 818 00:41:59,533 --> 00:42:01,933 {\an1}Not just to fight disease, 819 00:42:01,966 --> 00:42:03,933 {\an1}but also old age? 820 00:42:03,966 --> 00:42:06,233 {\an1}Could the bat, maligned and misunderstood as it is, 821 00:42:06,266 --> 00:42:10,066 {\an1}also teach us the secret to growing old healthier? 822 00:42:10,100 --> 00:42:15,433 ♪ ♪ 823 00:42:21,433 --> 00:42:26,000 {\an8}♪ ♪ 824 00:42:26,033 --> 00:42:29,400 {\an8}This is Beganne, a village in Brittany, France, 825 00:42:29,433 --> 00:42:34,000 {\an7}whose bell tower is a well-known refuge for bats. 826 00:42:34,033 --> 00:42:37,900 {\an7}Every summer, dozens of female greater mouse-eared bats 827 00:42:37,933 --> 00:42:41,600 {\an7}roost in its rafters, giving birth to their pups... 828 00:42:41,633 --> 00:42:44,666 {\an7}a species whose exceptional, long lifespans 829 00:42:44,700 --> 00:42:48,033 {\an7}fascinate scientists like Eric Petit. 830 00:42:48,066 --> 00:42:50,500 {\an1}But he must wait for nightfall 831 00:42:50,533 --> 00:42:54,500 {\an1}to spot the newborns and their mothers. 832 00:42:56,166 --> 00:42:59,266 {\an7}PETIT (translated): With the greater mouse-eared bat, you have to be patient. 833 00:42:59,300 --> 00:43:01,066 {\an7}They don't come out very early, 834 00:43:01,100 --> 00:43:04,766 {\an7}so we've often got to wait a long time. 835 00:43:04,800 --> 00:43:07,366 {\an1}(speaking French) 836 00:43:07,400 --> 00:43:10,100 (translated): We're in front of the exit. 837 00:43:10,133 --> 00:43:14,266 In this colony, there's about 90 adults. 838 00:43:14,300 --> 00:43:16,233 {\an1}We're hearing something over there. 839 00:43:16,266 --> 00:43:18,433 {\an1}I think they're just behind the drainpipe. 840 00:43:19,566 --> 00:43:21,700 NARRATOR: They're difficult to see, 841 00:43:21,733 --> 00:43:26,266 {\an7}discreetly slipping out from behind the drainpipe. 842 00:43:26,300 --> 00:43:29,133 {\an1}But a thermal camera reveals the frenzied 843 00:43:29,166 --> 00:43:32,833 {\an1}nocturnal ballet taking place around the church. 844 00:43:40,866 --> 00:43:42,600 {\an7}In the surrounding underbrush, 845 00:43:42,633 --> 00:43:46,900 {\an7}this nocturnal acrobat shows the full range of its agility. 846 00:43:51,000 --> 00:43:53,442 {\an7}PETIT (translated): The greater mouse-eared bat is known for hunting 847 00:43:53,466 --> 00:43:55,533 {\an7}between 12 and 24 inches from the ground. 848 00:43:55,566 --> 00:43:58,166 {\an1}They listen for beetles making noise 849 00:43:58,200 --> 00:44:00,000 walking through the underbrush. 850 00:44:00,033 --> 00:44:02,400 {\an1}(speaking French) 851 00:44:02,433 --> 00:44:05,533 (translated): As soon as they hear one, they jump on top, 852 00:44:05,566 --> 00:44:08,833 grab hold of it, and fly off. 853 00:44:10,333 --> 00:44:14,100 NARRATOR: But it's not their agile flight or unusual hunting methods 854 00:44:14,133 --> 00:44:17,666 {\an1}that have caught the attention of scientists the world over. 855 00:44:17,700 --> 00:44:18,933 {\an1}It's their amazing longevity, 856 00:44:18,966 --> 00:44:22,166 {\an1}which seems to defy the laws of nature. 857 00:44:23,466 --> 00:44:26,066 {\an1}PETIT (translated): There is a general rule in biology. 858 00:44:26,100 --> 00:44:28,566 {\an1}Smaller animals don't live very long, 859 00:44:28,600 --> 00:44:31,500 {\an1}while larger animals live much longer. 860 00:44:31,533 --> 00:44:33,733 {\an1}Mice live for a couple of years, 861 00:44:33,766 --> 00:44:36,066 {\an1}while elephants can live dozens of years. 862 00:44:36,100 --> 00:44:38,266 {\an8}NARRATOR: The oldest greater mouse-eared bat 863 00:44:38,300 --> 00:44:40,566 {\an7}ever recorded was 37 years old. 864 00:44:40,600 --> 00:44:43,166 {\an7}But the record for longest life 865 00:44:43,200 --> 00:44:47,733 {\an7}is actually held by a cousin of the greater mouse-eared bat. 866 00:44:47,766 --> 00:44:50,933 {\an7}The Brandt's bat weighs less than a quarter of an ounce, 867 00:44:50,966 --> 00:44:54,000 {\an7}yet researchers captured a specimen that was at least 868 00:44:54,033 --> 00:44:58,333 {\an8}41 years old... A lifespan ten times longer 869 00:44:58,366 --> 00:45:01,100 {\an7}than theoretically expected. 870 00:45:01,133 --> 00:45:04,666 {\an8}♪ ♪ 871 00:45:10,066 --> 00:45:12,433 {\an1}PUECHMAILLE (translated): What's really fascinating with bats 872 00:45:12,466 --> 00:45:14,100 {\an1}is that if you capture an individual 873 00:45:14,133 --> 00:45:17,166 {\an1}that is two years old, or one that is 15 or 20 years old, 874 00:45:17,200 --> 00:45:20,300 {\an7}you can't see any difference between the two. 875 00:45:20,333 --> 00:45:22,400 {\an7}With humans, dogs, and most other species, 876 00:45:22,433 --> 00:45:23,400 {\an7}you would see an individual 877 00:45:23,433 --> 00:45:25,100 that has aged. 878 00:45:25,133 --> 00:45:27,566 NARRATOR: Sébastien Puechmaille studies aging 879 00:45:27,600 --> 00:45:32,233 {\an1}at the Institute of Evolutionary Science in Montpellier, France. 880 00:45:32,266 --> 00:45:36,200 ♪ ♪ 881 00:45:39,766 --> 00:45:41,400 {\an1}(Puechmaille speaking French) 882 00:45:41,433 --> 00:45:44,266 (translated): When we study aging, one of the first things we look at 883 00:45:44,300 --> 00:45:47,100 {\an1}is the central part of the cell, which is shown here, 884 00:45:47,133 --> 00:45:49,500 the nucleus. 885 00:45:49,533 --> 00:45:52,000 {\an1}Inside the nucleus, you see these kinds of small Xs. 886 00:45:52,033 --> 00:45:54,633 {\an1}These are the chromosomes. 887 00:45:54,666 --> 00:45:56,176 {\an1}I've zoomed in on the most important part 888 00:45:56,200 --> 00:45:58,766 {\an1}of the chromosome here, its extremities, 889 00:45:58,800 --> 00:46:02,400 {\an1}which we see in red. 890 00:46:02,433 --> 00:46:07,700 {\an1}These are what we call telomeres. 891 00:46:07,733 --> 00:46:09,566 So this telomere is a long fragment 892 00:46:09,600 --> 00:46:13,733 {\an1}that is in charge of protecting the chromosome's extremity. 893 00:46:13,766 --> 00:46:17,133 On young cells, the telomere is very long, 894 00:46:17,166 --> 00:46:22,066 {\an1}and over time, as the cell ages, the telomere gets shorter. 895 00:46:22,100 --> 00:46:25,366 At some point, it will get so short 896 00:46:25,400 --> 00:46:28,233 {\an1}that it will directly affect the integrity of the chromosome 897 00:46:28,266 --> 00:46:29,900 {\an1}and the health of the cell. 898 00:46:29,933 --> 00:46:33,433 NARRATOR: Scientists think that the shortening of telomeres 899 00:46:33,466 --> 00:46:37,066 {\an1}over time is one of the key triggers of cell death, 900 00:46:37,100 --> 00:46:40,733 {\an1}influencing the aging process and the lifespan 901 00:46:40,766 --> 00:46:44,166 {\an1}of all mammalian species. 902 00:46:44,200 --> 00:46:46,566 {\an1}So what's the deal with bats? 903 00:46:46,600 --> 00:46:48,966 (bell tolling) 904 00:46:49,000 --> 00:46:51,900 {\an1}For the past ten years, the bat colony at the church 905 00:46:51,933 --> 00:46:54,533 {\an1}in Beganne has been at the heart of a study 906 00:46:54,566 --> 00:46:58,766 {\an1}to figure out the secret to bats' long lives. 907 00:46:58,800 --> 00:47:01,466 Every summer, Sébastien Puechmaille 908 00:47:01,500 --> 00:47:03,233 {\an1}meets up with Emma Teeling and her team 909 00:47:03,266 --> 00:47:04,800 {\an1}to collect samples that allow them 910 00:47:04,833 --> 00:47:09,433 {\an1}to follow individual bats and their aging process. 911 00:47:09,466 --> 00:47:11,866 {\an1}An implant gun is used to insert a magnetic 912 00:47:11,900 --> 00:47:15,333 {\an1}identification chip the size of a grain of rice 913 00:47:15,366 --> 00:47:18,133 {\an1}under the skin between the shoulder blades. 914 00:47:18,166 --> 00:47:22,533 {\an1}Dozens of juveniles had been tagged this summer. 915 00:47:22,566 --> 00:47:23,900 (translated): When we say "tag," 916 00:47:23,933 --> 00:47:26,233 {\an1}it means inserting these tiny microchips, 917 00:47:26,266 --> 00:47:30,100 {\an1}like we do with dogs and cats at the vet. 918 00:47:30,133 --> 00:47:31,633 {\an1}This allows us to recognize 919 00:47:31,666 --> 00:47:34,466 {\an1}the same individuals year after year 920 00:47:34,500 --> 00:47:38,066 {\an1}and to follow their aging. 921 00:47:38,100 --> 00:47:41,033 NARRATOR: The oldest tagged individuals are now ten years old. 922 00:47:43,066 --> 00:47:45,009 {\an1}These are our sample numbers, so what we take back to UCD. 923 00:47:45,033 --> 00:47:47,433 {\an4}Right. So we know who's who, and there she is. 924 00:47:47,466 --> 00:47:48,700 {\an1}TEELING: Isn't that beautiful? 925 00:47:48,733 --> 00:47:50,366 {\an1}WOMAN: Gorgeous. 926 00:47:50,400 --> 00:47:51,633 {\an1}Is that a baby? 927 00:47:51,666 --> 00:47:53,042 {\an1}TEELING: We're gonna find out now in a minute! 928 00:47:53,066 --> 00:47:54,142 PUECHMAILLE: It looks like an adult. 929 00:47:54,166 --> 00:47:55,542 {\an4}TEELING: Do you want to bet? WOMAN: Yeah! 930 00:47:55,566 --> 00:47:57,042 {\an4}TEELING: You say a baby or an adult? PUECHMAILLE: Adult. 931 00:47:57,066 --> 00:48:00,000 {\an1}TEELING: Okay, can we, will we check to see by shining? 932 00:48:00,033 --> 00:48:02,133 {\an1}It's an adult! 933 00:48:02,166 --> 00:48:04,266 {\an1}Now we are going to take the blood. 934 00:48:04,300 --> 00:48:05,833 {\an1}Quite dark, isn't it? 935 00:48:05,866 --> 00:48:08,033 NARRATOR: Whether it's a drop of blood 936 00:48:08,066 --> 00:48:10,566 {\an1}or a small skin fragment, the samples taken every year 937 00:48:10,600 --> 00:48:15,200 {\an1}are conserved carefully in liquid nitrogen. 938 00:48:15,233 --> 00:48:17,166 {\an1}TEELING: Do you see how relaxed the bat is? 939 00:48:17,200 --> 00:48:18,300 {\an1}WOMAN: Yeah. 940 00:48:18,333 --> 00:48:19,442 {\an1}TEELING: It doesn't hurt them at all. 941 00:48:19,466 --> 00:48:20,676 {\an1}As long as they're in capable hands, 942 00:48:20,700 --> 00:48:22,109 {\an1}with people who know how to hold them properly 943 00:48:22,133 --> 00:48:24,600 and correctly. 944 00:48:24,633 --> 00:48:26,266 {\an1}So there it is! 945 00:48:26,300 --> 00:48:29,733 {\an1}Secret of everlasting youth. 946 00:48:29,766 --> 00:48:31,400 ♪ ♪ 947 00:48:31,433 --> 00:48:34,633 NARRATOR: Some of the precious samples taken in Beganne are stored 948 00:48:34,666 --> 00:48:38,466 {\an1}in Sébastien's basement laboratory in Montpellier. 949 00:48:38,500 --> 00:48:40,009 {\an1}To see if the greater mouse-eared bat's longevity 950 00:48:40,033 --> 00:48:41,966 {\an1}could be linked to the length of its telomeres, 951 00:48:42,000 --> 00:48:44,700 scientists have compared them with those 952 00:48:44,733 --> 00:48:46,466 {\an1}of the common bent-winged bat, 953 00:48:46,500 --> 00:48:50,333 {\an1}a species of bat that usually dies before it reaches 20. 954 00:48:52,300 --> 00:48:54,866 (translate): What you see with the common bent-winged bat, 955 00:48:54,900 --> 00:48:56,433 {\an1}which has a short lifespan, 956 00:48:56,466 --> 00:48:58,433 {\an1}that the telomeres shorten with age. 957 00:48:58,466 --> 00:48:59,676 {\an1}You see that very clear progression. 958 00:48:59,700 --> 00:49:03,133 {\an1}On the other hand, the greater mouse-eared bat 959 00:49:03,166 --> 00:49:06,033 {\an1}shows absolutely no shortening of the telomeres. 960 00:49:06,066 --> 00:49:07,866 On the contrary, you can see clearly 961 00:49:07,900 --> 00:49:11,300 {\an1}that they remain constant as the individual ages. 962 00:49:11,333 --> 00:49:13,166 {\an1}So an individual bat which is ten years old 963 00:49:13,200 --> 00:49:15,100 or one year old, 964 00:49:15,133 --> 00:49:18,500 {\an1}the telomeres will be exactly the same length. 965 00:49:18,533 --> 00:49:20,500 TEELING: What we found was extraordinary. 966 00:49:20,533 --> 00:49:24,766 {\an7}In the longest-lived genera of bats, the myotis bats, 967 00:49:24,800 --> 00:49:28,166 {\an7}their telomeres do not shorten with age. 968 00:49:28,200 --> 00:49:29,966 {\an1}And this was very unique. 969 00:49:30,000 --> 00:49:32,366 {\an1}We didn't really see this in any other mammal. 970 00:49:32,400 --> 00:49:36,533 {\an1}Telomeres shorten in us, in badgers, in sea lions. 971 00:49:36,566 --> 00:49:37,966 {\an1}So this was extraordinary. 972 00:49:38,000 --> 00:49:40,866 NARRATOR: Emma and Sébastien believe 973 00:49:40,900 --> 00:49:42,433 {\an1}that the greater mouse-eared bat's 974 00:49:42,466 --> 00:49:44,700 {\an1}extraordinarily long life 975 00:49:44,733 --> 00:49:47,000 {\an1}is linked to the resilience of its telomeres. 976 00:49:48,533 --> 00:49:50,766 But how does this genetic material 977 00:49:50,800 --> 00:49:53,733 {\an1}withstand the passage of time? 978 00:49:57,600 --> 00:50:00,133 {\an1}To find out, scientists compared the genes 979 00:50:00,166 --> 00:50:03,400 {\an1}of the greater mouse-eared bat with other mammals 980 00:50:03,433 --> 00:50:07,133 {\an1}and uncovered some key differences. 981 00:50:07,166 --> 00:50:09,266 TEELING: We found two or three genes 982 00:50:09,300 --> 00:50:12,100 {\an1}that we think are evolving in a different way in bats, 983 00:50:12,133 --> 00:50:16,000 {\an1}that we think are the genes that allow this thing 984 00:50:16,033 --> 00:50:19,800 {\an1}called alternative telomere lengthening happen in bats. 985 00:50:19,833 --> 00:50:22,800 {\an1}So bats are able to use a different mechanism 986 00:50:22,833 --> 00:50:25,666 {\an1}to maintain their telomeres with age. 987 00:50:25,700 --> 00:50:30,233 NARRATOR: Are these genes the key to the bats' long and healthy lives? 988 00:50:30,266 --> 00:50:32,033 {\an1}And could they one day protect 989 00:50:32,066 --> 00:50:35,333 {\an1}against the effects of aging in humans, as well? 990 00:50:35,366 --> 00:50:37,866 {\an1}Scientists aren't about to turn this discovery 991 00:50:37,900 --> 00:50:41,466 {\an1}into an elixir of youth, but researchers like Emma 992 00:50:41,500 --> 00:50:43,466 {\an1}are optimistic for the future. 993 00:50:43,500 --> 00:50:47,233 {\an1}Their adventure with bats has just begun. 994 00:50:49,800 --> 00:50:53,433 (crow cawing) 995 00:50:53,466 --> 00:50:56,933 {\an1}Echolocation that allows them to see in total darkness. 996 00:50:56,966 --> 00:51:01,300 {\an1}Flight speed that is unrivaled by any other animal. 997 00:51:01,333 --> 00:51:04,266 {\an1}They are impervious to most viruses, 998 00:51:04,300 --> 00:51:06,366 {\an1}insensitive to aging, 999 00:51:06,400 --> 00:51:11,233 {\an1}and the masters of a marvelously controlled immune system. 1000 00:51:11,266 --> 00:51:16,366 {\an1}Not bad for an animal so long despised. 1001 00:51:16,400 --> 00:51:19,066 TEELING: Looking at bats, one of the most vilified 1002 00:51:19,100 --> 00:51:22,366 {\an1}and terrifying, potentially, of all mammals. 1003 00:51:22,400 --> 00:51:24,966 {\an1}If we look at them in a slightly different light, 1004 00:51:25,000 --> 00:51:29,433 {\an1}we will be able to find ways to improve human existence. 1005 00:51:29,466 --> 00:51:34,800 ♪ ♪ 1006 00:51:34,833 --> 00:51:38,333 NARRATOR: The product of millions of years of adaptation, 1007 00:51:38,366 --> 00:51:40,566 {\an1}bats are now emerging from the shadows 1008 00:51:40,600 --> 00:51:42,966 {\an1}as extraordinary creatures 1009 00:51:43,000 --> 00:51:44,900 {\an1}that could potentially light a path 1010 00:51:44,933 --> 00:51:50,533 {\an1}for longer, and healthier, human lives. 1011 00:51:50,566 --> 00:51:55,333 ♪ ♪ 1012 00:52:08,733 --> 00:52:11,666 ♪ ♪ 1013 00:52:13,100 --> 00:52:14,876 {\an8}ALOK PATEL: Discover the science behind the news 1014 00:52:14,900 --> 00:52:16,966 {\an7}with the "NOVA Now" podcast. 1015 00:52:17,000 --> 00:52:20,500 {\an7}Listen at pbs.org/novanowpodcast 1016 00:52:20,533 --> 00:52:23,633 {\an7}or wherever you find your favorite podcasts. 1017 00:52:23,666 --> 00:52:25,500 {\an8}ANNOUNCER: To order this program on DVD, 1018 00:52:25,533 --> 00:52:30,866 {\an8}visit ShopPBS or call 1-800-PLAY-PBS. 1019 00:52:30,900 --> 00:52:33,733 {\an7}Episodes of "NOVA" are available with Passport. 1020 00:52:33,766 --> 00:52:37,066 {\an7}"NOVA" is also available on Amazon Prime Video. 1021 00:52:40,033 --> 00:52:46,700 ♪ ♪