(dramatic music)
(tiger growling)
Any one fascinated by the natural world
has probably wondered why some animals
have such strange looking sense organs.
The elephant with its huge ears,
the antennae of a butterfly,
which up close look like feathers,
the snake with its split tongue.
And what about less obvious enhancements?
Like the sensory cells on a crocodile's skin.
Surely these evolutionary traits aren't just for decoration.
In fact, the size, shape, and location
of these animals sense organs is all for a purpose.
And just like us, animals rely on their senses
to communicate with each other,
find their way around, stay safe,
and most importantly to find food.
When you see how superior some animal senses are
compared to those of humans,
you might wonder how we ever managed
to stay on top of the food chain.
Animal Super Senses, you won't believe what's possible.
(dramatic music)
Hello, and welcome to another installment
of Animal Super Senses.
The show where animal instincts
and perception are the stars.
In this episode, we examine how every animal
has what could be called the sense of rhythm,
the human animal included.
To give an obvious example,
there's our internal body clock
that responds to circadian rhythm.
That's the 24 hour day and night cycle.
Circadian rhythms are synchronized
with what is known as photoperiod.
In simple terms, the length of a day.
Changes in the amount of available light
are detected by mammals in a tiny area
of the brain called the SCN.
It's like a master clock,
which responds to the environmental cycle.
Some animals of course are diurnal,
mostly active during the day, while others are nocturnal.
they sleep through the day
and are busiest after the sun goes down.
But, there are other rhythms with a longer cycle,
often in tune and affected by the seasons.
For example, biologists recently identified
a photoreceptor cell deep inside the brains of birds,
which responds to daylight and nightlight,
but also regulates breeding activity
according to seasonal changes.
Animals synchronize their body clocks
for biological purposes, such as reproduction,
hibernation,
fur color changes and migration.
But exactly what senses are at work
to help animals keep in tune
with the rhythms of day and night and the changing seasons?
The answers coming up in this episode may just surprise you.
Did you know that all vertebrate animals,
which, of course, includes human beings,
have a special organ, the pineal gland.
Also known as the third eye,
which detects daily changes in the amount of light.
(tribal singing)
In human beings, the pineal gland is located
in the center of the brain.
But in birds, reptiles, and fish,
it is located on the forehead, just underneath the skin.
For workaday diurnal animals,
the light sensitive pineal gland releases more melatonin
during the night than by day.
This helps animals set their body clocks,
letting them know when to be active
and when to go to sleep.
As mentioned, humans have a pineal gland
and this so-called third eye,
has long been attributed
with mystical powers since ancient times.
Whatever it's spiritual properties,
the pineal gland seems to help animals adhere
to a 24 hour rhythm
and regulate their sleeping and waking cycles.
Some lizards, frogs, lampreys, and species of fish
literally do have a third eye, known as the parietal eye.
The tuatara is a reptilian survivor of the dinosaur age
and is found only in New Zealand.
In mammals the pineal gland
is buried deeper inside the forehead
meaning that it can not receive light directly.
So how does it sense changes between day and night?
Recent research has found
that the pineal gland is directly linked
to the retina in eyes.
In diurnal mammals, and again, it includes us,
the melatonin hormone makes us sleepy.
(peaceful music)
Scientists have recently shown that in nocturnal animals
the pineal gland still secretes melatonin
even during darkness,
during the period when night creatures
become the most active.
So clearly melatonin is not the universal sleeping pill.
In some species, it may have the opposite effect.
Incidentally, do you know how much sleep
the average adult requires?
That's right, only five more minutes.
Excuse the levity.
Of course, the whole cycle of life
is in so many ways, dependent on timing.
The changing seasons has an impact
on reproductive cycles in many species.
Animals like these Rocky Mountain Bighorn sheep
found in high places from British Columbia to Arizona,
live their entire lives
in sync with the changing of the seasons.
Changes in temperature and the lengthening
or shortening of days,
these are keenly felt at high altitudes.
The timing of the mating season
becomes vitally important in harsh climates.
Meeting occurs at a particular time
so that the young may be born when the weather is
at its mildest and resources are most abundant.
Staying in Arizona, where these pronghorn antelope
are most definitely seasonal breeders.
Mating season begins
with a head-butting contest between males.
as they compete for mating rights
and access to females.
Bucks separate from others in August
and begin hanging around with the does.
Male pronghorns grunt and snort pushing
and fighting the other bucks
to gain the attention of females.
They rub their antlers on trees
and bushes marking areas with their scent.
It's an impressive display,
but it won't be totally unfamiliar
to anyone who watches so-called,
reality television dating shows.
This sense of timing is found
throughout the animal realm
in such phenomenon as hibernation.
Fur color changes, or migration.
We'll take a look at all
of these in due course, but first up, let's see
if we can both get our lips and your heads around a state
of suspended development called embryonic diapause.
It's just what it sounds like.
Embryonic diapause that is.
The embryo takes a pause,
meaning the embryo does not immediately implant
in the uterus,
but is maintained the state of dormancy.
By far the most famous case
of this state of arrested development
takes place in the Outbacks of Australia.
This is a reproductive strategy
so kangaroo moms can time the birth of their young
in order to avoid going into labor
during unfavorable environmental conditions,
such as droughts.
When the time is right, the embryo is reactivated.
The little joey kangaroo is born and then crawls
into its mother's pouch.
This phenomenon occurs in a number of marsupial species
but is especially prevalent among kangaroos and wallabies.
This is also known as delayed implantation.
It's something common to rodents,
bears, weasels and badgers too.
The arrested development of a joey
almost pales in comparison,
with how some animals are able to shut down everything
but vital signs
during that state of suspended animation,
we know as hibernation.
(water gushing)
And the world's super-hibernator is undoubtedly
this fearsome looking predator, the black bear.
(mischievous music)
Also known as the American black bear,
though they can be found in large numbers
across the border in Canada as well.
American or Canadian, it doesn't matter.
In any case, the black bear hibernates five to seven months
of the year during which time it does not eat,
drink, urinate or defecate.
During this period,
they completely throw all their other circadian rhythms
out the window.
As they move from summer to autumn,
black bears and indeed bears in general
begin feeding even more than usual.
Males and females will gorge themselves
on an average of 30,000 calories a day.
We don't advise that you try this at home.
This conspicuous consumption is all for a reason.
It creates a layer of fat,
which will act as insulation
and kind of a metabolic reservoir
for their time in super-hibernation.
Now chipmunks are, of course hibernators too,
so let's compare what they get up to
with the habits of the black bear.
When the chipmunk goes into a deep sleep,
its body temperature can drop
by more than 6.6 degrees Celsius.
The upshot, is that the chipmunk must wake up
every few days and feed like nobody's business.
(upbeat music)
The metabolism of a black bear on the other paw,
will slow to where they are taking just one
or two breaths per minute,
and their hearts beat eight to 12 times per minute.
(bear growling)
But this is not a competition.
And there's no doubt
that many small mammals, such as chipmunks
but also woodchucks and ground squirrels
are some world-class hibernators.
The hibernation habits
of the Arctic ground squirrels are surely worthy of note.
A year round resident of the Arctic tundra,
this ground squirrel has a hybrid issue period
of up to seven to eight months.
During its deep sleep,
the Arctic ground squirrel's core body temperature drops
just below freezing.
Once every two to three weeks or so,
it shivers and shakes without waking
for more than a dozen hours at a time to reheat its body.
Another way in which animals have the sense
to register changes in seasons,
is by changing into their winter wardrobes.
The Arctic fox is a classic case in point.
Life could be difficult
for this elegant looking little creature,
but the Arctic fox makes the best of its lot.
Preying on whatever creatures it can find for survival,
including lemons and voles,
and perhaps to make life on the Tundra a little less
solitary of a journey,
the Arctic fox is a monogamous creature and mates for life.
They're also relatively involved parents with mother
and father helping to raise the average
of five to eight cubs.
Be that as it may,
let's get back to the Arctic fox's fashion sense.
During the short Arctic summer, it's fur is a brown color.
As winter sets in,
the fur thickens and turns white.
Thicker for obvious reasons,
white so that the creature's camouflage matches the season,
and that of course means white as snow.
Animals body clocks can last longer than a day or a season
or even a whole year.
To illustrate, we leave the frozen Tundra
of the Arctic behind and travel to the deciduous forests
of the Eastern United States.
The principal habitat of the periodical cicadas,
also known as Magicicadas.
Cicadas spend a lot of time underground.
In fact, the vast majority of their lives.
(soft piano music)
For a period of either 13 or 17 years,
both prime numbers you will note,
cicadas stay under foot feeding on the roots
of deciduous trees and yet slowly,
ever so slowly over this time, they develop and mature.
Then finally, for a bit of few glorious weeks
when the almost adult cicadas
are at the so-called nymph stage,
they emerge from the ground in large numbers.
They shed their skins one last time
and after a few days their exoskeletons harden completely.
(tinkling music)
Then they take to the skies,
singing the familiar cicada mating call to find a mate.
The question is, after every 13 or 17 years,
how do they know when to come out in such precise intervals?
Recent research thinks they may be keeping track
of the sap cycles in trees,
but still no one knows for sure.
One thing we haven't really touched on in our examination
of animal timing is the effect of the moon on animals,
for the lunar cycle, governs the timing of natural events
as much as the sun.
(dramatic music)
A long way from cicadas,
at the edge of the ocean in this case,
the coral reefs around the gold coast of Australia.
We can see clearly how life is affected
by the lunar cycle, especially in underwater life.
For just one week of every year in spring,
after a full moon, millions of corals will release
their eggs and sperm in a symphony of reproductive activity.
(soft piano music)
This spectacular example of group sex,
which is what it is if you think about it,
has long been a source of fascination.
But up until less than a decade ago,
it was a mystery how these seemingly primitive beings,
which somehow get through life without brains or eyes,
synchronize their annual mass spawning.
But in 2007, scientists were able to isolate an ancient gene
in the corals, which is capable of detecting moonlight.
(intense music)
On Animals Super Senses,
every episode serves to demonstrate that
while we like to think of ourselves
at the top of the food chain,
when we look at our senses,
compared to the phenomenal abilities of other animals
we are just fumbling in the dark with earmuffs on.
See you next time on, Animals Super Senses.
(intriguing music)