WEBVTT - How Did the Smallest Primates Get Such Big Eyes?

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<v Speaker 1>Welcome to brain Stuff, a production of iHeartRadio, Hey brain

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<v Speaker 1>Stuff Lauren bogelban here. The unique characteristics of tarsiers have

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<v Speaker 1>caused people to call these tiny primates many names, from

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<v Speaker 1>goblins to gremlins to grogu. To be fair, they do

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<v Speaker 1>have prominent and sometimes pointed ears and an uncanny eyeballed

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<v Speaker 1>ahead ratio for a creature that's so closely related to us.

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<v Speaker 1>The tarsier is a small type of primate found living

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<v Speaker 1>in the forests of Southeast Asia and the Pacific Islands.

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<v Speaker 1>The taxonomical tarsiar family contains three genera, some sixteen species

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<v Speaker 1>and seven subspecies depending on who you ask. It's an

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<v Speaker 1>ongoing field of research, and I'm pretty sure biologists enjoy

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<v Speaker 1>arguing about taxonomy. But whatever their exact classification, tarsiers all

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<v Speaker 1>occupy the dense forests of Malaysia, Indonesia, Brunei, and the Philippines,

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<v Speaker 1>though every species has different characteristics. Tarsiers tend to range

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<v Speaker 1>in side from around three and a half to six

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<v Speaker 1>inches long that's about nine to fifteen centimeters, making them

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<v Speaker 1>among the smallest known primates. Like owls, they can rotate

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<v Speaker 1>their head nearly one hundred and eighty degrees in both directions.

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<v Speaker 1>Tarsiers have round heads with a small snout and large

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<v Speaker 1>ears that look a bit like muscleshells. They also have round,

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<v Speaker 1>furry bodies. Their thick, short fur can range in color

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<v Speaker 1>from gray to black or tan to yellow, orange to

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<v Speaker 1>red to brown, or some combination. They have long arms

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<v Speaker 1>and legs. Their ankle bones, or tarsals, are particularly long.

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<v Speaker 1>That's where they get their name. Those long legs and

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<v Speaker 1>ankles allow them to jump and leap like lemurs. Their

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<v Speaker 1>fingers are also exceptionally long, with small sticky pads at

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<v Speaker 1>the ends to help them cling to trees where they

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<v Speaker 1>live and hunt for prey. Their tails can be twice

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<v Speaker 1>their body length. Some species of tarsiers have hairless, a

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<v Speaker 1>rat like tails, while others have tufts of fur along

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<v Speaker 1>the length of the tail or at the end. Altogether,

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<v Speaker 1>they look sort of like someone stuck frog legs on

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<v Speaker 1>a highly caffeinated teddy bear. Tarsiers like hanging out in shrubs, trees,

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<v Speaker 1>and other vegetation above ground level. This vantage point allows

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<v Speaker 1>them to rest more at ease from predators and also

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<v Speaker 1>to hunt for their small prey. They are the planet's

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<v Speaker 1>only primate species that is entirely carnivorous, but within that category,

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<v Speaker 1>they eat whatever their forests have to offer, including insects, frogs, crabs, lizards, birds, bats,

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<v Speaker 1>and snakes, and different species are variably social, but they

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<v Speaker 1>tend to form small groups that gather to share food,

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<v Speaker 1>protect each other from predators, play, groom, snuggle, and mate.

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<v Speaker 1>They communicate with calls that are outside the range of

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<v Speaker 1>human hearing. But okay, we have to talk about what

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<v Speaker 1>large eyes they have. Even four nocturnal mammals, their eyes

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<v Speaker 1>are enormous compared to their body size. They're the biggest

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<v Speaker 1>eyes of any mammal relative to their body weight. Their

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<v Speaker 1>eyes are very round in shape and often a striking

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<v Speaker 1>gold color. A tarsiar's lack a tpedum lucidum, which we've

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<v Speaker 1>talked about before on the show. It's a reflective layer

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<v Speaker 1>inside the eye behind the retina that most other animals

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<v Speaker 1>have if they are active at night. The tpedum lucidum

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<v Speaker 1>is important to nocturnal vision because it bounces light back

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<v Speaker 1>at the retina, giving the eye a second chance to

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<v Speaker 1>gather that light. For the article of this episode is

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<v Speaker 1>based on how Stuff Works. Spoke with Myron Shekel PhD,

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<v Speaker 1>a biological anthropologist imprimatologist with Western Washington University. He said,

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<v Speaker 1>one of the things we know is when you take

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<v Speaker 1>your flashlight and you shine it into a forest at night,

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<v Speaker 1>lots of animals have a very strong eye shine that

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<v Speaker 1>comes to right back at you. Cats and dogs, lemurs,

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<v Speaker 1>bush babies, and lorises. Tarsiers don't have that. Humans, monkeys

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<v Speaker 1>and apes don't have that. So the tarsier I had

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<v Speaker 1>to compensate and became a lot bigger than you'd expect.

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<v Speaker 1>Shikehl has conducted decades of research contributing to what we

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<v Speaker 1>know about tarsiers and about primate evolution in general, he said.

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<v Speaker 1>When I handed in my first grant proposal, which would

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<v Speaker 1>have been in nineteen ninety three nineteen ninety four, one

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<v Speaker 1>of the reviewers commented, Shakelle has outlined a career's worth

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<v Speaker 1>of research, and now I'm just about to the point

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<v Speaker 1>where I can publish the answer to the questions I

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<v Speaker 1>posed in that research grant proposal all those years ago.

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<v Speaker 1>It's exactly the tarsiers lack of this reflective layer that

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<v Speaker 1>offers an exciting insight into primate evolution. When primates became diurnal,

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<v Speaker 1>a meaning active during the daytime, they eventually lost the

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<v Speaker 1>need for a pedem lucidam, Schakel said, So it looks

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<v Speaker 1>like tarsiers spent some amount of time in their history

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<v Speaker 1>as a diurnal primate. If they then reversed and became

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<v Speaker 1>nocturnal again, they had perhaps already lost that topedum lucidum.

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<v Speaker 1>Since the first scientific description of tarsiers was published around

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<v Speaker 1>seventeen seventy seven, scientists have debated where tarsiers belong on

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<v Speaker 1>the primate evolutionary tree. They jump, climb, and live like lemurs,

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<v Speaker 1>but have physical characteristics similar to apes and humans, like

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<v Speaker 1>that lack of a topedum lucidum and the fact that

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<v Speaker 1>they have a dry nose instead of a wet one,

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<v Speaker 1>which is one of the main ways that researchers categorize primates.

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<v Speaker 1>Chakel said, At the level of genomic data, where we

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<v Speaker 1>can look at really major changes, the evidence is becoming

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<v Speaker 1>clearer that tarsiers are our cousins. However, tarsiers are notoriously

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<v Speaker 1>elusive and difficult to study, especially without the dead giveaway

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<v Speaker 1>eyeshine that other nocturnal species have. Chakel and his colleagues

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<v Speaker 1>identified several new species of tarsiers on the Indonesian island

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<v Speaker 1>of Sulawesi, where there was long thought to be just

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<v Speaker 1>a single species. But unfortunately, tarsiers do poorly in captivity.

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<v Speaker 1>No group that's been brought into captivity for study or

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<v Speaker 1>tourism has survived. It's hard to replicate their prey rich

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<v Speaker 1>natural environment, and like other primates, they're easily stressed out.

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<v Speaker 1>Tarsier conservation is becoming an increasingly important topic, as some

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<v Speaker 1>species of tarsiers have made the endangered or Vulnerable species

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<v Speaker 1>list due to their limited population, a lack of protected areas,

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<v Speaker 1>and deforestation and mining of what territory they do inhabit.

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<v Speaker 1>Just for one example, take the main island of Sangi

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<v Speaker 1>Hey in Indonesia. Sangi He has an endemic species of tarsiers, endemic,

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<v Speaker 1>meaning that the species is only found there. The saying

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<v Speaker 1>gie Hey tarsier was recently added to the list of

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<v Speaker 1>twenty five most endangered primates in the world after the

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<v Speaker 1>island opened to gold mining. Because there are more tarsier

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<v Speaker 1>species than there are scientists studying them, it's difficult to

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<v Speaker 1>know precisely how endangered some species are across these many islands,

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<v Speaker 1>but hopefully some intentional conservation efforts will help bring species

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<v Speaker 1>back from the brink and prevent more species from becoming

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<v Speaker 1>critically endangered. It'll take a concerted effort and coordination with

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<v Speaker 1>local researchers and experts. Shaquel said, If we keep tarsiers

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<v Speaker 1>in their habitat like in Indonesia, and we simply throw

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<v Speaker 1>a cage around them and use somebody who actually knows

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<v Speaker 1>how to keep tarsiers alive, they stay alive and they breed.

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<v Speaker 1>Today's episode is based on the article the tarsier is

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<v Speaker 1>one weird primate and Yes We're related on how stuffworks

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<v Speaker 1>dot Com, written by Alison Trautner. Brain Stuff is production

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<v Speaker 1>of iHeartRadio in partnership with HowStuffWorks dot Com and is

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<v Speaker 1>produced by Tyler Klain. Four more podcasts from my heart Radio,

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