Why the orangutan is the least understood of the world's primates
They're solitary, they rarely give birth and their habitat is threatened
Biological anthropologist Cheryl Knott and wildlife photojournalist Tim Laman are speaking in Calgary on Sunday and Monday about orangutans.
Knott spoke Thursday to Doug Dirks on The Homestretch.
This interview has been edited for clarity and length.
Q: Why do you believe orangutans are one of the world's least understood animals?
A. Orangutans are one of the animals — of the primates especially, of the great apes — that we know the least about. They've had less study than a lot of the African apes, like chimpanzees and gorillas, so we know less about them than we do with those two species.
Q: Where do they live?
A: Indonesia and Malaysia on two islands, Borneo and Sumatra.
Q: How do you get close to the orangutans?
A: They are solitary, so it's hard to find them and hard to follow them. It could take a week of searching to find the wild orangutan in our study area, and then we have to stay with them until they make a nest.
At night, they are arboreal. So we're following them on the ground floor of the forest while they're up in the trees. And we use binoculars.
We try to get close to them, but we also don't want to harass them. So we don't get too close. Mostly they're usually about 10 metres from us.
Q: You've been researching them actively since 1992. What are some of the things that you've learned about them so far?
A: One of the things that's really fascinating is they only give birth once every 7.6 years, on average, and that's the longest birth spacing of any mammal. And that's the first thing I actually went out there to study.
Q: Why is that?
A: It's a combination of what's going on with the female reproduction and the rainforest where they live, [which] goes through these really big booms and busts in food availability. That affects their hormonal levels. I developed this method of collecting urine and that was able to show that during a lot of the time they actually have really low hormonal levels, because they have pretty low energy intake.
Q: How is their behaviour unique or different from other primates like gorillas or apes?
A: Behaviorally, they're really different, because they're solitary. They don't live in in groups.
I guess the biggest difference, though, is probably the social structure — they're by themselves, the females with her baby — and the males are kind of by themselves most of the time, too. They do come together when there's a lot of food.… They will travel in larger groups, as a female may travel with her older offspring, for example.
Q: How is their habitat doing these days?
A: Their habitat is very severely threatened. It's from illegal logging, from the expansion of palm oil that's sort of taken over large expanses of the rainforest that are being cut down for oil palm plantations.
Q: How is that impacting their populations?
A: They're critically endangered in both Sumatra and Borneo now from habitat destruction. Also, from the illegal pet trade of animals that are killed, mothers that are killed to take babies for the pet trade.
Q: How many orangutans are left in the wild?
A: The numbers vary. So somewhere like less than 10,000.
(Knott later corrected this number. There are about 62,000 in the wild).
Q: What got you researching them in the first place? What piqued your interest?
A: The main thing that really got me interested was why they had these long birth intervals. That's the first question I wanted to to answer. But another really unique thing is that males come in two different types. There are two different kinds of adult male. You might have seen orangutans in the zoo that had a big cheek pads in the males — but they also have another kind. They can be 40 years old and never develop big cheek pads and they're reproductively mature.
That's one of the things that we're really been trying to figure out now.
Q: And do you have any theories as to why that is?
A: In the wild, these big males can really only maintain that form for a fairly brief period. At our site, we've found maybe up to like three years they can really have these big cheek flashes and then, essentially, they get in fights. So they die of infections or just kind of energetic depletion after that time.
Whereas in zoos, of course, they can maintain that for their whole life, because they're not subjected to the same things.
Adventures Among Orangutans will be presented Sunday afternoon and Monday evening at the Jack Singer Concert Hall.
With files from The Homestretch.
- Cheryl Knott misspoke when asked how many orangutan are left in the wild. There are more than 6,000 orangutans on Sumatra, and about 55,000 on Borneo, according to the Government of Indonesia.May 03, 2019 11:41 AM MT