Watching Lemurs

In 1992 I wanted to do something different. So I signed up for an Earthwatch expedition to help study Lemurs in Madagascar.

I didn’t know what Lemurs were, but I thought it would be interesting to see Madagascar. And I could use my French.

I learned that the center for Lemur studies in the US was the Duke Primate Center, right down the road from where I’d grown up (and I never paid it any attention then). So I went back home to visit it.

Lemur turns out to be a somewhat ambiguous term. There is a genus Lemur, with one species, Lemur catta. These are probably the most common “Lemurs” seen in zoos, the ringtails. There is another genus Eulemur, or “true lemur”. There is a family, Lemuridae, containing these two genuses and 2 or 3 others (taxonomy changes every time I look). Finally any non-human primate in Madagascar may be called a lemur — 5 whole families of primates.

Fifty million years ago there were lemurs all over the world, but once monkeys evolved, the lemurs were out-competed everywhere but Madagascar. The monkeys didn’t get to Madagascar until their ape descendents arrived from Borneo about 2000 years ago — whereupon they promptly began to render lemur species extinct. 2000 years ago there were about 60 species of lemur on the Island, now there are about 40.

Madagascar is big. It’s the fourth largest island in the world. Several times the size of California. It’s almost all in the tropics, so it’s generally warm to hot. But it has deserts, prairies, mountains, rainforests, cloudforests, coral reeves…

Madagascar used to be a French colony, but there was a series of revolutions around the 60s, then it was a communist dictatorship, quite inimical to Western scientists. By the late 80s it was starting to open up to the west, and there were the beginnings of civil unrest.

I was going to the Berenty private reserve in the dry south of the island to help Alison Jolly study the way three diurnal species of lemur interacted in the same area. There were about 20 of us, and we were split into teams of about 3, each team following one troop of lemur. There are three diurnal lemurs in Berenty (or there were then), Lemur catta, Eulemur fulvus spp. and Propithecus verrauxi verrauxi. The fulvus were introduced to the reserve, and were a hybrid between two subspecies. Alison was worried about what effect they would have on the native lemurs.

Our job was to find our troop by 6am, then stick with them until 6pm, and write down everything significant they did.

Finding a troop of lemurs is not easy in the dim light of dawn. There are lots of troops, they are generally well up in trees at that hours. The reserve isn’t big, but it is densely populated. The trick is to find a distinctive animal. My team was following a fulvus troop, and our marker animal was a hybrid who looked nothing like any other. He had a large orange mane against a grey body and so was called “Lion”.

There were a dozen animals in Lion’s pride (as we named our troop — though Lion turned out to be rather peripheral to the troop, so it wasn’t really his). Lemur troops at Berenty ranged from about 4 to about 30 individuals.

We learned they had a fairly standard route. In the morning they would head into a certain group of tamarind trees — unfortunately for us, so would about 2 other troops of fulvus. Eventually we would find the troop we wanted.

These lemurs, Eulemur fulvus, and to a lesser extent Lemur catta have an activity pattern called cathemeral. This means their aren’t exactly diurnal, and aren’t nocturnal. They get up a little before dawn, and start eating. They eat until about 10am or so (it depends on how hot the day is; it can get very hot at Berenty, and when it does, the animals snooze), then they go to sleep through the hottest part of the day, get up again around 3 or 4 and eat on into the night.

So although we had to be up at the crack of dawn, after about 10 we could generally relax. There would always be someone following our troop, the but others could wander off until afternoon.

We took data on what the animals ate (we did not track every mouthful). Lemurs eat mostly plants — at Berenty they mostly eat Tamaridus indicus, the tamarind tree, they’ll eat leaf buds, and leaves, flower buds and flowers, fruit green, ripe, and dessicated on the ground. Occasionally they’ll eat caterpillar. Even less frequently lizards. We were to keep track of what species was eaten and what part of that species. Luckily the troop tended to eat the same thing. A tamarind tree is huge, mature trees may have a canopy diameter of 60+ meters, there’s plenty of room for a troop. A large Banyon fig can be even bigger, and much, much taller and when in fruit could (and did) hold several troops at once.

Lemur catta are territorial — or they want to be. They mark the boundaries of their territory with scent. The females mark with scent glands near the genitals, the males with scent glands near their wrists. Often a female will mark a sapling, and then all the males in the troop will line up behind her and mark the same sapling. Other troops will notice these scent marks; they go up and sniff them. Sometimes they agree with them, sometimes they don’t, and will invade. If the owning troop is in a different part of its territory the invasion is generally successful, the invaders eat for a bit and leave. If the owners are nearby and notice the invasion they will run over and attack.

Generally the females will attach (often with babies hanging on their backs), while the males wave their tails from the edges.

Lemur catta are female dominant. The females get first pick at any food item. If a female sees something a male is eating, and wants it, she just takes it. The male will almost never resist.

Sometimes there are bullies. In some troops the dominants just liked to attack their subordinates and fight.

So we were to note down any scent marking we saw, and any sniffing — so that Alison could learn what troop made a scent mark, and what other troop reacted to it. Having us following multiple troops meant that she was getting data rare for primatologists who generally follow one troop (or one animal) at a time. We were to note any close approaches to other troops, and whether the animals reacted to their neighbors (did they stare? did they rush over and fight? did they run away?) or simply ignored them. We also noted any aggression within the troop, any vocalizations, etc.

Lemur catta are adapted to a fairly arid climate. They don’t need to drink much, they can usually get enough water by eating leaves. But sometimes they’d climb down into the river bed (which was mostly dry with puddles that first year), or after a rain they would put their arm into a pool of water caught in a hole in a tree and drink from that.

Perhaps the oddest food preference is their fondness for dirt. They eat dirt. Not just any old dirt, they are very particular about what dirt they will eat (to a human eye, there is no difference between dirt eaten and the rest of the forest floor). They will get into fights over prime patches of dirt.

Lemurs make noises sometimes. The most obvious ones are the predator alerts. They have different noises (and different behaviors) for ground predators and for aerial ones. At Berenty they don’t seem to take ground predators very seriously. There aren’t any native mammals there who are a real danger to the lemurs — oh, when they see a cat they climb up trees and hiss at it (and they once mistook my backpack for something dangerous and chattered at me), but it doesn’t seem a real problem. But when a large raptor flies by they react quite differently. They make a huge racket, they run down from the trees. We found lemur skeletons in the midden pile of the local Harrier Hawk. There used to be an even larger bird, the Fish Eagle (now extinct) which would have been an even greater menace.

Sadly, perhaps the most dangerous predators on the lemurs are the lemurs themselves. Rival troops will steal infants. Sometimes they will eat them, sometimes they just leave them to starve. And it’s not even rival troops, in Eulemur macaco a female was observed to kill the infant of a dominant female — after which the dominant became inferior to the killer.

Successful predation events happen rarely. I have never seen one.

Reaching across species

As I mentioned our troop had certain habits. And every day, around 10am, they would take a nap in a certain part of the forest. And every day, at about 10am another troop of lemurs, Propithecus verrauxi, would come bouncing through the forest glade. Our lemurs paid them no attention. But one of the props, was interested in us (not the lemurs, the observers). Every day she would come a little closer before bounding off. Finally she came right down to us in easy touching distance — so I reached out my hand, and she reached out her hand — and we touched. It’s a marvelous moment when another primate feels safe enough and is interested enough that they want to touch you too.

Our troop didn’t care about us. We didn’t have any food so we weren’t in the least interesting to them.

I spent a marvelous two weeks watching and learning in that forest. And then it was over, and we had to go back. When we got out to the nearest airport we discovered that the unrest had turned into a strike which meant that no fuel was available on the island. There was some question as to whether our flight would arrive. I decided I would not mind staying longer in the forest — but then the plane did come after all.

A few months later there was a revolution, the dictator was kicked out, and they elected a president.

Leaping Lemurs!

Cactus-like plants of Berenty

The next year I went back, and stayed for a month.

In 1995, I got an email from Alison’s group inviting me to join them — they weresn’t going through Earthwatch, but did want some helpers. So I kept going.

I also started going to Ranomafana. Another protected area in quite a different part of the country. While Berenty is arid, and almost like a desert (except right next to the river), Ranomafana is a cloud forest up in the mountains that form the spine of the continent. It always rains in Ranomafana. In July, the “dry” season there is a constant cold drizzle. In the “wet” season the days are generally dry — until the late afternoon when a torrential downpour sets in.

Rano means water

Ranomafana has 12 species of lemur. Berenty has 6 (at the time we thought it had 5, but one species got split in two). Berenty is crowded with animals, even I can find them without much effort. In Ranomafana they are much scarcer even though there are more species.

Pause a moment.

Ranomafana has 12 species of primates. That’s actually quite difficult to believe. I don’t know anywhere else in the world with that species density of primates. The places I have visited in Central America had at most 3, in India, 3, in Brazil 2. Having 12 species in one reserve is amazing.

In 1996 we drove from Ranomafana to the capital of Madagascar and found a riot going on in front of our hotel — they were impeaching the president, and the parliament was around the corner from us. We had just come back from the wilderness and had no idea of politics. The president was impeached and later they re-elected the old dictator (who promised to be good).

In 1998 I had several projects of my own. I was going both to Berenty and later to Ranomafana. I had been wondering if I could become a primatologist myself, so I was going to be a field assistant for a grad student (Chia Tan) working on the bamboo lemurs in Ranomafana. I figured if I liked spending 4 months with the lemurs that would be a good sign for becoming a grad student myself. That was my main project. I took a leave from work.

I was also concerned about the quality of maps available in both Berenty and Ranomafana. So I taught myself surveying, and then I wrote a program to correct errors in surveying data and finally to make maps.

I intended to do most of my work with GPS units — this was in the days of selective availability when a hand-held GPS had an accuracy of 100 meters. 100m wasn’t good enough. There were tricks one could play, if you had two expensive units, and placed one at a known location, that could get the accuracy down to a few meters, which would be fine. I didn’t have a known location, but I could get data relative to a location, and spend a long time averaging GPS readings (days of readings) at that one spot to get a good handle on it’s real position.

Unfortunately GPS units don’t do very well under dense tree cover, which described the area around the river at Berenty, and almost everywhere at Ranomafana. So I knew I would need to learn traditional techniques as a backup. How much of a backup, I wasn’t sure.

At Berenty, it turned out, I almost didn’t need traditional techniques. At Ranomafana, the GPS units were completely useless, the trees were too dense. So I trained some of the local Malgach in simplified surveying techniques, and surveyed as much of the reserve as I could. After I left, I continued to pay them to finish the job, and several other graduate students lent me some of their workers. Eventually we made maps of the three main study sites at Ranomafana.

So that project went well.

My other project began well. I was helping Chia run an earthwatch of her own. There were three species of bamboo lemur (Hapalemur simus, aureus and griseus), they lived in the same areas, and they ate the same species of bamboo. That isn’t supposed to happen. But it did. Chia was interested in seeing how the three managed to live together, and was also studying the simus more intensely. She was using the Earthwatchers to gather data on all three species.

(At about the same time we were studying these species, DNA relatedness studies came out which showed that Hapalemur griseus & aureus were more closely related to Lemur catta than they were to Hapalemur simus, and in 2001 it was proposed that Hapalemur simus be moved to a different genus and become Prolemur simus.)

In 1980 Hapalemur simus were thought to be extinct. Chia’s thesis advisor (Patricia Wright) and others went looking for them in the late 80s. They were camped out about 6km from the village of Ranomafana when they stumbled on a new lemur species (Hapalemur aureus), and then later found the desired simus.

The area where they found these animals was scheduled for logging. Patrica Wright began a desperate compaign to turn the forest around Ranomafana into a National Park before it was destroyed.

Somehow she succeeded.

And now her student was studying these rare species.

The Hapalemurs were fascinating. Chia had worked out how they partitioned the niche of bamboo eater. The species of Hapalemur were separated in size, the smallest (griseus) about half the mass as the middle species (aureus), which in turn was about half the mass of the largest (simus). Although they all ate the same species of bamboo, they ate different parts of that plant. One ate bits of the leaves, another ate different leaf bits and small shoots, and the third, the simus, ate large shoots (so big they were hard for me to carry, and I out-massed the simus by a factor of 30). When there were no shoots, the simus tore up mature culms (stalks) of bamboo and ate (essentially) wood. How they digested it was unclear. The bamboo they ate was full of cyanide. The aureus could eat enough cyanide in a day to kill several adult humans. But the Hapalemurs weren’t bothered by it.

Although they lived in the same area, ate, essentially the same food, were subject to the same predation pressures, same climate, etc. the three species had very different social organizations. The griseus lived in multi-male/multi-female groups (rather like the Lemur catta, to which they were all closely related), the aureus lived in monogamous family units, and the simus (of which we could only find one troop so the results were statistically questionable) lived in a single-male, multi-female male-dominant group. And that was really amazing because no lemur species before then was known to be male-dominant.

This was different work from what I had done before. At Berenty we had followed whole troops, now I was following one individual animal within a troop. It is relatively easy to keep track of a whole troop — as long as you have one or two animals you can recognize you are set. But if you can’t distinguish the animal you are following from the others in his troop — things are not good. I never seemed to be able to learn to recognize lemur faces. Some people I knew had no trouble, they saw individual lemur faces as clearly as they saw individual human faces, they couldn’t explain how they could see differences, the lemurs were as different as humans were, to them. Other people really worked at it: “OK this animal has three small dots on her left cheek and is missing a chunk out of her tail.” If someone like that helped me I could sometimes see what they were talking about, but I could never figure out the distinguishing features without help.

I’m color-blind. Most of the time this is completely irrelevant in my life (which is why humans can be color-blind — color-blind monkeys are dead), but I can’t tell if my lemur is eating ripe or green fruit. (With bamboo lemurs that’s not much of an issue. The Hapalemurs Chia studied ate bamboo. Leaves, shoots and stalks.

It was lonely at the research cabin. Exciting when the Earthwatchers were there, but they left. Not so bad when Chia was there, but then she had to go to the capital for a month. Now I was the only native English speaker in the cabin. A few Malgache were there, but I didn’t speak Malgache, and both French and English were foreign languages to them.

On the week-ends there was just me. I didn’t have to work much on the week-ends, and would just take a book out into the forest and sit. Wonderful the first time you do it. But this is Ranomafana, not Berenty. There won’t be a troop of lemurs ambling past every five minutes. The ground is damp if you sit on it. Trees are uncomfortable to lean against. In short it became boring.

And then there were the leaches. Berenty is dry as a bone. No leaches. Ranomafana is always wet. It’s cloud forest. Everything is wet. Leaches don’t just live in streams and ponds, they live everywhere. On leaves, on the sides of trees, everywhere. Walking through the underbrush can get you covered with leaches.

My letters home became rather interesting.

Now a real primatologist would be niggling away at trying to figure out why the simus were male-dominant when every other lemur species was thought not to be. People had spent years trying to work out why lemurs were so often female-dominant although most other primate species were the reverse, male-dominant. I’d never found the explanations for that particularly compelling. Now we had the opposite situation. As the months passed I could not think of anything that could explain it. And eventually I stopped thinking about it, it just seemed an unsolvable problem. Oh if someone else worked it out I would have been fascinated in hearing about it, but I didn’t find it something I wanted to spend time on.

Yet that problem was the essence of studying this species. And if I weren’t interested in it…

Somehow the thought of becoming a primatologist did not withstand the discomforts. It’s fun to be out in the wild for 2 weeks or a month with lots of other excited people around. After two months it is less fun. If you are all by yourself and three months have passed — it feels like time to come home.

So that dream did not pan out. I left the forest before I should and returned home with my tail between my legs.

It’s sad that I could not live up to my dreams. I’m glad I had a chance to try…

I went back to both Berenty and Ranomafana the following year. I did some more mapping, but it wasn’t the same. I tried to provide money to protect another area in which Hapalemur simus were known to live, but no one could figure out who owned the land, and that fell though.

In 2001~2002 there was a real civil war. There had been an election and the dictator lost, but he refused to leave office. The provinces supported the old dictator while the center of the country supported the new president. There was a blockade and shortages in the center. But in spite of that there was surprisingly little blood. Eventually the army gave up on the dictator, the blockade was broken, the dictator fled and the new president took office.

I went back one more time to Berenty.

When I first went to Berenty the forest was very lush, but over time the great tamarinds had been falling. Tamarinds spread herbicides beneath them, which keeps things like strangler figs from attacking them, but means that there are no little tamarinds growing underneath them either. When a Tamarind falls in the forest it makes a huge bare patch of dirt which lasts for years. Some dirt patches have been there for more than a decade, and still nothing will grow. The great trees all seem about the same age, ~400 years old, and it seems that is the lifespan of a tamarind. As they die nothing can replace them, not for years. The wonderful forest I loved 15 years ago isn’t the same.

We believe that the forest was formed hundreds of years ago when the river flooded its banks and changed course (the old banks are still obvious and edge the forest). The old river bed, lush fertile ground, was quickly seeded with tamarinds which grew into the forest I knew. But now the trees are old and dying. The next time the river shifts its banks humans will just plant corn and beans there and no tamarinds will be allowed to sprout.

The lemurs can (and do) live in the scrubby desert around the forest. But they have completely different behavior patterns in a resource poor environment.

Years ago, the owners of the reserve had been concerned about erosion, and had planted a quick growing hardy tree (Leucaena leucocephala) on the banks of the river to hold them in place. Now we see completely bald lemurs dying. The leaves of the tree (which the lemurs ate) contained a toxin similar to those used in chemotherapy — it stopped cells from dividing. So hair didn’t grow, and many other metabolic pathways broke down. The owners now tried to remove the trees, but they were very hardy and had spread far and wide across the reserve.

As the long period of civil unrest has come to a close, Madagascar has become a much more popular tourist destination. People who were happy to have researchers visit ten years ago would now much rather have 60 tourists who each stay 1 night than a researcher who stays 2 months, they make more money that way. So research has become a more expensive proposition now.

And I have come to realize I’m just not a lemur researcher.