Rachel Jacobs and Red Bellied Lemurs

It was pouring rain in Mangevo, and leeches were everywhere.

Primatologist Rachel Jacobs crouched beneath a tree, using her binoculars to observe a black-and-white ruffed lemur. It was rainy season in the rainforest, and she wanted to observe their feeding behavior, even during the area’s incredible downpours. It was difficult to see through the thick raindrops running down the lenses of her binoculars, and Rachel had to wipe them frequently to maintain visibility.

After one such wipe, Rachel lifted the binoculars to her face without looking at them first. . . which, as Rachel says, “is something I never forget to do now!”

“I put them up to my face, and a leech jumped right into my eye. I started yelling at my teammate Zaka: ‘Get it out! Get it out!’”

Rachel said, “This was before I had contacts, and I wasn’t used to touching my own eye. . . and I certainly wasn’t used to having someone else touch my eye.”

Zaka found that Rachel wouldn’t hold her eye open long enough for him to grab the leech, so Rachel’s other team mate, Louie, sprang into action. Louie was from the local Mangevo village, and he had seen a situation like this before.

Louie pulled an old plastic film canister from his pocket and poured something into Zaka’s hand.

“I asked what it was. Louie said, ‘medicine’ and immediately threw it in my eye. Wow, did it burn! In fact, that’s what I yelled… ‘It burns! It burns!’”

Zaka and Louie looked at Rachel’s eye again. The leech was still there.

Zaka threw more “medicine” in Rachel’s eye, and again, it burned intensely.

This time, when they looked in her eye, the leech was gone. And so was her vision in that eye—at least temporarily.

“I couldn’t see out of my right eye. I would learn later that the “medicine” was tobacco. Tobacco, I was told, burns the leech. Not sure if that’s true, but it certainly burns the eye.”

The next day, she couldn’t even open her eye. Rachel—and her one working eye—made the six hour hike from Mangevo back to her base at the Centre ValBio facility just outside Ranomafana. She had a blood blister on her pupil for several weeks. “People could barely stand to look at me.”

An Unforeseen Encounter

Rachel Jacobs and red bellied lemurs
A red-bellied lemur poses for the camera while chewing a fruit from a Ficus tree.
(photo credit Joseph Falinomenjanahary of the Centre Valbio)

Red Bellied Lemur
Red-bellied lemurs spend much of their time in the middle story of the forest canopy (low/high) in the trees.
(photo credit Joseph Falinomenjanahary of the Centre Valbio)

photo 686
Red-bellied lemurs live in small pair-bonded family groups, with group sizes ranging between 2 and 6 individuals. They are active during the day and night (an activity pattern known as cathemeral). They spend much of their time foraging on fruit and resting in the trees.
(photo credit Joseph Falinomenjanahary of the Centre Valbio)

red bellied mom and baby
A baby red-bellied lemur hangs out with his mother while she feeds on Ficus fruit (Voararano) in a site called Vatoharanana in Ranomafana National Park.
(photo credit Joseph Falinomenjanahary of the Centre Valbio)

Rachel spent the next week at the Centre ValBio, on the edge of Ranomafana, recuperating and regaining her vision. Toward the end of her recovery, she began to feel “cooped up,” and decided to go for a walk around the main tourist trail system at Ranomafana. Rachel recalls,

“It was then that I saw red-bellied lemurs for the first time…or rather, really noticed them for the first time. They were feeding on the nectar of this bright yellow flower that was everywhere in the forest. It is called Vahimberana. There was a female with a baby…its head just sticking out of the side of her stomach. I stayed there for a while, snapping photos and just enjoying them. I fell in love with the flower as well.”

Color-blind lemurs

Rachel was studying black-and-white ruffed lemurs, with a particular emphasis on color vision. In some species, two different types of color vision occur. One is full color vision (with no color blindness) and the other is “red-green color blindness,” where the lemur cannot distinguish red from green. This is caused by differences in a part of the eye called the “cone photo-receptors” (tiny cones that receive light).

In some species of lemurs, both conditions occur. In such cases, some females have full color vision, while all males and some other females, are red-green color blind.

“This is the case in black-and-white ruffed lemurs (and some other lemurs), and I wanted to understand why this variation occurs. In particular, many scientists think full color vision is an advantage in detecting red fruit against a green background. I wanted to examine this in black-and-white ruffed lemurs.”

Rachel’s field work with black-and-white ruffed lemurs helped her realize that these lemurs spent so much of their time high in the trees that it would be very difficult to get the detailed data that she wanted for her questions. She also started thinking about different questions…How important are visual cues like color to a lemur who is foraging for food? How about smell? Because of the difficulty studying black-and-white lemurs in the wild, she explored the idea of doing foraging/feeding experiments on captive lemurs to better understand the roles of vision and smell in food detection.

“When it came down to it, though, I realized that I really enjoyed field work…and I wanted to continue doing it. So, I redesigned my research to address color vision questions in a lemur type that foraged more frequently at shorter heights…and in a type where I could distinguish individuals without using collars.”

Enter red-bellied lemurs!

After encountering them on her chance walk in Ranomafana, Rachel realized they were the perfect type of lemur for her research. They were all over Ranomafana, so she could get a decent sample size. They live in small family groups with small territories, so troops could be identified and located fairly regularly. Males and females have different coloring, so it is easy to tell the boys from the girls at a glance. Finally, they have a lot of variation in their facial “pelage” (hair) patterns, so they can be individually identified more easily than many other lemurs.

So, in 2009, not long after her leech experience and red-bellied lemur encounter, Rachel went back to Madagascar for a pilot study on red-bellied lemurs.

Now, you might be wondering, how does this work? And why are only some females red-green color blind?

The answer seems to be found in their genes. And their, um, well. . .

“And how do I learn about their genes, and what type of color vision they have? I collect their poop!”

Rachel obtains DNA from individual fecal samples, then sequences the samples. From this, she can determine the type of color vision an individual has.

Her findings were unexpected, and unique.

All of the published literature on the color vision red-bellied lemurs’ close relatives (other “Eulemur” species) has found that they have either two genetic variants (medium and long wavelength opsins) or one genetic variant (medium wavelength opsin). However, the red-bellied lemurs in her study were different. They have only the long wavelength opsin. Now the question is, “Why are they different?”

“One reason might be that something happened in this population to reduce genetic diversity…something we call a genetic bottleneck. I am currently looking at this by studying the genes of all the lemurs in the troop. Thanks to all of that poop I collected, I can do it!”

“My research has taken a lot of twists and turns, but I’m breaking new ground in our understanding of the evolution of primate color vision, and helping to ensure healthy lemur populations in Ranomafana.”

We look forward to sharing more from Rachel’s updates in a future post. In the meantime, if you have questions for her, e-mail them to misterlemur@misterlemur.com and we will select and ask some for a future post!

Rachel Jacobs is a Ph.D. candidate in the Interdepartmental Doctoral Program in Anthropological Sciences at Stony Brook University in New York. Her dissertation research addresses hypotheses related to the evolution of primate color vision. Her current research also aims to better understand the social structure and demographic patterns of red-bellied lemurs in Ranomafana National Park using genetic data and long-term monitoring of the population.

Hans and Jen Hartvickson write books and stories for elementary students under the pen-name “Mister Lemur.” Their newest title, The Scheming Lemurs: Rivals in Rhyme is available on Amazon. Leveled for grades 3-4, this fictional story features a group of lemurs on an adventure in Ranomafana National Park and Madagascar’s capital city of ‘Tana. Hans holds a bachelor’s degree in Economics from Stanford University and an M.B.A. from The University of Pennsylvania’s Wharton School. Jen earned a bachelor’s degree in Sociology and a master’s degree in Education from Stanford University. Visit www.misterlemur.com