Secret Eaters: Baboon Edition

Having spent all my life in North America, living several months in England this year was very much a culture shock: everything was different, from the accents to food. Slowly but surely, I’ve adjusted, and I’ve even developed a few guilty pleasures like Bakewell tarts and Secret Eaters, an unapologetic reality TV show in which the participants don’t understand why they’re not losing weight because they’re always making healthy choices. Until of course it is revealed that Channel 4 has sent camera crews to follow them for a week and oops maybe they shouldn’t have eaten that third cheeseburger.

It reminded me of observational studies done with the Pumphouse Gang, a famous baboon troop from Laikipia, Kenya, who has starred in award-winning documentaries, including David Attenborough’s Life of Primates. Primatologists have been following these baboons for almost thirty years, so we have a good record of what they have been seen eating… but watching wild animals is difficult, so do we really have a good record of what they actually eat? Or are the Pumphouse Gang baboons just secret eaters who’ve managed to evade the observation?

PHG - Beasley 2

A baboon from the PHG eating an Opuntia (credit for this photo and the feature image: M. Beasley)

Answering this question was one of the aims of a project I collaborated on at the University of Oxford earlier this year. Our goal was to learn about the seasonal and yearly changes in the diets of these baboons and what might influence these changes. We can get information on the diet of animals by measuring the ratios of heavy to light stable isotopes – a chemical tracer of ecology – in feces, hair, nails, bones or teeth. In this project, we focused on carbon isotopes in feces because they reflect diet over just a few days at the most. We can then compare the behavioral records to the chemical signatures and look for differences or patterns – a more accurate and scientific method than sending a Channel 4 camera crew to Laikipia.

I’ve written before about fossilized poop, known as coprolites, but my work at Oxford was outside my usual comfort zone: the samples were not 10,000 years old, but relatively “fresh” at just 10 years old. Collected by primatologists and then dried in Kenya, the samples were shipped to the University of Oxford for analysis at Research Laboratory for Archaeology and the History of Art (RLAHA).

Spending a month studying dried baboon feces at the University of Oxford might not be everyone’s cup of tea, but for me, it was an unmissable opportunity to collaborate with Dr. Julia Lee-Thorp and to learn more about the research of dozens of graduate students, postdoctoral scientists and other researchers from all around the world who work at RLAHA.

My day to day work was far from glamorous. In order for each sample to be analyzed, the dried feces had to first be ground. You might expect the grinding to be performed by some fancy equipment – this is science at Oxford, after all. “The best way,” said the lab manager, Dr. Peter Ditchfield, “is an industrial coffee grinder.” And when that didn’t do the trick, I took out a trusty mortar and pestle. I also got to wear a Darth Vader-esque mask to protect my lungs from all the dust created by the grinding.


Wearing my “Darth Vader” mask

After the sample was ground, then came the weighing. I weighed a teeny-tiny amount of the feces powder and put it in an equally small foil capsule. The foil capsule is then combusted by the mass spectrometer, a fancy piece of equipment which will spit out the chemical results – and voilà! Now repeat 190 times.


In front of the mass spectrometer (credit: S. Blumenthal)

I also analyzed the results, which I always enjoy – it feels like getting your paycheck after weeks of hard work. Combining my results with samples that had already been analyzed gave us 340 data points from 15 baboons of different age and sex. In some cases, we were able to study the variation in their diet through a 12-month cycle for a period of up to seven years. This kind of dataset is unprecedented in our field and so rich and interesting! The combination of chemical and behavioral methods means we are able to have a refined understanding of the dietary patterns of a species in a given environment, as well as how those patterns vary according to monthly, seasonal or annual changes. We were also interested in comparing the breadth of the data from the baboons to that seen in similar studies done on our human ancestors, to possibly learn more about their dietary patterns.

My experience at Oxford was inspiring and fun – many thanks to the University of Oxford, Dr. Julia Lee-Thorp, Dr. Peter Ditchfield, Dr. Scott Blumenthal and all the colleagues at the lab who made me feel welcome.

So are baboon secret eaters? You will have to stay tuned to find out!

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