Today, I finished my first week collecting data at the Trentham Monkey Forest. I am hoping to make another post later about the town we are living in (Kingsley, Stoke-on-Trent, England), on the monkey park (Trentham Monkey Forest) that we are working in, and the species that we are working with (Barbary macaque), but for now, a quick recap on the last week!

We arrived at the park first thing on Monday (7 May 2018) morning to meet with the director of the park. He was super friendly and helpful. We went over the rules of the park, met with some of the staff, and then finally headed through the front gate to meet the monkeys first hand!

As I mentioned in an earlier post, Trentham Monkey Forest is home to 140 Barbary macaques. Unlike some of the other field sites that I have worked at in the past, these monkeys do not have easily visible tattoo IDs. This means that we have to learn all of the monkeys by sight — no easy task!

How do we tell all the monkeys apart? There are a few tricks that help us distinguish one monkey from another.

First, Barbary macaques live in large social groups, and they typically stay in these groups for their entire lives. Because the monkeys at Trentham Monkey Forest are allowed to live freely like they would in the wild, they too live in two large social groups. For us, the first step is generally to figure out what social group we are working in, so that we can narrow down the list of possible monkeys.

Next, we identify the sex of the monkey. Though the monkeys only exhibit very subtle sex differences after they go through sexual maturity (around 5/6 years old for females and 7/8 years old for males). I was really terrible at this when I first arrived, but got better over the week. Males are generally larger than females, have a larger build, and more pronounced canine teeth [1].

(A quick aside: It is pretty rare that we get a glimpse of the teeth as the monkeys only show them when they yawn. Monkeys will yawn when they are trying to warn another individual to stay away [2], so we have luckily not had any of those directed at us.)

Last but not least, adult female Barbary macaques have sex skin swellings which show individual differences: the swellings manifest as large, cushion-looking pads of skin on their butt [3]. They can be pink or deep blue/purple (or some combination of the two colors), and have different patterns and scars. While these help us distinguishing female versus male adults, they are not as pronounced in young Barbary macaques.

Once we know the group and the sex of the individual, we start to flip through our monkey ‘Facebook’. Every day we carry around tablets that have a folder of close-up monkey faces (like the images I shared above), and compare the monkeys sitting in front of us to the monkey face images that we have where we verified the individual identity with a staff member or the professor that we are working with. The monkeys have different patterns of freckles, moles, and scars on their faces, different nose and general face shapes, and different face and surround hair coloration patterns. To my surprise, with some practice, we have become pretty good at distinguishing one monkey from another. Each day is a little easier than the last!

Alright, well it is time for me to get back to working on the monkey Facebook. Check in again next week for more on the Barbary macaque and where I am living for the summer. Thanks for following along so far.

 

REFERENCES

[1] Paul, A., Kuester, J., Timme, A., & Arnemann, J. (1993). The association between rank, mating effort, and reproductive success in male Barbary macaques (Macaca sylvanus). Primates, 34(4), 491-502.

[2] Deputte, B. L. (1994). Ethological study of yawning in primates. I. Quantitative analysis and study of causation in two species of Old World monkeys (Cercocebus albigena and Macaca fascicularis). Ethology, 98(3‐4), 221-245.

[3] Nunn, C. L. (1999). The evolution of exaggerated sexual swellings in primates and the graded-signal hypothesis. Animal Behaviour, 58(2), 229-246.