After three days and three nights of bus travel that took me from Cusco through Bolivia to the northwestern most province of Argentina, I finally arrived in Formosa, the site of Owl Monkey Project (the other half of the monogamy project) where I’ll be working for the next five weeks. It was quite a relief to finally sleep in a bed for the first time in four nights, but probably because I had gotten caught up in the thrill of traveling during the past month, I wasn’t initially quite as excited to start work in a new research site as I had been upon leaving Tiputini. Once I got out in the field, however, my excitement quickly returned, and the first time I stood in the middle of the forest here and the sharp, clear beep of the telemetry told me my first owl monkey sighting was near, I was thoroughly eagerness to immerse myself in the lives of a new species of monkey quickly returned.
The work has felt both remarkably similar and considerably different from what I was doing in Tiputini. To begin with the setting, the landscape here looks almost nothing like the rainforest. The field-site itself is on a huge cattle ranch called the Estancia Guaycolec, so the area is dominated by large grass plains filled with cows, and then the occasional clump of forest which the monkeys inhabit. The vegetation in these gallery forests is nothing like the dense, multi-layered, growth of the rainforest, as mid-sized trees make up the large majority of the flora, and there’s relatively little ground cover to get in the way of a field researcher trying to move about and follow his or her monkeys. At times I almost feel like I could be in a forest in the northeast United States until I see something distinct like a bromeliad (or a monkey) that reminds me I’m far from it. Nonetheless, the openness of the forest can make following the owl monkeys a good deal easier and more pleasant, as I’ve been able to avoid the frustration so common in Tiputini of following a group of monkeys you simply cannot see because the foliage of trees is so dense.
The owl monkeys do make up for this, however, by spending a large portion of their daytime hours sleeping. Most species of owl monkeys are completely nocturnal, but the variety here, Aotus Azarai, are cathemeral, meaning they have periods of activity and rest during both the night and day. Such daytime activity luckily means the monkeys can actually be studied in the wild, but the sleeping they do in the daytime also makes for some fairly dull observation periods. Interestingly, the activity patterns vary according to the cycle of the moon, with more nighttime activity during a full moon, but even though there has been very little moon in the time I’ve been here, I’ve still spent a lot time watching owl monkeys nap. But at least they are napping in plain view, right? And while sleeping monkeys aren’t particularly exciting (though they are adorable), the cathemeral habits of the owl monkeys do give allow us to take a lengthy lunch/siesta break from field work in the middle of the day, and avoid 10+ hour days in the field.
Another difference that I suspect is at least somewhat caused by the increased openness of the forest (as well as its less expansive boundary) is the increased number of groups that are being monitored by the project. While there are just five groups and one individual with radio collars (the Monogamy Project had four at Tiputini), there are over twenty groups in the area with at least an individual and a territory identified. Keeping track of so many
uncollaredgroups in the rainforest would take a huge amount of effort, but when the forest space is limited and the forest itself is more open, its possible to do periodic checks on a larger number of groups in order to get data on group composition. As a result, in addition to just doing the behavioral data that I focused on in Tiputini, I will be helping check up on the less frequently monitored groups, checking to see whether any juveniles have dispersed or adults have been displaced.
More differences from research in the rainforest come from the fact that this area of Argentina is sub-tropical and thus relatively dry, and can get quite cold in the winter while being boiling hot through most of the summer. It is winter here now and also the dry season, so it hasn’t rained in weeks and my first few days in the field were freezing cold. Bundling up in gloves, a hat, and essentially all my warm clothes to go out into the field makes following the monkeys here feel a good bit different than it did in the temperate but oppressively humid and wet rainforest. Its warmed up some since the first few days, but the more extreme temperature conditions are even more noticeable because we’re roughing it a bit more when we’re out in the field. We sleep in tents and while there is a building where do our cooking and store our food and equipment, there is no regular electricity (meaning no refrigerator) and no showers, and there certainly isn’t anyone to cook our meals or do our laundry like in Tiputini. At the same time, we are less than an hour from the city of Formosa, so on the weekends we get a short respite from camping and field work, as we return to the city and to do data entry, shower, wash our clothes and reconnect with the world a little.
Despite the substantial differences between here and Tiputini as a result of the setting and the owl monkeys’ activity patterns, the behavior I have thus far observed feels very familiar. The owl monkeys are monogamous just like the titis and sakis, and thus generally live together in groups consisting of a male, female and one to three infants or juveniles (interestingly it is not always the case that both the adults in the group are the parents of the young). When its time to sleep, the family finds a suitable branch and huddles close together as tightly as possible for warmth just like the titis would, with the youngest generally squeezed between its parents, The males are heavily invested in paternal care, so the infants and younger juveniles can be quite attached to their fathers, but are also particularly curious about the human observers that follow them around from time to time. And in all, the monkeys’ days consist largely of sleeping and eating, with a little bit of movement and perhaps grooming mixed in to keep things exciting. In comparing the titi and owl monkeys, in fact, its quite remarkable that species from two distinct genera inhabiting two very different environments have such similar social structures and behavior.
Of course, there do seem to be important differences between the owl monkeys and the titis. One that became noticeable within my first few days of research was intensity with which the monkeys seem to protect their territory. One morning I was following a male and female monkey that made up the group D800 when I realized that within plain view and no more than 30 meters away was a neighboring group of three monkeys passing through the area. I was expecting a dramatic inter-group encounter to follow, but neither group of monkeys was particularly concerned. Dionisio and Doli of D800 watched the other group with some interest, but no apparent concern, eventually the two groups parted without event. This was quite surprising to me given how intensely territorial I had experienced titis to be, and that owl monkeys have even smaller territories despite similar weights. It is of course quite possible that such uneventful inter-group encounters occur in titis and no one notices them, but every such encounter I saw or heard of consisted of a quite a bit of vocalizing and stress for all parties involved. A few days later, I did witness another inter-group encounter among the owl monkeys with stronger reactions by both groups (consisting of intensely watching, running back and forth, and vocalizing), and I also have seen the intense response of a group to the recording of an aggressive male call, so it is not as if the owl monkeys don’t care much for their territories. But if the owl monkeys are in fact less guarded about their territorial boundaries (which do overlap in the first place), it is interesting to think about what that might say about the importance of mate-guarding and resource-guarding in comparison to the titis.
At any rate, I am happy to be thinking about such questions and spending time in the field again, and overall I feel quite satisfied with the mix of interesting fieldwork and a pleasant atmosphere here at Formosa. I like the openness of both the forest itself and the surrounding savannah, and how it allows you to actually see the large variety of birds that live in the area. It also allows for some stunning views of the sunrise and sunset, in the mornings we walk to the forest at the very tranquil crack of dawn, and practically every evening we walk back under a sky painted orange and red. The flora and fauna are not as diverse and spectacular as the rainforest, but the environment is interesting nonetheless, and the monkeys here have just as much to offer, so I’m excited to continue researching.