It’s humid and hot, and the taxi has finally arrived at the attraction of the day for this foreigner’s vacation – a Hindu temple situated in a lush Malaysian rainforest. As you pay the taxi driver and get out of the car, you notice a visitor approaching you from the corner of your eye. You turn to greet them only to realize that it is instead a monkey that seems to have a remarkable interest in your backpack .
You follow the line of gaze to a side pocket where you had stored a banana as a snack for later – yet unfortunately the banana’s “outta the bag” since you left the tip of the stem exposed, thus providing a clue of the treat that lies inside. You’ve instantly realized your mistake, and you return your gaze to the monkey that has suddenly approached to an uncomfortably close distance. While tracing their eyes, you see them fluctuate between gazing back at you and glancing at the pocket that holds the banana. You try to back away, but the monkey follows your every step, keeping the pocket of interest within sight. After several minutes of the monkey’s persistence, you decide to give up the battle and reach in to retrieve the banana. The monkey instantly becomes more alert and sits at your feet with a hungry glimmer in its eye. After a few seconds, its arm extends in a sort of begging gesture, eager to receive the treat it now has extensively pursued.
After basking in the surrealness of the scene, you finally cave and toss down the banana. The monkey ravenously grabs it, runs up a tree and devours it within a few minutes time.
Although this was a rather tame anecdote on a common interaction that occurs in urban areas of Southeast Asia, these interactions can also be more dramatic and dangerous. Of course, this all depends on the circumstances under which the populations of monkeys are living. For example, in places like the Ubud Monkey Forest in Bali, the monkeys are managed by people and are fed several times a day which has led to a rapid explosion in population growth on the island.1
This increase in the density of monkeys has led to increased competition among monkeys and humans alike, resulting in higher frequencies of aggression. Many of these negative interactions surround competition over food resources and some result in injury or in rare cases death.2 A better understanding of these interactions will allow us to strike a balance between the needs of both species and develop solutions for minimizing conflict between them.
As a burgeoning conservationist, I have dedicated my PhD to understanding how wildlife populations adapt to urban environments, using long tailed macaques (Macaca fascicularis) as a model species. Specifically, I am interested in the cognitive, physical, and behavioral differences that arise between populations that live between urban cityscapes and forested rural environments. I plan to explore how the flexibility of an individual macaque’s behavior may contribute to their ability to live under a variety of environmental conditions. Behaviorally, certain individuals or groups may be considered more flexible if they have a larger behavioral repertoire (i.e. perform more behaviors), or if they respond more quickly to environmental changes by switching to optimal behaviors that align with the current context. Physically, animals may be considered more flexible if they are less affected by external stressors and expand their hormonal responses and feeding regimes to cope with the additional uncertainty of resources and interactions in the urban environment. I aim to test whether urban macaques exhibit higher levels of flexibility compared to rural counterparts, first with cognitive experiments, then with hormonal profiles and diet analysis, and finally with direct observations of behavior.
But this piece is about the first set of experiments I ran on my trip to Malaysia last summer to visit my advisor’s new field site at a tourist park outside of Kuala Lumpur (so stay tuned for future Field Notes updates!). Shortly after arriving, it was clear that the monkeys that live in Templar Park do not behave quite like the bold, banana-begging monkeys of Bali. Although there are ample opportunities to interact with people in the core areas of the Templar Park tourist site, it is also surrounded by lush forest which provides more space for the groups that live in this area to spread out, thus reducing the amount of competition amongst groups. The major attraction for humans to this park is a set of three consecutive waterfalls that can be reached by walking a concrete path that climbs rather sharply but only runs only a few kilometers in length.
During the day when most tourists are present, the monkeys emerge from the leafy cover of the forest and come to the ground to take their chances at snatching ice cream cones from toddlers and ripping open shopping bags filled with picnic lunches. Even bags left covered by towels and zippered closed are not safe when left unattended, as the monkeys will often approach them and open them up in the hopes of finding food inside.
This kind of sneaky, but rather ingenious behavior of uncovering food resources from enclosed places got me wondering about the extent of extractive foraging problems these monkeys can solve. Has living in the urban environment led to a higher exposure of foraging extraction problems, thus leading to increased problem-solving abilities?
In the search to find answers to these questions, I developed a simple experiment to test the individual problem-solving abilities of long tailed macaques in Templar Park. I based my study off a paper that tested the extractive foraging abilities in bonnet macaques,3 where they tested urban and rural groups with both a common and novel problem. The expectation is that urban monkeys would be more proficient at solving the common problem compared to the novel problem since they have prior experience with those objects. However, rural counterparts would be incompetent at solving either task due to an overall lack of experience.
For this pilot study (mini-experiments to test instruments and methods), I was only in Malaysia for a couple of weeks, so I tested the urban groups in Templar Park to see if 1) my experimental protocols would work, 2) if the monkeys would be interested or motivated to participate in the experiment, and 3) if they would actually participate- to see the level of variation in technique and ability to problem-solve among these populations. For my experiment, the common problem used was a plastic water bottle filled with a juice reward. This is considered a common problem to urban monkeys because they encounter these objects frequently, as tourists often bring them into the park. On the other hand, the novel problem used was a clear plexiglass puzzle box with several peanuts inside. The box itself was designed for durability, made from thick clear plastic and tough steel so the monkeys couldn’t cheat and bite through it (as was one of the common strategies for the water bottle). For each test it was very important for both the bottle and box to be transparent, so the monkeys could see the food reward inside, providing them with motivation to engage in the task. For each trial, I would wait to begin until the target monkey was “alone” (defined as having no other monkey within 3 meters). Once this criterion was met, I dropped the test apparatus (either bottle or box) within 3 meters of the target and began video-recording the trial while I backed away slowly to give the target some space to work. The recording would continue until either the problem was solved (i.e. the monkey received the food reward), or the apparatus was abandoned for 5 minutes or more.
For the water bottle experiments, we found that there was plenty of variation in how individuals solved the problem and received the juice reward. Common techniques included creating a puncture to drink from, creating an opening big enough to reach the hand inside and simply removing the top. Funnily enough, there were some monkeys that seemed very aware of the concept of gravity and would be careful not to spill a drop during their trial, while others seemed rather oblivious to that idea and would lose most of their juice in the process. There were even a few select individuals that would remove the top of the bottle and drink the juice just like a human would! This was by far the most efficient technique of them all.
For the box experiments, there was tons of variation in how quickly it was solved by opening it and retrieving the peanuts inside. There were certain individuals who would solve the problem immediately without trying any other techniques, or without any time for exploring the apparatus itself. On the other hand, there were others where individuals seemingly had little interest or ability to open it. There were several trials that ran long, either because there were many animals that approached and tried to solve it, or because an individual with little experience or capability, such as a juvenile, attempted to solve the task with little or slow success.
Overall, the experimental trials went rather well, much better than I had expected considering it was the first time I had ever run experiments, let alone with free-ranging animals in the field. Although urban monkeys can be quite forward when it comes to food, the groups at Templar Park are relaxed enough that doing experimental trials with them was a breeze. I was very relieved to discover that most individuals were interested in both the water bottle and the box and would be motivated enough to work for the reward. I was also pleasantly surprised with the number of trials my research assistant and I were able to complete, with nearly 75 box trials and over 100 bottle trials in only a few weeks’ time!
Over the course of conducting all these trials, there were instances when my expectations for how the macaques would interact were confirmed and others where my expectations were contradicted, and I was left surprised at the way some of the social dynamics played out. One thing I truly expected was that high-ranking animals would be the most proficient in the problem-solving tasks because they have un-impinged access to high value resources. To my surprise, the highest-ranking individuals of the group showed very little interest in the puzzle box problems. They would often look them over, try a little bit, then give up and move on.
This puzzled me at first (hehe), but after some consideration it began to make more sense. Since high ranking individuals have priority of access to valuable resources, it may not be in their best interest to work for food that they may be able to get for free by displacing lower ranked individuals. This realization was met with some frustration on my part considering it was much more difficult to test high ranking individuals that I had previously expected. These kinds of unexpected results can be a common occurrence in pilot studies and can also be the most illuminating in redefining your research questions. These insights may lead you to new directions of research and new predictions of how these dynamics are occurring and playing out. To me, this is one of the most exciting aspects of scientific research, defining and redefining our understanding of the natural world as we know it, to predict its behavior despite the complexity of its interconnected parts.
Moving forward, I am grateful for my summer spent in Kuala Lumpur. It has given me great confidence in designing experimental protocols for field research and reinforced my interest in urban ecology. Those weeks spent walking amongst the long-tailed macaques in Malaysia was a breath of fresh air for a scientist that constantly craves fieldwork. I am eager to return this fall to conduct some new and exciting experiments exploring more directly my question of behavioral flexibility among urban and rural populations. As this research develops, I will continue to make progress in our understanding of the interconnected nature of humans and wildlife living at urban interface zones.
Stay tuned for some funny field fiasco stories of days gone wrong during this past field season, and field frame Fridays for cute pictures of urban monkeys!
Josie Hubbard is a second-year graduate student in the Animal Behavior Graduate Group at UC Davis in the McCowan Laboratory for Welfare and Conservation. She is broadly interested in how different wildlife species adapt to urban landscapes.
1 Wheatley, B. P. (1999). Sacred monkeys of Bali. Waveland Press, c
2 Priston, N. E., & McLennan, M. R. (2013). Managing humans, managing macaques: Human–macaque conflict in Asia and Africa. In The macaque connection (pp. 225-250). Springer, New York, NY.
3 Mangalam, M., & Singh, M. (2013). Flexibility in food extraction techniques in urban free-ranging bonnet macaques, Macaca radiata. PloS one, 8(12), e85497.