Category Archives: Caleb

Foraging habitat preferences and predator avoidance in the Central American Agouti

An agouti in the open (photo by K. Yap)
An agouti in the open (photo by K. Yap)

For our conservation project, we focused on the foraging behavior of the agouti in Refugio Bartola, Nicaragua. We were interested in the potential effects of selective logging on agouti fitness, which may have important conservation implications due to their importance as an important seed disperser and as a food source for many large predators. It is known that selective logging can reduce understory cover, which is known to serve as protection from predators for some species of small mammals.

From previous studies, we knew that agouti restrict their activity to times when predator activity (primarily ocelot and other large cats) is lowest. This is an important general concept in animal behavior – all organisms must acquire resources to survive, but foraging exposes them to increased levels of predation, and thus they must evolve behaviors that resolve this tradeoff. We were curious if agouti might also utilize spatial mechanisms of predator avoidance to do this, selectively foraging in areas in which they are better hidden from predators, and whether this preference varies during the day as predator pressure varies. From a conservation standpoint, this is important because decreases in understory cover from logging may have significant and complex effects on agouti fitness if this is indeed the case; given their important roles as prey and dispersers, this could have cascading effects on the structure and functioning of rainforest communities.

In order to test whether populations of agouti and other small mammals in the Nicaraguan rainforest exhibit such a preference, we studied their foraging habitat selection through a camera trap study. We baited sites of both dense understory cover and open understory cover, with at least one of each near previous agouti sightings, but with a minimum distance exceeding that of the agouti home range size, in order to minimize resampling the same individuals. The sites were restocked with bait every other day, and we observed them for between 4-12 days. We then were able to convert the images into foraging rates (visits per unit time) for different periods of the day in open and closed understory, which allowed us to examine the interaction of time of day (as a proxy for predator pressure) with preference for these different degrees of cover.

Our study yielded interesting but counterintuitive results – interestingly, the primary interaction of foraging rate with time of day was in closed understory. In dense understory, at times when predation is highest (just following dusk according to the literature) agouti foraged at much lower rates than at times when predation is thought to be lower (dawn and day). However, in open understory, there was much less of a difference between dusk and daytime foraging rates, and no difference between dawn and dusk foraging rates. This is the exact opposite of what we predicted: we would have expected that there would be a larger response to predation pressure in open understory, where the agouti are more exposed. However, this may make sense – agouti are known to cache food in open areas, and their main – and successful – means of escape from predators is to observe them before they attack and run away. Thus, open understory might actually be more protective from predators than closed understory – while agouti can be seen more easily, they can also see predators more easily. To get at this question more deeply in the future, studies would need to quantify the actual levels of predator pressure at different times in different areas of cover, which we were unable to do due to time constraints.

Last Thoughts

Caleb
Caleb with the giant flower of Dracontium gigas

As I find myself again in the proverbial armchair, which disappointingly happens to have no armrests, I’m curious: did my experience change my perspective on biology, or on science more generally? How did my first time out there in the field make me think differently?

First and foremost, I’ve come to realize how hard it really is to get things done when you’re out there – especially when you’re not well equipped with a background on your study system or on how to attack your problems in a methodological sense. However, I think that was part of the fun of this trip – knowing absolutely nothing, figuring out a way to figure it out without an extensive literature on the subject, and coming away with some new knowledge (even if it was less than we’d hoped). The limitations we had – for example, exhausting all our possible methods for marking flies, only to find out that they’re all lethal or a good method for turning craneflies into spider food, or finding out that your camera traps aren’t keeping proper time after being out at the sites for days – gave some excellent perspective on the challenges faced by all the researchers whose work I read – challenges that you never see in the final product. It’s easy to try to poke holes in someone’s work without seeing how it may be a triumph against many great odds. Although criticism is obviously part of the dialectical process of science and difficulty is not an excuse for poor work, this experience gave me another perspective that I may have been lacking – to appreciate of the ingenuity and simple elegance of many experiments, rather than just look for flaws as a knee-jerk reaction.

Secondly, it’s really fun to figure out new things. While out there in the field, I often reminisced on Richard Feynman’s “The Pleasure of Finding Things Out,” especially with the things that not much was known about, such as cranefly behavior. There was definitely a new joy I hadn’t felt before – that of having my speculation be bounded by experiment and observation. This, I think, was one of the most well-met expectations for this FBQ. I spent a lot of time simply observing and coming up with ideas, as I have often done before, but it was fascinating to then have to turn around wonder – well how should I test that? What further quantitative observations should I make? Although time constraints, and to some extent poor planning, kept us from really getting at many of our questions, this was just further motivation for me to improve my research skills (a favorite quote of mine is “the first step to being good at something is to really suck at it”) and also made me want my own questions – the ones that I can spend years on in that iterative process of speculation then experimentation.

Waterfall Reflections

After one last circuit through the maze of trails cutting down tape, removing various instruments, every trace that we were even here is gone (excepting the muddy mess of our footprints). This leads me to wonder – what am I taking with me? This mass of numbers, some carefully planned in their collection and others no more than a shot in the dark, don’t have me convinced of any new breakthroughs, unsurprisingly. Although I know nothing too significant can really be accomplished balancing two projects in three weeks, it’s still tempting to ruminate on what more I could have done. This, combined with the monotonous days of hiking endless trails counting craneflies and rebaiting camera traps – with the occasional punctuation of a new observation which once again sparks some innate sense of curiosity and wonder – led me to want to leave with something more. With that in mind, myself and a few close colleagues made the decision to spend our last day conducting some general exploration of the non scientific kind.

Our expedition up the Rio Gaitan foiled by a fear of landmines in the creek and a drawing of straws to decide whether to turn back, we opted to spend the afternoon absorbing the atmosphere of a picturesque tri-tiered waterfall. A surreal view down into the mist and the canopy of the forest below and above us, with brilliant blue morpho butterflies and pollen filtering from the long tendrils of a nearby tree filling the air provided a sublime backdrop for reflection on the lessons I’ve learned in these past weeks here. Primarily, I’ve realized that I came here to learn how to conduct field research – not necessarily carry out some sort of dissertation-quality project. My failures – real or perceived – should not be a source of negativity or self-doubt in my propensity for field research, but rather a source of ideas on how to change course in the future as I proceed in my research career.

There are many other learned lessons I could delve into, but instead, I’ll focus on one overarching insight I think I’ve gained. To me, it seems that the sole driver of good science is the motivation of a curious mindset. When this becomes overshadowed by external motivators – grades, meeting deadlines, appeasing research partners or otherwise pleasing people, or as one moves further along in their career, publishing, it all falls apart. Signaling to others that you’re making progress is nowhere near the same as, and is often counterproductive to, making actual progress. Curiosity means not accepting half measures or subpar methodology; signaling means having results to show when the deadline hits. My biggest disappointment here is, I think, falling prey to this latter mindset due to time constraints; the inability to backtrack on experiments or methodology that upon further reflection seem poorly though out, for example. The bright side, however, is that this is a learning experience, and the deep seated ennui I feel of half measures has cemented the idealism of my original motivations for studying science. Long story short: take the time to appreciate nature and remember why you’re doing what you’re doing or there’s no point in doing it at all, because you’ll probably end up doing it poorly.

Sticks: the Secret to Science

Not having enough questions is not usually my problem – and after a day or two of utilizing the quintessential sampling method known as poking things with a stick, it began to become clear that a head too full of them would be a distraction from gaining traction, much to my dissatisfaction. My investigative companion and I slowly whittled away at the long list of potential problems to attack, both through intense discussion and abject failure in our pilot experiments – underestimating by an order of magnitude or several how many species we would find in the cavities of the buttress trees, or being thwarted by agouti too ungrateful to accept our offers of food/trap bait. We finally realized we’d have to stop beating around the bush and get down to business.

After throwing around a few ideas about agouti foraging for our conservation project, we eventually settled on looking into the foraging preferences of agouti. We’re interested in finding out whether they selectively forage in areas with open or closed understory cover, and whether they choose differently between them depending on the time of day, which is an interesting question for a few reasons. First, we know that they alter their foraging behavior depending on predation pressure, which understory cover may effect – either it could provide protection when it’s thicker, or it may likewise provide cover for potential predators (like the mountain lion we caught on one of our camera traps). There’s some suggestion that they like to feed in open areas, but it doesn’t seem to have been quantified yet. If predation is a factor, then we might expect the difference in preferences between open and closed areas to vary when predation is strongest, in the very early morning and later in the evening after dusk. Anthropogenic factors, such as logging activity, are likely to affect the level of and heterogeneity in cover, so the project is potentially interesting from a conservation point of view as well as from a purely behavioral standpoint. To do this, we’ve set up several sites where agouti have been spotted, in each of which we have a matched pair of open and closed patches with bait and a camera trap. It sounds simple enough, but when you factor in camera malfunction, human error (a nice euphemism for my carelessness), rebaiting, opossum, paca, and spiny rats eating all our fruit, and of course Murphy’s law, it’s actually ended up being a pretty challenging project to maintain.

However, in both projects, even all of the failures we’re experiencing aren’t all that bad. I was once told that reading papers, it can seem that every research project is a perfectly executed sequence, but that failure is one of the most important steps to reaching a better answer and finding the right methods. Like every bit of wisdom you get, it’s just a string of words until it’s illuminated by experience, and I’m starting to appreciate the truth in it. Even with the occasional panics over not being able to answer our questions to the fullest extent in the time we’re here, I’m starting to realize how much I enjoy doing this.

Out of the Armchair and into the Jungle

Hi, I’m Caleb, an ecology student here at UCLA. It’s still a bit surreal for me to think about the fact that in just a few weeks, I’ll be traveling up a river in a remote rainforest to build my research skills. Besides seeming like something from a childhood dream, there are few things I enjoy more than being immersed in nature and asking “why” – it’s the reason I’ve wanted to be a biologist since as early as I can remember. So it might be a bit of understatement to say that I’m excited and grateful for this opportunity – I’m sure that so many things that I can’t even anticipate await me there.

A big reason why I want to do this is that I’ve been doing research for the past few years now, but mostly from the perspective of treating ecological phenomena as some abstract idealization on a computer or in some equations. Although I find theory fascinating, it’s hard not to feel as though there’s something missing in my scientific education when I’ve never actually formulated and tested ideas that were generated by my own primary observations of the natural world. I guess you could say I feel like an armchair ecologist. This really struck me last year while reading Ernst Mayr’s “The History of Biological Thought” – repeatedly, I saw examples of how, since the origins of biological inquiry, movement away from direct observation into the realm of abstract reasoning has been a slippery slope, often leading to dead ends at best and harmful distractions at worst. That really made me start to think more seriously about the consequences of this significant gap in my training – a gap which I hope this time in Nicaragua will begin to fill in. Spending every waking moment surrounded by seemingly boundless biodiversity and getting my hands off the keyboard and my eyes and ears into the tropical rainforest will, I hope, inspire me and teach me to develop better ideas of how things are working around me in nature, rather than in abstract models of nature, and how to address and test these ideas in an empirically rigorous fashion.