Interview with a social insect scientist: Katja Kwaku

You can read Katja’s recent research article about leaf transfer behaviour in Atta cephalotes here.

IS: Who are you, and what do you do?

My name is Katja Kwaku and I am a Master’s student in the Biology department of Tufts University. I’m an ecologist; I’ve worked on a variety of projects, but I’m generally interested in behavioral ecology and global change biology.

IS: How did you develop an interest in your research?

I’ve been fascinated by animals and their behavior since I was little, but I only really became interested in social insects and leafcutter ants in particular in 2019 when I worked as an educator at the Montshire Museum of Science in Vermont. The Montshire has a colony of honey bees and a colony of leafcutter ants. The leafcutter ants constituted one of the museum’s most popular exhibits and visitors of all ages always asked great questions. Sometimes, I didn’t know the answer to a question, and moments like these inspired me to delve into the primary literature and start researching leafcutter ants.

Social insect researcher Katja Kwaku.

IS: What is your favorite social insect, and why?

Clearly, I am biased, but I have to go with leafcutter ants. There are so many strong interspecific interactions at play! Leafcutter ants have a mutualistic symbiotic relationship with the fungus they cultivate in their underground nests, they rely on bacteria in many ways to mediate this ant-fungus interaction, and they are voracious herbivores of many tree species. Also, they’re just so adorable when they’re carrying leaf fragments.

IS: What is the best moment/discovery in your research so far? What made it so memorable?

I’m relatively new to research, but I would say the best moment so far was witnessing leafcutter ants transfer leaf fragments to one another for the first time. My classmates and I had spent several months reading articles about leaf transfer and had finally travelled from Boston to Costa Rica to do a project about it, so it was such a relief seeing leaf transfer with my own eyes and knowing that the entire basis of our project wouldn’t fall through. It was also really exciting to see leafcutter ants transfer fragments directly to one another on tree trunks because leaf transfer in that context, to my knowledge, has not been explicitly documented before.

IS: Do you teach or do outreach/science communication? How do you incorporate your research into these areas?

Yes! I am currently a teaching assistant and have served as an educator at various science museums in the past. I love highlighting the connections between my research and the material I’m teaching, even if they’re not directly related, because it shows how everything in science is connected and relays why I’m excited to teach the material and why I think it’s important.

Leafcutter ants on their foraging trail. Photo: Katja Kwaku

IS: What do you think are some of the important current questions in social insect research, and what’s essential for future research?

Some important research questions involve understanding how insects use specific cues to drive foraging decisions and communication. Understanding the mechanisms behind fundamental behaviors will give insight into how to best conserve insect species and associated ecosystem services such as pollination and decomposition.

IS: What research questions generate the biggest debate in social insect research at the moment?

One topic of debate relevant to social insect research is whether or not global insect decline or the “insect apocalypse” is actually happening. There is evidence of insect population declines in many areas, but there are so few insect monitoring programs around the world that we run into the issue of having insufficient data to make a generalized conclusive statement about it.

IS: What is the last book you read? Would you recommend it? Why or why not?

The last book I read was Silent Sparks: The Wonderous World of Fireflies by Tufts professor Sara Lewis. I would recommend it because it’s scientific in content but written like a novel, so it’s an interesting and easy read!

Katja Kwaku and her co-author Elena Gonick observing leafcutter ants in Costa Rica.

IS: Outside of science, what are your favorite activities, hobbies, or sports?

I love dancing and doing yoga. I also enjoy making videos with my family and friends.

IS: How do you keep going when things get tough?

Things often don’t go as planned in ecology, so I like to laugh about all the unexpected field work mishaps; they make great stories for later. I also like to reach out to and talk with friends and get exercise when things get tough.

IS: If you were to go live on an uninhabited island and could only bring three things, what would you bring? Why?

I’m the cautious type, so my immediate instinct would be to bring first aid supplies! Otherwise, I would bring a hammock to relax in, binoculars to better enjoy the landscape and wildlife, and a notebook to document my experiences.

Leafcutter ant on an artificial foraging trail. Photo: Katja Kwaku

IS: Who do you think has had the most considerable influence on your science career?

Dr. Colin Orians has been an excellent mentor and professor during my time as a Master’s student. He was always happy to spend lots of time with me discussing science, but ultimately encouraged me to make my own research decisions and let me think for myself.

IS: What advice would you give to someone hoping to be a social insect researcher in the future?

Be patient, since insects don’t always cooperate with experiments right away. Also, if possible, try to send time outdoors observing wildlife outside of dedicated research hours. Your observations will remind you of insects’ magnificence and might inspire your next research question!

IS: What is your favorite place science has taken you?

This is such a hard question since every place is different and has its own positives. One of my favorite places is Long Point, Ontario, where I helped study the endangered Fowler’s toad population. The auditory experience of several frog species chorusing in addition to the sounds of birds and insects at night was enchanting.

Can desert ants take the heat?

by Sean O’Donnell

Based on research for the paper “O’Donnell, S., S. Bulova, V. Caponera, K. Oxman, & I. Giladi. In press. Species differ in worker body size effects on critical thermal limits in seed-harvesting desert ants (Messor ebeninus and M. arenarius). Insectes Sociaux.”

A key puzzle in understanding animal biodiversity is how species with similar ecological needs, sometimes even closely related species, can coexist in a habitat. Why doesn’t competition for shared resources lead to some of the competing species going extinct? If we can understand how species manage to partition their environments, we may gain insights into how high species diversity is maintained. 

In the deserts of the Mediterranean and Middle East, seed-harvesting ants of the genus Messor provide a great study case of this conundrum. Several Messor species often co-occur and all harvest the seeds of desert plants for food. Within nests, Messor ant workers differ widely in body size, and species can further differ in average worker body sizes. Body size affects seed choice, but Messor species still overlap widely on the types of seeds they harvest. Do other factors help reduce interspecific competition?

Deserts are challenging to animal life in many ways, including their famously extreme temperatures. Many deserts, including the Negev, swing from being exceptionally hot to very cold. Small-bodied animals like ants, unable to thermoregulate when working outside their nests, are especially vulnerable to local temperature extremes. 

My lab’s earlier work on army ants (Baudier et al. 2015, 2018) showed that worker body size differences within and among species were associated with the ants’ abilities to withstand temperature extremes. Smaller workers are generally more vulnerable to extremely high temperatures. We hypothesized that Messor species differences in thermal sensitivity, perhaps associated with body size variation, could affect their ability to function in extreme desert temperatures. Differences in thermal biology could influence the species’ relative abilities to harvest seeds under different temperature conditions. A first step in exploring this possibility was to test whether worker ant thermal physiology was related to body size with and between species. We chose two Messor species that co-occur in the northern Negev desert in Israel as research subjects: M. ebeninus and M. arenarius. Messor ebeninus workers range smaller, and M. arenarius workers range larger, but there is some species overlap in worker body sizes.

Ein Avdat National Park provides a stunning setting for the Ben Gurion University Desert Research Center

We collected workers from several nests of each species. Then we brought them to Itamar Giladi’s lab at the Desert Research Center of Ben Gurion University for physiological analysis. We placed single workers in vials in either a digitally-controlled heating or cooling device. By slowly ramping the temperatures up or down and watching for cessation of the ants’ behavioral responses, we determined the maximum or minimum critical temperature for each worker. After the thermal physiology trials, we measured each worker’s head width as an indicator of body size variation. We asked whether worker body size was associated with critical thermal maxima and minima both within and between the species.

The research crew hiking in Ein Avdat Park (left to right: PhD student Karmi Oxman, co-PI Itamar Giladi, research associate Susan Bulova, PhD student Virginia Caponera)

We found that body size was related to maximum thermal tolerance in complex ways. In the larger species, M. arenarius, workers of all sizes were similarly tolerant of high-temperature extremes. In contrast, body size was strongly related to maximum tolerated temperature in M. ebeninus: smaller workers were more thermally sensitive and could not function at temperatures as high as their larger nestmates; larger M. ebeninus overlapped in size with smaller M. arenarius and were similarly thermally tolerant. Worker size showed no relationships with low-temperature tolerance in either species.

Messor ebeninus ant workers returning to their nest from foraging

These results suggest extreme high desert temperatures could differentially affect these two Messor species and their abilities to forage for seeds. We expect smaller M. ebeninus workers to be restricted to foraging at cooler temperatures. Whether the smaller workers only, or the entire foraging force, drop out at higher temperatures remains to be tested (Baudier & O’Donnell 2017). But our results do suggest that temperature effects differ between ant species that share the same habitat and food resource. Species differences in thermal physiology may promote species coexistence.

PI Sean O’Donnell collecting workers from a nest of the ant Messor arenarius
PhD students Karmi Oxman (l) and Virginia Caponera running thermal tolerance trials on Messor ant workers in Itamar Giladi’s lab


Baudier KM, D’Amelio CL, Malhotra R, O’Connor MP, O’Donnell S. 2018. Extreme insolation: climatic variation shapes the evolution of thermal tolerance at different scales. American Naturalist 192: 347-359.

Baudier KM, Mudd AE, Erickson SC, O’Donnell S. 2015. Microhabitat and body size effects on heat tolerance: implications for responses to climate change (army ants: Formicidae, Ecitoninae). Journal of Animal Ecology 84: 1322-1330.

Baudier KM, O’Donnell S. 2017. Weak links: How colonies counter the social costs of individual variation in thermal physiology. Current Opinion in Insect Science 22: 85-91.

All images taken by the author.