Edited by: Caitlyn Finton and Alexander Ophir
Many researchers purchase their animal subjects, such as mice and rats, from biomedical research institutions to answer their scientific questions. But not all animal species can be bought commercially for behavioral studies. One such example are prairie voles, which are small rodents that live in the grassy fields of the Midwest (1). The Ophir lab has to actually walk through overgrown grassy fields, gardens, or agricultural areas to catch wild prairie voles for our experiments. More specifically, lab members regularly drive cross-country to several field sites in Illinois to trap and transport the voles back to Cornell University. Why do we study a species that takes so much time and effort to get? It turns out that prairie voles are an excellent mammalian species for understanding how the brain controls social behaviors. Prairie voles are a highly affiliative and socially monogamous species (2). In other words, they like to interact and spend time closely with one another, they form long lasting relationships with their opposite sex partners (3), and both parents take care of their young (4). The social behaviors of prairie voles are very interesting because they are one of the few 3-5% mammalian species that exhibit social monogamy (5) and one of the 5-10% of mammalian species where males help take care of their young (6).
So how do we trap our animals? I had a chance to learn this for a couple of reasons. First, due to the COVID-19 pandemic and travel restrictions, it was not possible for the Ophir lab to travel to Illinois this year to catch wild prairie voles. Second, the lab members that know how to do it have either moved on (Dr. Marissa Rice and Dr. Danielle Lee) or are about to graduate (Caitlyn Finton). Seeing as we can’t buy prairie voles, this puts us in a perilous situation: we have essentially no students or postdocs that know the ins and outs of catching prairie voles in Illinois in order to maintain a lab colony for our current and future studies. Prairie voles don’t live near Cornell, but a recent project gave us a great chance to trap locally, led by our remaining vole-catching expert Caitlyn. She spent the past few weeks teaching us (Santiago Forero, Rikki Laser, Jesus Madrid and me) to catch meadow voles. This is a promiscuous (not monogamous!) vole species that is naturally found in low wetlands and grasslands throughout the northern US and Canada (7). There are important distinctions between prairie voles and meadow voles in regard to their neurobiology and social behaviors (8), but that is a topic for another blog (stay tuned!). Importantly, catching prairie voles is the same as catching meadow voles, so this was a great opportunity for Caitlyn to pass on these vital skills. As a neuroscientist, with zero experience in field biology, I was eager and excited to learn from Caitlyn.
On Day 1, we met a couple hours before sundown to learn how to operate Fitch and Sherman live-traps. These traps are completely harmless to the voles – they even get a free meal! In each trap, we added a handful of grass and sunflower seeds as bait (they seem to really like sunflower seeds). Then we placed traps at the end of grassy runways throughout various field sites and crossed our fingers that we were going to catch a vole, and not a field mouse or a shrew. On Day 2, we checked the traps at daybreak. We wanted to start early in the day to make sure the voles are transferred to lab housing cages before they ate all the seeds in their trap and got hungry. Once in the lab, the voles get more food, water, and materials to make nests. When we did catch a field mouse or shrew, we found a nice patch of grass far away from where we caught them and let them go so that they wouldn’t just go back to the trap the next night. As we checked the traps for critters in the morning, we closed them so that no animals would get caught and left in the heat all day. Then we returned to the field sites a couple of hours before sundown and set up the traps again with more seed bait. For the next week or so, the days were basically the same as Day 2, with the aim of catching voles overnight. Eventually we started catching fewer and fewer voles and we stopped setting up traps when we had no luck catching voles for 2-3 consecutive days. We instead looked for another field site and began trapping again until we caught all the meadow voles we needed.
Trapping meadow voles in Ithaca, NY, was hard work, but it does not compare to the immense amount of work required to trap prairie voles in Illinois. Several plans have to be set in motion before traveling. This includes getting all the necessary approvals to catch voles including ethics and animal care approval (at multiple universities), and permission from the farm/property owners in Illinois. Once you’re down in Illinois, you spend a lot of time coordinating lodging (for us and the voles) and transportation to and from trap sites and back to Ithaca, as well as feeding and caring for the voles until returning to Cornell. Our lab typically goes down to trap in Illinois for 2 full weeks, working every day from sun-up to sun-down.
Overall, I found trapping a lot of fun. It was always exciting to see what we caught in the traps. Besides catching a lot of field mice, one time I found a grasshopper. Another time while checking the traps, Rikki and I saved a bird that was caught in some nearby netting. It was also really nice to see each other in person and getting some fresh air after working from home for so many months. Even with all the fun I had, I’m excited to get back into the lab and do some neuroscience. This experience gave me a newfound appreciation for field work, and I want to give special thanks to Caitlyn Finton, Marissa Rice and Danielle Lee, who have travelled to Illinois multiple times to catch prairie voles. My dissertation work in Dr. Mohamed Kabbaj's lab at Florida State University would not have been possible without the Ophir lab's hard work in trapping voles and their collaborative effort to share them with the prairie vole research community. It has really reminded me of how much better science is when we collaborate and work with each other, and I can’t wait to see what future collaborations have in store for me.
References:
1. Getz, L. L., Carter, C. S. & Gavish, L. The mating system of the prairie vole, Microtus ochrogaster: Field and laboratory evidence for pair-bonding. Behav. Ecol. Sociobiol. (1981) doi:10.1007/BF00299829.
2. Madrid, J. E., Parker, K. J. & Ophir, A. G. Variation, plasticity, and alternative mating tactics: Revisiting what we know about the socially monogamous prairie vole. in Advances in the Study of Behavior (2020). doi:10.1016/bs.asb.2020.02.001.
3. Williams, J. R., Catania, K. C. & Carter, C. S. Development of partner preferences in female prairie voles (Microtus ochrogaster): the role of social and sexual experience. Horm Behav 26, 339–349 (1992).
4. Finton, C. J. & Ophir, A. G. Prairie vole offspring only prefer mothers over fathers when mothers are a unique resource, yet fathers are the primary source of variation in parental care. Behav Process. 171, 104022 (2019).
5. Kleiman, D. G. Monogamy in mammals. Q. Rev. Biol. (1977) doi:10.1086/409721.
6. Kleiman, D. G. & Malcolm, J. R. The Evolution of Male Parental Investment in Mammals. in Parental Care in Mammals (1981). doi:10.1007/978-1-4613-3150-6_9.
7. Reich, L. M. Microtus pennsylvanicus. Mamm. Species (1981) doi:10.2307/3503976.
8. Ophir, A. G. Towards meeting Tinbergen’s challenge. Hormones and Behavior (2011) doi:10.1016/j.yhbeh.2011.03.012.