Department of Biology
Aaron R. Krochmal
Assistant Professor of Biology
E-mail: akrochmal2@washcoll.edu
Phone: (800) 422-1782, ext. 7123
Office: Toll Science SG20
In the agricultural landscape of Maryland's Eastern Shore, turtles and snakes are the proverbial canaries in a coal mine. When humans manipulate their natural habitat to support crops and waterfowl hunting, how can turtles and snakes survive, and even thrive? Their habits and patterns of movement can tell biologists a lot about their responses to environmental disturbances, but first you have to catch 'em.
Aaron Krochmal, a biologist interested in aspects of the behavioral, physiological and evolutionary ecology of vertebrates, has enlisted the aid of his students to hunt snakes and trap turtles at nearby Chesapeake Farms, a 3,300-acre agricultural and wildlife management managed by DuPont.
Last summer, Kristin Bircsak '10 and Taylor Robinson '10 put on their heavy boots and prowled around the fields and ponds at Chesapeake Farms. Krochmal implanted a microchip transmitter in each captured snake and turtle so he and his students can monitor their movements through the agricultural landscape.
"What makes it interesting to me is that the land is managed to maximize waterfowl habitat," says Krochmal. "The ponds are drained in the spring and flooded each fall. That's great for geese and ducks, but not so good for turtles and snakes. It presents a great experimental situation in which we can examine what turtles and snakes do under duress. The question becomes, how do issues of agricultural management affect non-target species? How do they adapt to a heavily managed agricultural landscape where crops are planted and harvested, where ponds are drained and flooded? More specifically, where do they go and how do they get there and back?"
While scientists have long studied the migratory patterns of animals such as whales, penguins, caribou, songbirds and waterfowl, non-migratory patterns remain largely undocumented. He suspects that the turtles are seeking refuge in a 100-acre lake on the property a half-mile away—an epic journey for a species whose legs are only 3 inches long. How do they know the way?
Krochmal points to this fieldwork as a prime example of student-centered learning. "The snakes and turtles are really secondary. For me, the primary objective is to give students an opportunity to learn and grow by experience. It's about putting students in a scientifically relevant setting and seeing them apply what they've learned in the classroom."
In addition to their animal tracking skills, students are learning the critical thinking skills and modern research techniques that make them fluent in modern science.
"Fundamentally," says Krochmal, "science is a process. This project presents important questions about basic biology and about wildlife management with methods that are easily accessible. The question is intellectual, the labor is hands-on."
Education
- B.S., Union College (NY), 1996
- M.S., New York University, 1998
- Ph.D., Indiana State University, 2003
Courses Taught
- Comparative Vertebrate Anatomy
- Comparative Animal Physiology
- General Biology
Office Hours
MW 9-11am, T 1-4pm, or just drop by anytime!
Summary of Research Interests
I am a broadly trained integrative organismal biologist interested in aspects of the behavioral, physiological and evolutionary ecology of vertebrates. I use an array of techniques, including behavioral manipulations, metabolic measurements, neurological recordings, gross- and micro-anatomical studies, physical analyses, and computational modeling to investigate biological phenomena at both the proximate (i.e. mechanistic) and ultimate (i.e. evolutionary) levels.
A brief discussion of two of my current projects follows —
The functional utility and evolutionary origins of the facial pits of pitvipers
The pitvipers (Viperidae: Crotalinae) are named for their paired, thermally sensitive facial pits located midway between the eye and nostril on either side of the head. These organs detect infrared radiation, providing these snakes with a "thermal vision" of sorts. The facial pits have been shown to aid in acquiring prey, and, as I discovered, in regulating body temperature. I am particularly interested in the uses, spatial acuity and evolutionary origins of the facial pits. I use an array of behavioral techniques to investigate additional and alternative uses of the facial pits of pitvipers, observing behavioral abilities in the lab, and in the future, the field. I combine thermographic imagery, radiative heat transfer analyses and optical physics to reconstruct the thermal image perceived by the facial pits and calculate its effective detection distance. I also use histological approaches, 3-D image analysis software and CT scans to document the exact internal shape of the facial pit, allowing for a more exact approximation optical properties of the facial pit. Results from all these studies are interpreted across a broad phylogenetic context, providing an evolutionary perspective to my work and enabling me to investigate the functional utility and evolutionary origins of the facial pits of pitvipers within a broad, integrative context.
The adaptive value of scavenging behavior in snakes
Most animal carcasses produced in terrestrial ecosystems are recycled by scavenging rather than by decomposition. Despite this, scavenging is often summarily dismissed as a potential foraging mode in the majority of terrestrial vertebrates, leaving our understanding of the resource needs of species, the impact of these species on prey populations, and the flow of energy through food webs incomplete. I am especially interested in the prevalence, behavioral correlates and ecological implications of carrion utilization in snakes.
Although nearly all snake species readily accept dead prey items in captivity, carrion foraging by snakes has traditionally been discounted or ignored. Recently, I have demonstrated that scavenging in snakes is far more common than previously though and that it may represent a common or preferred foraging mode in some species. Optimal foraging theory dictates that profitability, not encounter rate, determines an item's presence in an animal's diet, implying that 1) carrion represents a meal that is equally as profitable as a live prey item, or 2) snakes achieve some other intrinsic benefit, unrelated to diet, by consuming carrion; such benefits could include more relaxed thermoregulatory requirements or more efficient digestion. I combine direct metabolic measurements, microbiological and immunological assays, behavioral manipulations, and biochemical and caloric assays of carrion to evaluate completing hypotheses explaining the adaptive value and evolutionary origins or scavenging by snakes.
Representative Relevant Publications
- Bakken, G.S. and A.R. Krochmal. 2007. The imaging properties and sensitivity of the facial pits of pitvipers as determined by optical and heat-transfer analysis. Journal of Experimental Biology. 210: 2801-2810.
- Krochmal, A. R., G.S. Bakken, and T.J. LaDuc. 2004. Heat in evolution's kitchen: evolutionary perspectives on the functions and origin of the facial pit of pitvipers (Viperidae: Crotalinae). Journal of Experimental Biology. 207 (24): 4231-4238.
- Krochmal, A.R. and G.S. Bakken. 2003. Thermoregulation is the pits: use of thermal radiation for retreat site selection by rattlesnakes. Journal of Experimental Biology. 206 (15): 2539-2545.
- DeVault, T.L. and A.R. Krochmal. 2002. Scavenging in snakes: a review of the literature. Herpetologica. 58 (4): 429-436.
Sample Popular Press Coverage
Television
- Bright, M. (Producer). "Rattler: Behind the Fangs". British Broadcasting Corporation in conjunction with the National Geographic Society. Filmed September 2006. Initial airdates 1-3 March 2007.
Radio
- Orem, W. Heat sensing pits. "Moment of Science". National Public Radio — Indiana Affiliate WFIU. February 2004.
- Blackburn, L. 2007. Thermal Vision? Journal of Experimental Biology — Inside JEB. 210(16).
- Torr, G. 2005. This heat's the pits. Nature Australia. Spring 2005.
- Reese, K.M. 2003. Snake pits avoid heat. Chemical and Engineering News. 81 (July 14):112.
- Milius, S. 2003. Snake pits: Viper heat sensors locate cool spots. Science News. 163 (June 21):388.
Sample Research Figures
A close-up of the Western diamond-backed rattlesnake (Crotalus atrox) showing the right facial pit.
Dr. Aaron Krochmal (left) and Dr. George S. Bakken (right; Indiana State University) prepare to block the facial pits of a Western diamond-backed rattlesnake (Crotalus atrox) for behavioral study.
A close-up of the Western diamond-backed rattlesnake (Crotalus atrox) showing the facial pits blocked in preparation for a behavioral study.
Thin histological section of the cranium of a Northern Pacific rattlesnake (Crotalus oreganus) showing the internal cavities of the paired facial pits.
A computer-generated model of the 3-D structure of a facial pit from a Northern Pacific rattlesnake (Crotalus oreganus; red= neurological tissue, green= skin; click for movie).