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Biology

Aaron Krochmal

Assistant Professor of Biology
Education
  • B.S., Biology, Union College (NY), 1996
  • M.S., Biology, New York University, 1998
  • Ph.D., Ecology and Systematics, Indiana State University, 2003
Teaching
  • General Biology I and II
  • Comparative Vertebrate Anatomy
  • Comparative Animal Physiology
  • General Endocrinology
  • Behavioral Ecology
  • Research Techniques in Herpetology

Research Interests

I am a broadly-trained, integrative organismal biologst interested in the behavior, physiology, and ecology of reptiles. Specifically, I combine these disciplines to investigate how reptiles perceive, interact with, and navigate their environments. 

What follows are summaries of three of my current projects:

Behavioral and neurological mechanisms of spatial navigation in a rapidly changing environment

Animals that live in changing environments tend to show high levels of plasticity in behavior and cognitive ability as well as the morphological correlates that underlie those behaviors. However, studies that examine the evolution of cognitive abilities seldom compare populations where change is rapid and selection pressures are strong. Although overland movements are central to the biology of aquatic turtles, the severity of factors influencing the terrestrial movements due to habitat degradation seems to be changing. As severe droughts increase in frequency and standing water sources become more ephemeral as a function of global climate change, aquatic turtles will be forced more often and more quickly to make overland movements in search of suitable habitat. 

Using a population of Eastern painted turtles (Chrysemys picta) that has experienced a human-induced, predictably ephemeral water source for nearly100 years and has been forced to search for new aquatic habitats seasonally, my students and I have had the unique opportunity to investigate the behavioral and neurological mechanisms of spatial navigation in a rapidly changing environment.  Working at Chesapeake Farms, a 3,300 acre wildlife management property owned by DuPont where several ponds are drained annually as part of a wetland management regime, we have used radiotelemetry to monitor the movements of turtles as they are forced to take to land in search of new aquatic habitats.  Our work has demonstrated the key roles of local experience and habitat familiarity in navigating upland habitats. We found substantial evidence for the formation and use of complex spatial memory and a cognitive map, particularly at a very young age; forming such memory appears to be only possible in juvenile turtles.  Preliminary investigations of the anatomical underpinnings of these navigational abilities, conducted with Dr. Timothy C. Roth (Franklin and Marshall College), revealed evidence for differences in neurological structures within the brains of turtles with strong navigational abilities compared those lacking such abilities.  Forthcoming work will investigate the sensory cues that form and drive the spatial memory and navigational abilities of these turtles, the neuroanatomical correlates of differential navigational abilities, and the selection pressures acting on both.

 

Learning and Decision-Making Abilities of Pitvipers

Learning, a relatively permanent change in behavior as a result of experience, is an essential phenotype contributing to the fitness of all animals.  The importance of learning has been demonstrated in an array of ecologically-relevant contexts, including navigation and orientation, the establishment and maintenance of territories, predator avoidance, thermoregulation, and mate selection.  Though commonly thought of as being unique to vertebrates, learning is actually present across a wide array of animal taxa, from Arthropods and Echinoderms, to Molluscs and Protozoa. Despite the importance of  learning across so many animal taxa, our understanding of the learning within an ecological and phylogenetic context is decidedly limited.

Together with my colleagues Dr. Travis J. LaDuc (University of Texas, Austin) and Dr. Aaron J. Place (Northwestern Oklahoma State University,  I have been investigating the learning and decision-making abilities of the pitvipers (rattlesnakes and their relatives) within an ecologically- and phylogenetically-relevant context.  By focusing on snakes, we aim to fill a substantial gap in our knowledge of learning within a phylogenetic context thus refining our understanding of the evolution of learning in vertebrates. We surveyed wide breadth of taxa, including ancestral and derived lineages, and sampled taxa from disparate ecological niches (e.g. grassland, montane, forest and semi-aquatic lineages), and we assessed the learning abilities of these disparate taxa relative to thermal stress and behavioral thermoregulation, central aspects of the biology and ecology of these snakes and forces currently considered to have driven major evolutionary changes in this lineage.  By assessing the learning abilities of these taxa within the context of an ecologically- and evolutionarily-relevant task, we cast our phylogenetic patterns of learning within relevant, functional framework. 

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.

 

Recent Presentations at Professional Meetings

(*- presenter;  - undergraduate coauthor)

Krochmal, A.R. Habitat Familiarity Drives Successful Terrestrial Navigation in Eastern Painted Turtles (Chrysemys picta picta).  7th World Congress of Herpetology.  Vancouver, BC.  7-14 August, 2012.  

Krochmal, A.R., T.J. LaDuc and A.J. Place. Proximate and Ultimate Perspectives On One-Trial Learning In Rattlesnakes . Annual Meeting of the Society for Integrative and Comparative Biology, Charleston, SC (3-7 January 2012).

Provine, S.R*., H. O’Malley*, A.R. Krochmal, and T.C. Roth. Memory use as a possible mechanism for over-land movements in Eastern Painted turtles (Chrysemys picta picta): behavioral and neurological evidence. Annual Meeting of the Society for Integrative and Comparative Biology, Charleston, SC (3-7 January 2012). 

Krochmal, A.R*.  Overland Movements and Habitat-Seeking Behavior of Eastern Painted Turtles (Chrysemys picta picta) in Response to Habitat Perturbations. 12th annual meeting of the Northeast Partners in Amphibian and Reptile Conservation (NE PARC), Millersville, MD (August 17-18 2011).

O’Malley, H.E. * and A.R. Krochmal. Overland Movements and Habitat-Seeking Behavior of Translocated Eastern Painted Turtles (Chrysemys picta picta): Implications for Land Management and Turtle Conservation. 12th annual meeting of the Northeast Partners in Amphibian and Reptile Conservation (NE PARC), Millersville, MD (August 17-18 2011).

Krochmal*, AR., T.J. LaDuc  and A.J. Place “Burly and Bright!” - Rattlesnakes appear to exhibit one-trial learning. Biology of the Rattlesnakes Symposium, Tucson, AZ (20-23 July 2011).

Eckenrode, K.M. , W. Schindler* III and A.R. Krochmal“What’s for dinner? Rethinking relative utility factors to better model resource potential in prehistoric diets”. 2011 Middle Atlantic Archaeology Conference. Ocean City, MD (17-20 March). 

Broomell, E.R.*, H.E. O’Malley* and A.R. Krochmal. Eastern painted turtles (Chrysemys picta picta) use habitual routes when traveling over land. 22nd Annual Saint Joseph’s University Sigma Xi Student Research Symposium, Philadelphia, PA (8 April 2011)

Schindler III, W*.,K.M. Eckenode, and A.R. Krochmal. “Finish Your Plate!  Rethinking Relative Utility Factors to Better Model Resource Potential in Prehistoric Diets” 1st Annual Reconstructive and Experimental Archaeology Conference, Gastonia, North Carolina (16-18 October 2010).

Schindler III, W*. K.M. Eckenrode, and A.R. Krochmal. “Finish Your Plate!  Rethinking Relative Utility Factors to Better Model Resource Potential in Prehistoric Diets” 75th Anniversary Meeting of the Society for American Archaeology, St. Louis, MO. (14-18 April 2010)

Krochmal, A.R.* T.J LaDuc, and A.J. Place. “Ultimate explanations for differences in learning patterns and decision-making abilities of pitvipers (Viperidae: Crotalinae)” Annual Meeting of the Society for Integrative and Comparative Biology, Seattle, WA (3-7 January 2010).

Krochmal, A.R. T.J LaDuc, and A.J. Place*. “Proximate explanations for differences in learning patterns and decision-making abilities of pitvipers (Viperidae: Crotalinae)” Annual Meeting of the Society for Integrative and Comparative Biology, Seattle, WA (3-7 January 2010)

Krochmal, A.R.*  G.S. Bakken, and T.J LaDuc. “Phylogenetic perspectives on learning in pitvipers (Viperidae: Crotalinae) with comments on one-trial learning in rattlesnakes” Annual Meeting of the Society for Integrative and Comparative Biology, Boston, MA (3-7 January 2009).

 

Recent and Forthcoming Publications

( - undergraduate coauthor)

O’Malley, H.E. * and A.R. Krochmal. An evaluation of the suitability of translocation of 

aquatic turtles as for conservation and mitigation. In preparation for Chelonian Conservation and Biology.

 

Brice, T. * and A.R. Krochmal. Rapid vernal drawdowns do not adversely affect aquatic turtle populations. In preparation for Journal of Herpetology

Krochmal, A.R. and T.C.Roth.  Using perception, spatial learning, and memory to shape wildlife management regimes: Conservation at the psychology-ecology nexus. In preparation for PLoS One

 

Schindler, W., A.R. Krochmal, and K. Eckenrode. Rethinking relative utility factors to better model resource potential in prehistoric diets. In Press.  American Antiquity.  

 

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.