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In 2009 my students and I began to monitor the turtle community at the Huntsdale Fish Hatchery in Huntsdale, PA (9 miles SW of Carlisle): Painted turtles for the past 4 years, Snapping turtles for 3 years and Musk turtles for 1 year. Preliminary analyses have provided us with some interesting patterns in terms of density shifts, basking behaviors, and movement. To date my students and I have marked a total of 948 Painted turtles, 123 Snapping turtles (Chelydra serpentina), and 17 Musk turtles (Sternotherus odoratus) at this site. Our goals are to analyze these data to estimate population parameters such as survival, mortality, and population size. While researchers have published studies with data similar to our own, our work will not only add valuable information on Painted turtles in Pennsylvania but will also enable us to conduct comparative analyses to understand life-history evolution in this species. In addition to the population study, we have been monitoring the nesting behavior of female Painted turtles for the past 3 years. This companion study aims to evaluate the environmental and ecological parameters influencing Painted turtle nests and ultimately hatchling survival. Turtles are found by walking around the pond during early morning and late afternoon surveys. When a female is found digging her nest, we allow her to finish creating the nest and then process the nest. Students and I carefully excavate the nest, measure all the eggs, replace the eggs, and deploy a temperature recording device in the nest. In Painted turtles, the temperature of the nest determines the gender of the hatchlings: warm temps result in female hatchlings while cooler temps result in male hatchlings. As a result, painted turtles are susceptible to climate change. We aim to understand how increases in average daily temperature may affect how females choose suitable sites to lay their eggs and whether these nests are successful in producing hatchlings We are also collaborating with Gene Wingert to study the population biology of Painted turtles at Wildood Park in Harrisburg PA. Check out the video of some of this work.
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 Above my research students with a gaggle of snapping turtles caught in July 2012 using baited hoop traps (from left Dani Staunton '13, Andrew Veselka '15, and Julia McMahon '15).
Hatchling Painted turtle from one of our monitored nests. Hatchlings are measured, photographed, marked and released.i |
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Snakes are considered to be gape-limited predators since they can't chew their food and thus swallow their prey intact. As a consequence, the snakes' head shape and ultimately its gape size, creates a physical constraint on the size of the prey it can consume. Snakes with larger gapes can consume a wider variety of prey sizes compared to snakes with smaller gapes. However if your head is too big there is a cost. Snakes with huge heads should be prevented from accessing some prey such as those that live in narrow tunnels or rock crevices. Therefore snake head shape (and gape size) is often correlated with the type of prey it consumes and marked differences can exist among populations and between sexes.
Boas from islands off the coast of Belize have different head shapes compared to mainland boas. Island boas have more attenuate snouts and larger eyes compared to mainland boas and this could be a reflection of their unique island diet: migratory passerine birds. I have explored the question of whether observed differences in head shape are due to genetics or the environment by performing basic feeding experiments on neonates in the lab. Representative publications: Boback, S.M. 2006. A morphometric comparison of island and mainland boas (Boa constrictor) in |
 The above figure illustrates variation in head shape among populations of island and mainland boas in Belize. The black circle represents the mainland population and the gray symbols represent the four island populations. Compared to the mainland population, some island populations show larger eyes and narrower heads (negative numbers on x-axis, Canonical Function 2) while others show more attenuate snouts (positive numbers on x-axis, Canonical Function1). |
| The field of macroecology has revolutionized how ecologists think of species interactions and biodiversity. Simply defined, macroecology is the study of how organisms interact with each other and their environment on large spatial scales to explain patterns of abundance, distribution, and diversity. This approach allows one to examine patterns and test hypotheses not possible with traditional ecological approaches. For the past 7 years, I have collaborated with Bob Reed (USGS) and my Ph.D. advisor, Craig Guyer ( We have found that snakes differ from other taxonomic groups in exhibiting a body size distribution that is not skewed. However there is evidence to suggest that there are fundamental constraints on body size and that snakes are influenced by similar constraints as endotherms. For instance, if we look at a bunch of island snake assemblages across the globe and we selectively plot, on landmass area, the size of the largest and smallest species in each assemblage, we see the pattern in the figure to the right . As we decrease island area (i.e., as we get smaller and smaller islands), the size of the largest species decreases while the size of the smallest species increases. On single species islands, the best fit lines through these data converge on a single, moderate, size. This size has been proposed to be "optimal" since it is the size that is predicted for snakes in the absence of competition. Reproductive power describes the energetic capacity to produce offspring and has been used to explain body size distributions in mammals, birds, and bivalves. Thus it has been suggested that body size diversity is determined by energetics. How could this be? Evolutionary theory tells us thatl organisms should be adapted to maximally produce offspring in their environment. For instance, small snakes generally have small litters whereas large snakes like boas can have really big litters (see photo on right). But we know that compared to the smallest species, very large species are limited in the RATE they can produce these litters. This suggests that there might be a trade-off with being big - and there is. To determine the generality of this model, we tested the reproductive power model on snakes, a markedly different vertebrate group compared to birds and mammals. We found that basic allometric functions describing reproductive output and population productivity in snakes accurately predicted the mode and the left side of the snake body size disribution. But it did not predict the right side. What does this mean? Well, we suggested one of two things could be going on. First, the reproductive power model as it currently stands might not be appropriate for taxa with size distributions that are not right-skewed (like snakes). Alternatively, if the reproductive power model is correct, then diversity in snakes may be limited in the largest size classes since the model over-predicted the right side of their body size distribution. Representative publications: Reed, R. N. and Boback, S.M. 2002. Does body size predict the dates of species description among North American and Austrailian reptiles and amphibians? Global Ecology and Biogeography. 11(1): 41-48. Boback, S.M. and C. Guyer. 2003. Empirical evidence for an optimal body size in snakes. Evolution. 57(2):345-351. Boback, S.M. and C. Guyer. 2008. A test of reproductive power in snakes. Ecology. 89(5):1428-1435. |
The above graph shows the relationship between body size of the largest (black dots) and smallest (white dots) snake species in an assemblage and island area. Best fit lines bisect one another at a body size that would be predicted on the smallest islands that support only a single species. This body size (1 meter) actually matches the modal size from a representative sample of the world's snakes.
The above photo is a litter of 44 boas produced by a large (10 kg) female captured on the mainland of Belize, Central America. What determines litter size and/or the rate (or frequency) a female can produce a litter? Are snakes limited in their reproductive capacity in the same way as mammals or birds? Read "A test of reproductive power in snakes" to see if we found out. |
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Many snakes feed relatively infrequently and, as a consequence, have adapted the ability to down-regulate their digestive system during periods of fasting. This energy saving feature has a downside - when the snakes do feed, their digestive system is completely atrophied, and thus incapable of performing the tasks needed to digest a meal. Consequently, the digestive system must be rapidly up-regulated immediately after feeding and the magnitude and speed of this up-regulation is unrivaled among tetrapods. Within 24 hours of feeding, the small intestine doubles in mass (this includes a 14-fold lengthening of the microvilli) and their metabolic rate increases up to 1500% of fasting levels. As a result of this dramatic regulation, the snake digestive system is a model system for understanding the mechanisms responsible for physiological regulation of digestion. In Stephen Secor's lab at the University of Alabama, we used pythons as a model to test the idea that cooking played a major role in human evolution. By experimentally feeding pythons cooked and uncooked steak we were able to demonstrate that cooking significantly decreases the cost of digestion. The mechanism for this energetic savings is unclear but is likely related to the effect that cooking has on animal flesh - the conversion of tough collagen fibers into a more pliable compound, gelatin. This work is consistent with the idea that cooking played a pivitol role in human evolution. Boback, S. M., C. L. Cox, et al. 2007. Cooking and grinding reduces the cost of meat digestion. Comparative Biochemistry and Physiology 148: 651-656.
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