“Somewhere, something incredible is waiting to be known” –Carl Sagan
Description of Research
My broad research interests are in the ecology and conservation of animal populations. I enjoy employing and testing new statistical techniques for understanding species abundances and distributions across landscapes. I use information from these observed patterns to inform and help design experimental tests of ecological and conservation theories. Further, I employ experiments over a wide variety of scales from the laboratory to aquatic and terrestrial mesocosms to large-scale forest manipulations. The diversity of scales allows for understanding different ecological processes while balancing control and realism.
Forecasting Climate Change Effects on Trout and Salamander Populations
I am working with collaborators at UMass, USGS, and USFS to model climate change effects on brook trout and stream salamanders. We are using hierarchical Bayesian models to estimate abundance, occupancy, growth, survival, and recruitment while accounting for imperfect detection probabilities. We are also partitioning model uncertainty to help inform Structured Decision Models for managers and policymakers to develop evidence-based plans. You can find more information on the SDM portion of the project here and here and some press here). Our Spatial Hydro-Ecological Decision Support system (SHEDS) related to this project is under development at www.ecosheds.org.
Modeling Stream Temperature
Temperature is a driving factor in many species distributions, not only across elevational gradients. As part of my current postdoctoral research, I developed a Bayesian autoregressive mixed-effects model to predict daily stream temperature across broad spatial and temporal scales. I am using derived metrics from this model as covariates of abundance, occupancy, and detection in various fish and salamander population models and to identify potential climate refugia for these populations. Our research group is working with state agencies to incorporate our findings into management and policy decisions through structured decision making processes and developing an interactive web application tool.
The Role of Amphibians in Ecosystem Functions and Services
Terrestrial salamanders of the genus Plethodon can be incredibly abundant in forest ecosystems. In many eastern US forests they are the most abundant vertebrate and can makeup twice the biomass of all the breeding forest birds. As abundant predators of forest floor invertebrates, salamanders have the potential to affect ecosystem processes through alteration of the detrital food web and through direct nutrient cycling. I am specifically testing how the removal of salamanders from forest plots affects nitrogen mineralization rates, leaf litter decomposition rates, and oak seedling growth and survival. Additionally, I am examining how salamanders affect other top forest floor predators including spiders, centipedes, and carabid beetles. These predators are likely competing for resources and their roles in the food web and ecosystem may be altered in the absence of salamanders. Given the global decline of amphibians, it is important to understand how amphibians contribute to ecosystems services and what we’re losing. This knowledge can help to inform and prioritize conservation and management decisions. http://www.unh.edu/unhtoday/2012/08/hut-hut-hike-team-salamanders-tackle-ecosystem
Hocking, D. J. and K. J. Babbitt. 2014. Amphibian Contributions to Ecosystem Services. Herpetological Conservation and Biology. 9(1): 1-17. (Open Access)
Hocking, D. J. and K. J. Babbitt. 2014. The role of red-backed salamanders on ecosystem functions. PLoS ONE 9(1): e86854. DOI:10.1371/journal.pone.0086854
Changes in Salamander Elevational Distributions with Climate Change
Collaborators: Bill Peterman, John Crawford, & Joe Milanovich. Models using habitat suitability and climate projections suggest that many salamanders through the southern Appalachian Mountains will experience significant declines over the next century. High elevation endemics are expected to be especially susceptible to climate warming. High elevation species can’t shift their entire distribution higher, so if the lower extent of their distribution moves higher, they lose a large area in these range contractions. We are studying the elevational distributions of Plethodontid salamanders in Great Smoky Mountains National Park. We are also comparing these findings with historic presence-only data from museum specimens to understand how distributions have changed over time.
Here is a great video on Appalachian salamanders: http://vimeo.com/23474410. Most people don’t realize that the southern Appalachian mountains host the greatest diversity of salamanders of anywhere on the planet. The southern Appalachians are like the coral reefs of salamander biodiversity!
Human Land-use Effects on Amphibians
My master’s research while at the University of Missouri focused on the effects of forest management practices on amphibian populations. My research was conducted as part of the Land-use Effects on Amphibian Populations (LEAP) project. This was a collaborative project with the University of Missouri, University of Maine, Syracuse University, and University of Georgia. We used multiple experimental forest treatments simultaneously in three regions of the country to compare regional effects of different forest management techniques. My individual research examined the breeding and recruitment response of gray treefrogs (Hyla versicolor) to these different management techniques in central Missouri. While clearcutting was detrimental to most amphibian species, we found that small cuts might be tolerated by gray treefrogs. Males were found in the clearcuts and females moved from the forest to artificial pools 10 m into clearcuts for breeding. Tadpoles developing in these open canopy pools had greater growth and survival than those in closed canopy pools.
I have continued examining the effects of human land-use on amphibians in the northeastern US. We are currently comparing the effects of various forestry practices with natural disturbance from severe ice storms on red-backed salamander abundance and demographics. Additionally, we have started surveys of stream salamanders over an urban gradient to examine the relative effects of local and landscape-scale characteristics on salamander abundance.
Hocking, D. J., K. J. Babbitt, and M. Yamasaki. 2013. Comparison of silvicultural and natural disturbance effects on terrestrial salamanders in northern hardwood forests. Biological Conservation. 167: 194-202.
Hocking, D. J., G. M. Connette, C. A. Conner, B. R. Scheffers, S. E. Pittman, W. E. Peterman, and R. D. Semlitsch. 2013. Effects of experimental forest management on a terrestrial, woodland salamander in Missouri. Forest Ecology and Management 287:32-39
Semlitsch, R.D., S.M Blomquist, A.J.K. Calhoun, J.W. Gibbons, J.P. Gibbs, G.J. Graeter, E.B. Harper, D.J. Hocking, M.L. Hunter, D.A. Patrick, T.A.G. Rittenhouse, B.B. Rothermel, and B.D. Todd. 2009. Effects of timber management on amphibian populations: understanding mechanisms from forest experiments. Bioscience 59(10):853-862.
In addition to research on ecology and conservation, there are frequently times when field and laboratory techniques can be improved. These types of projects can be both fun and useful. This creates good opportunities for undergraduate and graduate students to publish papers that benefit a variety of researchers and help move science forward. Examples I’m involved with include the use of alpha-numeric tags for marking juvenile amphibians, validation of candling for non-invasively assessing fecundity and reproductive status, and the use of various artificial cover objects for surveying salamander populations.
Osbourn, M.S., D.J. Hocking, C.A. Conner, W.E. Peterman, and R.D. Semlitsch. 2011. Use of fluorescent visible implant Alphanumeric tags to individually mark juvenile ambystomatid salamanders. Herpetological Review 42(1): 43-46.
Scheffers, B., E. D. McDonald, D. J. Hocking, C. A. Conner, and R. D. Semlitsch. 2009. A comparison of two artificial cover objects for sampling amphibians and reptiles. Herpetological Review 40(4): 419-421.
Undergraduate Research: The Confluence of Research and Teaching
I am passionate about ecological research and increasing human understanding of how the natural world works. One of the greatest parts of being a scientist is that moment when you first get the results of an experiment and glean something new about this world we live in. Then following up with the excitement of sharing this new finding with others. It doesn’t matter how small the finding, it’s always something new, something that no one else has ever known before. I try to instill this excitement of discovery in my students and there is no better opportunity than through undergraduate research projects. I have been fortunate to work with a number of enthusiastic and talented students who never fail to inspire and challenge me. You can read more about undergraduate projects I’ve been involved with here.