Environmental determinants of turtle distributions in a national wildlife refuge

Background/Question/Methods

In recent years, anthropogenic stressors have drastically altered both terrestrial and aquatic ecosystems. One of the greatest threats to organismal health are agricultural pesticides that commonly run off or drift into wildlife habitats. A group of organisms that are particularly susceptible to the effects of pesticides are turtles, which are exposed to the chemicals in both aquatic and terrestrial landscapes. Another threat to turtle health are ranaviruses, a group of viruses with low host specificity; reptiles, amphibians, and even fish can be lethally or asymptomatically infected and can serve as reservoirs for other vulnerable species. While ranaviruses are extremely lethal and have been attributed to mass herpetofaunal die offs, ranaviruses may persist in populations without causing immediate die-offs. Working with the Wapanocca National Wildlife Refuge (WNWR), we tested the hypothesis that environmental determinents act as predictors for turtle species distributions and ranavirus occurrences in natural populations. 

Results/Conclusions

In a year-long, ongoing effort, we have collected water samples, to test for residues of  >90 pesticides, and assessed turtle distributions and ranavirus occurrences in populations that are either in relatively contaminant-free areas, or areas that are heavily contaminated through direct agricultural runoff. We found that habitat type, along with pesticide occurrence, are predictors of turtle diversity and abundance. Moreover, seasonality plays an important role in ranavirus occurrence due to flora change, water level, and amount and type of pesticide residues found in agricultural runoff. We conclude that agricultural contamination may play an important role in turtle diversity and distributions and may also affect disease dynamics in natural populations.