Influences of Water Management on Alligator Nesting

After last week's discussion on wetland use by turtles, I decided to research some literature on wetland use by alligators. I came across an article about the influences of water patterns on nesting behavior and nest survival in alligators in the Everglades. The article focused on the fact that due to their sensitivity to changes in ecosystem hydrology as far as reproductive success is concerned, alligators are a great indicator species for the effects of wetland availability and hydrological modifications.

According to the article, there are two main factors of altered water patterns that affect alligator life in terms of wetlands: reduction of wetland area for reproduction and changes in annual water (hydrological) patterns. During the study researchers measured hydrological patterns using harmonic models and examined their effects on alligator nest survey data over a 20 year period. Surveys were done in Shark Slough, Everglades National Park. The water levels in this area of the Everglades are controlled by water holding and discharge mechanisms North of the research area that allow for use of water by humans for residential and agricultural practices. Modulations to these mechanisms and subsequent water availability in the research area were shown to be primary causes in nest failure and reproductive success of alligators Researchers found that there were larger numbers of nests in years when average annual water depth was greater. This told researchers that increasing water levels delivered into the Everglades would allow for more suitable wetland habitat for alligators. At times when there was severe drought and more water was withheld from flowing into the Everglades, alligators were found to nest at sites of lower elevation. In general withholding of water in drought is generally accompanied by a large discharge from the withholding mechanisms early in the wet season producing high nest flooding and failure rates since nests were built at lower elevations. Thus greater nest failure/flooding was correlated with extreme dry seasons and extreme wet seasons. The authors believe that better management of wet season water discharge, and in particular gradual water release into the Everglades, could help prevent high alligator egg mortality due to flooding of nests.

I think that this research is very important in the field of herpetology because it presents more long term evidence about the nature of reproductive survival of herps depending on wetland habitat availability and modulation. The authors also mention at the end of the article that the effect of hydrological pattern modulations are not just affecting alligators but other non-herp animals such as fish and wading birds whose nesting and primary food sources come from wetland areas. I think the data from this article supports efforts of wetland conservation as well as better water management practices. The information from this article has the potential to open the eyes of the general public to how their residential water usage can affect a truly charismatic species and the ecological treasure that is the Everglades.

http://onlinelibrary.wiley.com.nuncio.cofc.edu/doi/10.1002/jwmg.463/full

Ugarte, C. A. et al. 2013. The Influence of Regional Hydrology on Nesting Behavior and Nest Fate of the American Alligator. Journal of Wildlife Management. 77 (1): 192-199.