Regional Alligator Diet and Utility as Indicators of Contaminants of Emerging Concern

Human activity is the largest contributor of environmental contaminants at the global level. In many areas, legacy contaminants like mercury and contaminants of emerging concern, including per- and polyfluorinated substances (PFAS) and microplastics, enter the environment through surface waters. These contaminants pose risks to natural resources, including water and wildlife, mainly where wildlife is consumed as part of recreational or commercial harvest. As contaminants of emerging concern, research on PFAS and microplastics is critical to addressing data gaps to quantify and understand potential impacts on wildlife; one management strategy to assess and monitor water quality is using indicator species that reflect the biotic or abiotic state of the environment. 

American alligators (Alligator mississippiensis) are ubiquitous in freshwater and brackish wetlands throughout the southeastern United States, including the coastal plain of South Carolina. Alligators are currently used as indicators of exposure to contaminants, particularly metals and persistent organic pollutants. Moreover, they are a highly managed species, captured annually for research and management programs and harvested legally through public and private hunting. As such, there is potential to explore alligators as candidate indicator species for PFAS and microplastics in South Carolina and across their range. In addition to contaminants, there is a lack of data regarding alligator diet throughout much of the range. As the primary exposure pathway for contaminants, determining trends in the alligator diet is vital to elucidating patterns of contaminant exposure in alligators.   

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This project leverages an 8-state collaborative network to collect alligator stomach contents, blood, and tail muscle from wild alligators through live capture and stomach flushing, as well as from hunter-harvest. We have collected over 400 samples in the first two years from North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, Louisiana, and Texas. We have analyzed preliminary data of diet for 300 alligators, finding notable differences in prey prevalence between tidal and non-tidal habitats. Although waterfowl and waterbirds are present in some stomachs, we found little evidence of duck depredation, with one blue-win teal recovered from east Texas. However, we recovered four wood duck web tags from one adult alligator on Lake Moultrie, SC, and one web tag from Apalachee WMA, FL. These tags were deployed as part of the large wood-duck project supported by the Kennedy Center and Nemours Wildlife Foundation. We are working with B. Bauer of Nemours Wildlife Foundation to publish these results.  

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In conjunction with our diet data, we analyzed 100 blood, 100 muscle, 100 water, and 100 sediment samples from South Carolina for PFAS in collaboration with Dr. John Bowden at the University of Florida. Data analysis and peak integration are in progress, and this work may expand in 2025. In partnership with Dr. Kylie Rock at Clemson University, we are also analyzing the largest multistate dataset of alligator blood and muscle samples for mercury. We also engaged 12 undergraduate students on the project through a Clemson Creative Inquiry course, and three of these students completed 2024 summer internships with the Kennedy Center. The results of our diet, PFAS, and Mercury analyses will contribute to the first regional datasets of this scale for American alligators.