Clemson student finds alligator movements may be related to water drawdowns
CLEMSON – Clemson University doctoral candidate Abby Lawson is helping lead a tracking study that could be instrumental in understanding how to effectively manage alligator populations.
Clemson and the South Carolina Cooperative Fish and Wildlife Research Unit are conducting the study, now in its fourth and final year. Researchers are tracking alligator movements using Global Positioning System (GPS) satellite transmitters. Lawson, a doctoral candidate in the Clemson forestry and environmental conservation department, is studying alligator population ecology and how alligator movements may affect population estimates used to inform management decisions.
“We have 27 adult male alligators that we’re tracking,” Lawson said. “Many people assume alligators don’t move much, but it’s time to rethink that.”
The study shows water level manipulations in South Carolina’s freshwater impoundments appear to influence alligator movements. The impoundments are managed to provide habitat for wintering waterfowl.
“As the water levels are drawn down, this concentrates aquatic prey like fish and creates an easy feeding opportunity for alligators,” she said. “One of our least active alligators suddenly made a beeline movement to another impoundment four miles south of his core range.”
This puzzled Lawson and her colleagues, so they dug deeper.
“When we talked to the property manager, the alligator’s movement directly coincided with an emergency drawdown in the same southern impoundment, which probably created quite the feeding frenzy,” Lawson said.
How alligators are aware of water level manipulations from so far away remains a mystery, she said. The male alligators could be getting cues from other species like birds, or they could be using their senses of smell or hearing.
Previous alligator movement studies in South Carolina have been restricted to spring and summer. This is the first to provide year-round data on alligator movements so researchers can evaluate the impact of extreme weather events or winter warm spells on alligator behavior.
The satellite tracking effort began in 2015 and is part of a study designed to provide scientific support for a long-term adaptive alligator harvesting strategy the researchers are designing. Researchers are analyzing the alligator movements to understand how landscape features affect habitat use and how movement between habitats affects the accuracy of population estimates.
“We see a lot of variation in our population survey counts from night to night,” Lawson said. “As it turns out, alligators are hard to count because they’re always on the move.”
Lawson and others are in the process of analyzing telemetry data that will help them better understand how to accurately estimate population size so that informed conservation and management decisions can be made.
Alligators are an important part of the South Carolina economy. The South Carolina Department of Natural Resources manages alligators as a valuable renewable resource. The department currently issues 1,000 alligator harvest permits among four alligator management units per year under the Public Alligator Harvest Program for use during a season that runs from the second Saturday in September to the second Saturday in October.