Scientists ‘surprised' to find abundance of alligators in city's sewer system

Independent

14-02-2025

The sewer systems of Florida are teeming with an 'abundance' of alligators, racoons, and a dozen other animals using the drain pipes to traverse the city, scientists reveal in a new study.
Wildlife across the world are forced to navigate human-altered environments as rapid urbanisation continues.
A new study, published in the journal Urban Naturalist, examined how wild animals use Florida's well-connected subterranean stormwater sewer systems (SSS).
Researchers used camera traps to find how wildlife exploited this pathway, particularly in the state's Alachua County.
Overall, scientists found a total of 35 species of vertebrates using the sewer system to navigate, including amphibians, reptiles, and birds.
'The abundance of animals down there was surprising,' study co-author Alan Ivory from the University of Florida told the New York Times.
Seven species of reptiles were also found, including the American alligator species Alligator mississippiensis ' documented across the greatest number of sites'.
Most of the reptiles were found at sites that held water for more than half of the study period, researchers said.
Some reptiles, including the turtle species Yellow-bellied Slider, appeared to be using the pipes as corridors between ponds, scientists said.
The study suggests several animals are using the sewer system to avoid crossing busy roads.
A few other animals, especially smaller ones, appear to be swept into sewers after storms carry large amounts of water into the system, researchers say.
'Of the 5 sites, 4 of the sites where alligators were observed were simple culverts, and for this reason most of the alligator observations were of animals swimming from one pond to another (35 of 50 observations), thereby avoiding crossing busy roads,' scientists wrote.
Raccoons and small bats native to the southeastern US made most of the observations in the sewer system, pointing to their widespread presence in the subterranean pipes.
Among other animals spotted by the camera traps included, possums, armadillos, cats, black rats, squirrels, egrets, wrens, and toads.
'Our research offers a comprehensive exploration of vertebrate diversity within an unconventional urban habitat and provides valuable insights into the relationship between SSS and species utilisation patterns,' scientists wrote.
They hope the findings could lead to more ecologically conscientious urban planning strategies.
Citing a limitation of the research, scientists said the true count of some reptiles could be greater in the sewers as the camera trap system used in the study relied on an animal being warmer than its surroundings to trigger image capture.
'The detection probabilities of amphibian and reptile species are likely lower than the detection of the endothermic species,' they said.
Researchers call for further studies to better understand why some amphibians and reptiles enter the sewer system to help prevent them from becoming trapped.
'If amphibians are falling in from the curb, and are unable to exit, exclusion devices and climbing aids could be implemented to prevent such wildlife from being trapped within SSS,' they said.