Alligators Abound in Florida’s Sewer System

Researchers have discovered alligators, bats, raccoons, and many other creatures wandering through the sewer pipes in an urban area of Florida.

Cameras recorded crocodiles using stormwater drains to move between ponds. Photo: Alan Ivory

A recent study published in Urban Naturalist reveals that alligators and dozens of other species use the stormwater drainage system in an urban area of Florida to move safely through the city environment. While there has been extensive research on rats in sewer systems, other animals have received far less attention. Alan Ivory, a graduate researcher at the University of Florida and the study's lead author, suspected that the underground maze designed to channel stormwater may serve as an important passageway for urban wildlife, People reports.

The research team focused on stormwater drains beneath the city of Gainesville, Florida. They installed motion-activated cameras with magnetic mounts beneath manhole covers. In total, 39 cameras were deployed in 33 different storm drains. The cameras were left running for 60 days, though not all survived the duration. Some were washed away by rainwater, while others were damaged by animals. According to Ivory, some raccoons climbed the ladder rungs and pried cameras off the manhole covers.

Despite these setbacks, the researchers managed to recover most of the cameras, recording nearly 3,800 animal appearances from 35 different species. The American alligator (Alligator mississippiensis) was one of seven reptile species found in the stormwater system and was observed at more locations than any other reptile.

Other sewer-dwelling creatures included opossums and Norway rats, but some of the more surprising species for scientists were tree frogs, armadillos, and 12 different bird species. Small birds were seen in six different storm drains, sometimes bringing in nesting materials. Mammals were the most common sewer inhabitants, with raccoons making over 1,800 recorded appearances. The second most frequently seen species was the southeastern myotis bat, which appeared 700 times. According to Ivory, bats use the tunnels to hunt insects.

Larger animals, such as white-tailed deer and bobcats, were recorded near the sewer entrances, but very few ventured deep inside—except for alligators.

The team documented 50 instances of alligators using the sewers. Most used the system as a shortcut between ponds, but some were seen swimming into dead-end tunnels to hunt fish. It appeared that the alligators were deliberately herding fish into dead-end spaces to make them easier to catch, effectively using human infrastructure to aid in their hunting strategies. While the research focused on Gainesville, the scientists believe similar species use stormwater drains throughout urban areas in Florida.

Ivory and his colleagues suggest that Florida’s storm drain systems could be improved to be more wildlife-friendly. During their study, they observed snakes and frogs being washed into drains during heavy rain and struggling to climb back out. Constructing ramps near storm drains could help trapped animals escape more easily and safely.