A famous urban legend holds that the sewers of New York are filled with blind albino alligators. These mythical reptiles have taken root in the city’s tradition, and some New Yorkers even celebrate Alligator Day in the Sewer every February.
In Florida, however, alligators in the sewers are not just a myth. These reptiles frequently infiltrate municipal drainage systems. In late January, a 3.5-meter alligator was rescued in Cape Coral after getting stuck in a sewer.
Study reveals the use of sewers by various species in Florida
Not all alligators end up in sewers by accident. A recent study published in the Urban Naturalist journal reveals that alligators and nearly three dozen other species use stormwater drainage systems in an urban area of Florida to safely navigate urban environments.
“It’s like something out of ‘Teenage Mutant Ninja Turtles’,” said Alan Ivory, a doctoral student at the University of Florida who led the research. “The abundance of animals down there was surprising.”
While rats in sewer systems have been extensively studied, what other animals do beneath the streets is less documented. Ivory and his team suspected that these underground labyrinths, designed to redirect stormwater and separated from sewer systems, serve as important pathways for urban animals.
Ivory and his colleagues focused on stormwater sewers beneath the city of Gainesville. The scientists placed motion-activated tracking cameras with magnetic mounts under sewer covers. In total, 39 cameras were installed in 33 stormwater sewers.
The cameras remained in place for 60 days, but not all survived that long. Some were washed away by stormwater, while others were stolen by a particular species.
“Sometimes, raccoons would steal our cameras,” Ivory commented. “They would climb up the stairs and rip them off the mounts.” The team was able to recover most of the cameras, which recorded nearly 3800 sightings of 35 animal species.
Among the sewer inhabitants were the usual suspects, such as opossums and rats, but there were also surprises: tree frogs, armadillos, and 12 bird species, including Carolina wrens. These small birds were spotted in six different sewers, sometimes with nesting material.
Mammals were the most common creatures in the sewers. The cameras captured raccoons over 1800 times. The second most seen animals were southeastern bats, observed nearly 700 times. These small bats used the sewers to hunt for insects and seemed to perch under manholes, which is novel behavior for the species, according to Ivory.
Some larger species, like the white-tailed deer and a bobcat, were seen near sewer entrances, although few large animals ventured inside, except for the alligators.
Sewers teeming with alligators
The team recorded 50 alligator sightings. Most seemed to use the sewers as passageways between ponds, but they also observed an alligator swimming towards a dead-end alley in search of fish. “It’s almost as if they corner the fish in this dead-end alley, using human infrastructure to aid in their hunting,” Ivory explained.
Although the scientists only studied the Gainesville area, they believe similar species use stormwater sewers in urban areas throughout Florida. The state has even built tunnels to help endangered Florida panthers avoid busy streets.
Ivory and his colleagues believe that stormwater sewers in Florida could be improved to make them more accessible to wildlife. During the study, the team observed snakes and toads frequently getting into the sewers during heavy rains and sometimes struggling to get out. Installing ramps near storm drains could help trapped creatures escape to safety.
These modifications could also be vital for other sewer inhabitants. Southeastern bats hanging from sewers are at risk of getting trapped without additional escape hatches. And some populations of these bats are declining due to the lack of suitable caves in urban areas of Florida.
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