How Florida crocodiles, moved away from your neighborhood, likely find their way back

Lisa J. Huriash, South Florida Sun-Sentinel
·7 min read

Remove a crocodile from its chosen habitat — and you’ll have a croc intent on getting back to where it came from. And what’s more, it has a knack for homing in on its destination.

That’s the essence of a study released this year that tracked GPS-equipped crocodiles’ movements across South Florida. Seven crocodiles in the study were relocated many miles away, and four managed to find their way back. Notably, one female crocodile was relocated 95 miles away and was recaptured just a quarter-mile from its original capture site more than two years after its release.

“If you move a crocodile, sometimes they come back right away, sometimes it takes them awhile,” said Frank Mazzotti, one of the co-principal investigators. The study was commissioned by the Florida Fish and Wildlife Conservation Commission’s Fish and Wildlife Research Institute.

The study underscored how oftentimes, relocating crocodiles isn’t the best option when they get close to South Florida neighborhoods. “Moving is not the solution,” Mazzotti said. “Teaching people to be tolerant of them really is the solution.”

The wildlife conservation commission’s research institute says it relies on these types of studies to keep refining its best practices with crocodiles. “The FWC uses every opportunity to educate the public on living with crocodiles while focusing on public safety and the safety of the crocodiles,” it said.

In all, there were 17 crocodiles in the study. Ten of them were released at their original capture site to serve as a reference group. Those crocs seemed at ease, demonstrating “slow meandering movements within their home ranges, suggesting a familiarity and possible contentment with their surroundings.”

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But the other crocs — the ones moved anywhere from eight to 98 miles — began to act differently. They showed “fast, active directional movements.” That suggested they had “an uneasiness with their surroundings and a determination to find more suitable habitats.”

Even though the crocodiles may be skilled at getting back to their original location, how they figure that out is something researchers have yet to crack.

If crocodiles were to have some sort of built-in compass, “it’s useless unless you have a map,” said Mazzotti, of the department of Wildlife Ecology and Conservation at the University of Florida. “Where does the map come from? Do they get their map from the stars? I don’t know.”

“If you can answer that question someone will give you a prize.”

Tagging crocodiles

For the study, which began in 2018 and was published this year, the crocodiles were first caught and tagged for tracking. That process is like “minor surgery” while the crocs are awake, Mazzotti said.

First, the area on the croc is cleaned. Then they get numbed up with an anesthetic. The process, which uses a threading needle, is “equivalent like giving stitches, we use surgical wires, wires through the skin and underneath the bony plate,” all held together with epoxy glue. The transmitter is small, waterproof and runs on batteries. The lifespan of a transmitter is generally one year, and then investigators catch the crocodiles, and remove them.

The reference crocodiles were generally captured in southern Everglades National Park, including Cape Sable, Barnes Sound, Card Sound and the Naval Air Station Key West on Boca Chica Key.

The translocated crocs were captured in locations such as Key Largo, Pinecrest, North Miami and Key Largo. After they were tagged, the crocodiles were relocated, the ones sent farther away went to Collier-Seminole State Park, in southwest Florida, and the C-111 canal, in northeast Florida Bay.

“These two locations were chosen because they are both release sites used during past translocations,” according to the study. “These sites are considered the best available options, given that the majority of remote land available within crocodile range is federally managed and considered off-limits to the release of translocated crocodiles. We alternated between the release sites for mainland-captured crocodiles and for Keys-captured crocodiles.”

According to the agency, three crocodiles translocated 28 miles or less returned within two weeks, getting within 1.8 miles of their original capture location. Three crocs moved more than 68 miles were not documented returning. And then there was the female crocodile that was relocated 95 miles away, and managed to get within a quarter-mile of its original capture site, more than two years after its release.

“When you relocate crocodiles two things happen, they return or don’t return. What happens to the half that don’t? Do they take up residence where we release them? Do they try to get back and get lost? Do they try to get back and find another spot? We just don’t know,” he said. Relocating is a last resort, he said. Rather it’s teaching people to “live with crocodiles.”

The report noted that crocodiles have the potential to travel great distances, citing one past example in which a crocodile in northern Australia once traveled greater than 249 miles to return to its capture site. In previous studies, the longest reported distances traveled by relocated American crocodiles in Florida were 93 miles in 1989 and 157 miles in 2014, according to the report.

“There are extreme examples,” Mazzotti said. “It doesn’t mean it’s not going to come back. There doesn’t seem to be any particular barrier.”

Facing risks

At least two of the seven relocated crocodiles may have died, the study said. But the scientists weren’t sure about that: Those crocodiles lost transmitter receptions.

“We believe one translocated crocodile died approximately one month after translocation based on its movement into the Gulf of Mexico and sudden disappearance,” according to the report.

Mazzotti said it was the most logical explanation.

“We believe one of the crocodiles translocated (89 miles) may have died attempting to return because tracking data suggests the animal passively drifted out into the Gulf of Mexico during the last three days we received locations,” the report reads.

That croc, a female, was moved from Tavernier to Collier-Seminole State Park, a distance of 94 miles. She “made a significant move across Florida Bay” 17 months after her relocation. That journey got her within 24 miles of her capture site, “but unfortunately her transmitter failed immediately after we documented the crossing,” according to the study.

According to the report, there is no guarantee that crocodiles relocated at least 62 miles will not return, “but it is unlikely that they will return quickly. It appears that long-distance translocations place them in unfamiliar territory and that, although they might have some homing abilities, they seem less certain on how to return and therefore will take more time or even establish a new home range instead of returning.”

Drawing conclusions

The study suggested relocating crocodiles may only serve as a last resort. “Because of concerns regarding return rates and heightened stress as a result of capture and translocation, we suggest crocodile translocations have limited conservation value and may only be worth considering once all other reasonable options are exhausted,” according to the report.

In the end, the researchers’ theory proved correct that relocated crocodiles would return, or attempt to return, to their original capture sites.

“Results supported our prediction, as six out of seven translocated crocodiles either returned or attempted to return,” according to the study. “We predicted that translocated crocodiles would travel greater distances compared to non‐translocated reference crocodiles. This was supported by our data.”

Another study underway

In late 2021, investigators kicked off another study to figure out which crocs go where. They aimed to capture 15 adult crocodiles in urban areas in both the Keys and South Florida and outfit them with GPS and VHF transmitters. The next state report is expected to be completed in March.

Mazzotti outfitted his first caught croc with a radio transmitter in 1978. Scientists were “following baby crocodiles around to see how they move.”

The technology has since gotten smaller and more efficient.

And the result could be greater understanding of what not to do with crocs: “Almost every single study where people have relocated crocodiles, the overwhelming (result) is they come back,” Mazzotti said. “If they’ve been hanging out in a particular spot it means it’s a good spot — food, water and cover. If you move them away they just return. They remember it as a good spot.”

The study’s intent is to “increase our understanding of crocodiles,” Mazzotti said. The findings will help keep “us more safer and more secure,” including how to manage the crocodile population, knowing what areas are frequently used, and “that can inform people how then they can behave,” such as minding their pets.

Lisa J. Huriash can be reached at lhuriash@sunsentinel.com. Follow on X, formerly Twitter, @LisaHuriash