Florida panther roadkill deaths up slightly, but numbers may not mean much now

Every year, dozens of Florida panthers are run over by cars. The speeding vehicles have become the endangered cats' biggest predator.

In 2018, 26 of the 29 panthers that were found dead by state biologists were killed by being hit by cars or trucks. That's one more than last year's number of roadkill deaths (25) and one down from the total deaths (30).

"The number of roadkills is slightly up," said Marc Criffield, a panther biologist with the Florida Fish and Wildlife Conservation Commission.

The number is well short of the record of 34 panthers that were run over in 2016, a year in which 42 panthers total died.

PREVIOUS COVERAGE: Florida panther killed on road sets grisly new record.

For two of the remaining panther deaths this year, the cause remains a mystery. The third one was recently solved. A panther that had been hit by a car and spent months in rehabilitation was released back into the wild — and then nine months later was killed in a turf battle with another panther.

Until the late 1990s such turf battles — known among biologists as "intraspecific aggression" because it occurs between members of the same subspecies — were the main cause of death for panthers. However, as the population grew from just 20-30 in 1995 to more than 200 now, and more development in panther habitat put more cars and trucks on the roads there, death by vehicles quickly overtook it to become No. 1.

To see only a single death from intraspecific aggression is a little unusual. The explanation, Criffield said, is simple: Comparing the deaths by intraspecific aggression from year-to-year no longer works because scientists made a major change in panther research.

For nearly 40 years, biologists learned about panthers by chasing them down with a pack of dogs, shooting them with a tranquilizer dart and putting radio-transmitting collars around their necks. It's a technique that some biologists jokingly called "collar and foller," because once the collar is attached, they spend three days a week flying over panther habitat, following the cat via the radio signals.

But biologists believe there are better ways to learn about panthers now, and so they have stopped putting collars on the panthers.

"Why go molest the animals if you don't need to?" Darrell Land, the panther team leader for the Florida Fish and Wildlife Conservation Commission, explained in 2017. "They would probably prefer not to be chased up a tree by dogs, shot in the butt, go into a drug-induced coma, fall out of a tree and wake up with bling."

PREVIOUS COVERAGE: After more than three decades, collaring panthers may come to an end.

If a collared panther died — either by being run over or being attacked by another panther — its collar would emit what biologists called a "mortality signal," giving them a clue both to the panther's demise and its location. In that way, they were able to track down cats that might otherwise have been lost in the swamp.

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Now, though, state biologists are tracking only four panthers with collars, with another four being tracked by federal biologists at the Big Cypress National Preserve. Without more collars, there's no telling what's happening with the rest of the panthers.

"We just don't have that many collars out there any more, and that may be why we don't have a lot of intraspecific aggressions," Criffield said.

Panther advocate Matthew Schwarz is sure there are more intraspecific aggression cases out in the wilds of South Florida, mostly because as the panther population has grown, the available habitat has been whittled down by development. That's why the one rehabilitated panther died, he contends. It had no place to go except into territory already claimed by another male.

"It's a full house now," said Schwartz, executive director of the Florida Wildlands Association.

Contact Craig Pittman at craig@tampabay.com. Follow @craigtimes.