Saturday, January 02, 2010

Florida: Rise in panther deaths good sign

January 2, 2010

Follows growth in population

by kevin lollar

Special coverage: Florida panther data and statistics

Last year’s Florida panther death count — 24, including a record 17 vehicle-related deaths — is almost seven times higher than the average mortality of the 1980s and more than four times the average of the 1990s.

At first glance, such a dramatic increase in deaths of an endangered species is disturbing.

But the rising body count is logical, even encouraging, in a morbid sort of way: The panther population has grown substantially since the mid-1990s, and more panthers mean more deaths, said Paul Souza, field supervisor of the U.S. Fish and Wildlife Service’s South Florida office.

“We’re tracking the animals in a way that’s helped us understand the health of the population,” Souza said. “If you put a graph up showing panther mortality per year and the population increase, they track almost perfectly.”

During the 1980s, an average of 3.2 panther deaths were recorded every year; in the 1990s, the average was 5.3; since 2000, the average was 18 — the record for panther deaths is 25, set in 2007.

While panther deaths have increased, so have panther numbers: Since the 1980s, the population has tripled to about 100.

Florida panthers, a subspecies of the cougar, once ranged through South Carolina, Tennessee, Georgia, Mississippi, Alabama, Arkansas, Louisiana and Texas and interbred with the Texas cougar and a now-extinct Northeastern subspecies.

As development destroyed panther habitat and panthers were killed for sport or to protect livestock, the shrinking panther population was restricted to South Florida, mostly in the southwest part of the state.

With the population confined to such a small area, inbreeding was common and led to genetic abnormalities such as heart defects and reproductive problems.

According to panther experts, the biggest reason for the increase in the panther population is the introduction in 1995 of eight female cougars into South Florida to mate with local panthers and improve the gene pool.

“What we’ve seen since the genetic restoration effort is that the population has a trajectory of improvement,” Souza said. “We had about 30 panthers in the early ’90s. Two years ago, we had the healthiest number we’ve ever counted: 117. Last year, we had 100 or so. We’re seeing the population peaked out in Southwest Florida.”

In scientific terms, Southwest Florida has reached its carrying capacity: The area can’t support a higher panther population.

So panthers have started heading north.

“Dispersing males fairly regularly cross the Caloosahatchee,” Souza said. “We’ve found them in south central Florida and as far north as Georgia. But we haven’t seen any females north of the Caloosahatchee.”

Earlier this year, however, panther experts found evidence of a female in the dispersal zone, 44 square miles in northern Hendry and southern Glades counties that is the last migration corridor for panthers across the river.

Four times over the past decade, including the past three years, the yearly panther death count was more than 20, which means that one-fifth of the population died in a single year four different years.

Meanwhile, enough kittens are being born and surviving to sustain the population.

This year’s most disturbing panther statistic is the number of roadkills — 17 in a population of about 100 died from a single cause. The most recent was Thursday when a 3-4-month old female was found on County Barn Road in Naples.

“That’s 16 percent of the population,” Dave Onorato, a research scientist with the Florida Fish and Wildlife Conservation Commission’s panther section, said before Thursday’s announcement of a 17th death. “The increase in roadkills comes with an increase in the panther population. It also comes with an increase in the (human) population of Florida: That’s going to increase traffic on our roadways.

“It’s kind of a bitter-sweet thing: There are more panthers, but we’re losing more of them on the road than we did before.”

Experts agree that the way to protect panthers from vehicles, is to build more wildlife crossings.

“But building underpasses and installing high fencing is an expensive proposition,” Onorato said. “Another thing we can do is tell people to be more aware when they’re driving at dusk and dawn. That’s when panthers are moving.

“With cold weather, like now, panthers are more likely to be up and about during the day.”

Additional Facts
• Scientific name: Puma concolor cory
• Taxonomy: The Florida panther is a subspecies of the cougar, also known as mountain lion, puma and catamount.
• Status: Endangered
• Population: About 100
• Distribution: South Florida
• Habitat: Hardwood hammock, pine flatwoods, saw palmetto and cabbage palm thickets, cypress forests, mangrove forests and freshwater marshes.
• Home ranges: Male panthers have home ranges of 150 to 200 square miles; a female’s home range is typically about 80 square miles.
• Size: Males average 130 pounds and measure 6 to 8 feet from nose to tip of tail; shoulder height is 2.6 feet. Females average 80 pounds and measure 5 to 7 feet with a shoulder height of 2.2 feet. Kittens weigh 4 to 8 ounces at birth.
• Diet: White-tail deer, feral hogs, raccoons, armadillos and small alligators.
• Reproduction: Males reach maturity at three years. Females reach maturity at 11⁄2 years and breed throughout the year, with peak breeding in the spring. Gestation is three months. Typical litter size is two kittens, which leave the den at 2 months and are fully independent at 11⁄2 years.
• Life span: 8 to 15 years in the wild, 10 to 20 years in captivity.
• Threats: Habitat loss is the main threat to the subspecies. The leading cause of death is intraspecific aggression (one panther killing another). Other causes of death include collisions with vehicles and disease.


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