By the numbers
Total deer counted during summer aerial surveys in the Stairsteps Unit of Big Cypress National Preserve:
2008: No survey
Source: National Park Service
BIG CYPRESS NATIONAL PRESERVE — A dramatic decline in the size of the deer herd in part of the Big Cypress National Preserve has scientists puzzled and hunters worried.
The National Park Service has been tallying the drop-off for the past decade in the preserve’s southernmost region, a wet wilderness known as the Stairsteps Unit for its jagged shared boundary with Everglades National Park south of U.S. 41.
With deer surveys this year showing the decline sliding toward a wipe-out, the Florida Fish and Wildlife Conservation Commission has called off this fall and winter deer hunting season on 100,000 acres, called Zones 3 and 4, in the Stairsteps.
Hunters still can take other game from the Stairsteps, and deer season is opening as usual on other parts of the 729,000-acre preserve where wildlife officials have found no decline in deer populations.
No one is blaming hunters for the drop, the Conservation Commission’s top official said last week, but continuing to take deer from the two zones in the Stairsteps wouldn’t be prudent.
“We’re really taking a careful, close look at this,” Conservation Commission Executive Director Nick Wiley told the Conservation Commission at its meeting last week in Pensacola Beach. “We’re trying to be cautious.”
The National Park Service and the Conservation Commission have formed a task force to try to figure out what’s behind the decline.
Theories include high water levels, disease and predators getting the upper hand.
But like solving a case that’s gone cold, scientists are piecing together a picture of what happened years after it was triggered in a complex ecosystem where answers will be hard to find.
“We wish there was a silver bullet we could point to but there’s not,” Big Cypress preserve Superintendent Pedro Ramos said.
The National Park Service conducts aerial surveys of deer populations in Zone 4 of the Stairsteps Unit twice each year — once in the spring to determine the ratio of does to fawns and once in the summer to measure the ratio of does to adult bucks.
Spring counts have been erratic but generally fell from a peak of 523 deer in 2003 to 4 this spring.
The summer counts show the deer population on the rise between 1996 and 2001, when monitors counted 393 deer. After 2001, the deer population declined each year until bottoming out at 18 deer in 2009.
The Conservation Commission flew its own surveys between April and June 2010 and estimated the population at 21 deer in Zone 4 and 27 deer for Zone 4 and Zone 2 combined.
On the ground, hunters have been sounding the alarm about the decline and urging wildlife officials to address it.
“There’s been a lot of e-mail exchanges on this the last couple months,” said Franklin Adams, a lifelong Big Cypress hunter and a pioneer of the movement that created the preserve in 1974. “It’s a concern.”
The Stairsteps has always had a good deer population, said Adams, the southern regional director for the Florida Wildlife Federation.
He said he’s heard old-timers tell stories about running their airboats along the Stairsteps edge and watching bucks run back into Everglades National Park to safety.
Airboats are the preferred mode of transportation in the Stairsteps Unit, unlike other parts of the preserve where swamp buggies bump across the landscape.
Historically, access to the Stairsteps was unlimited, but the preserve established a system of designated trails there in 2000.
Hunters are taking fewer deer from the Stairsteps, from a peak of more than 100 per season to as few as 20 last year, according to state figures.
Deer hunting season actually is three seasons that run from September into early January, one for archery, one for muzzleloading guns and then a general gun season.
With hunting season closed in parts of the Stairsteps this year, attention is turning to the search for clues about the cause of the decline.
The task force is poring over years of hydrologic data to try to find a correlation between fewer deer and longer stretches of wetter than normal weather in the past decade, the Conservation Commission’s deer management program coordinator Corey Morea said.
All or parts of deer hunting season were closed in the Stairsteps due to high water in 1999, 2004 — the year of hurricanes Frances and Ivan — and 2005, when Hurricane Wilma made landfall in southern Collier County.
High water levels mean food is scarcer and leaves deer, especially fawns, more susceptible to predators, Morea said.
Deer are a key part of the diet of endangered Florida panthers, and alligators and bobcats also prey on deer.
They face a new threat, though, from non-native pythons whose spread across the Everglades has alarmed scientists. Scientists have found fawn hooves in the stomach of a python, Morea said.
Disease hasn’t been found in the Big Cypress deer herd, he said. Hunting check stations will be collecting samples this year from deer harvested from other parts of the Stairsteps Unit not closed to hunting to check for problems.
The task force has no timeline for completing its study, which could last for years, Morea said.
“It’s difficult to determine the cause of a decline when you’re looking backward,” he said.