State’s Method of Counting Manatees Facing an Overhaul

By Curtis Morgan, The Miami Herald

Apr. 14–Grounded by a warm winter, Florida’s annual aerial head count of Florida’s manatees has been canceled.

It won’t make a difference in the debate over whether the population of beloved, blubbery marine mammals is booming or barely hanging on. Counting sea cows by air has not been what anyone, especially biologists who conduct it, calls exact science.

Skewed by whims of weather, numbers have yo-yoed year to year by the hundreds and, a few times, by more than 1,000 animals — significant swings for an animal on federal and state endangered species lists.

Things may change next year. The Florida Fish and Wildlife Conservation Commission hopes to unveil a new and more accurate approach. It also will be far more complicated, relying on arcane statistical calculations and computer modeling, and may prove as controversial as the method it replaces.

That’s largely because the new survey will take a crack at doing what scientists have long avoided — determining the total number of manatees in Florida.

It won’t simply count visible snouts and tails but estimate unseen animals, as well, all but ensuring numbers will rise from the past two decades of surveys — possibly to the highest counts ever.

“They should be higher because we know we miss animals,” said Holly Edwards, a scientist with the state’s Fish and Wildlife Research Institute in charge of the assessment. ‘We’re trying to give the best estimate we can. They’re going to be adjusted, and, yes, they will go up.”

Manatee advocates are reserving judgment, in part because the formula and a test run this year have not been made public, but are leery.

“I have some real concerns about what they might ultimately come up with,” said Pat Rose, executive director of the Save the Manatee Club.

Resolving the uncertainty surrounding the annual count isn’t just academic. It could play a key role in decisions about slow-speed zones for boaters and about the manatee’s controversial status as an endangered species.

Last April, the Wildlife Service said sea cows had stabilized to the point that they could be upgraded to threatened on the federal list, though the agency has not recommended that step. In December, Florida’s wildlife commission postponed knocking the manatee down a notch and ordered another population study — but only after Gov. Charlie Crist echoed environmentalists’ concerns about uncertain assessments.

Scientists have developed a number of good measures of the health of regional populations — primarily, the survival rates of adults and calves that can be identified by signature prop scars. But they acknowledge they need more tools in the box.

“People want to know how many manatees there are. If you can’t go out and tell people we’ve got more manatees or less manatees, there is going to a be certain amount of skepticism about what we do,” said Dave Hankla, field supervisor for the U.S. Fish and Wildlife Service in Jacksonville. ‘It’s important that we get a more statistically valid count.”

A FLAWED SYSTEM

The aerial survey, used since 1991, doesn’t measure up.

Biologists must wait for a string of days both cold enough to corral the temperature-sensitive sea cows at power plants and other warm-water havens and clear enough to spot animals from small planes making one pass overhead. Water clarity can vary from crystal to coffee, and the flights don’t cover vast areas with major manatee populations elsewhere — notably, the dark waters of the Everglades and southwest Florida, where scientists have a poor notion of numbers.

The current count amounts to a snapshot, a minimum number that varies wildly according to weather. A record high count of 3,300 under ideal conditions in 2001, for instance, was preceded and followed by counts of 1,000-plus fewer animals.

Finding a better way has proved challenging.

“People have been trying to do this for 20 years and not been able to do it,” Edwards said. “People say you can do it for whales, why not manatees? Manatees are a different creature.’

The manatee, though large and slow-moving, lives anywhere from coastal mangrove islands to suburban canals, sometimes swimming at the surface, sometimes munching sea grass below.

To address the uncertainity, Edwards said the state wants to adopt statistical methods scientists commonly use to assess birds and other wildlife that range over areas too large to fully survey.

The new approach will rank spots in three categories. Power plants and other warm-water spots where large numbers are expected will get longer, more intensive looks — five flyovers, not the current one.

‘LIKELY,’ ‘UNLIKELY’

In a bigger change, planes also would circle three times over areas ranked as “likely” to hold manatees and once over areas “unlikely” to hold them — spots randomly selected.

A computer program would then factor in counts, along with variances to account for weather and water conditions, and generate a total population estimate.

Edwards thinks the result will be “statistically robust” and remove weather from the equation. “We won’t need that bitterly cold front to come through.”

Rose said the Manatee Club supports developing better assessments but questioned where a system developed for a small area, primarily around Tampa Bay power plants, would work elsewhere.

“It’s questionable whether they can do that within a reasonable degree of accuracy,” Rose said. “If you want to extrapolate to all of the state of Florida, there are too many variables and you’re compounding any errors you have in your methodology.”

Ted Forsgren, executive director of the Coastal Conservation Association-Florida, a recreational fishing group that petitioned the state to down-list the manatee, said there is already plenty of data showing the population recovering. He’s been pushing the state to complete a genetics sampling program to verify it.

“Like every three or five years, they change what they want to do,” he said.

Edwards said the state is awaiting results of a test run before deciding when to roll out the new method and whether to use it selectively before going statewide. She expects it will take some time for people to trust results.

“The biggest problem is it’s difficult to understand,” she said.

“It’s not straight-forward like the last one, fly around and count heads.”

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