Local manatees got a little extra attention this week in the name of science.
The Sirenia Project, part of the US Geological Survey (USGS), with the assistance of myriad other agencies, carried out its annual health assessments on the Crystal River manatee population earlier in the week.
The good news: “They’re doing well,” said University of Florida veterinarian Dr. Craig Pelton.
The big mammals are spotted by volunteers as they leave the Three Sisters Springs area and swim under the King’s Bay bridge. Crews on boats guide them toward nets near the shore of Schatz Island (also called Paradise Point), which juts out into the bay and has several small, sandy beaches.
Once they’re in the nets, teams on the shore gently reel them in and lift them onto waiting, specially equipped boats. The captured creatures are motored over to another area of beach where measurements and samples are taken.
“We do body condition indices — we get the weight, the girth at the umbilicus, and the length,” explained Dr. Robert “Bob” Bonde, a lead research biologist with the USGS Wetland and Aquatic Research Center and Sirenia Project. “We can look at that and see how those trends are changing over time for the whole population, and those are the generalizations that the individuals teach us about the population as a whole.”
Veterinarians and biologists also use ultrasound equipment to measure how much blubber the manatees have.
“The reason we’re doing this study is to see how they look nutritionally, and so we want to know what their internal fat layers are,” Bonde said. “The ultrasound measures subcutaneous blubber, the fat layer underneath the skin. If it’s thick, that means there’s a lot of fat. If it’s thin, it means there’s less fat. So we can measure the thickness of that fat, and we can look at that and see how it’s changed over time.”
Bonde has been involved in manatee health assessments in Crystal River for decades, and chairs the Florida Manatee Genetics Research Working Group.
“It’s really important to understand the biology of manatees so that we can compare population yesterday, today, and tomorrow, into the next couple of decades when — who knows? Crystal River might have the population double again, and will there be carrying-capacity issues, habitat issues, associated with that — or even behavioral issues among the manatees,” Bonde continued. “We understand them biologically, we can predict how they’re going to respond to things — but it seems like every time they do, we learn something new.”
Over the years, about 263 manatees have been captured and studied. The scientists estimate the size of the group that migrates to the Crystal River area to be around 600.
Some manatees are repeat customers — one large male was captured Thursday for the fourth time. Catching the same manatee in multiple years provides valuable information about changes in the animal over time, which can indicate changes in their environment.
Those repeat catches indicate that the manatees aren’t learning to avoid the capture area or changing their behavior due to the health assessments, Bonde said.
“We keep them a short time,” he explained. “Even this animal we caught the fourth time — he’s not trying to avoid us, he’s just doing what manatees innately do, so we haven’t changed how he’s hardwired.”
Bonde explained that the geography of Schatz Island and the surrounding waterways provide a unique opportunity to capture manatees without disrupting normal behaviors.
“It’s perfect for this,” he said of the peninsula. “This is literally the safest place to catch manatees in Florida and probably in the world. We’re not going into the sanctuaries to catch them, we’re letting them swim out between areas. They’re choosing to leave the warm water, and we can take advantage of it by pulling them up onto the shore in a very safe way.”
“This is now the refuge’s property, which is beautiful,” he continued. “This Schatz Island — Paradise Point — is really the jewel. ... I think part of the concession was that they were to allow us to do these health checks, because the community realized how important they were, and the federal government does. And now everybody is buying into this because the common denominator isn’t taxes, it’s not greed — it’s a manatee.”
That community buy-in will continue to be important to preserve the progress that’s been made in increasing manatee numbers, Bonde said.
“We need to be diligent in our guard. ... The next 30 years is not going to be the same as the previous, because things change — that’s what we have to be aware of, we can’t just become complacent and let things go,” he said. “I’d be the first person to say ‘Don’t swim with manatees’ if I thought it was bad for them. I think people come out of the water better for the experience.
“I think they have a better appreciation for wildlife,” Bonde continued. “If we don’t tune in to that, if we ignore that, we’re going to cause problems societally with preservation of all of our wildlife.”