The last intact predator-prey interaction can be found in Southwest Florida. Warnell Researchers had front-row seats. It wasn’t the howls of hurricane Irma that put Heather Abernathy on edge while stationed in a remote part of Southwest Florida doing field work. Nor was it hunkering down under a tarp during an afternoon thunderstorm or keeping an eye out for water snakes during what was one of the wettest seasons the state has seen in recent memory. Rather, it was the bobcats that gave her pause. “They are competing for essentially the same dry land as panthers, and panthers are a lot bigger than them. So, I think they compensate by being more aggressive,” said Abernathy (BS ’13, MS ’17) who, as a doctoral student at Virginia Tech, was part of a field crew stationed in South Florida during a 3-year study of deer mortality in and around the Florida Panther National Wildlife Refuge and Big Cypress National Preserve. The goal of the study, funded by the Florida Fish and Wildlife Conservation Commission, was to understand how predators, hunting and changes to the area’s waterflows are affecting the population of deer. The study was published last year in the Journal of Applied Ecology. Turns out, said Richard Chandler, study co-author and associate professor at the Warnell School of Forestry and Natural Resources, the number of deer killed by Florida panthers was very high compared to previous studies. Of the 241 deer captured and fitted with GPS collars during the study, 96 were killed by Florida panthers. This is a shift from the 1990s, when few deer were killed by panthers and the main sources of mortality came from bobcats and hunter harvest. In the new study, only seven deer were killed by bobcats, and only one deer was harvested by hunters. “Panther predation went from a very small source of mortality to now being the dominant source of mortality for deer,” Chandler said. To learn this, crews had to navigate swamps, scrub, violent thunderstorms and even a hurricane. While coastal Florida is considered a vacation destination, the inland pockets of South Florida are wild and untamed. Never a dull moment Field work of any kind comes with its own set of challenges. In South Florida, researchers grappled with extreme weather—the study was conducted year-round, through the sweltering heat of summer and perils of violent afternoon thunderstorms and hurricane seasons—along with a variety of unusually dangerous animals that live in the humid, flood-prone area. Plus, they needed to navigate to far corners of a remote, swampy area. Mike Cherry (BSFR ’10, PHD ’14), who coordinated the project as a postdoctoral researcher, said these challenges created the ideal environment to study wildlife in an untamed system. “In the Southeast, it’s the last intact predator-prey interaction,” said Cherry, who is now the Stuart W. Stedman Chair for White-tailed Deer Research at Texas A&M University Kingsville. At the time, he was studying coyote-deer interactions with the Jones Center for Ecological Research, so the panther project was a natural extension of his expertise. “So, to me, it was like going to the last great wilderness of the Southeast with a true apex obligate-carnivore, predator-prey dynamic,” he added. “South Florida was really exciting for also studying disturbance. You had this big predator and fire and flooding, and I was very excited to get down there—there’s very few places east of the Mississippi like that country.” The crew relied on local biologists and agencies to prepare. Abernathy said she also read blogs about hiking through the wilds of Florida and studied venomous snakes. She and others were certified in wilderness first aid. Technicians left their housing on the panther preserve in pairs for safety. To conduct the study, they first needed to capture deer and fit them with GPS collars. This required flying over the area in a helicopter and using nets to catch groups of deer at a time. Post-doctoral researchers and graduate students flew alongside and hopped out when a herd was netted; each deer would get a GPS collar and ear tags. The teams also installed 160 wildlife cameras around the study area, which needed to be checked every three weeks to replace the memory cards and batteries. If a deer was killed, the GPS collar would send out a distress signal. That’s when researchers sprang into action. “Our field crews would head out within 24 hours to find that deer, which you’d imagine is not an easy task in these swamps and hammocks and everything,” said Chandler. “They were truly remarkable—it’s just truly incredible, the work that went into this.” The team had a process: First locate the head and remove the collar. Then look for evidence of how it died, such as patterns of bite marks or bruising. Everything is photographed and measured. Then the team looks for additional cache piles—Florida panthers have a penchant for removing internal organs and burying them separately, in case another predator stumbles upon their meal before they’re finished. Before carefully re-burying the carcass before leaving, they remove the deer’s teeth and jawbone to estimate its age. “Think of it as ‘Wildlife CSI.’ We were essentially detectives trying to determine where the animal was killed by the panther, and essentially dragged by the panther and buried,” said Abernathy. A few times the team took the carcass back to be examined in a lab—for example, if there was evidence of poaching. But more often than not, the death was due to a panther and the carcass would not be removed. Before leaving, they also identified and documented the kill site and set up a camera to capture activity after they left. That’s because while all this is happening, a panther is watching and waiting. After the crew left, cameras recorded images of panthers returning for their food. A changing landscape Listed as endangered by the U.S. Fish and Wildlife Service, the Florida panther represents the only population of pumas in the eastern United States. Genetic restoration efforts began in the mid-1990s in response to low population and inbreeding concerns, and the panther population has increased substantially over the last 20 years, from 20 to 30 in the 1990s up to 200 in 2017. The increase in panther predation on deer comes amid a larger shift taking place across the landscape. The Comprehensive Everglades Restoration Plan now underway will restore natural waterflows and benefit many aspects of the ecosystem, but it may also flood land that was already marginally hospitable to deer. The study found that deep water had a negative effect on female deer survival, although no cases of drowning were recorded. Amid the landscape changes, Florida wildlife officials strive to maintain sustainable deer hunting opportunities. As in other parts of the country, there is a long, culturally important tradition of deer hunting in South Florida, and hunters provide a large amount of the funding for wildlife conservation in the state. Agencies must balance hunting opportunities with other public interests and panther conservation efforts. “They don’t want to shut down hunting opportunities, but they don’t want harvest to be so high that it suppresses the prey population and keeps the panthers from recovering,” said Chandler. “That’s a big challenge, and it’s not easy. Our results emphasize how difficult that will be. Future work is needed to determine if additional habitat management can bolster the deer population for the benefit of panthers and people.” The study is part of a larger set of data collected by the Warnell researchers that will help inform the state agency’s next steps. More than one predator These days, Abernathy is a postdoctoral researcher at the University of Wyoming investigating deer and elk ecology. Learning how deer eked out a living in Southwest Florida’s unforgiving landscape is helping her current work. But after spending a year in Southwest Florida, she never saw a panther in person—they are notoriously quiet and secretive. “Often, you’d never have any indication that they were nearby,” she said. “I’ve heard some stories from my colleagues that they could hear the cat shifting around in the vegetation, but often you wouldn’t hear that.” Cherry noted a few encounters, always from a distance. Another student was at a kill site when the panther, which had climbed a tree during the investigation, fell out and bounded away. Ultimately it wasn’t the nearby panthers that put the researchers on alert. Rather, it was other predators in the swamp—alligators, snakes and bobcats, for example—that stoked concerns. Man-made risks also abounded—Cherry notes perils with ATVs on uneven ground, or the dangers of flying in helicopters. Abernathy recalled a close encounter with a bobcat that left her a bit shaken. It was during the wet season, when the berries of the native saw palmettos begin to ferment on the plants. Deer eat them and get a bit tipsy as a result; sometimes, they’ll sit for hours, waiting for the effects to fade. This is when the GPS collar sends off a false alarm. Chasing down one such call, Abernathy and her colleague arrived on a small patch of land in a sea of glades and swampy grasses. “I’m on my hands and knees looking for any sign of an animal or a cache pile, and all of a sudden I hear a low growl,” she said. “I have bear spray and (my colleague) has a machete, but the bobcat could be anywhere. We start backing up slowly with our backs to each other, and as soon as we get to the edge where the deep water is, I jumped, because I know this animal isn’t going to jump into the water.” Given the options of an alligator in the water or a bobcat on land, Abernathy said she’d rather face an alligator. Cherry, on the other hand, said snakes and alligators put him a bit more on edge. A couple times, his crew came upon a GPS collar floating in the water. “You definitely get a sense of wildness when you’re in a system that has predators that can kill you,” he added. But while the job had plenty of heart-thumping moments, it also had its moment of pure beauty. Working in that environment, the researchers said, was a once-in-a-lifetime opportunity. “Just walking upon things you never see, like more than 50 ibis right as sunup was happening—it was just incredibly beautiful,” Abernathy added. “And I saw a very secretive marsh bird, an eastern bittern. ... Just seeing animals in their natural habitat, it was really a gift.” Previous page: Researchers used nets to capture and tag deer as part of the study. Above: A researcher picks up hobbles after releasing a deer that has been fitted with a GPS collar. Left: Deer in Southwest Florida have adapted to the harsh surroundings. Throughout the year they deal with flooding and fierce storms in addition to a variety of predators not found elsewhere in North America. Researchers said despite the harsh conditions, Southwest Florida offered dazzling scenery, such as this sunset.
