DESANTISLAND
Manatees might be relatively recent arrivals to Florida, USF study finds
Research suggests they may not have become Sunshine State fixtures until after Europeans colonization began
image:
Manatees and tourists crowd the Three Sisters Spring at Crystal River, Florida, on a cold morning.
view moreCredit: Thomas J. Pluckhahn
TAMPA, Fla. (Nov. 20, 2024) – New research suggests that while manatees are an indelible part of Florida’s seascape, they might also be relatively new residents in the Sunshine State.
The findings are detailed in a study co-authored by University of South Florida anthropologist Thomas Pluckhahn and David Thulman, an archaeology professor at George Washington University, and scheduled to publish in PLOS ONE on Nov. 20 at 2 p.m. The embargo will lift at that time.
The paper, “Historical Ecology Reveals the ‘Surprising’ Direction and Extent of Shifting Baselines for the Florida Manatee,” (link will be live when the embargo lifts) concludes that for centuries, manatees might have occasionally swum in Florida waters, but possibly more so as tourists than residents, staying for a short visit before returning to their Caribbean homes like Cuba.
It is possible that they did not become Florida fixtures until after Europeans colonized the future state, the research suggests.
In Tampa Bay, the manatee population wasn’t deemed plentiful until the 1950s. And, in a twist of irony, manatees’ Florida residency was fueled by the same factor that now threatens their existence – climate change.
“It is commonly assumed that Florida manatee populations were once larger than they are today,” Pluckhahn said. “Many will find the results surprising, not only because it contradicts this assumption but also because it indicates the complexity of changes that have taken place in the Anthropocene,” the current period during which human activity has most-influenced climate and the environment.
The motivation for the research was fueled by Pluckhahn’s realization that there was a lack of evidence pointing to a large population of manatees in Florida’s pre-colonial era.
“Based on my own experience and talking to other archaeologists, we agreed there was a rarity of manatee bones on archaeological sites,” said Pluckhahn, who has been a part of archaeological excavations in the Tampa Bay area since 2008. “It was particularly impressive to me because I’ve worked at Crystal River, which is an epicenter for manatees. We became more curious and decided to do a comprehensive review of archaeological and archival sources.”
That analysis involved reviewing around 70 archaeological reports that detailed the systematic collection and analysis of nearly two million animal bones. Essentially none of them were manatee.
An expanded review of other excavations did find a dozen reports of manatee bones that had been modified into tools or ornaments, but that is not enough to proclaim that the sea mammals had a large pre-colonial Florida population.
The paper hypothesizes that it is possible that manatees were not present at all in precolonial Florida and the tools and ornaments arrived here via Native Americans trading with those from the Caribbean.
“The problem with that is people have been looking for proof of contact between Florida and the Caribbean during the pre-colonial era for a long time and haven’t been able to nail it down,” Pluckhahn said.
Or, perhaps, manatees were in abundance but there is a lack of bones at excavation sites because the mammals were not hunted. However, manatees are not described in accounts of expeditions by explorers who landed in Tampa Bay in between 1528 and 1595.
The most logical hypothesis is that manatees were then later “present only in very low numbers in Florida as occasional visitors from the Caribbean and then settled here permanently,” Pluckhahn said.
The first reliable written narratives of manatees in Florida date to the period of British rule in the late 1700s, the paper says. But, even then, sightings were rare.
Beginning in the 1920s and 1930s, the print media began writing of routine sightings in Miami and St. Augustine, and by the mid-1950s “there were reports that manatees were ‘becoming more plentiful’ in Tampa Bay and a few were said to have become permanent residents’ of Crystal River,” the paper says.
What changed?
In short, Florida’s waters were once too frigid for manatees due to what is known as the Little Ace Age, a period of intermittent cooling beginning in the 1200s and lasting through the 1800s.
The authors suggest that as the effects of the Little Ice Age faded, manatees began extending their range northward to Florida. Warming waters caused by the advancements of humans subsequently helped convince the manatees to stay and breed.
Newspaper accounts from the late 1800s and early 1900s describe manatee sightings in warm water refuges like yacht basins and canals harbors, and later in areas near power plants.
The state’s current manatee population is between 8,350–11,730, according to the Florida Fish and Wildlife Conservation Commission. That’s enough that, in 2017, they were reclassified from endangered to threatened under the federal Endangered Species Act.
But manmade climate change is still a threat to Florida manatees, Pluckhahn said. “Pollution is killing a lot of the sea grass that the manatees eat. Plus, as we wean ourselves off fossil fuels and shut down power plants, we are taking away a refuge from them.”
Fossilized bones of Sirenians (the order that includes past and present manatee species), such as these examples from a site in Tampa Bay, are not uncommon on archaeological sites in Florida. But unfossilized bones of more recent manatees (from the last 12,000 years) are quite rare — suggesting sea cows may have been infrequent visitors to the Florida peninsula before the modern era.
Credit
Thomas J. Pluckhahn
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Journal
PLOS ONE
Method of Research
Observational study
Subject of Research
Animals
Article Title
Historical Ecology Reveals the ‘Surprising’ Direction and Extent of Shifting Baselines for the Florida Manatee
Article Publication Date
20-Nov-2024
Scientists develop groundbreaking method for detecting DNA of invasive snakes in Florida
University of Florida
image:
Melissa Miller in the Florida Everglades taking measurements of an invasive species.
view moreCredit: UF/IFAS Croc Docs
Scientists at the University of Florida have developed a pioneering tool to bolster Florida’s defenses against invasive species: a DNA-based environmental monitoring test that can pinpoint where they’ve been, aiding eradication efforts.
Once a nonnative species gets into an environment, it is often too late to get rid of it, and the focus shifts to containment or long-term management. Both approaches come with heavy costs concerning native wildlife and funding, explained Melissa Miller, lead author on the study and an invasion ecologist at the UF/IFAS Fort Lauderdale Research and Education Center (UF/IFAS FLREC).
“We hope this novel eDNA sampling tool we have designed will help increase efficiency in invasive species management, allowing for early detection and rapid removal of nonnative species,” she said.
Known as a tetraplex digital PCR assay, this method of testing allows researchers to use water or soil samples for rapid and precise identification of Burmese pythons, northern African pythons, boa constrictors and rainbow boas from environmental DNA -- which scientists refer to as eDNA -- collected in the wild. The test can identify four invasive snake species simultaneously.
That eDNA refers to genetic material shed by organisms into their surroundings. Published in the journal of Ecology and Evolution, scientists at UF’s Institute of Food and Agricultural Sciences (UF/IFAS) tout this as a significant advancement in detecting invasive snakes and a strategic tool for protecting Florida’s ecosystems.
“Cryptic species, like most snakes, are problematic when introduced outside of their range, as detectability is low, even in high densities. With this new method, we increase our ability to detect these cryptic species tremendously, no matter how many there are,” said Sergio Balaguera-Reina, co-author and research assistant scientist at the UF/IFAS FLREC.
Florida is home to over 500 nonnative species, with reptiles leading the way. More than 50 nonnative reptile species are now established across the state, with many posing severe threats to agriculture, native ecosystems, public safety and the state’s economy.
Current monitoring methods depend on visual surveys by scientists, which often fail to detect invasive constrictors because they’re elusive and cryptic. Traditional survey techniques are estimated to identify less than 5% of Burmese pythons. In contrast, the newly developed tetraplex assay by UF/IFAS scientists can identify DNA traces of these snakes even weeks after they have left an area.
This breakthrough offers wildlife managers a crucial tool to verify the presence of these hidden species and assess the success of removal efforts. “While eDNA sampling has been applied to detect non-native wildlife, the benefit of our methodology is that we can now sample for numerous target species within a single sample. This can aid natural resource managers by reducing costs required to survey for non-native species in multi-invaded ecosystems,” Miller said.
“With the high accuracy and specificity of this testing for detecting invasive constrictor snakes, resource managers can implement effective management strategies, such as removal efforts, quickly and with confidence,” Miller said.
The test was designed to operate seamlessly in Florida’s varied and challenging environments, from dense Everglades habitats to urban areas where non-native constrictors are now found. With this DNA-based approach, wildlife managers can implement programs that monitor multiple species, prioritize response efforts and ultimately mitigate the ecological impacts of these snakes on Florida’s ecosystems and Everglades restoration efforts.
Developing this tool required considerable work and significant technical advancements to ensure each target snake species’ DNA is precisely identified.
“The initial stage was designing the molecular test, which is essentially four tests in one,” said Brian Bahder, a senior author who developed the eDNA methodology and an associate professor of vector entomology at UF/IFAS FLREC. “Each test is specific to a different snake species and was designed to detect DNA from the Burmese python, northern African rock python, rainbow boa and boa constrictor, ensuring no cross-detection among species.”
Bahder, whose expertise traditionally involves detecting lethal bronzing in palm trees, explained that the fundamental process of molecular testing is similar across different organisms, with the main difference being the DNA sequence. This makes many of the techniques easily transferable.
Once the researchers successfully got the molecular test working, they conducted controlled experiments using known concentrations of DNA placed in water. They then used a vacuum pump to concentrate the DNA on a filter, which they tested to confirm that they could extract DNA from the samples and obtain accurate results.
Following this, they conducted an experiment by placing a Burmese python in water and taking water samples at different time intervals to demonstrate the method’s effectiveness. The data estimated the amount of snake DNA present in the water if sampled nearby. A field experiment also showed that snake DNA could be detected in soil where a snake had been resting up to two weeks after its removal.
“These concentration estimates are the first steps in a larger monitoring effort, with further experimentation needed to determine the effects of time, distance and environmental factors on DNA detection rates,” said Bahder. “Ultimately, this technology will be used to monitor and locate these invasive snakes, thereby validating removal efforts.”
The new assay aligns with ongoing efforts by state and federal agencies, which have invested more than $10 million from 2004 to 2021 to manage the Burmese pythons alone.
“Successful detection and monitoring programs for invasive wildlife hinge on rapid detection and accurate identification of nonnative species,” said Miller.
The UF team plans to explore the tool’s potential further, by expanding the assay to include additional invasive species and applications for monitoring ecological restoration outcomes.
“There are two important next steps for harnessing the power of this eDNA analysis. First, we plan on adding additional species that can be identified using the tetraplex digital PCR assay, especially fish such as Asian swamp eels and bullseye snakeheads,” said Frank Mazzotti, co-author and professor of wildlife ecology at UF/IFAS FLREC. “Second, to fully take advantage of this new methodology, we plan on implementing a regional multi-species sampling network with the purpose of early detection for rapid response to new invasions and evaluating success of removal efforts on existing invasions in the Comprehensive Everglades Restoration Plan footprint.”
A Burmese python is submerged for eDNA analysis
Credit
Analise Fussell
Brian Bahder in the lab extracting samples
Credit
UF/IFAS Tyler Jones
Article Title
Development of a Tetraplex Digital PCR Assay for the Detection of Invasive Snake Species in Florida, USA
Article Publication Date
20-Nov-2024
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