Plight of Florida’s Diamondback Terrapins (Malaclemys terrapin)

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Plight of Florida’s Diamondback Terrapins (Malaclemys terrapin)

Fri, 05/08/2020 - 07:26
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Article by Alice Mary Herden and Brittany Hall-Scharf, Marine Agent II UF/IFAS Extension Hernando

Hernando County has amazing wildlife, and our previous article, “Manatees of Hernando County” was a way to introduce residents to understand the species that thrive in our county and how to bolster their survival.  

The Diamondback Terrapin is one of Florida’s native freshwater turtles that live within the coastal marshes, tidal creeks, mangroves, and other brackish and estuarine habitats. Florida has five subspecies of the diamondback terrapin: the Mississippi Diamondback Terrapin (Malaclemys t. pileata), the Ornate Diamondback Terrapin (M. t. macrospilota), the Mangrove Diamondback Terrapin (M. t.rhizophorarum), the Eastern Florida Diamondback Terrapin (M. t. tequesta), and the Carolina Diamondback Terrapin (M. t. centrata),

Three of those species are only in Florida: Mangrove, Eastern Florida, and the Ornate Diamondback Terrapin. 

 

History

Diamondback Terrapins began experiencing a decline in population during the late 18th century and throughout the 19th century. Terrapin soup or stew was a delicacy (adding Sherry for flavor, a must-have in a turtle soup recipe) in the United States and European countries as well. Over 300,000 pounds of terrapin were harvested annually during that time period but decreased immensely after the early 1900s. 

During the Great Depression and Prohibition diamondback terrapin harvesting was reduced, which gave them time to rebound from being close to the state of extinction. 

 

Nesting

The nesting season for the diamondback terrapin occurs during late spring and summer. Females dig their nest in beaches, coastal dunes, and other areas that are in a combination of sandy soils and thinly dispersed vegetation. She can lay up to 18 eggs, and hatchlings will begin making their way to the coastal waters after their incubation period.

“Nesting season of a terrapin overlaps with the nesting season of sea turtles in Florida. Both terrapins and sea turtles come out of the water to nest (terrapins come out of the brackish water where sea turtles come from offshore/saltwater) on coastal beaches in the sand where there is little to no vegetation. Because diamondback terrapins are coastal turtles, they are often confused with or mistaken to be a sea turtle,” explained Brittany Hall-Scharf, Marine Agent II UF/IFAS Extension Hernando.

Three species of sea turtles do nest regularly in Florida; Green, Loggerhead, and the Leatherback. Hernando County is not a sea turtle nesting beach, but is an in-water nursery habitat for juvenile green sea turtles, loggerheads, and Kemp’s Ridleys. 

“One way we can identify if it is a sea turtle nest or a terrapin nest is by the size of the tracks and nest. Mature sea turtles are much larger than terrapins and will create a much wider trail from the water to the nest. Additionally, the different species of sea turtles can be identified by the “tracks” that they make with their flippers as they push themselves up the beach to dig the nest,” Hall-Scharf said.

 

FUN FACTS ABOUT THE DIAMONDBACK TERRAPIN

  • Diamondback terrapins have webbed feet with distinct “claws”, whereas sea turtles have paddle-like flippers.
  • To get all those periwinkle snails, they use their strong, bony jaws to crush their shells for a yummy and nutritious snack.

 

She explained further, “I often receive calls about sea turtles nesting; however, these have all been diamondback terrapins nesting.” 

Hall-Scharf asks residents to send her photos of the turtle and tracks so she can identify it.  She suggests:

  1. While keeping a safe distance, take a photo of the turtle and, if possible, include a picture of the turtle tracks.
  2. Send the photo to Brittany Scharf at [email protected] 

Diamondback terrapins face many challenges during nesting season. There is around a 20% survival rate during nesting to the hatching stages because they are naturally preyed upon by raccoons, birds, and other wildlife predators for their survival. 

The females instinctively seek coastal beaches, and sometimes it is the same location where they hatched, others may have to travel a great distance to reach their nesting habitat. Some will travel safely, as others would need to cross low to high traffic roads. This path is also the same route the hatchlings will follow as well.

Unfortunately, road mortality numbers are elevating as the Florida population increases. The high demand for waterfront/beachfront property takes away their only natural habitat.    

 

Diamondback Terrapin Research

According to the Red List of Threatened Species Report from the International Union for Conservation of Nature (IUCN),  little information can be found about terrapin populations along the Gulf Coast. Historical accounts suggest large populations once existed in this part of the range. Still, overexploitation has reduced those populations which are slow to recover in the face of heavy crabbing pressure. 

Since 1995 USGS research ecologist Kristen Hart has conducted research on rare, threatened, endangered, and invasive species of reptiles, including Diamondback terrapins. 

For the last twenty years, part of Hart and her staff’s dissertation research has focused on a capture-mark-recapture process solely of the mangrove terrapins. The research has taken place in South Florida since 2001. With a multitude of supplies and equipment, they wandered into the depths of the mangrove forest that surrounded the Florida Everglades. Documentation about the mangrove terrapins was slim, and this allowed Hart to conduct thorough research about this subspecies. 

Hart and her research team are completing a twenty-year analysis. Even though this research is ongoing, their conclusion is not what they expected.  

“Unfortunately, we have seen a decline in the last three sampling years, which is really alarming,” Hart said. “So, we are trying to figure out why.”

The process in which individuals are added to a population is called recruitment. Terrapins must survive many challenges, such as predation and other environmental factors, to eventually reach maturity and reproduce. Variation in recruitment is natural; however, poor or low recruitment for extended periods of time can be devastating to a population of organisms, such as terrapins.  

“Maybe from 2009 through 2014, I was just experiencing a pulse of good recruitment in the sampled population. We had recaptures and new captures and young animals coming into the population, and then it just started declining,” Hart said. “Something real is going on.”

Because hurricanes are episodic events that would affect a single nesting season, researchers expect to see some sort of rebound in the population numbers of terrapins in the following years. However, this has not been the case. Thus, researchers hypothesize that this decline has something to do with either the terrapins moving to a different location or recruitment dropped off or some combination of the two. They could also have been intentionally harvested… “That’s a really hard scenario to swallow,” Hart said.

In an upcoming project, Kristen’s research team is incorporating satellite telemetry to see the extent of movement of an individual terrapin. Transmitters are safely placed on the back of a terrapin’s shell to collect movement data. Researchers can monitor and track terrapin movements to learn more about their habitat use in specific locations.  

The mangrove creeks in the southwest coastal areas of the Everglades are dense and thread into the deep, dense mangrove forests, which can make it difficult for boats to access. Bringing satellite telemetry accessibility will ensure accurate data and find answers to those uncertainties of their population. 

“The numbers have been steadily declining...very concerning,” said Hart.

 

Diamondback Terrapin Conservation Concerns

George L. Heinrich is a field biologist and environmental educator specializing in Florida reptiles. His company, Heinrich Ecological Services, is based in St. Petersburg, Florida, and conducts wildlife surveys and research, natural history programming, and nature-based tours.

Heinrich was one of the founders of the Florida Turtle Conservation Trust incorporated in 1999 to address the conservation needs of Florida turtles with the emphasis on non-marine species. 

Diamondback terrapins are a key element in the coastal ecosystems and are believed to help maintain an ecological balance within these coastal habitats.

“Diamondback terrapins are molluscivores; they eat crabs and snails. And one of the snails they eat is a little marsh periwinkle, this little snail eats coastal plants,” Heinrich said. “We believe that diamondback terrapins help control marsh periwinkle populations.”

“We are the most turtle-rich country in the world; Mexico being number two. We have incredible species diversity, and because of our habitat diversity in this country. The threat to turtles in the US is a long list. Poaching, problems with fishery gear, road mortality, and disease, there are just a number of different threats,” Heinrich added. 

The original work of Roger Wood Pb.D Director of Research & Conservation, The Wetlands Institute and Professor of Zoology, Richard Stockton College of New Jersey, put in motion the bycatch reduction device. 

“The diamondback terrapins are drawn into blue crab traps by the bait that the crabbers use to attract the blue crabs,” Heinrich said.

Terrapins need to come up for air, and while they are drawn to the bait inside the crab pots, terrapins will go through the funnel opening and are unable to get out, resulting in thousands of terrapins drowning.   

“Our eventual goal is to see a number of bycatch reduction devices regulations range-wide,” Heinrich said.  

It’s a simple device, actually. 

“These are small little plastic devices that can be attached to the inside of each funnel and exclude the terrapins. So, it prevents them from going into the traps. It mostly works for the female terrapins because they are taller,” Heinrich said.

The width and height of the bycatch reduction device (BRD) may help save more of the female terrapins but may exclude a higher survival rate for juvenile or adult males. 

After a study conducted in the early to mid-2000s around the state, the results were extremely satisfactory.

“We tested 15 control and 15 experimental and came up with... that you can prevent 73% of the terrapins from drowning by using these devices,” Heinrich said. “They are really inexpensive, readily available, and easy to attach.”

“My partner, Dr. Joseph Butler and I approached the Fish and Wildlife Conservation Commission to initiate some discussions about the possibility of having a regulatory change requiring BRD’s on both commercial and recreational pots in Florida waters. At that time in the early 2000’s we were told that there was no data suggesting that terrapins drowned in crab pots in Florida,” Heinrich said. “So, funded by grants we spent four summers testing this throughout Florida from the panhandle to the Florida Keys at eight different locations. We finally got the information we needed and submitted a report to the Wildlife Commission in 2006, we then published a paper in a pre-review journal in 2007 the following year.”

The decline in turtle meat did help the population of the terrapins to recover; however, two other conversation concerns are on the rise. The issue of illegal poaching and crab traps mortality.

“There are regulations protecting turtles in Florida from commercial exploitation, but poaching is a huge issue,” Heinrich said. “The bottom line is wild turtles belong in the wild and not in a 10-gallon aquarium or on dinner plates.” 

Elise Bennett is a staff attorney for the Center for Biological Diversity, a non-profit organization. Her job is mainly the protection of reptiles and amphibians in the Southeastern United States. 

“We are working on both of those aspects of protection; commercial exploration and mortality in crab pots. When it comes to the trapping of turtles, the Center has been working to close down all commercial turtle trapping in the United States. As you can imagine that is a very big endeavor,” Bennett said. “We are lucky in Florida that we don’t have commercial turtle trapping anymore. The state banned (commercial trapping) back in 2009, and that’s really wonderful.”

As some of Florida’s neighboring states have not implemented strong laws protecting wild turtles from trapping, Bennett and others noticed a correlating rise in illegal practices, including smuggling and illegal trapping.

“Unfortunately, while we are working with strong protections here in our state, part of our protection here depends on what our neighboring states do as well. So certainly, weaker laws in other states---which can provide cover for illegal operations---might contribute to some of the instances of poaching that we’ve seen for turtles here in our state even though we have some pretty strong commercial trapping laws.”

“I think we have been trying to really highlight that there are many threats for these terrapins like habitat loss, sea-level rise, and poaching where there just aren’t easy solutions. They either take political will, significant enforcement work or changes in our behavior toward wildlife and their habitat. But preventing terrapins from drowning in traps is something we can do fairly easily,” Bennett said referring to bycatch reduction devices. “While that is just a small part of the conservation picture, the reason why these devices are important is, they give these terrapins a reprieve from at least one of those threats...the threat of drowning in a trap,” added Bennett.

The petition submitted to the Florida Fish and Wildlife Conservation Commission on January 2020--Petition To Protect Diamondback Terrapins (Malaclemys Terrapin) From Mortality In Blue Crab Pots By Requiring Bycatch Reduction Devices In Recreational And Commercial Fisheries can be read online here: https://www.biologicaldiversity.org/species/reptiles/pdfs/Petition-Florida-DiamondbackTerrapin-BRD-2020-01-28.pdf

“An important thing to look at with the petition is that it's part of a bigger conservation picture. We can really make a difference for terrapins while not having a significant impact on the community who does the crab trapping,” Bennett said. “It is particularly important here because we have so many linear miles of coast where terrapins can live. We have five of the seven subspecies here, three of which are only in the state of Florida. And so, there are a lot of really good reasons to take this common-sense conservation tool and to put it to use.” 

 

What we can do to help

The COVID-19 virus may deter funding reaching non-profit conservation organizations; however, this may be the perfect storm to reintroduce conservation awareness about the diamondback terrapins.

Observation can help researchers….  

“In Florida it is illegal to trap turtles to commercially sell them,” Bennett said. “If you see someone with a boat full of turtles or someone out pulling out traps full of turtles, that would be a reason to call FWC for sure.”

Wildlife Hotline: Call: 888-404-FWCC (3922) Website: https://myfwc.com/contact/wildlife-alert/

Hernando County Coastal lands are essential for wildlife diversity, from birds, sharks, and sea turtles. 

To learn more about coastal wildlife, check out the series of educational seminars; Bite-sized Science by Brittany Hall-Scharf. For more information, please visit this website: http://sfyl.ifas.ufl.edu/hernando/

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