Diamondback Terrapin

Samie Hermann & Mallory Munden

Introduction

What's your opinion on prohibition? That is an interesting topic of discussion to bring up at a party. The answers will undoubtedly vary and create some interesting dialogue. But if you ever go to a party with a diamondback terrapin, the answer will always be that they were absolutely in favor of prohibition.

Diamondback terrapin was the number one ingredient in turtle soup in the 19th century. The number two ingredient? Sherry. When prohibition started sherry production stopped, plummeting the turtle soup market and saving the species from extinction.

Once again the diamondback terrapin species is on the brink of extinction. This unique species is the only turtle that live in brackish water ecosystems along the Atlantic coast. Unfortunately, living in close proximity to humans has lead them to being reintroduced to the IUCN Red list.

Learn more about this keystone species and how they keep finding themselves dwindling on the brink of extension. There is also a lesson plan link at the bottom of this page that focuses on diamondback terrapins and the food web dynamics in the salt marsh ecosystem.

Taxonomy

S. (2015). [Diamondback terrapin color variation]. Retrieved from http://www.dnr.sc.gov/wildlife/diamondbackterrapin/index.html

Unique History

Diamondback terrapins have adapted to living in brackish or salt water but have been found in the Cape Fear River and other freshwater bodies as well. Seven subspecies of diamondback terrapins exist, all with varying coloration, spotting, and shell patterns both between subspecies and within a subspecies. In North Caroline, we see the Northern and the Carolina subspecies which intermingled when terrapins were released from commercial hatcheries, diluting the genes of local populations (Conant, 2011).

Scientific name

Malaclemys terrapin

Common names

Diamondback terrapin, diamondback turtle, terrapin, "wind turtle"

Full Taxonomy

Niche and Habitat

The diamondback terrapin is the only turtle in North America that lives in brackish water ecosystems. The terrapin can be found in a geographic region along the Atlantic coast from Cape Cod, Massachusetts to the Florida Keys and to the west along the Gulf coast from southwest Florida to Corpus Christi, Texas (Blanvillain et al., 2007). The brackish water that these terrapins call home can come in a variety of habitats such as salt marshes, estuaries, sounds, tidal rivers, and mangroves. In North Carolina, they are primarily found in salt marshes, basins, and sounds.

The diamondback terrapin is often an apex predator in the brackish ecosystem. As adults and sub-adults, they primarily feed on invertebrates such as crustaceans, bivalves and gastropods By foraging within vegetated habitats such as the salt marsh, the diamondback terrapins assist in ecological feedbacks, ranging from top-down control of grazers to dispersal of ingested seeds. This means that they are also a keystone predator (Woodland, Rowe, & Henry, 2017).

North Carolina distribution of Diamondback Terrapin. Obtained from: http://www.basic.ncsu.edu/ncgap/sppreport/araad06010.html

Distribution map from: http://explorer.natureserve.org/servlet/NatureServe?searchName=Malaclemys+terrapin

Evolutionary History

Since diamondback terrapins call such a dynamic habitat their home, they have adapted to tolerate many different abiotic variations in their ecosystem. The terrapins can handle extreme tidal and seasonal fluctuations such as varying temperatures, water levels, salinity and oxygen availability (Akins et al., 2014).

Diamondback terrapins are reptiles and therefore are cold-blooded animals. However, they have adapted to handle environmental temperature fluctuations very well. It has been documented that terrapins can survive 7 °C summer temperature variations and 9 °C winter temperature variations (including sub-zero temperatures), both within 24-h time periods (Akins et al., 2014). Adults hibernate during the winter. They submerge themselves in the mud of tidal creeks in deep water where the mud is less likely to freeze (NC Wildlife Resources). Although these turtle populations are on the decline, it is not due to their inability to adapt to an ever changing environment.

Environmental Impacts

Diamondback terrapins are a keystone species, a species that helps to regulate the salt marsh ecosystem. Terrapins eat marsh periwinkle snails (Littoraria irrorata) which graze on the marsh cordgrasses that dominate salt marshes along North Carolina's coast. Without these keystone predators to keep marsh periwinkle snail populations in check, entire marshes would perish (Bertness, 1984).

While terrapins spend much of their lives in the water, females nest on sandy sloping shores near marshes. This semi-aquatic lifestyle means that hatchlings and eggs allow energy transfer between the water and the land. Additionally, adult terrapins disperse the seeds of marine plants through their wastes (Browne, Kanonik, Vanek, Crown, & Burke, 2015).

V. (2014). [We estimated 900,000 blue crabs are killed each year in derelict pots in Virginia, which could mean a $300,000 potential annual economic loss to the fishery.]. Retrieved from https://response.restoration.noaa.gov/orr-weekly-report/may-16-2014/derelict-crab-traps-hitting-virginia-blue-crabs-hard.html
Kreen, J. (2012). [A small terrapin does not fit through an orange bycatch reduction device (BRD) on a crab pot]. Retrieved from https://vaseagrant.org/terrapin-files/

Conservation

Diamondback terrapins have a long history of facing human threats that have earned them both state and federal listing as a species of concern. In the 19th century their populations were decimated as they were harvested for turtle soup. Today, they face the threats of habitat destruction and road mortality as females cross streets to nest. The greatest threat that they face is bycatch, or being accidentally caught in pots targeting blue crabs (Grosse, n.d.).

Terrapins are attracted to the same bait as blue crabs. They crawl into the pots to dine on the food and get stuck. Unlike crabs, diamondback terrapins use lungs to breath. Once trapped in a crab pot they have a high mortality rate due to drowning. This issue is the greatest for male and juvenile terrapins which are smaller than adult female terrapins. A simple solution for keeping terrapins out of crab pots is to outfit them with a bycatch reduction device, a piece of plastic that is narrow enough to allow crabs to enter but not terrapins. These devices save turtles but do not impact the number of crabs or size of crabs captured (BRDs, n.d.).

Friends or Foes?

Diamondback terrapins live in an area that is teaming with life. Brackish water habitats like salt marshes are considered nursery grounds. Large adult fish come to these protected habitats to lay eggs. Organisms that live alongside terrapins are juvenile fish such as silversides, mud snails, mullet, and pompano. Blue crabs and marsh periwinkles are two of the terrapins' favorite meals.

The main competition diamondback terrapins face is dealing with anthropogenic impacts such as pollution, habitat destruction, and bycatch. Larger terrestrial mammals such as raccoons are also a concern for terrapins. Raccoons will prey on the adults, juveniles, and eggs of terrapins (US fish and Wildlife Services).

Videos

Web Resources

Herps of NC: Diamondback Terrapin

Herps of NC is an online field guide for reptiles and amphibians found in North Carolina. This page provides information about the appearance, range, reproduction, and behaviors of diamondback terrapins as well as additional photos.

Wildlife Resources Commission

This species profile from the NC Wildlife Resources Comission provides fast facts about diamondback terrapins as well as a full profile of habitat, habits, history, human interactions, and protections. The last page has a "Q&A-Resources for Teachers" section with questions for students to answer after reading the profile.

Diamondback Terrapin Information for Kids

This page is geared toward educating kids about diamondback terrapins. It describes their appearance, provides some general information about their lifestyle, and gives "fun facts".

Diamondback Terrapin Curriculum

If you want to bring diamondback terrapins into your classroom, this link provides a K-12 curriculum developed by educators. It includes background information, worksheets, and activities for each age range.

Adopt a Terrapin (Symbolic)

Through The Wetlands Institute in New Jersey, you can symbolically adopt a diamondback terrapin. Adoption packages start at $25 and the donations benefit conservation efforts and the group's headstart program for terrapins.

References

Bertness, M. (1984). Habitat and Community Modification by An Introduced Herbivorous Snail. Ecology, 65(2), 370-381. doi:10.2307/1941400

Browne, J. P., Kanonik, A., Vanek, J. P., Crown, C. A., & Burke, R. L. (2015). Quantifying New York's diamondback terrapin habitat. Northeastern Naturalist 22(3): 630-642.

BRDs: Terrapin Lifesavers! (n.d.). Retrieved from https://www.vims.edu/research/units/projects/terrapin_brds/_docs/terrapin_bdr_brochure.pdf

Conant, T. (2011). Diamondback Terrapin. Retrieved from https://www.ncpedia.org/wildlife/diamondback_terrapin

Grosse, A. M. (n.d.). Diamondback Terrapin (Malaclemys terrapin) (J. D. Wilson, Ed.). Retrieved from https://srelherp.uga.edu/turtles/malter.htm

Kreen, J. (2012). [A small terrapin does not fit through an orange bycatch reduction device (BRD) on a crab pot]. Retrieved from https://vaseagrant.org/terrapin-files/

Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2019. The Animal Diversity Web (online). Accessed at https://animaldiversity.org.

Blanvillain, G., Schwenter, J. A., Day, R. D., Point, D., & al, e. (2007). DIAMONDBACK TERRAPINS, MALACLEMYS TERRAPIN, AS A SENTINEL SPECIES FOR MONITORING MERCURY POLLUTION OF ESTUARINE SYSTEMS IN SOUTH CAROLINA AND GEORGIA, USA. Environmental Toxicology and Chemistry, 26(7), 1441-50.

Akins, C. D., Ruder, C. D., Price, S. J., Harden, L. A., Gibbons, J. W., & Dorcas, M. E. (2014). Factors affecting temperature variation and habitat use in free-ranging diamondback terrapins. Journal of Thermal Biology, 44, 63-69.

Woodland, R. J., Rowe, C. L., & Henry, P. F. P. (2017). Changes in habitat availability for multiple life stages of diamondback terrapins (malaclemys terrapin) in chesapeake bay in response to sea level rise. Estuaries and Coasts, 40(5), 1502-1515.

Marsh Ecosystem Food Web Lesson: Terrapin Focus

https://docs.google.com/document/d/1St4dUiehDn3JqgBbpYF7CnHKnVk01GM27ciHs1D9eM0/edit?usp=sharing

Google Sites

Report abuse