Northern Diamondback Terrapin … Delaware Nature 101

Northern Diamondback Terrapin …

Malaclemys Malaclemys

Status: Species of Special Concern  

 Delaware Nature 101 … Kara Okonewski

The Northern Diamondback Terrapin is one of Delaware’s most unique turtles. This species is native to our waters and depends on our beaches for nesting. Delaware has 15 different species of turtle but only one like this. Diamondback terrapins are not pond turtles but they are not sea turtles, either. The diamondback terrapin lives in brackish water. Brackish water isn’t fresh water, but it doesn’t have the full salt levels of the ocean, it is right in between. So if you want to find a diamondback terrapin, you have to look to the bays and estuaries. Bombay hook, Port Mahon and Kitts Hummock are just some of the places you can find terrapins.

Northern Diamondback Terrapin Nesting season at Port Mahon

My experience with diamondback terrapins goes back to six years ago during a fishing outing. Among the waves were triangular floating rocks bobbing in the water. A closer look revealed those floating triangular rocks were actually the heads of terrapins. Like an ice burg, terrapins show very little of themselves above the water while the rest of their body hides below. I started to return to my fishing spot, but not to fish. Instead I would count the turtle heads. Six years ago I could count 300-400 turtles in the water. One day I watched a female dance in the sand as she was digging a hole to lay her eggs. There is something about a turtle digging in the sand and laying eggs on the beach that is such an incredible experience. And it is an experience you can have right here in Delaware.

Diamond Back Terrapin
Diamondback Terrapin

Fast forward to today and now I am lucky to see half the number of terrapins bobbing in the water. Still I go during nesting season to check population numbers, report nesting females, remove females from the road, and pull trapped terrapins from the rip-rap. The thousands of feet of boulders and piled rocks make up the rip-rap that is put into place to reduce erosion of the road at Port Mahon. However, the history of human versus nature says nature always wins and the road continues to wash out.

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There are several subspecies of diamondback terrapins. Here in Delaware, we have the northern subspecies that comes in a collection of colors from dark gray and black to a golden carapace (top shell) with black designs. The terrapins live 25-40 years and females are larger than males. To be fair, she does have to carry eggs. She can lay up to 15 eggs at a time. She can also lay several times in a season. One of the really cool things about turtle eggs is that the nests are temperature-dependent sex determination. This means that the temperature of the nest will determine if the turtles will be male or female. Lower temperature nests produce males. Warmer nests produce females.


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The “beaches” at Port Mahon are rock walls that make it difficult for terrapins to cross on to land to lay eggs

While there is a lot of information on terrapins, what you need to know is why you need to care about them. The diet of the Northern Diamondback Terrapin consists of small marine life like crabs, mollusks and snails. Snails can do a lot of damage to your fishing spots. When snail populations go without predation, populations explodes and the algae and marine plant life that produce oxygen for fish can be wiped out. When an area in the water has no oxygen, it has no fish. Therefore, if you enjoy fishing in Delaware waters, you need to thank a diamondback terrapin.

If you are interested in learning more about diamondback terrapins, I recommend the book “Diamonds in the Marsh” by Barbara Brennessel. If you are interested in helping Delaware terrapins, contact Dr. Nathan Nazdrowicz at Feel like you want to do even more? Consider joining the Diamondback Terrapin Working group. You can check them out at

Kara Okonewski … Delaware Nature 101

Delaware Nature 101 is committed to bringing you education about local plant and wildlife as well as local environmental news and events. This resource was started by Kara Okonewski, former Delaware State Park Naturalist and informal environmental educator. She has been studying, teaching and interacting with local Delaware wildlife for six years. Originally from a big city in Michigan, Kara is loving her Delaware adventures, from rescuing a harbor seal to coming face-to-face with a copperhead snake, recording nesting turtles to tagging monarch butterflies. Now you can follow the adventures and learn about Delaware nature on Facebook at Delaware Nature 101.

Delaware Nature 101

Kara Okonewski

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