Diamondback Terrapin
Nesting Ecology Activity

Egg, hatchling and juvenile
survivorship




Activity developed through the Marine Academy of
Technology and Environmental Science in Manahawkin.
New Jersey. Produced through students in “Project
Terrapin” with the generous support of the following
supporters.





Terrapin Egg and Juvenile Survivorship Activity
1
Diamondback Terrapin Egg and Juvenile Survivorship Activity

Introduction for the Educator (100 egg activity)

Diamondback terrapins are turtles that inhabit estuaries along the east and Gulf coasts of
the United States. They range from Cape Cod, Massachusetts to northern Mexico.
Terrapins were harvested in the late 1800’s through the early 1900’s as a food source
with a high demand leading to reductions in their populations across their range. In the
1930’s, terrapins became less desirable food sources and populations increased in areas
with good habitat, but not much is known about populations in certain areas. What make
terrapins so interesting are their markings, which are highly variable and prominent.
Reasons for the variation include genetic diversity and some variations in their patterns
could be linked to environmental conditions.

Female terrapins grow larger than males and some females could be as large as 23 cm (9
inches) in carapace length. Males are smaller and may reach sizes of 15 – 18 cm (6 or 7
inches) as adults. In terms of maturation, females in New Jersey can mature in 7 – 9
years, while males can mature in 3 – 5 years. Females will nest on bay beach areas
adjacent to marshes where they can deposit up to 18 eggs (called a clutch of eggs). The
mean clutch size at Sedge Island, Barnegat Bay, New Jersey is around 12 eggs (Wnek,
2006 and 2007). The nesting female terrapin will dig a nest, deposit eggs and
immediately return to the water. The depth of the nest depends on the compaction of soil
and depth at which the female can dig. Eggs are deposited as deep as 21 cm (9 inches).
Temperature of the nest influences the gender of terrapins; Eggs incubated at
temperatures above 28 Celsius will mostly develop as female and below this temperature,
male.

Eggs are somewhat soft, considered cleidoic, which allows for gas exchange during
incubation. After approximately two months, terrapins emerge from their nest and make
their way to vegetation and nearby marshes. From this point, little is known about their
growth and life stage, but we know they live and feed within marsh habitats. Some of
their food resources include snails, shrimp, crabs, and fish to name a few.

The goal of this activity is to learn about the basic life history characteristics of the
diamondback terrapin. You will be assigned a specific egg number. Although there may
be 4 – 18 eggs in a nest, we have an activity for 50 and 100 eggs that would be from
multiple nests on the North Sedge Island, Barnegat Bay, New Jersey. The goal is to
successfully hatch, emerge from the nest, and become an adult terrapin. Gender will not
be addressed at this point.

A PowerPoint addressing the life history, biology, research and conservation of this
species is available for additional information. Also, please see the terrapin reference list
for additional information. Here we go…



Terrapin Egg and Juvenile Survivorship Activity
2
Items recommended for the activity:

You can use 100 ping pong balls or plastic practice golf balls and number them from 1 to
100 using a permanent marker. These represent the egg numbers and types

Depending on the number students in the class they could be divided in groups. For
example, with a class of 32 students, there can be 8 groups of 4 students. Each of the
students in the group would get 3 numbered eggs at random. The group of 4 students with
a total of 12 eggs would represent an entire clutch of eggs. The remaining eggs can be
distributed at random to individuals in different groups so that some of the groups have
13 eggs total and four individuals have 4 eggs.

At the end of the activity, the surviving individual within the clutch is the one
remaining!

If you cannot get plastic balls to simulate eggs then number pieces of paper. Remember,
there are typically 9 – 16 eggs at Sedge Island, Barnegat Bay, New Jersey. You can
divide the groups up accordingly to meet the requirements of the clutch and class sizes.

References for the classroom:

www.dtwg.org (an organization of terrapin biologists, conservationists and educators)

www.wetlandsinstitute.org (a leader in terrapin conservation, research and education)

www.terrapininstitute.org (a non-profit in Maryland dedicated to terrapin conservation)

Diamonds in the Marsh: A Natural History of the Diamondback Terrapin by Barbara Brennessel,
2006. University Press of New England, New Hampshire,
ISBN: 13:978-1-58465-536-7

A Day in the Salt Marsh by Kevin Kurtz. Sylvan Dell Publishers,
ISBN: 978-0-9777423-1-8 (appropriate for children 3 – 7 years of age).

Marine Academy of Technology and Environmental Science “Project Terrapin” at
www.ocvts.org (Lessons and basic presentations for all grade levels)

http://www.pwrc.usgs.gov/bioeco/terrapin.htm (US Geological Survey Information)

http://www.scaquarium.org (South Carolina Aquarium: Lessons for elementary school students)

http://www.aqua.org/animals_diamondbackterrapin.html (National Aquarium in Baltimore,
Maryland)


Research experiences for educators:

http://www.earthwatchexpeditions.org/US/exped/avery.html (EarthWatch expedition for
educators at Barnegat Bay, New Jersey
Terrapin Egg and Juvenile Survivorship Activity
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Stage one. Eggs dug in a nest in late June with a 60 day incubation period overall. There
is a 60% survivorship based on research at Sedge Island, Barnegat Bay, New Jersey.
Here is the first 30 days…
Egg #
Factors contributing to failed egg development
4
Rainstorm flooding the nest
8
Rainstorm flooding the nest
9
Soil compaction preventing gas exchange
13
Soil compaction preventing gas exchange
16
Eaten by egret
23
Eaten by crow
33
Eaten by crow
35
Eaten by raccoon
42
Eaten by raccoon
50
Eaten by mink
51
Eaten by mink
54
Eaten by mink
60
Eaten by mink
65
Dessication
69
Dessication
71
Eaten by mink
77
Eaten by mink
83
Inadvertently dug up
90
Eaten by a crow
92
Eaten by a crow

Stage two. Congratulations! Eggs continue to incubate in late July with a 60 day
incubation period overall. There is an overall 60% survivorship of embryos.
Egg #
Factors contributing to death
5
Dessication
6
Eaten by red fox
14
Eaten by red fox
20
Eaten by crow
26
Soil too compacted; improper gas exchange
28
Eaten by raccoon
34
Dug up by a mink and eaten
36
Too low in the nest and waterlogged at high tide
46
Accidentally dug up by caretaker putting up a fence
47
Overcrowded nest with lack of oxygen
53
Overcrowded nest with lack of oxygen
57
Dug up by a mink and eaten
62
Dug up by a mink and eaten
64
Dug up by a mink and eaten
70
Inadvertently dug up
74
Ants got into the egg
76
Flood inundated nest with water
Terrapin Egg and Juvenile Survivorship Activity
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79
Flood inundated nest with water
88
Roots penetrated the egg
97
Roots penetrated the egg

Emergence. The terrapins have developed well and two months later, in mid-August are
emerging from the nest, making your way to the salt marsh. Congratulations! You have
emerged, but…

Hatchling #
Factors contributing to death
1
Eaten by a Herring gull
15
Eaten by a crow
22
Eaten by a red fox
24
Accidentally stepped on by a person walking on the Island
32
Exhaustion
37
Bit by a fiddler crab
40
Starvation
56
Starvation
59
Accidentally hit by lawn mower on Island
68
Eaten by egret
73
Eaten by a Herring gull
75
Eaten by a Herring gull
81
Cold stunned in late fall
86
Cold stunned in late fall
93
Cold stunned in late fall

Juvenile Stage. You are living in the marsh and growing during your first years of
development. There are many obstacles and challenges ahead.
Hatchling #
Factors contributing to death
7
Made way to low marsh ditch and eaten by blue crab
11
Eaten by an Osprey
17
Didn’t survive your first winter
18
Eaten by a red fox that came to the marsh during low tide
19
Caught in a commercial-style crab pot and drowned
21
Boat propeller cut you
25
Ventured to the next marsh and current took you.... exhaustion
29
Went off marsh to swim in shallow water – Striped Bass ate you
38
Exhaustion
41
Eaten by an Osprey
44
Eaten by a River Otter
52
Eaten by a River Otter
58
Crossed from one marsh into another, across the roadway & a car hit you
61
Eaten by red fox at marsh edge
72
Eaten by red fox at marsh edge
80
Caught in strong current and taken out to the ocean during outgoing tide
84
Caught in a commercial-style crab pot
Terrapin Egg and Juvenile Survivorship Activity
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85
Caught in commercial-style crab pot
89
Illegally taken by someone who saw you basking and sold you
96
Big storm tide in winter disrupted your hibernation and you died
99
Big storm tide in winter disrupted your hibernation and you died
100
Disease

Sub-adult Stage. You are living in the marsh creeks and water bodies in the estuary
growing to adulthood.
Juvenile #
Factors contributing to death or removal from the system
2
Too curious… drowned in a commercial-style crab pot
3
Eaten by a red fox
10
Got too close to a motor boat and its propeller
12
Ended up in a market as a food source
31
Storm caused you to emerge during winter and you froze
39
Fought with a blue crab and lost
43
Small enough to be eaten by an Osprey
45
Too much time in a commercial-style crab pot
49
Disease
55
Disease
66
Got too close to motor boat and its propeller
67
Big storm disrupted your hibernation and you froze
78
Got too close to the high marsh and a red fox grabbed you
82
Drowned in a commercial-style crab pot
87
Drowned in a commercial-style crab pot
95
Caught under a pier and you couldn’t get out
98
In commercial-style crab pot with numerous blue crabs – they won

Adult Stage. You almost made it to the adult stage. Congratulations! You are
approximately 5 – 7 years old.
Adult #
Factors contributing to death
30
Made landfall at Island Beach and didn’t make it across the roadway
48
Drowned in a commercial-style crab pot
91
Drowned in a commercial-style crab pot
94
Too close to a motor boat and you were hit by the propeller

Congratulations to Adults #27 and #63! You have made it. In actuality you
haven’t, because if you are nesting females, it will be approximately 7 years to nest.

Based on becoming a reproductive female adult…. #63 you tried to go into a
commercial-style crab pot and couldn’t access it because it had a “bycatch reduction
device” (terrapin excluder) and #27 you crossed the roadway to nest at High Bar
Harbor on Long Beach Island and were hit. Therefore, #63 – Congratulations!