The Effects of Urbanization and Habitat Fragmentation on Box Turtle Biology
Lauran Halpin
Davidson College
In recent years, urbanization and development have reduced populations of many
reptilian and amphibian species. Road construction and housing developments
create fragmented habitat and increase the chances of human contact with reptiles
and amphibians (Hall, 1987). Many reptiles are frequently killed on highways
and by people who find them in their lawns or gardens and who deem them dangerous
or destructive (Belzer, 1997).
The eastern box turtle (Terrapene carolina), North Carolina's state reptile,
is very popular with the public and is commonly found in developed areas. However,
little is known about the effects of development and resulting habitat fragmentation
on box turtle biology. The objective of my study will be to determine the effects
of habitat fragmentation on the local box turtle population in the Davidson,
NC area. Specifically, my study will examine the effects of habitat fragmentation
on box turtles' home range size, activity patterns, and habitat use. I will
also examine the effects of urbanization on age distribution, body condition,
reproduction, and sex ratios of the box turtles in the Davidson, NC area.
To determine the impact of urbanization on the home range size, activity patterns,
and habitat use of the eastern box turtle, I will use a combination of radiotelemetry
and thread-spooling techniques. Using each method, I will monitor the movement
and activity of six turtles from undeveloped areas and six turtles from developed
areas (total sample size=24) around Davidson during the summer of 2001.
Each turtle's locality will be obtained upon the time of capture using a global
positioning system (GPS). Turtles monitored using thread spools will have tiny
thread spools attached to them at their point of capture in the field. One end
of the thread will be attached to a stationary object at the point of capture,
and the other end of the spool will be duct taped to the turtle's
carapace. Movement from the turtle's initial locality will be monitored by following
the thread
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to the turtle's end locality once per day. Each day's location will be measured
using a global positioning system (GPS). Turtles monitored using radiotelemetry
will be transported back to the lab where a transmitter will be secured to their
carapace using epoxy. These turtles will then be returned to their initial locality.
Their movement and activity will be monitored once a day using a radio receiver
and directional antenna. Each turtle will be located daily and their exact location
will be measured using a GPS.
Data collected from my thread-spool and radiotelemetry studies will be entered
into a geographic informational system (GIS; ArcView 3.2, ESRI, Redlands, Ca).
The GIS will allow me to combine my location data with satellite imagery, aerial
photography, and topographical information to determine habitat usage, activity
patterns, and home range size of box turtles in and around the Davidson area.
I will use measurements taken on turtles collected during 1999 and 2000 combined
with data I collect in 2001 to examine the effects of urbanization on age distribution,
body condition (mass/carapace length), egg number and size, and sex ratios.
I will use ANOVA to compare all parameters between turtles inhabiting developed
and undeveloped areas. Carapace length, plastron length, width and thickness
will be obtained using digital calipers and I will use a Pesola scale to measure
each turtle's mass. The age of each turtle will be determined by counting scute
growth rings. Egg number and size will be determined using X-ray.
My study will provide valuable information regarding the effects of habitat
fragmentation due to urbanization on local box turtle populations and data essential
to future box turtle conservation efforts.