Populations and Home Range Relationships of the Box Turtle Emily Marquardt February 15, 2007
Box Turtle Life History • Live in mixed habitat woods (thick leaf litter), open fields, streams • Omnivorous (mushrooms, berries, snails) • Long-lived (human lifespan) • Active April to October
American Naturalist 1886
Lucille Stickel’s 1950 paperPopulations and Home Range Relationships of the Box Turtle Goals: 1) To understand the home range relationships 2) To determine the size of the population
Home Range Definition An area over which an animal normally travels in the course of its daily activities “E. T. Go Home”
Methods Cagle (1939) notching technique (mark-recapture)
Methods Breder (1929) Trailing Device with spindle of thread to track turtles
Ranges of 15 turtles occupying parts of a 5 acre plot. Top: males, Bottom: females. Travels of adult male during 8 days in 1945.
Methods Population Size estimated 2 ways: • By collections in one season • Census trips, standardized for time and procedure
Results • 2109 turtle collections in 3 years • Adults occupy specific home ranges average male: 330 ft, female: 370 feet • Some turtles have 2 home ranges • Population size: 4.6 turtles/acre
Box Turtle Population Research1950 to present • Long term studies • Genetics • Herbivory • Conservation
Population Tracking Techniques • Mark-Recapture filing notches on marginal scutes • Trailing devices • Radio tagging • GPS • X-ray (eggs)
Long Term StudiesWildlife Research Center, MD Changes in Population (Stickel 1978) pronounced decline in population size -1965 to 1975 reduced by half Home Range Behavior (Stickel 1989) -size of home range did not differ significantly over 40 years Fifty year trends in Population (Hall 1999) - greater than 75% decline in population -found individuals greater than 70 years old
Genetics Promotion of Gene Flow by Transients Kiester et al. (1981) Transient: turtle that moves through the environment without recrossing areas passed previously Study documents true transients. - suggests their importance in maintaining genetic similarity between populations and in aiding spread of advantageous genes
Genetic Effects of Persistent Bottleneck Kuo & Janzen (2004) Loss of genetic diversity due to decrease in population size Bottleneck effects are different for long-lived vs. short-lived species
Kuo & Janzen 2004 cont. • Used microsatellite markers asses genetic diversity of small disturbed vs. large undisturbed population • Computer simulations: effective population size for small pop. (to maintain 90% alleles) is: 300 over 200 yrs Long-live species could mask accelerated rate of genetic drift!
Herbivory Seed Dispersal by Florida Box Turtle Liu et al. (2004) What plant species are dispersed? Does passage through turtle affect germination rate and percentage? Current Study by Chris Swarth Measuring stable isotopes of C and N in toenails and comparing to wetland food items to determine habitats
Conservation Box Turtle Population Decline • Habitat Loss and Fragmentation • Pets • Road Kill
Conservation Natural History of Box Turtle in Urbanized Landscape Budischak et al. (2006) Turtles persist and grow more quickly in urbanized areas, but suffer higher mortality rates compared to forested landscapes
Estimating the Effects of Road Mortality on Turtle Populations Gibbs and Shriver 2002 Modeling study: integrated road maps & traffic-volume data with movements of 1)small-bodied pond turtles 2) large-bodied pond turtles 3) terrestrial & semi-terrestrial “land” turtles Roads networks of Eastern and Central US will limit (3) and (2) but not (1).
Translocated Box TurtlesCook (2004) Site: abandoned airport in NY, 500 ha 335 turtles from Long Island Dispersal, home range establishment, initial survival monitored (radio tracked) Half developed home ranges 28% died and 24% left site Translocation potentially valuable but long term viability is uncertain