Population Ecology of the Eastern Box Turtle in a Fragmented Landscape

Abstract

In the mid‐Atlantic region, urban sprawl and development have resulted in habitat alterations and fragmentation; however, the effects on eastern box turtle (Terrapene carolina carolina) populations are unclear. To investigate the status of eastern box turtle populations in a fragmented landscape, we used mark—recapture and radiotelemetry to estimate population density, sex ratio, age structure, and survival on 4 study areas with differing degrees of isolation and human disturbance in northern New Castle County, Delaware, USA. We estimated adult population densities ranging from 0.81 turtles/ha to 3.62 turtles/ha among our 4 study areas. Sex ratios were male‐biased at 2 study areas and balanced at 2 study areas. Proportion of juveniles ranged from 0% to 31%. Estimated annual survival rate ranged from 0.813 to 0.977. Mortality of radiotagged and marked turtles was primarily due to natural causes, but mowing was the primary cause of human‐induced mortality. We found evidence of population decline at one study area due to low survival and recruitment. Human disturbances, isolation, and habitat composition appear to have the greatest influence on the box turtle populations we studied. To minimize mortality from human disturbance, we suggest planting crops adjacent to forest habitat that require no mowing or mowing at a height ≥15 cm. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):745–753; 2008)

Using Spatial Capture–Recapture to Elucidate Population Processes and Space-Use in Herpetological Studies

“…Our estimates of box turtles per area were similar to some of these past studies (Williams and Parker 1987;Quinlan et al 2003Quinlan et al /2004Nazdrowicz et al 2008), and substantially lower than others (e.g., Boucher 1999; Wilson and Ernst 2005;Langtimm et al 1996).…”

“…Results of surveys at two locations in Virginia provided estimates of 23.8 turtles/ha and 16 turtles/ha (Boucher 1999;Wilson and Ernst 2005, respectively). Nazdrowicz et al (2008) reported 0.81-3.56 turtles/ha across four study sites in Delaware.…”

Seasonal variations in plasma vitellogenin and sex steroids in male and female Eastern Box Turtles, Terrapene carolina carolina

“…Females of other box turtle subspecies often multi-clutch within a single season with clutch fertility varying from 0% to 95% [5]. Among these subspecies, few hatchlings survive to adulthood and females likely require decades to replace the adults in a population [2,13,43]. In addition to these reproductive hurdles, the means of finding mates appears to be a fundamentally random event [2,13].…”

Population structure leads to male‐biased population sex ratios under environmental sex determination

“…Male‐biased sex ratios have been further documented more recently in nonmarine turtles (Edmonds and Brooks ; Dodd ; Hailey and Willamsen ; Smith and Iverson ; Nazdrowicz et al. ), crocodilians (Platt et al. ), tuataras (Grayson et al.…”

“…Reviews of the ESD taxon with the next most available sex ratio data, the Crocodilia, similarly found more than twice as many male biases as female biases (Nichols and Chabrek 1980;Thorbjarnarson 1997;Lance et al 2000), with no evidence of early maturation of males that can explain this result. Male-biased sex ratios have been further documented more recently in nonmarine turtles (Edmonds and Brooks 1996.;Dodd 1997;Hailey and Willamsen 2000;Smith and Iverson 2002;Nazdrowicz et al 2008), crocodilians (Platt et al 2009), tuataras (Grayson et al 2014), and copepods (Voordouw and Anholt 2002).…”