Datové sady / Status and Distribution of the Gopher Tortoise (Gopherus polyphemus) in Southern Alabama


Status and Distribution of the Gopher Tortoise (Gopherus polyphemus) in Southern Alabama

Vydavatel US Fish and Wildlife Service, Department of the Interior

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A two year study was undertaken to determine the status and distribution of the gopher tortoise Gopherus polyphemus in 24 counties in southern Alabama. Habitat characteristics affecting tortoise density were also examined. Data on distribution were gathered through questionnaires, personal interviews and field surveys. Results of the distribution study showed Baldwin, Butler, Clarke, Coffee, Conecuh, Covington, Crenshaw, Dale, Escambia, Geneva, Henry, Houston, Monroe and Pike counties to have widely distributed tortoise populations; Barbour, Bullock, Macon and Russell counties to have only relict or disjunct populations; and Dallas, Lee, Lowndes, Marengo, Montgomery and Wilcox counties to have no known tortoise populations. Data on status were gathered by determining tortoise density per acre on sample plots in eight habitat types and then determining the acreage of each habitat type using Landsat satellite imagery. In counties with disjunct populations, direct censuring was used. The estimated number of tortoises in the study area was 482,848. Age class structures were obtained by measuring the width of occupied burrows and using a regression formula for estimating carapace length and thus age. The state age class structure showed a viable population. Two vegetation characteristics, basal area and canopy closure, were significantly related to population density. Low levels of each were correlated with higher tortoise density. Burning, thinning, and maximizing edge were recommended management practices.