Structure and Dynamics of Lithobates sylvaticus (Wood Frog) at the Periphery of its Range in Missouri

摘要

Lithobates (Rana) sylvaticus (Wood Frog) has an extensive distribution primarily in the Appalachian Mountains in the eastern US and throughout Canada and Alaska. However, peripheral populations exist along the southern edge of its range, including in the Ozark regions of Missouri and Arkansas. We present results on the structure and dynamics of 5 Wood Frog populations studied over 4 years (2004-2007) at the edge of the species' range in central Missouri. We used drift fences and pitfall traps surrounding breeding ponds to sample adults and metamorphosing juveniles. We captured breeding males between 7 February and 13 March, and females between 28 February and 16 March. The sex ratio was male-biased (M:F = 2.4), females were larger than males (mean SVL = 61.3 and 52.3 mm, respectively), and the larval period averaged 14 weeks. The metamorphs had a mean SVL of 18.1 mm and varied in number from 0 to 400 individuals per pond per year. The mean juvenile production per female was 8.7 (range = 0-52), and mean survival from egg to juvenile was 1.28% (range = 0-6.08%). Land managers should consider the species' small population sizes, low recruitment, survival rates of terrestrial stages, and the interaction of population dynamics with changing climate conditions when planning for conservation of Wood Frog populations at the periphery of the species' range.