Adult survivorship and juvenile recruitment in populations of Crawfish Frogs (Lithobates areolatus), with additional consideration of the population sizes of associated pond breeding species

Crawfish Frog populations have declined significantly in both the northeastern and southwestern portions of their range, and are listed as state endangered in both Iowa and Indiana. They are animals with a secretive nature, and comparatively little is know about their basic life history and natural history. To address this gap, and to obtain the information necessary to manage for this species in areas of decline, I studied the breeding biology of two Crawfish Frog populations during 2009 and 2010. Using data collected from drift fence and pitfall trap arrays around breeding wetlands, I estimated breeding population sizes, operational sex ratios, breeding adult size ranges, egg and larval survivorship, juvenile recruitment, and adult within-season and between-year survivorship. I also documented the timing of breeding and metamorphosis, spatial patterns of immigration and emigration from breeding sites by adults and recently metamorphosed juveniles, and the diversity and abundance of associated pond breeding species. Crawfish Frog sex ratios were approximately 1:1 (M:F), with male-biased operational sex ratios. Adult sizes were comparatively larger than those reported in other areas of their range, as were sizes of newly metamorphosed juveniles. Breeding occurred from March through May during both years, and metamorphosis occurred from June through August. The number of eggs deposited per wetland ranged from 45,000 to 189,000. Thirteen associated amphibian species (18,109 individuals) and 14 reptile species (435 individuals) were captured at the breeding wetlands. Crawfish Frog survivorship estimates suggest that mortality is high during the larval stage and relatively low during the egg, juvenile and adult stages. Thus, the adult population is likely regulated by larval survivorship. To help manage for declining populations, captive rearing of larvae could be used to help offset the high mortality experienced during the larval stage and be used to help restore and/or repatriate populations at suitable sites.