Vital rates and population demographics in declining and stable watersnake populations

—many snake populations have experienced significant declines, including the copper-bellied Watersnake (nerodia erythrogaster neglecta), a species listed as threatened under the federal endangered species act. here, we assess aspects of population biology and vital rates in n. e. neglecta to help elucidate potential mechanisms of their decline and inform more targeted recovery efforts. We use the common Watersnake (nerodia sipedon sipedon) as a benchmark for comparison. survey results indicate that the n. e. neglecta population may have experienced a 70% decline in abundance from 2001– 2006, whereas the n. s. sipedon population remained relatively stable. annual survivorship rates did not differ appreciably between n. e. neglecta (0.67) and n. s. sipedon (0.63). surprisingly, n. e. neglecta grew three times faster than n. s. sipedon, regardless of sex, with evidence of high growth rates across the entire size-range of the population, suggesting that food resource limitations or excess energy expenditures are not likely constraining n. e. neglecta. Frequency of mating encounters, sex ratios, and proportion of juveniles in the sampled population of n. e. neglecta showed little evidence of deviation from that of n. s. sipedon. While broad scale threats such as habitat fragmentation, the loss of shallow ephemeral wetlands, mining, road mortality, or declines in amphibian prey have likely driven range-wide declines of n. e. neglecta, the proximate mechanisms (i.e., fitness consequences) behind the decline of our study population remain unresolved. nevertheless, the vital rates presented here provide useful information for more informed management and recovery efforts.