Data from: Sunning themselves in heaps, knots, and snarls: the extraordinary abundance and demography of island watersnakes

King, Richard B., Northern Illinois University

Stanford, Kristin M., Northern Illinois University

Jones, Peter C., Northern Illinois University

Published May 03, 2019 on Dryad. https://doi.org/10.5061/dryad.kh022n1

Cite this dataset

King, Richard B.; Stanford, Kristin M.; Jones, Peter C. (2019). Data from: Sunning themselves in heaps, knots, and snarls: the extraordinary abundance and demography of island watersnakes [Dataset]. Dryad. https://doi.org/10.5061/dryad.kh022n1

Abstract

Snakes represent a sizable fraction of vertebrate biodiversity but until recently, data on their demography has been sparse. Consequently, generalizations regarding patterns of variation are weak and the potential for population projections are limited. We address this information gap through an analysis of spatial and temporal variation in demography (population size, annual survival, realized population growth) of the Lake Erie Watersnake, Nerodia sipedon insularum, and a review of snake survival more generally. Our study spans a period during which the Lake Erie Watersnake was listed as threatened under the U.S. Endangered Species Act, recovered and was delisted. We collected capture-mark-recapture data at 14 study sites over 20 years, accruing 20,000 captures of 13,800 individually marked adults. Lake Erie Watersnakes achieve extraordinary abundance, averaging 520 adults/km of shoreline (ca. 260 adult/ha) at our study sites (range = 160-1600 adults/km; ca. 80-800 adults/ha) and surpassing population recovery and post-delisting monitoring criteria. Annual survival averages 0.68 among adult females and 0.76 among adult males, varies among sites, and is positively correlated with body size among study sites. Temporal process variance in annual survival is low, averaging 0.0011 or less than 4% of total variance; thus, stochasticity in annual survival may be of minor significance to snake extinction risk. Estimates of realized population growth indicate that population size has been stable or increasing over the course of our study. More generally, snake annual survival overlaps broadly across continents, climate zones, families, subfamilies, reproductive modes, body size categories, maturation categories, and parity categories. Differences in survival in relation to size, parity, and maturation are in the directions predicted by life history theory but are of small magnitude with much variation around median values. Overall, annual survival appears to be quite plastic, varying with food availability, habitat quality, and other ecological variables

Usage notes

Lake Erie Watersnake encounter histories file

The file provides field collected encounter histories of Lake Erie Watersnakes. The first column provides the encounter history of individuals snakes for 2000-2015 with '0' indicating that a snake was not encountered and '1' indicating that a snake was encountered in a given year. Subsequent columns identify group membership ('1') as follows: Gibraltar Island male, female, Kelleys Island South Shore male, female, Kelleys Island State Park male, female, Kelleys Island Southeast Shore male, female, Kelleys Island Long Point male, female, Kelleys Island Minshall male, female, Middle Bass Island East Point male, female, Middle Bass Island State Park male, female, Middle Bass Island West End male, female, North Bass Island NNEE Shore male, female, North Bass Island South Shore male, female, South Bass Island East Point male, female, South Bass Island East Shore male, female, South Bass Island State Park male, female.

Nesi CJS 2017.inp

Location

North America