DOI: 10.5061/dryad.kh022n1
title: Data from: Sunning themselves in heaps, knots, and snarls: the extraordinary abundance and demography of island watersnakes

description: 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
description: Lake Erie Watersnake
 encounter histories fileThe 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