Nerodia Sipedon Research Articles

Effects of harmful algal blooms on stress levels and immune functioning in wetland-associated songbirds and reptiles

Harmful algal blooms (HABs), caused primarily by nutrient input from agricultural runoff, are a threat to freshwater systems worldwide, and are further predicted to increase in size, frequency, and intensity due to climate change. HABs occur annually in the Western Basin of Lake Erie (Ohio, USA), and these blooms become toxic when dominated by cyanobacteria that produce the liver toxin microcystin. Although we are making substantial inroads toward understanding how microcystin affects human health, less is known about effects of microcystin on wildlife exposed to HABs. Wetland-associated songbirds (barn swallows, Hirundo rustica, and red-winged blackbirds, Agelaius phoeniceus) and reptiles (Northern watersnakes, Nerodia sipedon, and painted turtles, Chrysemys picta) were sampled from wetlands exposed to chronically high microcystin levels due to a prolonged HAB event, and from unexposed, control wetlands. Physiological stress levels and several measures of immune functioning were compared between the HAB-exposed and control populations. Physiological stress levels, measured as heterophil:lymphocyte ratios, were higher in barn swallows, red-winged blackbirds, and Northern watersnakes exposed to a chronic HAB compared to unexposed, control individuals, but painted turtles did not differ in physiological stress levels between HAB-exposed and control individuals. Neither barn swallows nor red-winged blackbirds differed in immune functioning between populations, but HAB-exposed watersnakes had higher bactericidal capacity than control snakes, and HAB-exposed painted turtles had lower bactericidal capacity than control turtles. These results suggest that even when HABs do not cause direct mortality of exposed wildlife, they can potentially act as a physiological stressor across several taxa, and furthermore may compromise immune functioning in some species.

Biodiversity and demographics of a snake assemblage in a semi-urban environment in south central Pennsylvania

Abstract Worldwide, snake populations are threatened by anthropogenic impacts such as habitat alteration. Conservation efforts are being implemented, but many of these impacts are hard to overcome. Herpetological studies in anthropogenically affected areas are few and inconsistent. This study assesses the snake community at Shippensburg University, which is affected by urban and agricultural stresses. From 2011 to 2015, we deployed and checked 42 cover boards. Four species were detected: the eastern gartersnake (Thamnophissirtalis sirtalis), the northern watersnake (Nerodia sipedon sipedon), the eastern ratsnake (Pantherophis alleghaniensis), and the eastern milksnake (Lampropeltis triangulum). This anthropogenically impacted assemblage was uneven, dominated by the eastern gartersnake, and comprised fewer snakes than in natural habitats elsewhere in Pennsylvania. This study provides a measure of how snakes can respond in one of many kinds of human-impacted sites in the Commonwealth and highlights the effect that seasonal mowing can have on snake assemblages.

Preliminary Analysis of Morphometric Data for an Ongoing Autecological Study of the Northern Watersnake, Nerodia sipedon sipedon, in a West Virginia stream.

The northern watersnake, Nerodia sipedon, is a natricid ubiquitous across aquatic habitats of the eastern United States and is often found in high abundance. The prevalence of N. sipedon has garnered extensive research, much of which concerns its reproduction. However, thorough, long-term studies on the biology and ecology of N. sipedon in stream ecosystems, especially within Appalachia, are lacking. The purpose of this study is to analyze autecological data from ongoing research on a N. sipedon sipedon population within Short Creek, a rural stream in the northern panhandle of West Virginia. Morphometric, dietary, thermal, habitat and movement data were recorded for each capture. This analysis primarily focuses on morphometric data in an attempt identify any potential variation from data collected in past studies concerning different habitats. Future research will use neonate morphometrics as baseline data for growth estimations, employ mark-recapture data to estimate a population size, and build upon the established data set.

Ultraviolet Fluorescence as a Field-Applicable Screening Tool for Lesions Consistent with Ophidiomycosis in Lake Erie Watersnakes (Nerodia sipedon insularum).

Ophidiomycosis, commonly called snake fungal disease, has been linked to significant morbidity of free-ranging snakes in North America and Europe. Diagnosis of ophidiomycosis currently requires detection of skin lesions via physical exam or characteristic histopathology as well as detection of the causative agent, Ophidiomyces ophidiicola, through quantitative (q)PCR or fungal culture of a skin swab or tissue sample. While reliable, these methods require specialized training, invasive procedures (e.g., biopsy), and several days or weeks to receive results. Additionally, screening entire populations can quickly become costly. A fast, easy-to-use, cost-efficient, and sensitive screening tool is needed to optimize conservation strategies and treatment intervention. Our objective was to investigate the association between skin fluorescence under long-wave ultraviolet (UV) light (365 nm) and the detection of Ophidiomyces ophidiicola DNA using qPCR. Fifty-eight Lake Erie watersnakes (Nerodia sipedon insularum) collected in June of 2018 and 2019 from islands in western Lake Erie, Ottawa County, Ohio, US were visually inspected for skin lesions, photographed under natural light and UV light, and swabbed for qPCR analysis. Fluorescence was highly associated with the presence of skin lesions, and the presence of at least one fluorescent skin lesion was 86% sensitive and 100% specific for identifying animals with apparent ophidiomycosis, with a positive predictive value of 100%. While we recommend performing standard diagnostics along with fluorescence, our study supports the use of visual UV fluorescence identification as a preliminary, affordable, noninvasive, and field-applicable method to screen populations for ophidiomycosis.

Effects of snake fungal disease on short-term survival, behavior, and movement in free-ranging snakes.

Pathogenic fungi are increasingly associated with epidemics in wildlife populations. Snake fungal disease (SFD, also referred to as Ophidiomycosis) is an emerging threat to snakes, taxa that are elusive and difficult to sample. Thus, assessments of the effects of SFD on populations have rarely occurred. We used a field technique to enhance detection, Passive Integrated Transponder (PIT) telemetry, and a multi-state capture-mark-recapture model to assess SFD effects on short-term (within-season) survival, movement, and surface activity of two wild snake species, Regina septemvittata (Queensnake) and Nerodia sipedon (Common Watersnake). We were unable to detect an effect of disease state on short-term survival for either species. However, we estimated Bayesian posterior probabilities of >0.99 that R. septemvittata with SFD spent more time surface-active and were less likely to permanently emigrate from the study area. We also estimated probabilities of 0.98 and 0.87 that temporary immigration and temporary emigration rates, respectively, were lower in diseased R. septemvittata. We found evidence of elevated surface activity and lower temporary immigration rates in diseased N. sipedon, with estimated probabilities of 0.89, and found considerably less support for differences in permanent or temporary emigration rates. This study is the first to yield estimates for key demographic and behavioral parameters (survival, emigration, surface activity) of snakes in wild populations afflicted with SFD. Given the increase in surface activity of diseased snakes, future surveys of snake populations could benefit from exploring longer-term demographic consequences of SFD and recognize that disease prevalence in surface-active animals may exceed that of the population as a whole.

Multi-decadal trends in mercury and methylmercury concentrations in the brown watersnake (Nerodia taxispilota).

Mercury (Hg) is an environmental contaminant that poses a threat to aquatic systems globally. Temporal evaluations of Hg contamination have increased in recent years, with studies focusing on how anthropogenic activities impact Hg bioavailability in a variety of aquatic systems. While it is common for these studies and ecological risk assessments to evaluate Hg bioaccumulation and effects in wildlife, there is a paucity of information regarding Hg dynamics in reptiles. The goal of this study was to investigate temporal patterns in total mercury (THg) and methylmercury (MeHg) concentrations across a 36-year period, as well as evaluate relationships among and between destructive (kidney, liver, muscle) and non-destructive (blood, tail) tissue types in a common watersnake species. To accomplish this, we measured THg and MeHg concentrations in multiple tissues from brown watersnakes (Nerodia taxispilota) collected from Steel Creek on the Savannah River Site (SRS; Aiken, SC, USA) from two time periods (1983-1986 and 2019). We found significant and positive relationships between tail tips and destructive tissues. In both time periods, THg concentrations varied significantly by tissue type, and destructive tissues exhibited higher but predictable THg values relative to tail tissue. Methylmercury concentrations did not differ among tissues from the 1980s but was significantly higher in muscle compared to other tissues from snakes collected in 2019. Percent MeHg of THg in N.taxispilota tissues mirrored patterns reported in other reptiles, although the range of % MeHg in liver and kidney differed between time periods. Both THg and MeHg concentrations in N.taxispilota declined significantly from the 1980s to 2019, with average values 1.6 to 4-fold lower in contemporary samples. Overall, our data add further evidence to the utility of watersnakes to monitor Hg pollution in aquatic environments and suggest attenuation of this contaminant in watersnakes in our study system.

Brown watersnakes (Nerodia taxispilota) as bioindicators of mercury contamination in a riverine system

Mercury (Hg) is a contaminant that enters the environment through natural or anthropogenic means. Ecological risk assessments have examined Hg bioaccumulation and effects in many taxa, but little is known about Hg dynamics in reptiles, or their potential use as bioindicator species for monitoring Hg in aquatic systems. Numerous snake species, like North American watersnakes (Nerodia spp.), are piscivorous and are exposed to Hg through their diet. The purpose of this study was to identify factors associated with Hg accumulation in a common watersnake species and compare Hg concentrations of the snakes to those in fish occupying the same habitats. To this end, we sampled brown watersnakes (Nerodia taxispilota) from the Savannah River, a major river system in the southeastern U.S., and compared N. taxispilota Hg accumulation trends to those of bass (Micropterus salmoides), catfish (Ictalurus and Ameiurus spp.), and panfish (Lepomis and Pomoxis spp.) collected from the same reach. Total Hg (THg) in N. taxispilota tail tips ranged from 0.020 to 0.431 mg/kg (wet weight; mean: 0.104 ± 0.008). Snake tail THg was significantly correlated with blood THg, which ranged from 0.003 to 1.140 mg/kg (0.154 ± 0.019). Snake size and site of capture were significantly associated with tail THg. Snake tail THg increased at sites along and downstream of the area of historic Hg pollution, consistent with fish THg. Snake muscle THg was predicted based on tail THg and ranged from 0.095 to 1.160 (0.352 ± 0.022). To gauge Hg biomagnification in N. taxispilota, we compared predicted snake muscle THg concentrations to THg in fish of consumable size. Average biomagnification factors for THg in N. taxispilota were 3.1 (panfish) and 5.4 (catfish), demonstrating N. taxispilota likely biomagnify Hg through their diet. These results reveal N. taxispilota to be an effective bioindicator species for monitoring Hg in aquatic environments.

Targeting eradication of introduced watersnakes using integral projection models

AbstractProjection models are frequently used to identify and evaluate management actions to control or eradicate non‐native species. Integral projection models (IPMs) are an appealing option for many taxa because IPMs can model vital rates as a function of continuous variables, like size, without discretizing into a few classes. Despite their strengths, IPMs have yet to see widespread use in invasive species management. Here, we used an IPM to evaluate management actions for an introduced population of common watersnakes (Nerodia sipedon) recently established in California, USA, where they pose a threat to many highly imperiled native fauna. We developed the IPM using data on the survival, growth and fecundity of native and non‐native populations of N. sipedon to identify management targets that would facilitate its eradication. Population growth of N. sipedon was most sensitive to the growth and survival of snakes during their first year, when they grow from approximately 180 mm snout–vent length (SVL) to 350 mm, providing a clear target for eradication efforts. The IPM also provided finer resolution life‐history information for targeting eradication than a simple size class‐based matrix model. Simulated eradication effort showed funnel trapping, which targets all but the smallest and largest snakes, was more effective at decreasing population growth than hand capture focused on snakes >400 mm SVL. Our study highlights the value of IPMs for targeting eradication of introduced or invasive species, and we argue for wider adoption of these models for evaluating management actions.

Prevalence of Ophidiomyces ophiodiicola, the Causative Agent of Snake Fungal Disease, in the Interior Plateau Ecoregion of Tennessee, USA.

The fungal pathogen Ophidiomyces ophiodiicola, the causative agent of snake fungal disease, has been implicated in declines of North American snake populations since 2006 and the geographic range of this pathogen is still not fully known. In Tennessee, US, O. ophiodiicola has been detected since 2012, but large portions of the state have not been surveyed for this pathogen. Our primary objective was to monitor the prevalence of O. ophiodiicola in the Interior Plateau ecoregion of Tennessee by swabbing all snakes that were encountered during road cruising survey efforts in 2017 and 2018. Eleven snakes of four species, copperhead (Agkistrodon contortrix), common water snake (Nerodia sipedon), black kingsnake (Lampropeltis nigra), and smooth earthsnake (Virginia valeriae), tested positive for the presence of O. ophiodiicola. Overall, 9.2% (11/120) of snakes sampled tested positive for the presence of O. ophiodiiola, and we further observed a seasonal trend in detections with summer months having the greatest frequency of detections. Our results extend the known geographic range of O. ophiodiicola in Tennessee by adding four previously unconfirmed O. ophiodiicola-positive counties. Further sampling will need to be conducted across west Tennessee because this is the most data-deficient region of the state. Our results offer additional evidence of the presence of this pathogen in Tennessee and will help researchers further understand the geographic distribution and host range.

Preliminary Analysis of Mark-Recapture Data for an Ongoing Autecological Study of the Northern Watersnake, Nerodia sipedon sipedon, in a West Virginia stream.

The northern watersnake, Nerodia sipedon, is a natricine ubiquitous across aquatic habitats of the eastern United States. Found as far north as Ontario, as south as Florida, and stretching as far west as Utah, this species is ever-present and often in high abundance. The prevalence of N. sipedon has garnered extensive research, much of which concerns its reproduction. However, thorough, long-term studies, especially within stream ecosystems, are lacking. The purpose of this study is to fill that void, serving as an analysis of data from the first two years of ongoing autecological research on a N. sipedon sipedon population within Short Creek, a rural stream in the northern panhandle of West Virginia. Morphometric, dietary, thermal, habitat and movement data were recorded for each capture, however this analysis primarily focuses on mark-recapture data in an attempt to provide insight towards implementing radio telemetry during future activity seasons. Further research will investigate unanalyzed data, identify hibernacula, and build upon the established data set.

Prey Size and Feeding Rate Do Not Influence Trophic Morphology of Juvenile Water Snakes (Nerodia sipedon)

Gape-limited predators, such as snakes, might rely on phenotypic plasticity to cope with variation in prey size, but experimental studies have found mixed evidence for plasticity in snake head morphology. Our study sought to determine whether variation in prey size and feeding rate induce head size plasticity in Northern Water Snakes (Nerodia sipedon). We avoided limitations of previous studies by growing all neonates to a consistent final size (400 mm snout–vent length [SVL]), and uncoupling feeding rate and prey size as potential factors influencing head size through four feeding treatments: big–fast (one large prey item every week), big–slow (one large prey item every other week), small–fast (two small prey items every week), and small–slow (one small prey item every week). Snakes in fast treatments grew faster than snakes in slow treatments, but there were no strong effects of feeding rate or prey size treatments on multiple head size metrics. Females grew faster than males, however, and had longer jaw lengths at 400 mm SVL than did males. Unlike previous studies, our results do not support the presence of phenotypic plasticity in head size in N. sipedon, indicating that head size plasticity in snakes can be species and context specific.

Comparison of Body Temperatures across Physiological States in Syntopic Snake Species (Thamnophis sirtalis and Nerodia sipedon) from Pennsylvania

Physiological states in snakes, such as digestion, gestation, and ecdysis, have been associated with different body temperatures (BT), yet few studies have examined these associations in a comparative context for wild-caught animals. We collected body and environmental temperatures for 2 natricine snake species—Thamnophis sirtalis (Common Gartersnake) and Nerodia sipedon (Common Watersnake)—from 4 artificial wetlands at the Letterkenny Army Depot, Franklin County, PA. We measured thermal data and associated microclimates from snakes captured under tin cover boards during monthly searches from Spring to Fall of 2012 (April–October). From 47 Common Gartersnakes and 20 Common Watersnakes, we found that most individuals of both species had a BT between 20 and 30 °C, which is consistent with data from other populations. Inter- and intraspecific comparisons of snake BTs in different physiological states revealed that Common Gartersnakes operated at higher temperatures than Common Watersnakes. Common Watersnakes thermoregulated within a generally narrower range of temperatures than Common Gartersnakes. The wide-ranging thermal ecology of the Common Gartersnake may facilitate its flexibility to occupy many habitats across an extensive geographic distribution and perhaps predispose it to greater adaptability in a changing thermal environment. We summarize our data on snake BTs and their associations with relevant environmental temperatures, discuss snake BT ranges across distinct physiological groups, and compare our results to those of other snake populations. Our findings provide a baseline to understand the degree to which operating snake temperatures, and consequently physiological processes, will change because of future warming in the Northeast.

Evaluating Snake Density Using Passive Integrated Transponder (PIT) Telemetry and Spatial Capture–Recapture Analyses for Linear Habitats

Many snake species are elusive and difficult to study in field settings. As such, little is known about their population ecology despite conservation needs for many species. Advances in field techniques and statistical methods can improve our understanding of snake ecology. We used passive integrated transponder (PIT) telemetry to track Nerodia sipedon (Northern Watersnakes, n = 94) and Regina septemvittata (Queensnakes, n = 119) in six low-order streams in central Kentucky, USA from June to October 2016. We assessed snake density, spatial scale of detection, and detection probability using PIT tag relocations and spatial capture–recapture methods for linear habitats. Specifically, we modeled population density as a function of individual stream and land cover type, spatial scale of detection as a function of sex, and detection probability as a function of sex and time-varying covariates. Individual streams were a better predictor of snake density than land cover type; density estimates ranged from 6 ± 3 N. sipedon/km (mean ± standard error) to 107 ± 17 N. sipedon/km and 6 ± 5 R. septemvittata/km to 63 ± 10 R. septemvittata/km. Female R. septemvittata had a larger spatial scale of detection (55 ± 4 m) than male R. septemvittata snakes (40 ± 4 m). Spatial scale of detection did not differ between sexes for N. sipedon (females: 40 ± 4 m; males: 35 ± 3 m). The combination of PIT telemetry and spatial capture–recapture analyses can effectively estimate population densities and other population parameters for snakes and other reptiles and amphibians associated with linear habitats.

Traditional trapping methods outperform eDNA sampling for introduced semi-aquatic snakes.

Given limited resources for managing invasive species, traditional survey methods may not be feasible to implement at a regional scale. Environmental DNA (eDNA) sampling has proven to be an effective method for detecting some invasive species, but comparisons between the detection probability of eDNA and traditional survey methods using modern occupancy modeling methods are rare. We developed a qPCR assay to detect two species of watersnake (Nerodia fasciata and Nerodia sipedon) introduced to California, USA, and we compared the efficacy of eDNA and aquatic trapping. We tested 3–9 water samples each from 30 sites near the known range of N. fasciata, and 61 sites near the known range of N. sipedon. We also deployed aquatic funnel traps at a subset of sites for each species. We detected N. fasciata eDNA in three of nine water samples from just one site, but captured N. fasciata in traps at three of ten sites. We detected N. sipedon eDNA in five of six water samples from one site, which was also the only site of nine at which this species was captured in traps. Traditional trapping surveys had a higher probability of detecting watersnakes than eDNA surveys, and both survey methods had higher detection probability for N. sipedon than N. fasciata. Occupancy models that integrated both trapping and eDNA surveys estimated that 5 sites (95% Credible Interval: 4–10) of 91 were occupied by watersnakes (both species combined), although snakes were only detected at four sites (three for N. fasciata, one for N. sipedon). Our study shows that despite the many successes of eDNA surveys, traditional sampling methods can have higher detection probability for some species. We recommend those tasked with managing species invasions explicitly compare eDNA and traditional survey methods in an occupancy framework to inform their choice of the best method for detecting nascent populations.

A Synopsis of the Reptiles and Amphibians of Illinois

This synopsis is presented largely as it was written several years ago. Before a final report on our reptiles and amphibians is prepared, it is sincerely to be desired that examples of every Illinois species may be in the Illinois Laboratory collection for description, and that the local features of the fauna may be brought out by a critical comparison of Illinois specimens with collections from other parts of the United States. Specimens of the following species, and observations upon them, are especially desirable: Cistudo ornata, Chrysemys picta, Pseudemys hieroglyphica, P. concinna, Heterodon simus, Ophibolus rhombomaculatus, Nerodia sipedon var. fasciata, Rana areolata, R. sylvatica, Hyla cinerea, Desmognathus fusca, Spelerpes ruber, Amblystoma jeffersonianum and A. punctatum.

Angles and waves: intervertebral joint angles and axial kinematics of limbed lizards, limbless lizards, and snakes

Segmentation gives rise to the anterior-posterior axis in many animals, and in vertebrates this axis comprises serially arranged vertebrae. Modifications to the vertebral column abound, and a recurring, but functionally understudied, change is the elongation of the body through the addition and/or elongation of vertebrae. Here, we compared the vertebral and axial kinematics of the robustly limbed Fire skink (Riopa fernandi) representing the ancestral form, the limbless European glass lizard (Ophisaurus apodus), and the Northern water snake (Nerodia sipedon). We induced these animals to traverse through channels and peg arrays of varied widths and densities, respectively, using high-speed X-ray and light video. We found that even though the snake had substantially more and shorter vertebrae than either lizard, intervertebral joint angles did not differ between species in most treatment levels. All three species decreased the amplitude and wavelength of their undulations as channels narrowed and the lizard species increased wave frequency in narrower channels. In peg arrays, both lizard species decreased wave amplitude, while the snake showed no differences. All three species maintained similar wavelengths and frequencies as peg density increased in most cases. Our results suggest that amplitude is decoupled from wavelength and frequency in all three focal taxa. The combination of musculoskeletal differences and the decoupling of axial kinematic traits likely facilitates the formation of different undulatory waves, thereby allowing limbless species to adopt different modes of locomotion.

Ecology of Nerodia sipeodon (Common Watersnake) in North Fork Creek, Ohio County, West Virginia. Elijah Henderson, Dan Meyer and Zachary Loughman, West Liberty University, Dept. of Natural Sciences and Mathematics, West Liberty, WV

The ecology of Nerodia sipeodon (Common Water Snake) was studied concurrently with ecology of Regina septemvittata(Queen Snake) in North Fork of Short Creek, Ohio County, West Virginia. Snakes were captured via hand collection or aquatic funnel traps. All captured animals were measured, weighed, pit-tagged, and underwent gastric lavage when food boluses were present. Snake activity peaked in the spring, followed by a mid-summer brumation period. Activity reoccurred in mid-August through the fall. Trap captures outnumbered hand captures, though most juvenile animals were collected by hand. Frequently encountered food species included Black Nose Dace, Creek Chubs, and Long Nose Dace. Daily activity peaked in the morning hours, was reduced during the heat of the day, and began again in earnest during the late afternoon and early evening hours. Though concerted effort was undertaken to collect them, zero gravid females were collected with this study. Neonates appeared in the population beginning in late August. The most frequently encountered behavior was basking, followed by various defensive behaviors allied with capture. To date, close to 50 individual snakes have been PIT tagged and released at the study stream. Future efforts will focus on the use of radio telemetry, as well as the capture of gravid females.

Complete mitochondrial genome of Opisthotropis andersonii (Serpentes: Colubridae) determined using next-generation sequencing

The complete mitochondrial genome (mitogenome) of Opisthotropis andersonii was first determined using illumina next-generation sequencing. The total length of genome was 18,297bp with a slightly AT bias (59.57%), and contained 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, 2 control regions, and an origin of light-strand replication. All genes are distributed on the H-strand, except ND6 gene. A phylogenetic tree was constructed based on the 13 PCG sequences of O. andersonii and other related snakes to analyze their phylogenic relationship, exhibiting the closest relationship with Thermophis baileyi and Nerodia sipedon.

The complete mitochondrial genome of Opisthotropis latouchii (Squamata: Colubridae)

Opisthotropis latouchii is an endemic species which inhabits flowing streams in China. In this study, the complete mitochondrial genome of O. latouchii was determined using high-throughput sequencing data. The mitogenome was 17,051 bp in length and contained 13 protein-coding genes, 22 transfer RNA, 2 ribosomal RNA and 2 control regions. The total nucleotide composition was 34.09% A, 25.35% T, 27.39% C, and 13.16% T, respectively. The phylogenetic analysis showed that O. latouchii was closely related with Nerodia sipedon in Colubridae.

Sunning themselves in heaps, knots, and snarls: The extraordinary abundance and demography of island watersnakes.

Snakes represent a sizable fraction of vertebrate biodiversity, but until recently, data on their demography have been sparse. Consequently, generalizations regarding patterns of variation are weak and the potential for population projections is limited. We address this information gap through an analysis of spatial and temporal variation in demography (population size, annual survival, and 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 per km of shoreline (ca. 260 adult per ha) at our study sites (range = 160–1,600 adults per km; ca. 80–800 adults per ha) and surpassing population recovery and postdelisting 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.