DOI: 10.5061/dryad.41ns1rnsk
title: Data from: Population dynamics of a long-lived pitviper inferred from capture-recapture data spanning four decades

description: Long-term studies of plant and animal populations are rare, particularly
 for long-lived species with slow life histories. However, such studies are
 necessary to understand how variation in vital rates affects population
 dynamics. We used a large capture-recapture dataset spanning four decades
 (1983–2019) to estimate several population parameters for adult females in
 a metapopulation of a long-lived North American pitviper (Timber
 Rattlesnake, Crotalus horridus) near the northern extent of the species’
 geographic range. Apparent survival (ϕ, hereafter, survival) estimates
 were variable (0.595–0.938) among years but generally high, whereas the
 annual recruitment rate (f) was low (0.102, 95% confidence interval [CI]:
 0.088–0.117). Survival increased by a quadratic function of the mean mass
 of the adult female population, resulting in survival increasing with this
 temporally varying population-level covariate until the population average
 reached approximately 768 g; survival decreased with increasing mean mass
 thereafter. The proximate causes of decreased survival for the largest,
 and thus presumably oldest, snakes remain unknown but are likely related
 to senescence and increased predation risk with advancing age. The best
 predictors for encounter probabilities were the additive effects of color
 morph (higher for yellow snakes than black snakes), sampling site, and
 year. The model-averaged estimate of realized population growth (λ) was
 0.992 (95% CI: 0.980–1.005). Removal of sampling variance from the
 component of λ contributed by survival resulted in a 95% upper limit of
 0.9997, indicating a declining population. Reflecting attributes of the
 species’ protracted life history (late maturation, low fecundity, and
 infrequent reproduction), the contribution of survival was on average 8.9
 (95% CI: 7.6–10.4) times greater than the contribution of recruitment to
 λ, representing the slowest life history documented for any snake
 population to date. Our findings suggest management efforts to increase
 adult survival, such as reducing mortality from anthropogenic factors,
 should aid in the conservation of Timber Rattlesnakes and other imperiled
 species with similar slow life histories.
description: # Data from: Population dynamics of a long-lived pitviper inferred from
 capture-recapture data spanning four decades GENERAL INFORMATION 1. Author
 Information Name: Dr. Sasha J. Tetzlaff*,
 [https://orcid.org/0000-0001-5889-6573](https://orcid.org/0000-0001-5889-6573) Institution: U.S. Army Corps of Engineers, Engineer Research and Development Center, Champaign, Illinois, USA. Co-investigator 1 Name: Dr. Eric T. Hileman*, [https://orcid.org/0000-0002-7044-370X](https://orcid.org/0000-0002-7044-370X) Institution: West Virginia University, Morgantown, West Virginia, USA. Co-investigator 2 Name: Matthew G. Simon, Institution: Independent Researcher, Fort Ann, New York, USA. Co-investigator 3 Name: Dr. Gordon W. Schuett, [https://orcid.org/0000-0002-2133-3723](https://orcid.org/0000-0002-2133-3723) Institution: Chiricahua Desert Museum, Rodeo, New Mexico, USA; Department of Biology, Neuroscience Institute, Georgia State University, Atlanta, Georgia, USA. Co-investigator 4 Name: Dr. Mark A. Davis, [https://orcid.org/0000-0001-9034-9430](https://orcid.org/0000-0001-9034-9430) Institution: Illinois Natural History Survey, Prairie Research Institute, Champaign, Illinois, USA; Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, Illinois, USA. Co-investigator 5 Corresponding Investigator Name: Dr. William S. Brown, Institution: Department of Biology, Skidmore College, Saratoga Springs, New York, USA. Email: [wbrown@skidmore.edu](mailto:wbrown@skidmore.edu) Co-investigator 6 *Denotes co-lead authorship 1) Dates of data collection: 1983, 1985-1988, 1992-1994, 1996, 1998, 2000, 2002, 2004-2009, 2011-2016, 2018, 2019 2) Geographic location of data collection: Southeastern Adirondack Mountains, New York, USA. 3) Funding sources that supported the collection of the data: Self-funded. DATA & FILE OVERVIEW 1. Description of dataset These capture-recapture data were generated to investigate realized population growth of the Timber Rattlesnake (Crotalus horridus) using Program MARK version 11.1. 2. File list: File 1 Name: C_horridus__NY_USA_1983-2019_F.inp METHODOLOGICAL INFORMATION Apparent survival (phi), capture probabilities (p), recruitment rate (f) and realized population growth were estimated using Pradel's time symmetric survival and recruitment model, where phi, p, and f are estimated using maximum likelihood and realized population growth is a derived parameter. All functions of the above parameters were simulated in the r package 'mvtnorm' using estimates and associated variance-covariance matrix generated in Program MARK. DATA-SPECIFIC INFORMATION FOR: C_horridus\_ NY_USA_1983-2019_F.inp. Tetzlaff et al. 2025 Line 1: Description and title. Line 2: Authors. Line 4: study site. Line 5: Sampling years. Lines 7 to 33: Years and interval lengths adjusted to annual intervals Lines 35 to 47: Den names and groups (one factor with 12 levels), 6 dens for black morphs (B) and the same 6 dens for yellow morphs (Y). Lines 49 to 77: Left column: Years = the sampling intervals from which annual estimates are derived), Middle column: Popmass = average adult female mass; a temporally varying population-level covariate) Right column 11-yrs past_precip = Precipitation 11 years prior to the current occasion. Lines 79 to 111: Same as above but standardize by subtracting each covariate by its mean and divided it by 2*SD so that coefficients are directly comparable to untransformed binary predictors. Lines 113 to 819: capture histories (26 occasions) of females ≥ 500 grams, followed by the 12 den/morph groups. **Code/Software** Can be opened with any text editor