Data sheets & metadata for "When Introduced Prey Violates Trophic Hierarchy: Conservation of an Endangered Predator"

Published: 21 January 2021| Version 1 | DOI: 10.17632/8n5f23j4s8.1


Research objectives: • Management of long-established invasive species is complicated when endangered species use the invasive species as resource. • Understanding predator-prey interactions between natives and invasives can help improve conservation of endangered predators. • Understanding demographic response of endangered predators following invasive species control can help improve management regimes. • Some populations of the endangered San Francisco gartersnake co-occur with introduced bullfrogs, and the two predators potentially engage in reciprocal intraguild predation. This study explores the degree to which bullfrogs affect San Francisco gartersnakes through predation and competition. This study also explores how removal of bullfrogs can affect the demography of a San Francisco gartersnake population (site-specific analyses). Notable findings & interpretation: • San Francisco gartersnakes display reciprocal intraguild predation with invasive bullfrogs; competition, rather than predation, dominated the predator-invader interaction (see "diet patterns" and "diet overlap" data files). • Despite a potentially low frequency of predation by adult bullfrogs on juvenile San Francisco gartersnakes, juvenile snakes could remain vulnerable to bullfrog predation for a few years (see "abdominal scale measurement" data files). • Invasive prey removal was followed by an increase in native predator recruitment (see "capture-mark-recapture" data files). • Integrating diet studies and demographic studies of target species, following field-removal of invaders, can inform how to improve management decisions for conservation of endangered species and removal of invasive species.


Steps to reproduce

Study system and data collection: • Data were collected at two study sites: Site A, where San Francisco gartersnakes co-occur with bullfrogs; Site B, where bullfrogs do not co-occur. • Collected diet data from San Francisco gartersnakes by PCR analyses of fecal DNA. Collected morphological data and diet data from bullfrogs (stomach content identification), as a byproduct of bullfrog removal conducted by the site management. • Collected demographic data and morphological data on San Francisco gartersnakes from mark-recapture studies. • Collected abundance data of anuran prey species for San Francisco gartersnakes and bullfrogs from egg mass surveys, eye shine surveys, and trap bycatch during the snake mark-recapture studies. Steps to reproduce: • The title of each data folder includes the analytical methods used to interpret results. • Methods and Appendix of the manuscript include details on laboratory & field data collection and analytical methods (e.g. permits, types of models & equations, analytical software, laboratory equipment, PCR protocols...etc.).


US Geological Survey, San Francisco State University


Amphibians, Reptiles, Diet, Endangered Species, Abundance Estimation, Conservation Biology, Hierarchical Regression, Bayesian Analysis, Invasive Species Management