Population ecology of the federally threatened narrow-headed gartersnake (Thamnophis rufipunctatus) in Canyon Creek, Arizona

Abstract: The narrow-headed gartersnake (Thamnophis rufipunctatus) is a federally threatened species endemic to the Mogollon Rim in central Arizona and western New Mexico. This species has declined across its range primarily due to habitat loss, degradation and invasive species invasive species
An invasive species is any plant or animal that has spread or been introduced into a new area where they are, or could, cause harm to the environment, economy, or human, animal, or plant health. Their unwelcome presence can destroy ecosystems and cost millions of dollars.

Learn more about invasive species . Additional information on this species’ ecology, particularly empirical estimates of movement and demographic parameters, are particularly important for its management and conservation. We conducted a three-year mark-recapture study of narrow-headed gartersnakes in Canyon Creek in central Arizona to address the following objectives: (1) conduct three active seasons of intensive field sampling for narrow-headed gartersnakes; (2) use newly collected mark-recapture data to estimate survival and abundance; and (3) successfully implant harmonic transponder tags into syntopic western terrestrial gartersnakes (Thamnophis elegans), a non-threatened species, and, conditional upon this success, implant these tags into juvenile and adult narrow-headed gartersnakes in Canyon Creek to monitor space use and habitat selection. We used radio transmitters attached externally to document gartersnake movements due to their technological advantages to harmonic transponder tags. However, transmitters did not remain attached to gartersnakes long enough to collect meaningful movement data. We were, however, able to obtain meaningful movement data using recaptures of marked gartersnakes. We also compared capture rates, individual growth rates, movement, and apparent survival estimates between narrow-headed gartersnakes and western terrestrial gartersnake to provide a better understanding of their comparative ecology. We also documented the successful application of passive PIT tag arrays for monitoring PIT-tagged gartersnakes. While we captured more western terrestrial gartersnakes during our study, we did not find marked differences between these two species in individual growth rates, movement patterns, recapture probabilities, and apparent survival. We provide abundance estimates and their 95% credible intervals for both narrow-headed and western terrestrial gartersnakes, although data sparsity and tenuous model assumptions call for extreme caution when interpreting our abundance estimates. Our results fill geographical and ecological gaps in our knowledge of narrow-headed gartersnakes and can provide a foundation for future long-term monitoring studies at Canyon Creek.

DOI: https://doi.org/10.3996/css27007071