Bridging conservation across the ex situ‐in situ spectrum: Insights into the reproductive ecology of the threatened narrow‐headed gartersnake (Thamnophis rufipunctatus)

Abstract

Zoo‐based (ex situ) conservation breeding programs provide invaluable opportunities to uncover enigmatic behaviors and traits of focal species under managed care, which can support research and conservation management efforts. A suite of factors and a limited range have yielded population declines in the threatened narrow‐headed gartersnake (Thamnophis rufipunctatus). Better understanding its cryptic ecology and life history (e.g., reproductive ecology) offers conservation benefits. We analyzed data on courtship behavior, parity and litter size, offspring size, and neonatal growth from an ex situ T. rufipunctatus population at the Phoenix Zoo from 2009 to 2018. Courtship behavior and parturition phenology are likely linked with the North American monsoon season, yet the courtship window may be wider than realized. We document the first instances of interannual iteroparity and multigenerational rearing of successful breeders at the ex situ level. Litter sizes varied but were relative to maternal body mass, suggesting that fecundity may be driven by intrinsic condition (e.g., age and size) of breeding females. Mean offspring body masses were equivalent between sexes, and neonate growth trends were quadratic during their first 9 months. Sexual dimorphism became apparent around 4–5 months age. Much of these data are novel for T. rufipunctatus and provide insight into their reproductive ecology. Phenology of reproductive ecology and body size metrics can guide field surveillance, age estimations, and population ecology monitoring, as well as inform ex situ adaptive management practices. Strategies spanning the ex situ‐in situ spectrum are applicable to other imperiled taxa to better inform conservation management decisions.

Modeling a hot, dry future: Substantial range reductions in suitable environment projected under climate change for a semiarid riparian predator guild

“…rufipunctatus life history phenology (e.g., parturition timing) are linked to monsoonal precipitation and subsequent changes to aquatic habitat [50,125]. Other SDM studies for T. eques projected greater sensitivity to environmental extremes and, in support of our findings, that overwinter temperature is an important predictor [53,101].…”

“…eques is known to shift behaviors between active and inactive seasons [ 123 ], and often occupies aquatic drainages with flow regimes regulated by precipitation pulses [ 124 ]; and some T . rufipunctatus life history phenology (e.g., parturition timing) are linked to monsoonal precipitation and subsequent changes to aquatic habitat [ 50 , 125 ]. Other SDM studies for T .…”

“…Managing connectivity of the latter with populations in western New Mexico (see [63]) may be imperative to mitigate heightened extinction risks for a taxon that has little to nowhere to go. Applying other conservation actions, such as genetic rescue via translocations of ex situ or in situ stock [140] could help stave off existing burdens of already threatened species [125,134,141], including threatened T. eques and T. rufipunctatus [63].…”

Effects of disturbances and environmental changes on an aridland riparian generalist

“…For example, habitat loss and alterations to resource availability are attributed to rapid population declines in threatened Mexican gartersnakes ( T. eques ) and narrow-headed gartersnakes ( T. rufipunctatus ), which have proximal or sympatric overlap with T. cyrtopsis in some parts of their distribution ( Fleharty, 1967 ; Ryan et al, 2019 ; Holycross & Mitchell, 2020 ). Parturition phenology linked to summer precipitation ( i.e ., seasonal changes in aquatic resources) suggests that these taxa also have some life history commonalities with T. cyrtopsis ( Rossman, Ford & Seigel, 1996 ; Blais et al, 2022 ). Continued disturbances or drastic changes could disrupt phenological patterns or have more direct impacts on fragile populations ( Holycross & Mitchell, 2020 ).…”

“…Specifically, we binarily scored behaviors of individuals prior to any reactions to approaching observers. We based behaviors ( e.g ., inactivity, alertness, moving, water use, and foraging) upon known attributes of conspecifics ( Rossman, Ford & Seigel, 1996 ; Lillywhite, 2014 ; Blais et al, 2022 ) and T. cyrtopsis specifically ( Fleharty, 1967 ; Jones, 1990 ; Jones & Hensley, 2020 ; behaviors are described in Dataset S1 ). Individuals could display >1 behavior.…”