When introduced prey violates trophic hierarchy: Conservation of an endangered predator

Kim, Richard; Halstead, Brian J.; Routman, Eric J.; Andersen, John Rastrup

doi:10.1016/j.biocon.2021.109019

Cited by 4 publications

(5 citation statements)

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“…A key next step will be to identify candidate sites with suitable aquatic and terrestrial habitat and sufficient prey for all life stages of San Francisco gartersnakes [ 74 ]. Further, if the reintroduction site was previously occupied, management might be required to ameliorate the factors that caused San Francisco gartersnakes to be extirpated.…”

Section: Discussionmentioning

confidence: 99%

Comparing reintroduction strategies for the endangered San Francisco gartersnake (Thamnophis sirtalis tetrataenia) using demographic models

Rose,

Kim,

Schoenig

et al. 2023

PLoS ONE

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For endangered species persisting in a few populations, reintroductions to unoccupied habitat are a popular conservation action to increase viability in the long term. Identifying the reintroduction strategy that is most likely to result in viable founder and donor populations is essential to optimally use resources available for conservation. The San Francisco gartersnake (Thamnophis sirtalis tetrataenia) is an endangered sub-species that persists in a small number of populations in a highly urbanized region of California. Most of the extant populations of San Francisco gartersnakes have low adult abundance and effective population size, heightening the need for establishment of more populations for insurance against the risk of extinction. We used simulations from demographic models to project the probability of quasi-extinction for reintroduced populations of San Francisco gartersnakes based on the release of neonate, juvenile, adult, or mixed-age propagules. Our simulation results indicated that the release of head-started juveniles resulted in the greatest viability of reintroduced populations, and that releases would need to continue for at least 15 years to ensure a low probability of quasi-extinction. Releasing captive-bred juvenile snakes would also have less effect on the viability of the donor population, compared to strategies that require more adult snakes to be removed from the donor population for translocation. Our models focus on snake demography, but the genetic makeup of donor, captive, and reintroduced populations will also be a major concern for any proposed reintroduction plan. This study demonstrates how modeling can be used to inform reintroduction strategies for highly imperiled species.

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Section: Discussionmentioning

confidence: 99%

Comparing reintroduction strategies for the endangered San Francisco gartersnake (Thamnophis sirtalis tetrataenia) using demographic models

Rose,

Kim,

Schoenig

et al. 2023

PLoS ONE

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“…Fish & Wildlife Service, 2006 ). San Francisco gartersnakes primarily feed on amphibians (Kim et al, 2021 ) including native Sierran treefrogs ( Pseudacris sierra ), California red‐legged frogs ( Rana draytonii ), and Pacific newts ( Taricha spp.). San Francisco gartersnake populations have become more isolated as urbanization in the species’ range has altered wetlands and surrounding upland habitats (U.S.…”

Section: Methodsmentioning

confidence: 99%

“…The vegetation in aquatic and upland habitat at Site I was comparable to that at Site C, with the addition of mixed evergreen forest at higher elevations. Native amphibian prey taxa at Site I were similar to Site C, but invasive American bullfrogs ( Lithobates catesbeianus ) co‐occurred up until 2015; the bullfrogs were culled by site management between 2014 and 2015 (Kim et al, 2021 ).…”

Section: Methodsmentioning

confidence: 99%

“…We used a random emigration formulation of the robust‐design model that assumed availability for capture in one primary period did not depend on an individual's state in the previous primary period. We assumed random emigration because our sampling was focused near aquatic habitats where San Francisco gartersnakes are likely to forage for amphibian prey each spring (Kim et al, 2021 ), and therefore, we did not expect an individual's availability for capture in one year to influence their availability the next year. We created our robust‐design survival model in a Bayesian framework following the parameterization of Riecke et al ( 2018 ), which allows for unbiased estimates of apparent survival ( ϕ ), availability ( γ ), and capture probability ( p ).…”

Section: Methodsmentioning

confidence: 99%

Section: Study Species and Sitesmentioning

confidence: 99%

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Integrating growth and survival models for flexible estimation of size‐dependent survival in a cryptic, endangered snake

Rose

Kim

Schoenig

et al. 2022

Ecology and Evolution

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Estimates of demographic rates for animal populations and individuals have many applications for ecological and conservation research. In many animals, survival is size‐dependent, but estimating the form of the size–survival relationship presents challenges. For elusive species with low recapture rates, individuals’ size will be unknown at many points in time. Integrating growth and capture–mark–recapture models in a Bayesian framework empowers researchers to impute missing size data, with uncertainty, and include size as a covariate of survival, capture probability, and presence on‐site. If there is no theoretical expectation for the shape of the size–survival relationship, spline functions can allow for fitting flexible, data‐driven estimates. We use long‐term capture–mark–recapture data from the endangered San Francisco gartersnake ( Thamnophis sirtalis tetrataenia ) to fit an integrated growth–survival model. Growth models showed that females reach longer asymptotic lengths than males and that the magnitude of sexual size dimorphism differed among populations. The capture probability and availability of San Francisco gartersnakes for capture increased with snout–vent length. The survival rate of female snakes exhibits a nonlinear relationship with snout–vent length (SVL), with survival flat between 300 mm and 550 mm SVL before decreasing for females between 550 mm and 700 mm SVL. For male snakes, survival decreased for adult males >550 mm SVL. The survival rates of the smallest and largest San Francisco gartersnakes were highly uncertain because recapture rates were very low for these sizes. By integrating growth and survival models and using penalized splines, we found support for size‐dependent survival in San Francisco gartersnakes. Our results have applications for devising management activities for this endangered subspecies, and our methods could be applied broadly to the study of size‐dependent demography among animals.

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An invasive prey and changing climate interact to shape the breeding phenology of an endangered predator

Fletcher,

Beatty,

Elmquist

et al. 2024

Global Change Biology

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Changes in phenology are occurring from global climate change, yet the impacts of other types of global change on the phenology of animals remain less appreciated. Understanding the potential for synergistic effects of different types of global change on phenology is needed, because changing climate regimes can have cascading effects, particularly on invasive species that vary in their thermal tolerances. Using 25 years of data from 5963 nests and 4675 marked individuals across the entire US breeding range of an endangered predator, the snail kite (Rostrhamus sociabilis plumbeus), we isolated the effects of an invasion of novel prey and warming temperatures on breeding phenology and its demographic consequences. Over this time period, breeding season length doubled, increasing by approximately 14 weeks. Both temperature and the establishment of invasive prey interacted to explain the timing of nest initiation. Temperature and invasive prey played distinct roles: earlier nest initiation occurred with increasing temperatures, whereas late nesting increased with invasion. Ultimately, both nest survival and juvenile survival declined later in the year, such that effects from invasive prey, but not warming temperatures, have the apparent potential for mistiming in breeding phenology by some individuals. Nonetheless, relatively few nesting events occurred during late fall when nest survival was very low, and seasonal declines in nest survival were weaker and renesting was more frequent in invaded wetlands, such that total reproductive output increased with invasion. Variation in demographic effects illustrate that considering only particular components of demography (e.g., nest survival rates) may be inadequate to infer the overall consequences of changes in phenology, particularly the potential for mistiming of phenological events. These results emphasize that species invasions may profoundly alter phenology of native species, such effects are distinct from climate effects, and both interact to drive population change.

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When introduced prey violates trophic hierarchy: Conservation of an endangered predator

Cited by 4 publications

References 47 publications

Comparing reintroduction strategies for the endangered San Francisco gartersnake (Thamnophis sirtalis tetrataenia) using demographic models

Comparing reintroduction strategies for the endangered San Francisco gartersnake (Thamnophis sirtalis tetrataenia) using demographic models

Integrating growth and survival models for flexible estimation of size‐dependent survival in a cryptic, endangered snake

An invasive prey and changing climate interact to shape the breeding phenology of an endangered predator

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