Sex, season, and time of day interact to affect body temperatures of the Giant Gartersnake

Wylie, Glenn D.; Casazza, Michael L.; Halstead, Brian J.; Gregory, Christopher J.

doi:10.1016/j.jtherbio.2009.01.006

Cited by 9 publications

(5 citation statements)

References 18 publications

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“…Rice fields generally remain flooded until sometime in late August or early September, when water is drawn off the fields to allow them to dry enough for harvest. The giant gartersnake active season extends from April through September (Wylie et al 2009); rice therefore only provides appropriate emergent aquatic habitat for approximately one-third of the active season. For the remainder of the active season, rice field microhabitats could be alternatively classified as bare ground, open water, or litter.…”

Section: Discussionmentioning

confidence: 99%

Active Season Microhabitat and Vegetation Selection by Giant Gartersnakes Associated with a Restored Marsh in California

Halstead

Valcarcel

Wylie

et al. 2016

Journal of Fish and Wildlife Management

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Studies of habitat selection can reveal important patterns to guide habitat restoration and management for species of conservation concern. Giant gartersnakes Thamnophis gigas are endemic to the Central Valley of California, where >90% of their historical wetland habitat has been converted to agricultural and other uses. Information about the selection of habitats by individual giant gartersnakes would guide habitat restoration by indicating which habitat features and vegetation types are likely to be selected by these rare snakes. We examined activity patterns and selection of microhabitats and vegetation types by adult female giant gartersnakes with radiotelemetry at a site composed of rice agriculture and restored wetlands using a paired case-control study design. Adult female giant gartersnakes were 14.7 (95% credible interval [CRI] = 9.4–23.7) times more likely to be active (foraging, mating, or moving) when located in aquatic habitats than when located in terrestrial habitats. Microhabitats associated with cover—particularly emergent vegetation, terrestrial vegetation, and litter—were positively selected by giant gartersnakes. Individual giant gartersnakes varied greatly in their selection of rice and rock habitats, but varied little in their selection of open water. Tules Schoenoplectus acutus were the most strongly selected vegetation type, and duckweed Lemna spp., water-primrose Ludwigia spp., forbs, and grasses also were positively selected at the levels of availability observed at our study site. Management practices that promote the interface of water with emergent aquatic and herbaceous terrestrial vegetation will likely benefit giant gartersnakes. Given their strong selection of tules, restoration of native tule marshes will likely provide the greatest benefit to these threatened aquatic snakes.

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Section: Discussionmentioning

confidence: 99%

Active Season Microhabitat and Vegetation Selection by Giant Gartersnakes Associated with a Restored Marsh in California

Halstead

Valcarcel

Wylie

et al. 2016

Journal of Fish and Wildlife Management

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“…The greater loss in body condition of male snakes compared with females during hibernation is possibly caused by differences in body temperature between the sexes during hibernation. Male giant gartersnakes have elevated body temperatures relative to females during hibernation, particularly in the months just before emergence (Wylie et al , 2009). The positive correlation between body temperature and resting oxygen consumption (Al‐Johany & Al‐Sadoon, 1996) coupled with a negative correlation between body mass and metabolic activity in snakes (Calder, 1996) indicate that males use relatively more reserves than females during hibernation.…”

Section: Discussionmentioning

confidence: 99%

“…c DAIC for the random models (models 1-4) is DcAIC (see equation 10 in Vaida & Blanchard, 2005). DF, effective degrees of freedom for random effect models (Vaida & Blanchard, 2005) particularly in the months just before emergence (Wylie et al, 2009). The positive correlation between body temperature and resting oxygen consumption (Al-Johany & Al-Sadoon, 1996) coupled with a negative correlation between body mass and metabolic activity in snakes (Calder, 1996) indicate that males use relatively more reserves than females during hibernation.…”

Section: Discussionmentioning

confidence: 99%

Using time‐dependent models to investigate body condition and growth rate of the giant gartersnake

et al. 2009

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Identifying links between phenotypic attributes and fitness is a primary goal of reproductive ecology. Differences in within-year patterns of body condition between sexes of gartersnakes in relation to reproduction and growth are not fully understood. We conducted an 11-year field study of body condition and growth rate of the giant gartersnake Thamnophis gigas across 13 study areas in the Central Valley of California, USA. We developed a priori mixed effects models of body condition index (BCI), which included covariates of time, sex and snout-vent length and reported the best-approximating models using an information theoretic approach. Also, we developed models of growth rate index (GRI) using covariates of sex and periods based on reproductive behavior. The largest difference in BCI between sexes, as predicted by a non-linear (cubic) time model, occurred during the mating period when female body condition (0.014 AE 0.001 SE) was substantially greater than males (À0.027 AE 0.002 SE). Males likely allocated energy to search for mates, while females likely stored energy for embryonic development. We also provided evidence that males use more body energy reserves than females during hibernation, perhaps because of different body temperatures between sexes. We found GRI of male snakes was substantially lower during the mating period than during a non-mating period, which indicated that a trade-off existed between searching for mates and growth. These findings contribute to our understanding of snake ecology in a Mediterranean climate.

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“…Similar logic was used for proportion submerged vegetation, which we expected to provide richer prey communities, and proportion terrestrial vegetation, which would provide basking cover near steep canal or wetland banks. We hypothesized that proportion floating vegetation, which often forms thick mats during the active season (April–September; Wylie et al ., ), would negatively affect ψ because of its potential negative effects on prey communities, inhibition of locomotion by giant garter snakes or other mechanisms.…”

Section: Methodsmentioning

confidence: 99%

Ghost of habitat past: historic habitat affects the contemporary distribution of giant garter snakes in a modified landscape

2013

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Historic habitat conditions can affect contemporary communities and populations, but most studies of historic habitat are based on the reduction in habitat extent or connectivity. Little is known about the effects of historic habitat on contemporary species distributions when historic habitat has been nearly completely removed, but species persist in a highly altered landscape. More than 93% of the historic wetlands in the Central Valley of California, USA, have been drained and converted to agricultural and other uses, but agricultural wetlands, such as rice and its supporting infrastructure of canals, allow some species to persist. Little is known about the distribution of giant garter snakes Thamnophis gigas, a rare aquatic snake species inhabiting this predominantly agricultural landscape, or the variables that affect where this species occurs. We used occupancy modeling to examine the distribution of giant garter snakes at the landscape scale in the Sacramento Valley (northern portion of the Central Valley) of California, with an emphasis on the relative strength of historic and contemporary variables (landscape-scale habitat, local microhabitat, vegetation composition and relative prey counts) for predicting giant garter snake occurrence. Proximity to historic marsh best explained variation in the probability of occurrence of giant garter snakes at the landscape scale, with greater probability of occurrence near historic marsh. We suspect that the importance of distance to historic marsh represents dispersal limitations of giant garter snakes. These results suggest that preserving and restoring areas near historic marsh, and minimizing activities that reduce the extent of marsh or marsh-like (e.g. rice agriculture, canal) habitats near historic marsh may be advantageous to giant garter snakes. bs_bs_banner Animal Conservation. Print

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Sex, season, and time of day interact to affect body temperatures of the Giant Gartersnake

Cited by 9 publications

References 18 publications

Active Season Microhabitat and Vegetation Selection by Giant Gartersnakes Associated with a Restored Marsh in California

Active Season Microhabitat and Vegetation Selection by Giant Gartersnakes Associated with a Restored Marsh in California

Using time‐dependent models to investigate body condition and growth rate of the giant gartersnake

Ghost of habitat past: historic habitat affects the contemporary distribution of giant garter snakes in a modified landscape

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