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Alexandria M. Fulton

Publications and source records attributed to Alexandria M. Fulton.

6 recordsLinked to original sources
USGS2025

Rice cultivation supports growth and survival of a threatened semi-aquatic reptile

Integration of agroecosystems and other working landscapes with protected lands and waters is critical to the conservation of Earth's biodiversity. Rice agroecosystems support many species by providing aquatic habitat where natural wetlands have been altered or drained. In regions with long dry seasons, rice fields and associated irrigation canals provide essential habitat for wetland-dependent species. We quantified the spatial scale and magnitude of the effect of rice growing on the growth and survival of the giant gartersnake ( Thamnophis gigas ), a threatened species that persists primarily in areas of rice agriculture in the Central Valley of California, USA. We used structural causal models to identify drought condition as a key confounder to adjust for when estimating the total effect of rice growing on demographic rates. We analyzed capture-mark-recapture data from 19 populations of giant gartersnakes with an integrated growth–survival model and used distance-weighted covariates to account for the decline in influence of rice with increasing distance from our study sites. We found strong support for a positive effect of rice grown within 1.9 km of a canal on giant gartersnake growth. There was also support for a positive effect of rice on giant gartersnake survival, although the spatial scale extended out to 5 km or more. Our results demonstrate how active rice growing benefits giant gartersnakes inhabiting irrigation canals and demonstrate an approach for studying landscape effects on wildlife in agroecosystems.

California↗
USGS2022

Rural turtles: Estimating the occupancy of Northwestern Pond Turtles and non-native red-eared sliders in agricultural habitats in California's Sacramento Valley and Sacramento-San Joaquin River Delta

The Northwestern Pond Turtle ( Actinemys marmorata ; WPT) was once widespread throughout the Sacramento Valley and the Sacramento-San Joaquin River Delta. Much of its historical range has been converted into agricultural land, reducing and altering aquatic habitat and surrounding uplands. Red-eared Sliders ( Trachemys scripta elegans ; RES) have been introduced throughout much of the existing WPT range, particularly near urban centers, potentially competing with WPT for resources. Previous surveys for turtles in central California have primarily focused on rivers, lakes, and protected wetlands. Little is known about where WPT and RES occur in the vast expanses of agricultural land across the Sacramento Valley and Sacramento-San Joaquin River Delta. Using aquatic hoop nets, we surveyed 142 locations (102 irrigation canal sites, 39 wetlands, 1 tidally influenced slough) across 8 counties during the summers of 2018 and 2019. Both species were detected in agricultural habitats. Using occupancy modeling, we estimated that WPT occur at 44 (95% CRI = 38–53) of our trapping sites and RES occur at 51 (41–66) sampled sites. Co-occurrence of these 2 species was rare; the species were found together at only 6 sites. RES were primarily found in restored wetlands near major roads and the Sacramento metropolitan area, whereas WPT were more commonly found farther from urban areas in wider canals. Our work provides a picture of how WPT and RES occupy this modified agroecosystem that can inform future conservation efforts.

California↗
USGS2020

Distribution of giant gartersnakes (Thamnophis gigas) in the Sacramento–San Joaquin Delta, California, 2018–2019

Summary We examined the occurrence of giant gartersnakes in the Sacramento–San Joaquin Delta, California, in 2018 and 2019. We made eight captures of seven giant gartersnakes (three females, four males) in 2018, and six captures of six giant gartersnakes (four females, two males) in 2019. Detection probabilities were exceedingly low despite using methods that achieve much higher detection probabilities in the rice-growing regions of the Sacramento Valley, California. Our results indicated negative effects of salinity and prey abundance and positive effects of percent emergent vegetation on giant gartersnake occurrence in the Delta, but credible intervals of effect sizes broadly overlapped zero. Estimates of giant gartersnake probability of occurrence were characterized by substantial uncertainty. Additional study with a larger sample of randomly selected but accessible sites would help to further resolve the distribution of giant gartersnakes in the Delta and clarify how the physical and biotic environment in the Delta affects where giant gartersnakes exist. Methodological development to increase detection probabilities in the Delta also would improve inference about giant gartersnake occupancy in the region.

California↗
USGS2018

Thamnophis sirtalis fitchi (Valley Gartersnake). Coloration.

During surveys for Thamnophis gigas (Giant Gartersnake), I observed an adult T. sirtalis fitchi with unusual coloration— a yellow-cream background color with some typical red coloration laterally, but with very minimal amounts of the dark slate-black (along the sides of the yellow dorsal stripe and on top of the head) that normally predominates in this subspecies (Fig. 1; LACM [Natural History Museum of Los Angeles County] PC 2339, photo voucher). The snake was captured in a modified minnow trap on 21 May 2017, in Sutter County, Sacramento Valley, California, USA. Prior to this capture, our survey crew made two sightings of similarly marked T. s. fitchi at the same field location, and another snake with similar markings was captured at a nearby field location on 13 May 2016 (LACM PC 2341, photo voucher).

Herpetological Review↗
USGS2017

Behavioral response of giant gartersnakes (Thamnophis gigas) to the relative availability of aquatic habitat on the landscape

Most extant giant gartersnake ( Thamnophis gigas ) populations persist in an agro-ecosystem dominated by rice, which serves as a surrogate to the expansive marshes lost to flood control projects and development of the Great Central Valley of California. Knowledge of how giant gartersnakes use the rice agricultural landscape, including how they respond to fallowing, idling, or crop rotations, would greatly benefit conservation of giant gartersnakes by informing more snake-friendly land and water management practices. We studied adult giant gartersnakes at 11 sites in the rice-growing regions of the Sacramento Valley during an extended drought in California to evaluate their response to differences in water availability at the site and individual levels. Although our study indicated that giant gartersnakes make little use of rice fields themselves, and avoid cultivated rice relative to its availability on the landscape, rice is a crucial component of the modern landscape for giant gartersnakes. Giant gartersnakes are strongly associated with the canals that supply water to and drain water from rice fields; these canals provide much more stable habitat than rice fields because they maintain water longer and support marsh-like conditions for most of the giant gartersnake active season. Nonetheless, our results suggest that maintaining canals without neighboring rice fields would be detrimental to giant gartersnake populations, with decreases in giant gartersnake survival rates associated with less rice production in the surrounding landscape. Increased productivity of prey populations, dispersion of potential predators across a larger landscape, and a more secure water supply are just some of the mechanisms by which rice fields might benefit giant gartersnakes in adjacent canals. Results indicate that identifying how rice benefits giant gartersnakes in canals and the extent to which the rice agro-ecosystem could provide these benefits when rice is fallowed would inform the use of water for other purposes without harm to giant gartersnakes. Our study also suggests that without such understanding, maintaining rice and associated canals in the Sacramento Valley is critical for the sustainability of giant gartersnake populations.

California↗