Tunnel Diameter as a Noninvasive Method of Detecting Pocket Gopher (Geomyidae) Occupancy

Abstract

Challenges in monitoring rare and elusive species often involve low detection and sampling success. Noninvasive methods have allowed researchers to more efficiently monitor rare and elusive species while reducing costs of more invasive, traditional techniques. We evaluated the use of a noninvasive method as an alternative to live‐trapping pocket gophers. We found that tunnel diameter can be used to help distinguish between occupancy by the Wyoming pocket gopher (Thomomys clusius; a species of conservation concern) and its more abundant and widespread congener, the northern pocket gopher (T. talpoides). Our method reduces reliance on more invasive methods of monitoring occupancy (i.e., live‐ or kill‐trapping) for co‐occurring pocket gopher species, and likely can be extended to survey for other species of fossorial mammals. © 2020 The Wildlife Society.

Diet selection, commonness, and rarity in a pair of smooth-toothed pocket gophers

“…A correlation between body size, competitive dominance, and restricted resource requirements have held elsewhere, resulting in smaller species being restricted to less favorable habitats (Kennerly 1959;Best 1973). Wyoming pocket gophers are smaller than northern pocket gophers in both body length and weight (Thaeler and Hinesley 1979;Keinath et al 2014;Brito and Sanchez 2020), suggesting that they are confined to areas unusable by the competitively superior Northern Pocket Gopher.…”

“…1). At our study sites in south-central Wyoming, northern pocket gophers are approximately 150% heavier than Wyoming pocket gophers (81 g versus 54 g, respectively); males and females of each species do not differ in mass (Brito and Sanchez 2020). Although little is known about the ecology of the Wyoming Pocket Gopher, other Thomomys spp.…”

“…In June of 2017–2019, we surveyed for the presence of pocket gophers at eighteen 640-km 2 (i.e., quarter section) sites. Members of the genus Thomomys excavate chambers at the terminus of tunnels, creating diagnostic mounds that are conspicuous aboveground (Brown and Hickman 1973; Huntly and Reichman 1994; Brito and Sanchez 2020). Upon identifying active mounds at 16 sites, we livetrapped pocket gophers from June to October 2017–2019.…”

“…We developed an a priori path analysis model (Fig. 3A) based on research by Keinath et al (2014) using the piecewiseSEM package (Lefcheck 2016) in Program R. In the event that our a priori path model—in which gopher and saltbush distributions would be purely associational—had been supported, we would have focused our efforts on quantifying a broader range of soil properties, particularly soil resistance (which might be expected to differentially affect energetic costs of burrowing in the smaller Wyoming Pocket Gopher relative to the larger Northern Pocket Gopher; Brito and Sanchez 2020; see also Perissinotti et al 2009). We inspected variance inflation factors of covariates to check for collinearity.…”