Predictors of breeding site occupancy by amphibians in montane landscapes

Abstract

Ecological relationships and processes vary across species’ geographic distributions, life stages and spatial, and temporal scales. Montane landscapes are characterized by low wetland densities, rugged topographies, and cold climates. Consequently, aquatic‐dependent and low‐vagility ectothermic species (e.g., pool‐breeding amphibians) may exhibit unique ecological associations in montane landscapes. We evaluated the relative importance of breeding‐ and landscape‐scale features associated with spotted salamander (Ambystoma maculatum) and wood frog (Lithobates sylvaticus) wetland occupancy in Maine's Upper Montane‐Alpine Zone ecoregion, and we determined whether models performed better when the inclusive landscape‐scale covariates were estimated with topography‐weighted or circular buffers. We surveyed 135 potential breeding sites during May 2013–June 2014 and evaluated environmental relationships with multi‐season implicit dynamics occupancy models. Breeding site occupancy by both species was influenced solely by breeding‐scale habitat features. Spotted salamander occupancy probabilities increased with previous or current beaver (Castor canadensis) presence, and models generally were better supported when the inclusive landscape‐scale covariates were estimated with topography‐weighted rather than circular buffers. Wood frog occupancy probabilities increased with site area and percent shallows, but neither buffer type was better supported than the other. Model rank order and support varied between buffer types, but model inferences did not. Our results suggest pool‐breeding amphibian conservation in montane Maine include measures to maintain beaver populations and large wetlands with proportionally large areas of shallows ≤1‐m deep. Inconsistencies between our study and previous studies substantiate the value of region‐specific research for augmenting species’ conservation management plans and suggest the application of out‐of‐region inferences may promote ineffective conservation. © 2016 The Wildlife Society.

Multistate occupancy modeling improves understanding of amphibian breeding dynamics in the Greater Yellowstone Area

“…, Groff et al. ) and demonstrates the reward that long term monitoring of natural resources can offer when using an a priori multiple hypothesis approach to describe system dynamics. Further, the current multistate approach has the advantage of estimating the percentage of dry wetlands each year and allows for an expansion of additional wetland states.…”

“…We have employed consistent survey methods that account for imperfect breeding detection for a decade across a large geographic area mostly removed from anthropogenic influences (McMenamin et al 2008). With an average of 291 wetlands surveyed each year, our sample size is notably larger than most studies (Green et al 2013, Fellers et al 2015, Groff et al 2017 and demonstrates the reward that long term monitoring of natural resources can offer when using an a priori multiple hypothesis approach to describe system dynamics. Further, the current multistate approach has the advantage of estimating the percentage of dry wetlands each year and allows for an expansion of additional wetland states.…”

“…() and Groff et al. (). On each visit, we recorded site‐specific covariates (habitat characteristics) such as wetland size (m 2 ), percent cover of emergent vegetation, and maximum depth (<0.5 m, 0.5–1 m, 1–2 m, >2 m).…”

“…We separated replicate surveys by~15 min allowing no communication between observers until after survey completion. These methods are similar to that described in Zipkin et al (2012) and Groff et al (2017). On each visit, we recorded site-specific covariates (habitat characteristics) such as wetland size (m 2 ), percent cover of emergent vegetation, and maximum depth (<0.5 m, 0.5-1 m, 1-2 m, >2 m).…”

Beaver dams are associated with enhanced amphibian diversity via lengthened hydroperiods and increased representation of slow‐developing species

“…In some species, the relationship of amphibians to beavers seems to be context‐dependent. Wood frogs ( Rana sylvatica ) and spotted salamanders ( Ambystoma maculatum ) illustrate such dependency by running the gamut from positive association, to no association, to negative association with beaver dams depending on location and whether beavers are still present at the dammed site (Cunningham et al., 2007; Groff et al., 2017; Hokit & Brown, 2006; Karraker & Gibbs, 2009; Stevens et al., 2007). Pond‐breeding amphibians thus exemplify a group that generally benefits from beaver activity (Cunningham et al., 2007; Dalbeck et al., 2007; Vehkaoja & Nummi, 2015) but defies easy generalisation, highlighting the need for additional specific investigations, especially in areas where the environmental context is rapidly changing.…”