Mechanisms underlying increased nest predation in natural gas fields: a test of the mesopredator release hypothesis

Abstract

Anthropogenic activities are changing landscapes and the context in which predator–prey dynamics evolved, thereby altering key ecological processes and community structure. Yet, the specific mechanisms underlying such changes are rarely understood. We tested whether a mesopredator release explained increased rodent density and concomitant predation of songbird nests near natural gas development. From 2015 to 2016, we surveyed apex predators (coyotes, badgers, raptors, and corvids) and measured apparent survival and perceived predation risk of deer mice (Peromyscus maniculatus; a primary nest predator), at 12 plots spanning a gradient of surface disturbance caused by energy development in Wyoming, USA. Additionally, we measured densities of three nest predators: deer mice, least chipmunks (Tamias minimus), and thirteen‐lined ground squirrels (Ictidomys tridecemlineatus). Contrary to the mesopredator release hypothesis, counts of apex predators and perceived predation risk of deer mice increased with surface disturbance from energy development, whereas apparent survival of mice decreased. Densities of mice and ground squirrels, however, increased with surface disturbance, despite increased predation pressure. We therefore rejected the mesopredator release hypothesis as a potential mechanism underlying altered trophic dynamics near energy development. Our results suggest that apex predator control measures would not benefit declining songbirds on natural gas fields. Rather, apex predator abundance may be regulated from the bottom‐up by rodents in this system. Our results corroborate a pattern showing weakened effects of mesopredator release in habitats modified by humans. Understanding how predator–prey dynamics may be altered in novel environments requires an understanding of how predators and prey alike respond to habitat change under different contexts.

The effects of forest edge and nest height on nest predation in a U.K. deciduous forest fragment

“…These results are in contrast to previous findings that cast doubt on rodents willingness to predate quail eggs in artificial nest experiments (Niehaus et al, 2003). Natural experiments in the U.S. have found over 75% of ground nest predations are caused by terrestrial rodents (Sanders & Chalfoun, 2019).…”

The effects of forest edge and nest height on nest predation in a U.K. deciduous forest fragment

“…These results are in contrast to previous findings that cast doubt on rodents willingness to predate quail eggs in artificial nest experiments . Natural experiments in the U.S. have found over 75% of ground nest predations are caused by terrestrial rodents (Sanders & Chalfoun, 2019) These results are slightly higher than our experiment (63%), however my results underline the ubiquity of the significant impacts rodents have on ground nesting bird communities.…”

Does habitat reclamation following energy development benefit songbird nest survival?

“…In sagebrush habitats in Washington and Wyoming, lower nest survival in habitats fragmented by human activities was consistent across a suite of ground-and shrub-nesting songbirds (e.g., Brewer's Sparrows, Sagebrush Sparrows [Artemisiopiza nevadensis], Sage Thrashers). The increased nest predation in these fragmented habitats was attributed to rodent nest predators achieving greater abundance in these areas (Vander Haegen et al 2002, Hethcoat and Chaloun 2015b, Sanders and Chalfoun 2019. Therefore, we suggest that because Brewer's Sparrow nests are experiencing greater predation risk in sagebrush patches with less sagebrush cover and higher levels of active disturbance, it is probable that these co-occurring songbird species were also experiencing greater nest predation risk.…”

“…Anthropogenic habitat modification can result in heightened risk of nest predation due to changes in predator communities (e.g., expansion of novel predators that benefit from human subsidies), predator abundance, and predatorprey interactions (Winter et al 2000, Chalfoun et al 2002, Howe et al 2014, Kirol et al 2018. The specific mechanisms that drive impacts of energy development (i.e., increased predation risk) on songbird nest survival are not well understood (but see Sanders and Chalfoun 2019). Impacts of energy development on songbird nest survival have been attributed to the physical footprint (hereafter footprint) of development (native habitat removal, fragmentation, and anthropogenic edge; Hethcoat and Chalfoun 2015a, Bernath-Plaisted and Koper 2016, Sanders and Chalfoun 2018 and to specific energy infrastructure features such as power lines (DeGregorio et al 2014).…”