Shrub encroachment creates a dynamic landscape of fear for desert lagomorphs via multiple pathways

Abstract

Shrub encroachment is transforming arid and semiarid grasslands worldwide. Such transitions should influence predator–prey interactions because vegetation cover often affects risk perception by prey and contributes to their landscape of fear. We examined how the landscape of fear of two desert lagomorphs (black‐tailed jackrabbit, Lepus californicus; desert cottontail, Sylvilagus audubonii) changes across grassland‐to‐shrubland gradients at Jornada Basin Long Term Ecological Research site in the Chihuahuan Desert of southern New Mexico. We test whether shrub encroachment shapes risk differently for these two lagomorphs because of differences in body size and predator escape tactics. We also examine whether an ecosystem engineer of grasslands (banner‐tailed kangaroo rat, Dipodomys spectabilis) mediates risk perception through the creation of escape refuge and whether trade‐offs exist between shrub encroachment and the local reduction of banner‐tailed kangaroo rats caused by shrub expansion. We measured perceived predation risk with flight initiation distances (FIDs) and then used structural equation modeling to tease apart the hypothesized direct and indirect pathways for how shrub encroachment could affect perceived risk. A total negative effect of shrub cover on FID was supported for jackrabbits and cottontails, suggesting both species perceive shrubbier habitat as safer. Increases in fine‐scale concealment also reduced risk for cottontails, but not jackrabbits, likely because cottontails rely on crypsis to avoid predator detection whereas jackrabbits rely on speed and agility to outrun predators. Perceived risk was reduced when individuals were near kangaroo rat mounds only for cottontails because the smaller species can use banner‐tailed kangaroo rat mounds as refuge. Shrub encroachment greatly reduced the availability of mounds. Thus, a trade‐off exists for cottontails in which shrub encroachment directly reduced perceived risk, but indirectly increased perceived risk through the local extirpation of an ecosystem engineer. Our work illustrates how the expansion of shrub encroachment can create a dynamic landscape of fear for populations of prey species involving direct and indirect pathways contingent on prey body size, escape tactics, and activities of an ecosystem engineer.

The landscape of fear has individual layers: an experimental test of among‐individual differences in perceived predation risk during foraging

“…Mapping perceived predation risk is notoriously difficult (Gaynor et al 2019). Widely used approaches include indirect proxies, such as characteristics of the physical landscape (vegetation cover: Wagnon et al 2020; microhabitat: Hertel et al 2019; distance to cover: van der Merwe and Brown 2008), and spatiotemporal distribution of antipredator behaviour (Martínez et al 2017). However, these indirect proxies and behavioural responses only partially represent the distribution of perceived predation risk (Gaynor et al 2019).…”

Forager‐mediated cascading effects on food resource species diversity

“…The behavioral responses of prey can be mapped into a landscape of fear, which is defined as the spatiotemporal variation in perceived predation risk by the forager (Gaynor et al, 2019 ; Laundré et al, 2001 , 2014 ), which affect the distribution of multispecies resources in a landscape (Monk & Schmitz, 2021 ). The presence of a predator can be evident and perceived directly via sight or smell (Pustilnik et al, 2020 ; Saavedra & Amo, 2020 ), or just inferred indirectly by the forager through environmental conditions, such as habitat cover (Wagnon et al, 2020 ) or variable visibility conditions (Ranåker et al, 2012 ). Thus, even if no predator is present, foragers perceive predation risk.…”

“…The presence of a predator can be evident and perceived directly via sight or smell (Pustilnik et al, 2020;Saavedra & Amo, 2020), or just inferred indirectly by the forager through environmental conditions, such as habitat cover (Wagnon et al, 2020) or variable visibility conditions (Ranåker et al, 2012). Thus, even if no predator is present, foragers perceive predation risk.…”