Examining functional components of cover: the relationship between concealment and visibility in shrub‐steppe habitat

Abstract

Abstract. The term ''cover'' has been used broadly in ecology, with a wide range of meanings, from thermal cover to security cover, to escape cover. Some habitat features could provide both thermal and security cover, or both concealment and escape cover; but in other cases, habitat features such as vegetation could impose a tradeoff between opposing functions of cover. Cover that conceals an animal from a predator also could reduce the animal's visibility and thus, its ability to detect a predator early enough to escape capture. We quantified the opposing functional properties of cover (concealment and visibility) and evaluated the relationship between these properties using continuous measures in sagebrush-steppe and grassland habitats. We hypothesized that concealment and visibility would be inversely related and that the slope of this relationship would differ among sites with varying density and patchiness of shrub vegetation, imposing differing tradeoff scenarios. Concealment and visibility were inversely, but not perfectly related, implying that animals must make tradeoffs between the properties of cover, but they could achieve higher levels of one property while giving up relatively less of the other. In addition, we examined potential tradeoffs by pygmy rabbits (Brachylagus idahoensis) by comparing concealment and visibility at locations used by rabbits with measurements collected at random locations. At a small scale, pygmy rabbits traded off visibility for concealment in dense and sparse vegetation, but not in patchy vegetation. Although cover is an intuitively simple concept, it is functionally more complex, and this study provides insight into the opposing mechanisms of cover that might influence habitat use. Our work provides an initial step towards more fully understanding how cover functionally relates to predation risk.

Consistent nest-site selection across habitats increases fitness in Asian Houbara

“…Because the needs for concealment and a clear view for visual security (i.e. the ability of the incubating bird to observe potential danger at a large enough distance to allow it to escape) may conflict (Camp et al 2013), birds may potentially trade off these requirements when selecting a nest site (Götmark et al 1995, Lloyd 2004, Miller et al 2007, Magaña et al 2010.…”

Living and dying in a multi‐predator landscape of fear: roe deer are squeezed by contrasting pattern of predation risk imposed by lynx and humans

“…Cover is a key habitat element whose multiple functions depend on the species and context (Mysterud and Østbye 1999, Camp et al 2013). Cover represents relative safety in a plethora of cases across different systems and species (small mammals; Kotler et al 1992, freshwater snails; Turner et al 1999, ungulates; Hernandez and Laundré 2005, carnivores; Ordiz et al 2011), but its visual and locomotive obstruction can sometimes be to the advantage of the predator, rather than the prey (Camp et al 2013). There are well established field methods for quantifying horizontal and vertical cover (Mysterud and Østbye 1999), but these are time‐consuming and limited to point measurements in the field.…”

Unmanned aerial systems measure structural habitat features for wildlife across multiple scales

“…We estimated canopy cover by placing four 15 × 15 cm coverboards under each plant and took a digital photograph directly over the plant from a height of c . 1.5 m. A digital grid with n = 25 intersections was placed over each coverboard in the photograph to determine the percentage of the coverboard obscured by vegetation, which was used as an index of canopy cover (Camp, Rachlow, Woods, Johnson, & Shipley, ; Nobler, ). We obtained patch‐scale (3 m radius) estimates by averaging the plant‐scale measurements of height, volume and canopy cover.…”