Predation risk landscape modifies flying and red squirrel nest site occupancy independently of habitat amount

Abstract

Habitat choice often entails trade-offs between food availability and predation risk. Understanding the distribution of individuals in space thus requires that both habitat characteristics and predation risk are considered simultaneously. Here, we studied the nest box use of two arboreal squirrels who share preferred habitat with their main predators. Nocturnal Ural owls (Strix uralensis) decreased occurrence of night-active flying squirrels (Pteromys volans) and diurnal goshawks (Accipiter gentilis) that of day-active red squirrels (Sciurus vulgaris). Unexpectedly, the amount of preferred habitat had no effect on nest box use, but, surprisingly, both squirrel species seemed to benefit from close proximity to agricultural fields and red squirrels to urban areas. We found no evidence of trade-off between settling in a high-quality habitat and avoiding predators. However, the amount of poor-quality young pine forests was lower in occupied sites where goshawks were present, possibly indicating habitat specific predation on red squirrels. The results suggest that erecting nest boxes for Ural owls should be avoided in the vicinity of flying squirrel territories in order to conserve the near threatened flying squirrels. Our results also suggest that flying squirrels do not always need continuous old forests, and hence the currently insufficient conservation practices could be improved with reasonable increases in the areas left untouched around their nests. The results of this study demonstrate the importance of taking into account both habitat requirements and predation risk as well as their interactive effects when modeling the occupancy of threatened animal species and planning their conservation.

Large-scale spatial synchrony in red squirrel populations driven by a bottom-up effect

“…Red squirrels do well in human-dominated areas (e.g. Fey et al 2016, Jokimäki et al 2017, Turkia et al 2018a, where they find alternative food resources provided by humans. Pine martens have not yet settled to urban areas in Finland, and goshawks mainly visit urban areas in the winter (Vuorisalo et al 2003), although goshawks have recently also started to thrive near to and within cities (Solonen 2008).…”

“…Previous studies suggest that the effect of goshawks on red squirrels is not straightforward, but may vary depending on other factors than mere abundances of predator and prey. For example, Turkia et al (2018a) found support for habitat-specific predation by goshawks, whereby goshawks affected red squirrel occurrence most negatively in a mutually non-preferred habitat. Locally, predator avoidance can affect space use of red squirrels, but on a larger scale, common habitat preferences arise as the dominant phenomena causing positive correlation between their abundances.…”

The effect of landscape structure on dispersal distances of the Eurasian red squirrel

“…However, this hypothesis seems unlikely in our case (see also Fey et al, 2016) because the amount of unpreferred habitat along the dispersal routes did not affect dispersal distances. We think the association with edges observed in this study simply reflects the preference for edge habitats in our study areas (Turkia et al, 2018).…”

“…Perhaps this result reflects individuals spending time and/or moving along edges (see e.g., Latham, Latham, Boyce, & Boutin, ). Indeed, earlier studies have observed that red squirrels may prefer edge habitats (Dylewski, Przyborowski, & Myczko, ; Turkia, Korpimäki, Villers, & Selonen, ). In the case of the red squirrel, the reason to spend time at forest edges may be due to the possibly larger cone production of spruces growing on edges and getting more light for their growth (Dylewski et al, ).…”

Variation in behavioral traits of two frugivorous mammals may lead to differential responses to human disturbance

“…Proximity to human settlements and human disturbance influenced chimpanzees relatively less than gorillas (Figures 4 and 6), indicating that chimpanzees may experience a trade‐off between finding fruits and avoiding perceived predation risk. This trade‐off has been documented in wildebeests (M'Soka et al, 2017) and red squirrels (Turkia, Korpimaki, Villers, & Selonen, 2018). If a species experiences a trade‐off between access to a resource and predation risk, it may avoid predation or areas of high predation risk when it has an alternative area in which to find food (Frid & Dill, 2002).…”