Temporal scales, trade‐offs, and functional responses in red deer habitat selection

Abstract

Animals selecting habitats often have to consider many factors, e.g., food and cover for safety. However, each habitat type often lacks an adequate mixture of these factors. Analyses of habitat selection using resource selection functions (RSFs) for animal radiotelemetry data typically ignore trade-offs, and the fact that these may change during an animal's daily foraging and resting rhythm on a short-term basis. This may lead to changes in the relative use of habitat types if availability differs among individual home ranges, called functional responses in habitat selection. Here, we identify such functional responses and their underlying behavioral mechanisms by estimating RSFs through mixed-effects logistic regression of telemetry data on 62 female red deer (Cervus elaphus) in Norway. Habitat selection changed with time of day and activity, suggesting a trade-off in habitat selection related to forage quantity or quality vs. shelter. Red deer frequently used pastures offering abundant forage and little canopy cover during nighttime when actively foraging, while spending much of their time in forested habitats with less forage but more cover during daytime when they are more often inactive. Selection for pastures was higher when availability was low and decreased with increasing availability. Moreover, we show for the first time that in the real world with forest habitats also containing some forage, there was both increasing selection of pastures (i.e., not proportional use) and reduced time spent in pastures (i.e., not constant time use) with lowered availability of pastures within the home range. Our study demonstrates that landscape-level habitat composition modifies the trade-off between food and cover for large herbivorous mammals. Consequently, landscapes are likely to differ in their vulnerability to crop damage and threat to biodiversity from grazing.

Foraging theory upscaled: the behavioural ecology of herbivore movement

“…Disturbance by humans can alter the activity schedule as well as habitat features selected. Red deer subject to high hunting pressure in Norway remained inactive in forest cover for most of the day, moving into pastures to forage at night (Godvik et al 2009). Influences of predation on prey movements are discussed in more detail by Merrill et al (2010).…”

Determining habitat quality for species that demonstrate dynamic habitat selection

“…Individuals might employ different selection responses at different scales, so as to maximize fitness given the set of resources available (Resetarits 2005, Godvik et al. 2009). For example, within‐year habitat selection that correlates positively with survival in the short term could come at the expense of reproductive success in the long term (McLoughlin et al.…”

Improving broad scale forage mapping and habitat selection analyses with airborne laser scanning: the case of moose

“…Direct inclusion of structural variables is a common approach to ALS based habitat studies (Graf et al 2009, Coops et al 2010, Melin et al 2013), but the ecological links are not always obvious. Habitat selection studies that lack detailed field data on forage and cover availability typically characterize habitat as ''open'' or ''dense'' (Godvik et al 2009, Ciuti et al 2012, Tolon et al 2012) and assume these are ''forage'' and ''cover'' habitat types respectively. There are clear drawbacks to this, as we can expect variation in selection within habitat types (Blix et al 2014) linked to variation in one or multiple resources or characteristics within a habitat type.…”

“…Despite the strong influence of food resources on both habitat selection and population dynamics, quantification of food availability at large spatial scales remains challenging. Most studies rely on environmental proxies of forage availability and cover, such as NDVI (Mueller et al 2008), land cover classes (Uzal et al 2013), or forest stand characteristics like productivity (Godvik et al 2009), dominant tree species (Dussault et al 2005a) and age class (Mabille et al 2012). Often, such proxies are used without quantifying levels of food and cover, though exceptions occur (van Beest et al 2010b, Avgar et al 2013, Blix et al 2014.…”