Temporal scales of density‐dependent habitat selection in a large grazing herbivore

Abstract

Habitat selection is a density‐dependent process, but little is known regarding how this relationship may vary across different temporal scales. Over long time scales, grazing shapes the structure, diversity and functioning of terrestrial ecosystems, and grazing‐induced changes in forage production over time are likely to affect the level of density dependence in habitat selection. In this fully‐replicated, landscape‐scale experiment, we investigated how density‐dependent habitat selection by a large grazing herbivore, sheep Ovis aries, develops over the time scale of a decade. We also address an often‐neglected challenge in habitat selection studies; namely, whether there is variation in use within a particular habitat or vegetation type and why. We found clear evidence of density dependence in habitat selection, with a wider use of habitats at high density. Despite a change in the standing biomass of high‐productivity vegetation at high herbivore density over the years, with herb biomass declining and graminoid biomass increasing, there was no clear evidence that these grazing‐induced changes in habitat over the years were strong enough to affect the level of density‐dependent habitat selection. The difference in selection for high versus low‐productivity habitats remained similar, despite annual fluctuations in the strength of selection. We found strong variation in selection within each vegetation type, even when vegetation types were mapped at a fine‐resolution scale. Our study shows that despite the interactive effects of herbivores and habitats, they are not always sufficiently strong enough to affect the level of density‐dependent habitat selection.

Ecological dynamics in habitat selection of reindeer: an interplay of spatial scale, time, and individual animal's choice

“…However, multiple issues remain unclear, including (1) the temporal variations in space use within a particular habitat, (2) its driving forces (Blix et al 2014), and (3) the intraspecies variations in space use patterns (Anderson and Johnson 2014). In this study, we aim to explicitly address both the spatiotemporal and individual variations in habitat selection by domesticated reindeer in the southern fringe of their range in Norway.…”

Temporal patterns of deer–vehicle collisions consistent with deer activity pattern and density increase but not general accident risk

“…positively density dependent, remains difficult to assess. In general, habitat selection (Mobaek et al, 2009;Blix et al, 2014;van Beest et al, 2014), activity (Mobaek et al, 2012) and home range size (Kjellander et al, 2004) of large herbivores are density dependent. In particular, at high density, more habitats are used, which also forces deer into more urban environments, and one might therefore expect a more than proportional increase in DVCs with increasing density of deer.…”

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

“…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. By using ALS instead of subjective habitat classes, we have decoupled the physical structure of the habitat from other resources, and moved towards a direct investigation of animals' habitat selection on a functional gradient in cover that is fully quantitative.…”

“…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. It is well known that the physical structure of the habitat is also important for habitat selection as cover is used for concealment and thermal shelter (Mysterud andØstbye 1999, DePerno et al 2003).…”