Occupancy modeling of habitat use by white-tailed deer after more than a decade of exclusion in the boreal forest

The exclusion of herbivores in forest areas is a strategy used to reduce
the impact of selective browsing and increase the regeneration of desired
plant species. On Anticosti Island (Québec, Canada), selective browsing by
white-tailed deer prevents the regeneration of balsam fir – white birch
forests leading to their conversion into white spruce forests. Large deer
exclosures were established for ca . 10 to 12 years in clear-cuts with
patches of residual forest from 2001 to 2006 to assist in the natural
regeneration of fir stands and to provide shelter and food resources for
deer. Our objective was to assess how deer use exclosures after the
removal of fences according to their spatial configuration and habitat
composition. We randomly distributed automatic cameras for periods of 14
days during summer in six exclosures ranging from 3.1 to 11.2 km2 (n=25
cameras per exclosure) from which deer were reduced for 10 to 12 years. We
compared candidate occupancy models that included spatial configuration
and food resource variables while simultaneously controlling for variables
affecting detection probability. We obtained weak evidence that deer
habitat use increased by 19% when forage resources, represented by the
cover of Cornus canadensis, increased from 0 to 100%. None of the other
variables (distance between the border of exclosures and cameras and
distance between forest patches and cameras) was retained, suggesting that
the use of regenerating forests by deer in summer after a period of
exclusion is related to forage availability and therefore, any forest
management that improves food production during summer should help
maintain or increase habitat use by deer.