Resource selection of mule deer in a shrub‐steppe ecosystem: influence of woodland distribution and animal behavior

Abstract

Ungulates inhabiting arid ecosystems are reliant on productive forb and shrub communities during summer months to meet nutritional demands for survival and reproduction. In the western United States, expansion of woodland vegetation into shrub-dominated communities and the potential loss of habitat are of concern with regard to animal populations reliant on robust sagebrush shrub and forb vegetation. We used mixed-effects logistic regression to model resource selection of female mule deer (Odocoileus hemionus) during the summers of 2005-2008. We considered selection at two spatial scales, and during three daily activity periods (night, crepuscular, and mid-day) corresponding to resting and foraging. We evaluated habitat variables related to vegetation type, site productivity, terrain attributes, and fine-scale abundance of pinyon-juniper cover. Those attributes allowed us to account for variation in site productivity and animal behaviors that could obscure the true relationship between density of pinyonjuniper woodland and habitat use by mule deer. We detected observable differences in habitat use by mule deer among the three activity periods with significant differences in movement rates. Deer were most active during crepuscular periods corresponding with foraging activity, and least active mid-day when temperatures were highest. Summer habitat consisted of sites with high potential productivity, greater shrub abundance, and greater proximity to riparian areas. Deer avoided high levels of tree cover (>40% coverage) at all spatial and temporal scales, and in general selection declined with increasing pinyonjuniper cover, particularly during foraging periods. Nonetheless, mule deer selected areas with low to intermediate tree cover (10% to 40%) during resting periods and avoided areas of productive shrub and forb vegetation and riparian areas, when surrounded by denser stands of pinyon-juniper cover. These results emphasize the importance of productive shrub and forb vegetation to mule deer inhabiting semi-arid regions and suggest that low levels of tree cover are beneficial, especially during resting periods. Nevertheless, dense pinyon-juniper cover was generally avoided even in areas of high site productivity. These relationships lend support to the concern that increases in large, dense stands of pinyon-juniper reduce availability of summer habitat and alter patterns of resource selection for mule deer, a shrubdependent ungulate.

Sex‐Specific Behaviors of Hunted Mule Deer During Rifle Season

“…Generally, we found that during summer and pre-rifle period, males used areas with more open canopies at night and tended toward denser canopies during the day (~13-14% canopy cover on average). This is consistent with behavior during summer in previous studies on mule deer in arid climates (Hayes and Krausman 1993, Tull et al 2001, Ager et al 2003, Morano et al 2019, where deer are more active in foraging areas at night and select resting areas with moderate canopy cover during the day (other ungulates, Giotto et al 2013, Long et al 2014. During the rifle season, habitat use by males was not related to density of canopy, but males increased distance from motorized routes, suggesting that avoidance of human activity was a priority behavior, as is true during hunting season in other ungulates (white-tailed deer [Odocoileus virginianus], Kilgo et al 1998; roe deer [Capreolus capreolus], Bonnot et al 2013;and elk, Proffitt et al 2013, Paton et al 2017, Spitz et al 2019, Lamont et al 2020.…”

“…Our landscape configuration allowed animals to remain on a mix of public and private lands but in areas where motorized route density (<0.6 km/km 2 on average in our study area) mediated disturbance. Our finding that females used habitat that remained greener longer (i.e., locations with an average brown down of ordinal day 234-240) reinforces the importance of autumn nutrition (Tollefson et al 2010, Hurley et al 2014 and productive summer habitat (Morano et al 2019) for female ungulates (Cook et al 2004). Female use of productive habitat in summer and autumn also reinforces the need for females to replace lost calories from lactation (Oftedal 1985, Parker et al 2009.…”

Dynamic winter weather moderates movement and resource selection of wild turkeys at high‐latitude range limits

“…Resource selection can also be behaviorally motivated, such that individuals make different decisions as they transition among discrete behavioral states (Cooper & Millspaugh, 2001). For example, we may not expect animals to select the same land cover characteristics while foraging as they would during periods of rest or reproduction (Marzluff et al, 2004; Morano et al, 2019), and resident adults may differ in their selection compared with dispersing juveniles (Elliot et al, 2014). Unfortunately, quantifying variation related to individual characteristics and experiences is difficult and often impossible to measure fully, requiring alternative approaches to incorporate such information into models (Patterson et al, 2009).…”

Spatiotemporal patterns of male and female white‐tailed deer on a hunted landscape

“…We analyzed selection for each dominant cover type using a resource selection function (RSF), in which probability of use was defined as the proportional use of that cover‐type relative to its availability within the home range, resulting in a third‐order selection (Aebischer et al, 1993 ; Boyce et al, 2002 ; Johnson, 1980 ; McKee et al, 2015 ; Morano et al, 2019 ). Specifically, we used functions within the adehabitatHR package (Calenge, 2006 ) in R statistical software (version 4.0.2, R Core Team, 2020 ) to create 95% kernel home ranges, and functions within the raster package (Hijmans et al, 2020 ) to extract our covariate data (Karns et al, 2012 ; McKee et al, 2015 ).…”