Differences in dietary niche and foraging behavior of sympatric mule and white‐tailed deer

Abstract

Mule (Odocoileus hemionus) and white‐tailed deer (Odocoileus virginianus) are congeneric and share similar life histories, yet their distribution is segregated across much of North America. Extensive research on both species within and outside their zone of co‐occurrence has not fully explained these distribution patterns, especially the potential role of diet and foraging behavior. Therefore, we used a common garden experiment to compare diet composition, diet quality, foraging behavior, and intake of tractable mule and white‐tailed deer foraging together within the dry Douglas‐fir (Pseudotsuga menziesii)/ponderosa pine (Pinus ponderosa) forests of northeastern Washington. We sampled at 21 0.5‐ha sites from June to August 2016. We used standard bite count techniques coupled with forage biomass sampling, behavioral observations, and nutritional analyses to compare the foraging ecology of the two species. Mule and white‐tailed deer had similar activity patterns. However, mule deer took larger bites and harvested food faster than white‐tailed deer, and white‐tailed deer consumed more diverse but higher‐quality diets than mule deer. These differences resulted in mule deer acquiring ~25% more dry matter and digestible energy per day. About 90% of the diets consumed by both deer species consisted of deciduous shrubs and forbs, and they selected many of the same plant species. However, overall diet composition was 38% dissimilar, with mule deer consuming diets that were more likely to contain shrubs with higher levels of tannins and lower levels of dry matter digestibility than diets eaten by white‐tailed deer. Dietary overlap was greatest at both very low and very high forage biomass, indicating potential for modest resource competition or partitioning. Our research provides evidence that differences in diet composition of mule and white‐tailed deer do not merely reflect differences in habitat selection, but also suggest the species differ in their fundamental nutritional niches.

Ecological and behavioral mechanisms of density‐dependent habitat expansion in a recovering African ungulate population

“…S4). Our calculations suggest that waterbuck ate between 3.2% (savanna) and 3.4% (floodplain) of their body mass daily, which aligns with estimates from both captive and field-based feeding trials of female North American cervids (Berry et al 2019, Ulappa et al 2020. Waterbuck in the floodplain also consumed more protein per day than those in savanna (Fig.…”

Habitat use and spatio‐temporal interactions of mule and white‐tailed deer in an area of sympatry in NE Washington

“…However, they overlap across a broad zone of sympatry, primarily along the Rocky Mountains and in the surrounding Plains regions (Geist 1998, Jacobson 2003, Lyman 2006, Hygnstrom et al 2008. Habitat use by free-ranging deer of both species has been extensively studied in areas of both allopatry and sympatry (see review in Berry et al 2019), primarily using an animal-based approach (i.e., observing groups of animals, following individual animals using radio telemetry, collecting fecal samples for microhistology, stable isotope analyses of liver tissue) (Anthony and Smith 1977, Lingle 2001, 2002, Walter et al 2009, Whitney et al 2011, Dellinger et al 2019. These studies and others demonstrated varying degrees of resource and habitat partitioning, generally finding that large-scale topographic variation or habitat association facilitates the segregation of these two species (Smith 1987, Woods et al 1989, Avey et al 2003, Whittaker and Lindzey 2004, Brunjes et al 2006).…”

“…We first determined the environmental variables predicting probability of use by each species using single-species occupancy models (Mackenzie et al 2002) and compared model coefficients between species. Based on previous studies (as reviewed by Berry et al 2019), we expected that compared to white-tailed deer, mule deer would use sites (1) with higher elevations, steeper slopes, more rugged terrain, and further from roads that form easily traveled corridors for predators Pellis 2002, Dellinger et al 2019); (2) that had received thinning treatments that reduced conifer overstory, with a lower canopy cover and basal area and therefore less concealment cover and more shrubs; and (3) further from the edge of the protected National Forest boundary, and thus from human-altered landscapes such as agriculture (Table 1). We also expected, (4) mule deer to be more likely to use the western portion, and white-tailed deer the eastern portion, of the study area because whitetailed deer appear to be expanding their range in an east-west direction (Table 1; O'Farrell and Hedlund 1972, Dawe et al 2014, Dawe and Boutin 2016, Hanberry and Hanberry 2020.…”

Fenced community gardens effectively mitigate the negative impacts of white-tailed deer on household food security

“…White-tailed deer are generalist herbivores that can adapt to a wide variety of habitats and feed on a wide range of native and non-native plants (Weckerly & Nelson, 1990). Deer typically consume between 1 to 4 percent of their bodyweight in plants each day, representing approximately 1.0 to 1.2 kg of dry plant material (Berry et al, 2019). White-tailed deer are found across Canada east of the Rocky Mountains (Figure 1a) and can be commonly observed in human-dominated landscapes such as the Greater Toronto Area (Figure 1b).…”