Fifty years of European ungulate dietary studies: a synthesis

Abstract

Over recent decades, ungulate populations across Europe have undergone a rapid recovery. While this constitutes a conservation success, there is increasing concern about their impacts on shared resources with humans. Understanding ungulate food choices is crucial for predicting such impacts. Numerous studies have focused on single species or communities at narrow spatial scales. Here, we used 265 published diets from 87 European studies to investigate patterns of resource use by four common deer species (moose Alces alces, red deer Cervus elaphus, roe deer Capreolus capreolus and fallow deer Dama dama), and wild boar Sus scrofa at the continental scale. On average, deer diets separated mostly along a gradient from grass to browse. Fallow deer diets contained the most and moose diets the least amount of grass, but we also found large intraspecific variation among all deer species. Diets of roe deer, a presumed browser, frequently contained ≥ 25% grass. Wild boar diet contained grass in amounts similar to red deer but otherwise differed strongly from deer diets. All five ungulate species shifted to eating higher proportions of woody browse during winter. Habitat influenced variation in intraspecific diets, but the proportions of key forage types related to feeding type (i.e. grass for intermediate feeders red and fallow deer, and shrubs for the browsers moose and roe deer) remained fairly consisted across habitat types. In northern and central Europe, diet similarity between roe deer and red deer was highest during winter and spring and lowest during summer and autumn but remained constant across the seasons in southern Europe. We foresee that, as interspecific interactions driven by land‐use and climatic changes increase across Europe, further monitoring and testing will be needed to understand the dynamics of dietary niche partitioning among ungulates.

Wild ungulate species differ in their contribution to the transmission of Ixodes ricinus-borne pathogens

“…This may explain why we found a relatively low tick burden on moose, which have particularly long legs [ 48 ]. Moreover, we found the highest infestation prevalence and intensity of nymphs on the ears of fallow deer, which supports our hypothesis that feeding type influences tick infestation rates, since fallow deer graze more than the other deer species [ 17 ]. Ticks, which are mostly questing on ground vegetation, will more easily access grazing ungulates via the ears (and the head) than species that more frequently browse vegetation strata higher up, such as moose [ 49 ].…”

Nutritional niche separation between native roe deer and the nonnative fallow deer—a test of interspecific competition

“…We predict that (1) both roe deer and fallow deer show seasonal variation in nutrient composition of ingested forage, with more easily digestible forage (relatively high in nonstructural carbohydrates but low in digestible fiber and lignin) ingested in spring and summer compared to fall and winter because of the seasonal differences in availability of easily digestible forage (Van Soest 1994;Marshal et al 2005). In addition, we predict that (2) roe deer ingest forage higher in protein and nonstructural carbohydrates and lower in digestible fibers compared to fallow deer based on where these two ruminant species are placed on the continuum from browsers to grazers (Hofmann 1989), which is supported by findings by Spitzer et al (2020) and from the study area by Nichols et al (2016) who clearly show that fallow deer select grass to a much higher extent than roe deer. Grasses often contain higher concentrations of digestible fiber (both hemicellulose and cellulose) than herbs and browse (Hummel et al 2006;Verheyden-Tixier et al 2008).…”

“…Overall, cellulose and hemicellulose concentrations in rumen samples were positively correlated with each other. Roe deer in our study area are known to eat less graminoids compared to fallow deer (Nichols et al 2016), and other studies have shown that roe deer' intake of graminoids is low, ranging between 3.8% (winter) and ca 9% (growing season) (Cederlund et al 1980;Gębczyńska 1980;Obidziński et al 2013;Spitzer et al 2020). In contrast, there are several studies showing that the diet of fallow deer is frequently dominated by graminoids (e.g., Putman 1986;Poli et al 1996;Obidziński et al 2013;Nichols et al 2016), but sometimes it is dominated by trees or shrubs (Bruno and Apollonio 1991;Poli et al 1996) or acorns (Morse et al 2009).…”

Dynamics and predicted distribution of an irrupting ‘sleeper’ population: fallow deer in Tasmania

“…Our model of habitat suitability suggested that fallow deer prefer flat areas with grassy vegetation types, probably because of a dietary preference for grasses (Elliott, Barrett 1985;Nugent 1990;Spitzer et al 2020). Flatter, open areas are also favourable for gregarious behaviour and sight-based anti-predator responses of ungulates (Hopewell et al 2005;Underwood 1982).…”

“…For covariate details, see Table S3. We expected that grassy vegetation types would positively influence fallow deer abundance (King, Forsyth 2020;Nugent 1990;Putman et al 1993;Spitzer et al 2020). We expected that highly rugged terrain would negatively affect deer abundance, and that alpine treeless vegetation -a low-productivity vegetation group occurring in harsh climates -might negatively affect deer abundance.…”