A herbivore's food landscape: seasonal dynamics and nutritional implications of diet selection by a red deer population in contrasting Alpine habitats

Abstract

Dietary constraints for large herbivores tend to be most strongly linked to quality of the forage available. In highly seasonal environments, such as mountain areas, both plant quality and available biomass may act as constraints. However, studies addressing the nutritional basis of diet selection of wild large herbivores under harsh conditions in sufficiently large spatial and temporal frameworks are scarce. We studied the functional importance of relative variability in plant quality and biomass for diet selection by a migratory population of Alpine red deer (Cervus elaphus) at the landscape scale and across an annual cycle. Botanical diet composition at plant group level did not show a particular 'Alpine pattern' but was similar to known patterns from lowland areas. Sources of variability were season, habitat (either open land or forest) and sex. Red deer foraged selectively in all seasons, and preferences for plant groups were negatively linked to plant abundances. Use and selection of plant groups were associated with high nutritional value (high crude protein and organic matter, low fibre), but partly also with high levels of active tannins. In the cold season, deer made strong nocturnal use of fertilized valley floor meadows offering high-quality grass, but still showed some selection for tannin-and fibre-rich coniferous browse, indicating a need for supplementing grass intake. Altogether, the nutritional value of the diet exceeded that of the forage available in the forested habitat, which was at or below the lower threshold for fulfilling metabolic needs of red deer. High-quality grass on farmed meadows may thus be a critical source of food in mountainous areas during winter.

Plant constituents affecting food selection by sika deer

“…Rather, it may be that our study deer obtained sufficient protein to meet their daily requirements from a limited number of protein‐rich food items and then sought other food items that were high in other favorable constituents, such as fat, but had more modest protein content. This may be relevant for other ungulate diet studies reporting that crude protein contents of frequently eaten food items were similar to or even significantly lower than those of less frequently eaten items under some conditions using univariate analyses (e.g., Vourc'h et al , Verheyden‐Tixier et al , Zweifel‐Schielly et al ). It is possible that positive associations of protein content with food selection might have been detected if they had used multivariate analyses, as in our study.…”

“…However, these approaches all have weaknesses. It is generally difficult to identify plant parts to species in the rumen or feces, resulting in food items being combined into broad categories, such as grasses, forbs, and browse (Moser et al , Zweifel‐Schielly et al ), and the amounts of individual plant constituents may differ greatly among the species even within each of these categories. Fecal analyses are also confounded because digestibility can vary between food types (Verheyden‐Tixier et al , Wam and Hjeljord ).…”

Factors influencing the seasonal diet selection by woodland caribou (Rangifer tarandus tarandus) in boreal forests in Ontario

“…Ungulate diet selection is governed by many factors including food content (e.g., fibre, protein, nutrients, secondary compounds) (Renecker and Schwartz 2007;Forsyth et al 2005), forage availability (Danell and Ericson 1986), sex and age (Staines et al 1982;Mysterud 2000), time of day (Newman et al 1995), competition among ungulate species (Dailey et al 1984), and plant phenology (Bee et al 2010;Zweifel-Schielly et al 2012). Other behavioural factors related to avoiding hunters, predators, and insects may also play a role in habitat selection, which may affect diet selection (Belovsky 1991;Skogland 1991;Newman et al 1995).…”

Colonization in Mediterranean old‐fields: the role of dispersal and plant–plant interactions

“…Both herbivores have contrasting foraging strategies: whereas sheep feed mainly on grasses and eat seedlings of woody plants when present in open areas, woody plants such as J. sabina are a basic part of red deer diet (Zweifel‐Schielly et al. ; Ferreira et al. ).…”