Abstract
Social dominance is widely known to facilitate access to food resources in many animal species such as deer. However, research has paid little attention to dominance in ad libitum access to food because it was thought not to result in any benefit for dominant individuals. In this study we assessed if, even under ad libitum conditions, social rank may allow dominant hinds to consume the preferred components of food. Forty-four red deer hinds (Cervus elaphus) were allowed to consume ad libitum meal consisting of pellets of sunflower, lucerne and orange, and seeds of cereals, corn, cotton, and carob tree. The meal was placed only in one feeder, which reduced accessibility to a few individuals simultaneously. During seven days, feeding behavior (order of access, time to first feeding bout, total time spent feeding, and time per feeding bout) were assessed during the first hour. The relative abundance of each meal component was assessed at times 0, 1 and 5 h, as well as its nutritional composition. Social rank was positively related to the amount of time spent feeding during the 1st h (P = 0.048). Selection indices were positively correlated with energy (P = 0.018 during the 1st h and P = 0.047 from 1st to 5th) and fat (only during the 1st h; P = 0.036), but also negatively with certain minerals. Thus, dominant hinds could select high energy meal components for longer time under an ad libitum but restricted food access setting. Selection indices showed a higher selectivity when food availability was higher (1st hour respect to 1st to 5th). Finally, high and low ranking hinds had longer time per feeding bout than mid ones (P = 0.011), suggesting complex behavioral feeding tactics of low ranking social ungulates.
Highlights
Social dominance is widely known to facilitate access to food resources in many animal species, especially during food-shortage periods [1,2]
Social Rank and Food Access Differential access to food related to social rank has been reported in several ungulates, including red deer (Cervus elaphus) stags [1] and hinds [3,4], muskox (Ovibos moschatus [28]), reindeer (Rangifer tarandus [29]), chamois (Rupricapra rupricapra [30]), American bison (Bison bison [31]), Rocky Mountain goat (Oreamnos americanus [32]; [2] for salt blocks access), African buffalo (Syncerus caffer [33]), bighorn sheep (Ovis canadiensis [34]), dama gazelle (Nanger dama [35]), Cuvier’s gazelle (Gazella cuvieri [35]), pronghorn (Antilocapra Americana [36]), Barbary sheep (Ammotragus lervia [37]); and in farm ruminants as goats [38] and dairy cows [39]
Dominant hinds may benefit for a longer time selecting meal components with greater energy content, which is consistent with previous studies in red deer and other captive or free-ranging ungulates [29,30]
Summary
Social dominance is widely known to facilitate access to food resources in many animal species, especially during food-shortage periods [1,2]. Differential access to food related to social rank has been reported in several ungulates, including red deer (Cervus elaphus) stags [1] and hinds [3,4]. Dominance is supposed not to result in any benefit for dominant individuals under ad libitum access to food. Preference for those meal components with highest nutritive quality has been repeatedly shown for cervids [7,8] under different experimental settings. Under restricted access to feeders, dominant hinds would still benefit by selecting the most nutritive ration through a preferential access even if food is offered ad libitum, this has not been previously proved
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