September 18, 2013
Personality Differences: In Lean Times Red Deer With Dominant Personalities Pay A High Price
Saving energy is important for humans and animals alike when resources are limited. Scientists at the Research Institute of Wildlife Ecology of the University of Veterinary Medicine, Vienna, found out that although higher-ranked red deer gain privileged access to patches of food, they also have higher metabolic rates and thus use more energy. This can be a serious disadvantage in winter when red deer rely largely on their limited stored body fat to survive.
Energy budget adjustments
Dominance is costly
Red deer must withstand a negative energy balance over the winter season and maintenance of their body mass is critical to survival and reproduction. In lean times red deer, and other northern ungulates, save energy by drastically reducing their metabolism over cold winter nights – an energy-saving mechanism scientists refer to as “hypometabolism“. Socially dominant animals, however, are less good at this. The experimental results found that dominant individuals do have faster heart rates and higher body temperatures during winter compared to subordinates. Consequently, dominant individuals suffered higher rates of body mass loss during periods of low food availability than subordinates. Because the normally disadvantaged lower-ranked individuals do better in keeping their head low, slowing down, and chilling out, they seem to withstand severe winter conditions better.
Average values hide part of the picture
Physiological ecologists have long been surprised by the observation that individuals often exhibit large differences in physiological characteristics, such as metabolic rate, even under identical conditions. Why should they differ? A recent surge of interest in animal personalities has proposed a logical explanation: individuals exhibit particular combinations of behavioral, physiological and life-history traits that together characterize an individual ‘pace-of-life syndrome’. Walter Arnold, Head of the Research Institute of Wildlife Ecology, emphasizes: „Until recently physiologists have mostly been concerned with mean values of traits within wildlife populations. Our results show that there can be significant individual differences in physiological processes within one species, and these should not be ignored. After all, evolution builds on individual differences as the units of natural selection.“
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