Introduction, Energy Balance in Animals

Abstract

Man is an omnivore and originally met energy requirements by hunting and gathering. Man evolved in an environment of feast and famine: there were periods with either a positive or negative energy balance. As an introduction to human energetics, this book on energy balance in motion starts with a chapter on animal energetics. How do animals survive and reproduce in an environment with a variable food supply? The examples on animal energetics illustrate how animals grow, reproduce and survive periods of starvation. It is an introduction to methodology and basic concepts in energetics. Growth efficiency of a wild bird in its natural environment, here the Starling, is similar to a farm animal like the Domestic Fowl. Reproductive capacity is set by foraging capacity, determined by food availability and the capacity parents can produce food to the offspring. Birds feeding nestlings reach an energy ceiling where daily energy expenditure is four times resting energy expenditure. Starvation leads to a decrease in energy expenditure, where the largest saving on energy expenditure can be ascribed to a decrease in activity energy expenditure.