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Both economic theory and experimental data concur–increasing the distance traveled to find food incurs “negative fitness consequences”, by decreasing total energy for maintenance, repair and reproduction. Yet, most animals must travel to find food. Individual, small groups, and large herds of eutherian (placental) mammals–like wild buffalo, gazelles, lions, and elephants–often travel great distances to find food. This expenditure of energy, at the apparent risk of biological fitness, has puzzled zoologists for some time.

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A recent study by Herman Pontzer and Jason Kamilar (Proceedings of the National Academy of Sciences, July, 2009) suggests a powerful reason behind this seemingly non-advantageous behavior. According to the study, far-ranging mammals are not simply responding to the availability of food (or lack thereof), but rather, the behavior is a strategy for procuring more food energy.

The study analyzed the relationship between daily distance traveled and reproductive success in 161 divergent species of mammal. After controlling for body mass differences, the researchers found that, over evolutionary time (large time scales sufficient for selective pressures to accrue), distance traveled by a given mammal species corresponded to increases in total fertility (number of life-time off-spring) and total off-spring mass (total grams of life-time off-spring).

So, despite economic theory and experimental data, it seems that nature, having been around longer than human science, “knows” what it is doing. Distance traveling for food is an evolutionary trade off: short term energy conservation versus long-term survival fitness.

Note: the American Bison (in the lead photo), sometimes called the American Buffalo is only distantly related to the “true” buffaloes (the Asian and African varieties).

photo: Public Domain

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