Zoology: Meerkats size each other up for success

Wild meerkats (Suricata suricatta) adjust their growth rate and food intake in order to match and exceed the size of potential reproductive rivals, suggests a study published in this week’s Nature.

In many animal societies, social rank is related to age and weight, and thus to growth rate. Although growth rates have been shown to vary in relation to social environment in several vertebrates and mammals, it is not known whether individuals increase their growth rate in response to the growth of their competitors, who may displace them in reproductive queues.

Elise Huchard, Tim Clutton-Brock and colleagues studied 14 groups of wild meerkats living in the Kalahari Desert. They identified pairs of same-sex littermates and fed the lighter individual in each pair half a boiled egg twice per day for three months. They then compared the growth of the unfed animals with those of unfed control individuals of the same age from other litters over the same time period. They found that the unfed meerkats responded to increases in the growth of their fed littermates by increasing their average food intake and weight (both in absolute terms and relative to controls). In addition, once meerkats of either sex acquire dominance, there is a secondary phase of growth that increases in magnitude if the difference between the dominant meerkat’s weight and that of its heaviest same-sex subordinate is small. These findings suggest that subordinates can track changes in the growth and size of potential reproductive rivals and react by adjusting their own growth.

The authors speculate that similar adaptable responses to competition risk may also occur in other social mammals, including domestic animals and primates.