The habituation of the meerkats allowed the researchers to temporarily remove pups from or add pups to the mobs and weigh the same individuals several times each day, which gave the researchers an accurate measure of the meerkats feeding success and weight gain. "This has never been previously possible with a wild animal," said Clutton-Brock.
The research shows that reducing the ratio of helpers to pups' by adding additional pups to the mob reduces the daily weight gain of the pups and the helpers, which reduces pup survival rates and decreases their foraging abilities in later life.
In mobs that have a low helper-to-pup ratio, the helpers are unable to sufficiently respond to all the pups' yelps for food, nor do the helpers have enough food to maintain their own weight, the researchers note.
In mobs where helper-to-pup ratios are higher, helpers are able to both provide sufficient food to the young and maintain their own food intake and weight gain, which makes keeping a high helper-to-pup ratio in meerkat mobs advantageous for both helpers and pups.
"In colonies that are a little too small there are not enough [meerkats] to do the work," said Pam Wallberg, director of the Fellow Earthlings Wildlife Center, a captive meerkat facility in Morongo Valley, California. "They need a breeding pair, baby-sitters, a sentry…"
"Fifteen to 30 is pretty good," she said. "Less than five is too narrow of a number to do all the jobs effectively. Some jobs will be neglected, say guard duty, and they will have predator problems."
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