Alpha meerkat females have a surefire way of making sure they’re the top mongoose: They will kill and even eat their grandchildren. The dark side of Timon’s cuddly kind was described in Nature Communications last month.
Wild meerkats, Suricata suricatta, live in groups (called mobs or gangs) with a dominant breeding pair and several adult helpers. These cooperative superfamilies can contain up 50 members, and despite the alpha’s monopoly, subordinates females will still attempt to breed. Dominant meerkats will control breeding within their group using violence: banishing and attacking any other females (their daughters) who reproduce and killing their daughters’ offspring.
Yet, they do all this to make sure there are plentiful resources for the alpha pair's pups. “The meerkat way of life is a paradox,” says Matt Bell from the University of Edinburgh. This cannibalistic, yet apparently effective strategy has been observed in other animals, including ants and bees. “Benefits have always been assumed, but never clearly confirmed,” Bell tells the Washington Post.
To directly measure the impact of suppressing subordinate reproduction, Bell and colleagues gave contraceptive injections of Depo-provera to all 35 adult female helpers in six groups of meerkats in the Kuruman River Reserve in South Africa. They did this over the course of three breeding attempts, ensuring that the subordinates couldn’t reproduce for six to nine months. As a control, they injected all 38 subordinate females in another six groups with saline solution.
During this time, dominant females were less aggressive towards the treated helper females. They also foraged more, gained more weight, and delivered heavier pups who grew faster. These nannies experienced less violence and fewer evictions than usual from the alpha females, and they provided more care and food for the alpha pups.
The work confirmed assumptions that the Kalahari Desert alpha female flourishes when she maintains the sole right to breed. “Dominant animals are worse off when subordinates in their group try to breed -- explaining why they brutally suppress others much of the time,” Bell says in a news release. “We expected this result, but its impact exceeded our expectations."