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Meerkat moms kill rivals’ babies—and get rewarded for it

Oct. 7, 2013
Courtesy of the University of Cambridge
and World Science staff

A­dor­a­ble, in­tel­li­gent and even com­pas­sion­ate by some re­ports, the lit­tle Af­ri­can mam­mals known as meer­kats might not be ex­pected to have much of a dark side. But they do, a study sug­gests.

Meer­kat moms at the top of their group’s peck­ing or­der will kill ri­vals’ ba­bies—and as if that weren’t enough, they go on to re­ceive wet nurse ser­vic­es from the vic­tim­ized moth­ers, the re­search found. The same serv­ice is some­times ex­tracted from re­cently “ex­iled” meer­kats who have re­turned, sug­gest­ing it’s a sort of “rent” paid to stay in the com­mun­ity, ac­cord­ing to sci­en­tists.

Meer­kat moms at the top of their group’s peck­ing or­der will kill ri­vals’ ba­bies—and as if that weren’t enough, they go on to re­ceive wet nurse ser­vic­es from the vic­tim­ized moth­ers, the re­search found. The same serv­ice is some­times ex­tracted from re­cently “ex­iled” meer­kats who have re­turned, sug­gest­ing it’s a sort of “rent” paid to stay in the com­mun­ity, ac­cord­ing to sci­en­tists.


In meer­kat groups, a dom­i­nant fe­male usu­ally mo­nop­o­lizes breed­ing op­por­tun­i­ties, ex­plained Kirsty Mac­Leod of the Uni­vers­ity of Cam­bridge, who col­la­bo­rat­ed in the re­search. That fe­male “main­tains this po­si­tion through sup­press­ing breed­ing at­tempts by oth­er fe­males – ei­ther through evict­ing them or kill­ing their pups,” she added.

“These sub­or­di­nate fe­males are then al­so more likely to wet-nurse the dom­i­nant fe­male’s pups,” she went on. So the dom­i­nant fe­male’s mur­der­ous ten­den­cies seem to pro­vide “two ev­o­lu­tion­ary ad­van­tages for her – she re­duces com­pe­ti­tion for care for her own pups, and is more likely to se­cure” wet-nurs­ing for her lit­ter.

“Wet-nurs­ing by form­erly evicted meer­kats may be a way of ‘pay­ing rent’ to be al­lowed back in­to the group,” Mac­Leod added. Help­ing as pay­ment of ‘rent’ has been sug­gested in bird spe­cies in which helpers re­ceive great­er ben­e­fits from re­main­ing in their ter­ri­to­ries ow­ing to a lack of op­por­tun­ity to at­tract a mate from else­where, but has pre­vi­ously been sug­gested in only one oth­er mam­mal, the na­ked mole rat.

Wet-nurs­ing anoth­er moth­er’s off­spring – called al­lo­lacta­t­ion – oc­curs across a va­ri­e­ty of mam­mals. But lit­tle has been de­fin­i­tively known of why the fe­males who pro­vide the wet-nurse serv­ice do so. The new find­ings are pub­lished Oct. 7 in the jour­nal An­i­mal Be­hav­iour.

The 15-year study ob­served 40 so­cial groups of meer­kats in the Kala­hari region of South Africa. The re­search­ers recorded, among oth­er de­tails, preg­nan­cies and lacta­t­ion pe­ri­ods. Be­cause most pup nurs­ing oc­curs be­low ground, fe­males were iden­ti­fied as pro­duc­ing milk through the pres­ence of suck­le marks and the at­tach­ment of sand to damp nip­ples.

The study al­so found that sub­or­di­nate fe­males were more likely to wet-nurse if they were re­lat­ed to the lit­ter’s moth­er. This hints at an in­di­rect ge­net­ic “ben­e­fit” for the wet-nurses, she added, since they are in­di­rectly pass­ing on genes re­lat­ed to their own through the lit­ter’s moth­er.


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Adorable, intelligent and even compassionate by some reports, the little African mammals known as meerkats might not be expected to have much of a dark side. But they do, a study suggests. Meerkat moms at the top of their group’s pecking order will kill rivals’ babies—and as if that weren’t enough, they go on to receive wet nurse services from the victimized mothers, the research found. The same service is sometimes extracted from recently “exiled” meerkats who have returned, suggesting it’s a sort of “rent” paid to stay in the community, according to scientists. In meerkat groups, a dominant female usually monopolizes breeding opportunities, explained Kirsty MacLeod of the University of Cambridge, who collaborated in the research. That female “maintains this position through suppressing breeding attempts by other females – either through evicting them or killing their pups,” she added. “These subordinate females are then also more likely to wet-nurse the dominant female’s pups,” she went on. So the dominant female’s murderous tendencies seem to provide “two evolutionary advantages for her – she reduces competition for care for her own pups, and is more likely to secure” wet-nursing for her litter. “Wet-nursing by formerly evicted meerkats may be a way of ‘paying rent’ to be allowed back into the group,” MacLeod added. Helping as payment of ‘rent’ has been suggested in bird species in which helpers receive greater benefits from remaining in their territories owing to a lack of opportunity to attract a mate from elsewhere, but has previously been suggested in only one other mammal, the naked mole rat. Subordinate female meerkats who try to breed often lose their offspring to infanticide by the dominant female or are evicted from the group, said MacLeod and colleagues. These recently bereaved or ostracized mothers are those that tend to become wet-nurses for the dominant female. Wet-nursing another mother’s offspring – called allolactation – occurs across a variety of mammals. But little has been definitively known of why the females who provide the wet-nurse service do so. The new findings are published Oct. 7 in the journal Animal Behaviour. The 15-year study observed 40 social groups of meerkats. The researchers recorded, among other details, pregnancies and lactation periods. Because most pup nursing occurs below ground, females were identified as producing milk through the presence of suckle marks and the attachment of sand to damp nipples. The study also found that subordinate females were more likely to wet-nurse if they were related to the litter’s mother. This hints at an indirect genetic “benefit” for the wet-nurses, she added, since they are indirectly passing on genes related to their own through the litter’s mother.