Female hyenas kill off cubs in their own clans
Dominant females may keep low-ranking group members in check by crushing cubs’ skulls
![a female hyena and her cub](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2020/08/082020_cw_hyena_feat.jpg?fit=1028%2C579&ssl=1)
Hyena females are attentive, nurturing mothers. Yet competition within the clan seems to spur females to kill others’ cubs. Groups of females have even been observed ganging up on a lower-ranking rival to attack her cub.
Kate Yoshida
Female hyenas may be out for cubs’ blood — even within their own clans. New research suggests that infanticide may be part of a strategy females use to maintain their social standing.
“It’s not that these events are weird one-off things … this is actually a pretty significant source of mortality,” says Eli Strauss, a behavioral ecologist at the University of Nebraska–Lincoln. Strauss and his colleagues scoured three decades of data on spotted hyena populations in Kenya to study deaths of cubs less than a year old (SN: 4/23/02). Of 99 observed deaths, 21 could be attributed to infanticide, always by female killers. Starvation and lions also took many young cubs’ lives.
The infanticide observations made the team wonder why hyenas kill within their own group. It “seems sort of counterintuitive if animals benefit from living socially,” Strauss says. Though hyenas spend much of their time alone, group living allows them to defend their turf against rival hyena clans and to gang up against threatening lions, he says.
![female hyenas approacing a nursing mother hyena](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2020/08/082020_cw_hyena_inline1.jpg?resize=680%2C284&ssl=1)
Hyena mothers give birth in an isolated den. But typically within a few weeks, they move their cubs to a communal den. Such dens shelter little ones from large predators that can’t enter the sanctuary’s small access holes, says Ally Brown, an environmental biology student at Michigan State University in East Lansing. But the communal den presents other risks — all the cases of infanticide occurred in its vicinity, documented by researchers who either found the dead cubs or observed the clans from cars that serve as mobile blinds (SN: 4/23/02).
Female hyenas kill cubs in the same way that they attack small prey. A hyena “would just go up to a cub and grab it by the skull and crush it,” says Brown, who presented the work in a poster at the Ecological Society of America’s 2020 meeting held virtually the week of August 3. And close kin weren’t necessarily immune — one female targeted her sister’s two cubs, coaxing them out of the den before killing both.
![a hyena carrying a cub with a crushed skull](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2020/08/082020_cw_hyena_inline2.jpg?resize=680%2C403&ssl=1)
A hint at what spurs such slayings lies in the hyenas’ ranks. In hyena societies, males may come and go while females stick around as permanent members (SN: 3/28/16). Aggressive interactions and alliances help determine which hyenas are on top, and all individuals know where they stand, Strauss says.
Female cubs that reach adulthood can grow a maternal line, which helps boost that family group’s rank. In nearly all cases studied, killers ranked higher than the victim’s mother. That suggests that some females may use infanticide to keep their rivals’ bloodlines down.