As adults, they’re Africa’s most successful predators. But as cubs, spotted hyenas are a favorite snack for lions. For that reason, hyena cubs usually steer clear of the big cats, spending most of their time near their parents’ dens.  

That’s unless the young hyenas are infected with the parasiteToxoplasma gondii. Those unfortunate cubs get closer to lions and are four times more likely to be killed by the big cats than their healthy peers, according to decades’ worth of data collected in Kenya’s Masai Mara National Reserve.

“I was stunned to see the big difference in how close the infected versus uninfected cubs actually got to lions,” says Kay Holekamp, a behavioral