A 26-year-old gorilla living in Rwanda's Virunga Mountains has chosen to leave her group to protect her baby, in behavior researchers are calling "rare" and "remarkable."

Back in May, Pasika was a new mother to Mashami, who was born in March.

Suddenly, things changed when the silverback gorilla, the male leader of Pasika's group, died. The female gorillas of the group broke up and joined other groups that still had a silverback leader.

One mother gorilla's baby was killed when she joined a new group — something that often happens with many kinds of social mammals, so the new leader can assert his dominance.

"Normally, female mountain gorillas like Pasika spend their entire lives living in groups and rely on the adult male — called a silverback — to protect their young," the Dian Fossey Gorilla Fund (DFGF) said in a statement. "If the silverback dies, the group may stay together if there is another male who can assume leadership; if not, females will immediately transfer to another group. They never live completely on their own — until now."