Male silverback gorillas, with their muscular chest and sharp teeth, emanate raw power—but they can also be total softies when it comes to their offspring.

Some evidence suggests that might be part of what makes the 400-pound apes so attractive to females in their group. “We think what’s going on is that females prefer the males who are nice to kids, and spend time with kids,” says Stacy Rosenbaum, a biological anthropologist at the University of Michigan who studies social behavior among central Africa’s mountain gorillas. (Read why male gorillas really beat their chests.)

The sacrifices of animal mothers are well documented (take the octopus that watched over her eggs for nearly