the cheryl and philip willstein family. bernard and irene schwartz. roslyn p. walter. corporate funding is provided by mutual of america. designing customized, individual and group retirement products. we're your retirement company. additional support is provided by -- the corporation for public broadcasting. and by contributions to your pbs station from viewers like you. thank you. narrator: why would a goat never leave a horse's side... for 16 years? what would possess a big lion to bond with a little coyote? man: mother nature is teaching me something every time i see a relationship like this. narrator: scenes like these are overturning the conventional wisdom -- that only humans forge friendships. there's a lot of people that don't want to admit that animals have emotions. narrator: is it compassion or companionship that bonds two animals of different species together? woman: when they greet each other, i've never seen anything like it. it's not a deer greeting a deer, it's not a dog greeting a dog. it's definitely something that they have between the two of them.

the cheryl and philip willstein family. bernard and irene schwartz. roslyn p. walter. corporate funding is provided by mutual of america. designing customized, individual and group retirement products. we're your retirement company. additional support is provided by -- the corporation for public broadcasting. and by contributions to your pbs station from viewers like you. thank you.