According to Dr. Marc Bekoff Ph.D., emotions like joy, love, empathy, compassion, kindness, and grief can readily be shared by improbable friends including predators and prey such as a cat and a bird, a snake and a hamster, and a lioness and a baby oryx.

The popular PBS series, Nature, featured Bekoff in a documentary called "Animal Odd Couples", which aired last week.

The Professor Emeritus of Ecology and Evolutionary Biology at the University of Colorado, Boulder presents solid science to help explain the cross-species relationships, including the biological similarities between all mammals, including humans. They all share the same structures and neurochemicals in the body's limbic system, for instance.

Best of all, the Nature camera crews filmed endearing interactions between a cheetah and a dog, a lion and a coyote, a Great Dane and a deer, and even a tortoise and a goose. All these supportive connections from the animal world seem to challenge the conventional wisdom that humans are the only species capable of feeling compassion and forming long-lasting friendships.

Watch the excerpts from Animal Odd Couples below, or the full video at PBS.org.

Here are a few more examples of unlikely friendships in the animal kingdom from previous Good News Network stories involving a deer and goose pair, and an elephant and orangutan each bonding with a hound.

1) A cute preview of the show:

2) Great Dane Befriends Deer: After being abandoned by her mother, a baby fawn, Pippin, was adopted by a Great Dane, Kate, and they have been best friends ever since. Kate's owner Isobel Springett describes the uniqueness of their relationship: "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."

3) Some of the science: Primatologist and evolutionary biologist Dr. Lauren Brent discusses her research on the social behavior of nonhuman primates and the benefits of friendship.