Americans love their pets — as many as seven out of 10 households are home to cats, dogs, birds… or more unusual animal choices. What defines a pet in the first place? Plenty of people are pushing the boundaries of the kinds of animals we usually think of as pets, blurring the lines between wild and domestic, livestock and companion, pets and pests. On this episode, we look at unusual pets and why people love and keep them — while others find them objectionable. We hear stories about ferrets and why they’re banned in some parts of the country, how one woman befriended a wild fox, and the chicken that helped a widow cope with her grief.

Also heard on this week’s episode:

• We talk with James Serpell, an animal behavior researcher and professor emeritus at the University of Pennsylvania, about his neurotic parrot, treasure-hunting rat, and what defines a pet. Serpell has written “In the Company of Animals: A Study of Human-Animal Relationships.”
• Self-described “ferret people” are passionate about these mustelids, and say they’re funny, smart, and interesting pets. But owning ferrets is not permitted in California, New York City, and Hawaii — and these rules have gotten the attention of some of the most prominent politicians of our time. So why the ban on ferrets? Jad Sleiman looked into the backstory.
• Catherine Raven tells the story of how she befriended a wild fox — and what made their relationship different from that of owner and pet. Her book is called “Fox and I: An Uncommon Friendship.”
• Throughout the episode, we hear stories about people’s best, worst, and strangest pets — from a field mouse thirsting for freedom, to some very fertile gerbils, to some disappointing sea monkeys, and a cat whose love language is scratching.