I'm looking for a humorous non-fiction children's book, with accompanying cassette, about camels. I read it sometime between 1987 and 1995, likely closer to the earlier range, and it was probably published no later than 1975: it felt "modern" at the time. I recall the book being slightly larger format, softcover, and fully illustrated in a semi-cartoony style - and that it also had an audio cassette version which I believe was just the narrated book, without music. The conceit of the books may have involved a kid secretly adopting a wild animal as a pet: it introduced animal facts to explain how the animal's adaptations could help the child keep it hidden from their parents. One specific detail I recall is a fact that camels can close their nostrils to keep from breathing in sand - "or your dad's cigars!" as they illustrated by showing an unfazed camel in a living room where a man in a green armchair was smoking heavily. I'm fairly sure the book was part of a series, including one about penguins (where the kid tried to fill the bathtub with ice for them,) but I don't recall any other books in the series.