Women were less active in the field of zoology they were in botany. Many of the observations Darwin was sent were from amateur observers, rather than from people who had made a special study of the subject. Most people in the Victorian period lived closely with animals; horses were used for transport, and dogs and cats might be pampered pets or semi-independent household companions; even an invalid might have a bird for entertainment. Darwin's comments on animal behaviour, in Variation under domestication, Descent of man, and Expression of the emotions, attracted much interest. The analogies Darwin drew between human and animal behaviour struck a chord with many; and women in particular drew conclusions about human treatment of animals. Where Darwin's female correspondents made formal studies of animals, they were on insects, barnacles, and earthworms. The correspondence on animals has therefore being divided into two chapters: Companion animals and Insects and angels, ‘insect’ being the popular term for any small, apparently insignificant, creature. (No reflection is made on the actual companionableness of insects—John Lubbock had a pet wasp— or on the usefulness of companion animals; the distinction, which is admittedly loose, points only to a difference of approach.)

The following account of learned behaviour in a dog came from Jane Loring Gray, the wife of Darwin's Harvard correspondent, Asa Gray: