Thanks everyone for your input,
Edible pets are great ideas and I'll consider those suggestions carefully, but technically, ALL pets are edible.
@Fatboat, thanks for your very detailed and relevant information! I'm glad to hear that you felt confident letting your ferret play on the boat with supervision, which is what I would want to do. And I would probably want to walk it along the towpath just for the joy of it. Beautiful image!
@NB Watersnail, thanks for this - I admit I've been concerned about the temperature fluctuations & my first instinct is that budgies wouldn't do well on our boat. Cockatiels are awfully attractive, though, and that information is very useful! thank you!
@Caprifool, Rats do make lovely pets. Sadly not the right pet for our situation, but I think they'd do beautifully as narrowboat pets and would recommend them in the future.
@Nulife Micro pigs are a lovely idea
@Starcoaster Thanks for your informed source-cited opinion, I do appreciate that! I think ferrets would do well, especially as they are suitably narrow. Ferret-proofing will definitely be interesting.
@Chop! WELL DONE CHOP! That is a really interesting and unusual solution.
@patty-ann Chipmunks are wild animals where I come from - I've never understood the attraction of keeping them as pets! They are terribly adorable, though
@Doodlebug/Starcoaster Thanks for the input on hedgehogs; I'd considered them but am not attracted to them as pets, though I think there are many valuable reasons to promote awareness of the animal and conserve its genetics! Very educational conversation, though. (Also Doodlebug - thanks for understanding about fish; people say "Get a fish!" and I'm like, "Oh, I love fish! I used to raise and breed rare fish and was involved in a very cool zebrafish genetics project! Do you know how much constant 240V power, space, filtration, heat, maintenance and care they require, and would you like to see the spreadsheet in which I worked out how that doesn't factor into our current power audit? And how fish need to be protected from temperature fluctuations and rocking and woodstoves are very dehydrating, creating a high-ammonia - you were talking about keeping a half-dead fish in a teacup, weren't you.")
@Bunny, thank you so much for these useful tips about keeping Bunnies! The temperature tips are particularly useful. (I would love chinchillas but feel that I couldn't keep them cool enough... but I LOVE the image of your Bun with his fan!)
Other suggestions that I haven't responded to: it's probably because they were so good I was embarrassed not to have come up with them myself.