When we were kids we always had gerbils. There's something a bit challenging about gerbils: they're cannibals, eating their young if they are surplus to requirements (too many mouths to feed); they are, when newborn, pink and hairless and squirming; and their little cage always seemed to reek (cleaning out the cage, ridding it of its sodden kapok and sawdust, was a chore to be dreaded but endured if you wanted a pet). They also bite down with alacrity on the webs between your fingers, given half a chance, and don't let go. But they can be cute and snuffly, and have the advantage of being fairly accessible pets.
They were all too accessible, unfortunately, for a rotten, fat, yappy little Cairn terrier called Kirsty, with wiry grey pelt and mean button eyes, which belonged to some daft family friends: one terrible day I came into the bedroom where they were kept to discover the wire top of the gerbil cage askew and a smug Kirsty knocking back the last gerbil before licking her chops in a revoltingly satisfied fashion.
No matter how much any adult might subsequently explain that Kirsty was just following her instinct as a ratcatching kinda dog, I conceived there and then a powerful loathing for all yapping little terriers and their ilk which has endured to this day. I was more than pleased - I was triumphant when Kirsty subsequently got alopecia and her coat fell off.