Since rodents and birds are cats’ most commonly caught prey, how did they develop a taste for fish?
Cats use both their sense of smell and taste to determine what to eat. Cats have taste receptors in their tongue that are specialized for detecting a signal for meat, known as adenosine triphosphate (ATP). Some cats have a strong preference for specific protein sources, and others seem to be pretty open-minded about what they will eat. But a few studies of feeding preferences have demonstrated that cats have a strong liking for food of the fishy-variety.
It’s important to consider that what cats like to eat does not necessarily reflect what they would naturally hunt; cats are obligate carnivores with a strong taste for protein. Sure, you won’t see too many kitties hunting cattle, pigs, or turkeys (and for some reason, no one has yet released a mouse-based commercial cat food). So fish, high in protein and fats, and with a strong odor, likely ticks all the checkboxes for “food...glorious food” for your beloved feline.
Humans probably encouraged a liking for fish because we as a species eat fish. Cats have long lived with humans, and have also lived off of our leftovers and garbage. Humans offering food to stray and pet cats no doubt included fish among those offerings. And as cats spread around the world, from their ancestral home of the African savanna of Africa to port cities, there were likely opportunities to learn to catch fish, even though they are not cats’ preferred prey.