"The cat is black."
Translation:बिल्ली काली है ।
There is a generic, grammatical gender associated with every animal, because in Hindi, just like in Spanish, every noun is either masculine or feminine. So a cat is generically feminine, as are a butterfly, a fish, a sparrow, and a spider, while a camel is masculine, as are a turtle, a rhino, a centipede, and a mongoose.
There are a few animals with distinct words for male and female individuals though. For example (generic gender first): बिल्ली (she-cat), बिल्ला (he-cat); घोड़ा (stallion), घोड़ी (mare); लोमड़ी (female fox), लोमड़ (male fox); हाथी (male elephant), हथिनी (female elephant). Gender-specific names only exist for a small number of animals or class of animals, most, if not all, of which are local and well-known to people. So don't expect to find different names for, say, a male and a female capybara. :D
In order to be specific about the gender of an animal which doesn't have distinct male and female names, use the adjectives नर (male) and मादा (female). So, while "मछली" is grammatically feminine and can be used to refer to fish in general, "नर मछली" is a male fish and "मादा मछली" a female fish.