Russian differentiates between animate and inanimate nouns:
Я вижу кота
Я вижу дом
In principle all animate nouns are either masculine or feminine but cannot be neuter. So why "животное" and not "животная" or "животный"?
The real answer is the claim that "in principle all animate nouns are either masculine or feminine but cannot be neutral" is false. For instance, we consider obsolete yet existent word "дитё" (or "дитя") which is animate and neuter. Or "чадо", or "существо", or "чудовище" etc.
Animacy and gender are different grammar features and while relationships between them are complicated. That complicated that some researchers even go that far that they conclude that there's more than 3 genders in Russian and some other Slavic languages.
It's quite safe, however. to assume that animacy/inanimacy doesn't necessarily implies specific gender.
Here's a quote from wikipedia:
While animacy is viewed as primarily semantic when approached diachronically, a synchronic view suggests animacy as a sublevel of gender. Syntactic gender is defined through patterns in agreement, not necessarily semantic value. For example, Russian has "common gender" nouns that refer to traditionally masculine roles but act as syntactically feminine.