Several animals have a “default gender” in English — by which I mean that the word for either the male or the female also serves as the word for the species in general. The word man, which can (or could until very recently) mean either a human being in general or specifically a male human being, is an example.
My initial assumption was that, while most animal species do not have a default gender, those that do would be overwhelmingly default-male, in line with traditional “sexism.” In fact, they turn out to be pretty evenly split.
Default-male animals: dog (vs. bitch), fox (vs. vixen), lion (vs. lioness), tiger (vs. tigress), and of course man (vs. woman).
Default-female animals: cow (vs. bull), duck (vs. drake), goose (vs. gander), and hawk (vs. tercel). Interestingly, these are almost all bird species. The only exception is cow, which technically refers only to the female but in practice is used more inclusively.
The above are the only animals I can think of which have a default gender. If you know of one that I missed, leave a comment.
Among mythical creatures, most are default-male — dragon (vs. dragoness), giant (vs. giantess), ogre (vs. ogress), etc. The only exception I can think of is griffin; heraldry distinguishes between the griffin (winged, without horns or spines) and the male griffin (horned, spiny, and wingless). Perhaps not coincidentally, the griffin is a bird-like monster.