Female animals portrayed as males in cartoons

The default for everything seems to be "male". For some reason it's always been easier for us to call a dog we see walking on the street a "he" than a "she", before we identify its gender.
But I still can't get over the cartoons that show animals like ants or bees all being males, or where they introduce a king, as portrayed in the game "King's Quest 5", or even have a mixed community, as portrayed in the movies "AntZ", "A Bugs Life" and "A Bee Movie". And of course, all the gender roles are still there. The hardest work is being done by males.

It must really suck being a girl if the lead character has to be male in an animal community that pretty much only has females. 

Why is the human race so obsessed with male lead characters? We are a mixed community, and the numbers even show there are more women on this planet than men. Slightly more. But for some reason we're still more comfortable with a male hero than a female one. After all, in all the mentioned movies above, it's a male character who has the lead.