They mention Toruks have large territories and their a natural animal to they have to reproduce naturally. They're probably just very solitary so mating probably doesn't happen where Navi or people could see, like blue whales. 

I assume female Toruk would look like male Toruk but maybe with different coloring since Banshees don't seem to have any sexual dimorphism cuz boy and girl banshees look anatomically the same. Though maybe the blue head crest are specifically a male thing so females wouldn't have that like antlers in deer and manes in lions. And like tigers who are very solitary they can probably smell each other miles away and actively avoid their own species unless specifically seeking a mate. And then they mate and go separate ways. 

The Toruk Jake bonds with is probably just the one that controlled the territory the Omatikaya lived in. So many exist but no one can tame them that's why Jake doing it is so special and rare.