If you watch some documentaries on rare insects or birds, there are so few of them yet the range of their habitats is huge (or at least it seems there is no limit). Given that, how do these creatures find their species for mating? I mean, isn’t it super rare to accidentally encounter one of their species despite the helps of pheromones or sounds?
Birds have good vision and can fly. Insects can fly, see ultraviolet and use chemicals to find each other. That helps even endangered species.
I remember thinking that the reason why earth worms are still hermophrodites is because they can’t see, must tunnle through moist soil to live and have no limbs. Everyone wearing both hats makes reproduction easier with that life style. Good thing for the worms that they are super common.
A lot of times they don’t. This is why population fragmentation is a big deal – you can have a decent population but if they can’t find each other there might as well only be one left in the world.
If the population isn’t fragmented they use scents, migrations, and other methods of that sort to find each other. A great many animals will use x site to mate or clutch and find each other there even if they live solitary at every other point in their life.