They are hybrids of ancient life forms, alien transplants and millennia engineered items wherein vast swathes of a planet are engineered for their reproduction and maturation, the results of that in the billions of individuals per year. This is all done so as to provide sustenance, arguably not even that good (though cheap), to higher life forms and their pets or machines, with said life forms able to tinker with and map the very fabric of their being.
The universe be rather brutal.
The universe be rather brutal.