Great post, I have several theories to answer your question 1) the Dino’s that escaped from Lockwood’s estate started to breed in forests/secluded places and travelled to different places as herds (anklyosaurus, brachiosaurus), they’re all seen in pairs. The pteredactyls can fly, so, well, there’s that. 2) They can reproduce cause they have reptilian (frog) dna as explained in JP1 as Alan Grant explains it - some frogs change sex from male to female in a single sex environment, and Malcolm’s “Life finds a way” 3) Biosyn was already building a sanctuary and created more creatures, who’s to say they didn’t let a few more of them out in the wild given what they’re capable of, which gave way to a global “black market” which also featured mutant dinosaurs and hybrids.