The problem of isolates continues to exercise what is left of my brain. By isolates I mean cryptids that have been reported once, but they are never seen again. As creatures such as Bigfoot and Champ have been reported on sundry occasions, we know that, if they exist, there is probably a population of them. The same can not be said of the isolated cryptid which is seen once and seen no more.
The following is a list of possible explanations of such creatures.
 The witness is mistaken (or even mendacious) in reporting the animal. He has either misinterpreted the data or has not seen anything at all.
 The animal is a freak of nature, a mutant, and is the only one of its kind. It has nous enough to, as Joel Chandler Harris might have said, lie low and say nuffin.
 The animal exists in another dimension or universe and has somehow strayed into ours. This may seem beyond the bounds of possibility to some, but multiple universes are now receiving some interest from physicists and cannot be ruled out.
 The animal is an escapee from a laboratory and is the result of genetic experimentation. It may not survive or it may be recaptured.
 The animal may be hallucinatory. I suspect an hallucination caused by the temporal lobe of the brain might be responsible. The temporal lobe can produce two types of hallucination. Temporal Lobe Epilepsy has to be engendered by a blow to the head. Temporal Lobe Lability soes not require any such blow. Both can cause hallucinations. The animal may also be some kind of projection from the witness' brain.
 One must always leave the door open for other explanations that haven't occurred to me yet.