A down syndrome squirrel is a squirrel with a roughly developmental issue.
It’s not really “Down syndrome”, just a squirrel with neurological issues. Downs has become a colloquial catch-phrase for these special babies.
Down Syndrome Squirrel
According to my vet, what you refer to Downs is just a form of achondroplastic dwarfism in squirrels.
A squirrel with this has foreshortened limbs, ears are placed at the sides rather than the top of the head; GI system remains immature and these babies are often on formula for their entire (short) lives as they either cannot digest solids or don’t have any interest in them whatsoever. They cannot thermoregulate.
A lot of animals with such abnormalities don’t live for long in the wild and get eaten by something pretty fast.
Can Animals Have Down Syndrome?
Yes, but in the wild they get eaten or don’t have the necessary survival skills
Animals can be mentally retarded, have chromosomal abnormalies, or unknown bran issues. So, yeah, the squirrel you see might have been slightly mutated, retarded or both!