I don’t know about squirrels in particular, but most rodents have fairly short lifespans. If training took even half as long as an intelligent SAR dog, the rodent’s entire youth and middle age would be eaten up already, and any genetic timebombs like a tendency towards cancer would be approaching quickly.
There’s already an issue with various types of working dogs living a relatively short time compared to their training period...I can’t see this being any better.
The way around this problem is “mass production training”.
Dogs are difficult to train, because they are highly intelligent and individualistic. Squirrels, however, could be put through intensive Skinnerian training in a continual process at a centralized training facility.
The end result was that you take 20 squirrels, out of thousands, and release them on a big pile of building rubble. They scramble all over it until they can find or dig a passage inside it. And they keep going in until they locate living or dead people.
Then they give out one of two signals.
After a length of time they get a recall signal. But in the final analysis, they are very redundant and expendable.