Habit, and this almost implies that some benefit great or small is thus derived, would in all probability suffice for the work.

Brehm saw the young of an African monkey (Cercopithecus) clinging to the under surface of their mother by their hands, and at the same time they hooked their little tails round that of their mother.

Professor Henslow kept in confinement some harvest mice (Mus messorius) which do not possess a structurally prehensive tail; but he frequently observed that they curled their tails round the branches of a bush placed in the cage, and thus aided themselves in climbing.

I have received an analogous account from Dr.
Gunther, who has seen a mouse thus suspend itself.

If the harvest mouse had been more strictly arboreal, it would perhaps have had its tail rendered structurally prehensile, as is the case with some members of the same order.