60 ANIMAL INTELLIGENCE 
noticed in a large number of rodents.* The well- 
known note of the Chipmunk, from which it has 
derived its name, is the only one I have heard from it. 
After studying a colony of Red Squirrels for some 
weeks last summer, I came to the conclusion that they 
have a capacity of vocal expression much greater than 
is commonly believed. Their usual “barking,” or trill- 
ing, seems to be the commonest, the most instinctive, 
and not largely expressive of anything beyond general 
satisfaction ; but, I found that, under excitement, there 
were many other tones, associated with great complexity 
of emotion, which I am not prepared to analyse, but 
which there can be little doubt the creatures themselves 
employ as a means of inter-communication. Under 
marked excitement, as the result of repeated inter- 
ferences, I have heard a Red Squirrel so mingle tones 
of a musical kind that, a stranger arriving on the spot, 
would certainly have been deluded into the belief that 
he was listening to some bird, or rather to an excited 
pair of birds. The musical character of this combina- 
tion, together with its continuity and complexity, would 
perhaps justify the designation “song.” One of the 
writers on musical mice refers to their singing but 
little in certain instances, except when excited, which 
is a point of analogy with the Chickaree. 
It would appear, therefore, that it is likely that 
throughout the order Rodentia a genuine musical 
appreciation and executive capacity exists, and, in some 
instances, in a very high degree; and that apart from 
this, there is also considerable ability displayed in the 
expression of states of emotion, at least, by vocal forms. 
Manifestly, the degree to which animals can express 
their psychic states—and especially in vocal forms—is 
a matter of the greatest importance, and I have already 
* See especially Nature, vol. xv.; Popular Science Monthly, vol. i.; 
and the American Naturalist. 
