248 MENTAL EVOLUTION IN ANIMALS. 



delphia on February 18th, 1873, by Mr. W. K. G. Gentry. A 



rodent popularly known as the Chickaree (Scimis Imdsonius), 



which like most of its kind is normally herbivorous, has 



{ adopted in the neighbourhood of Mount Airy a habit 



j common among the Mustclidce, of climbing trees for the pur- 



I pose of catching birds and sucking their blood. Mr. Gentry 



suggests that this transition from herbivorous to carnivorous 



habits may have arisen from the propensity shown by some 



squirrels of sucking the eggs of birds — the passage from this 



liabit to that of sucking the blood of birds being but small. 



Lastly, in this connection I may adduce a precisely analogous 



case of a marked local variation of instinct taking place in a 



species of bird. 



Mr. I. H. Potts, writing from Ohinitahi to " Nature" (Feb- 

 ruary 1st, 1872), says that the mountain parrot {Nestor 

 notahilis) was then exhibiting a " progressive development of 

 change in habits from the simple tastes of a honey-eater to 

 the savageness of a tearer of flesh." For " the birds come in 

 flocks, single out a sheep at random, and each alighting on 

 its back in turn, tears out the wool, and makes the sheep 

 bleed, till the animal runs away from the rest of the sheep. 

 The birds then pursue it, and force it to run about till it 

 becomes stupid and exhausted. If in that state it throws 

 itself down, and lies as much as possible on its back to keep 

 the birds from picking the part attacked, they then pick a 

 fresh hole in its side, and the sheep, when so set upon, in some 

 instances dies. . . . Here we have an indigenous species 

 making use of a recently imported aid for subsistence, at the 

 cost of a vast change in its natural habits." Since this 

 account was written the change of habits in question has 

 grown to become a very serious matter to the sheep-farmers. 

 It appears that the birds prefer the fat parts of their victims, 

 and have learnt to bore into the abdominal cavity straight 

 down upon the fat of the kidneys, thus of course killing the 

 sheep. 



Another case of local variation of instinct is furnished by 

 the statement of Adamson, that in the island of Sor rabbits 

 do not burrow. This statement, however, although accepted 

 by Dr. E. Darwin, has not, so far as I know, been^either con- 

 firmed or refuted. But with reference to variations in the 

 instinct of burrowing, I may allude with more confidence to 

 tlie case given by Mr. Darwin in the Appendix on the 



