100 YEARS AGO

A few interesting facts with regard to the kea, or sheep-eating parrot, of New Zealand are related in the July number of Leisure Hour by Dr. F. Truby King. The intense curiosity of these birds is stated to be sufficient to account for the habit of eating sheep acquired by them. Dr. King thinks it is probably a mistake to suppose that the kea designedly makes at once for the kidney fat of the sheep upon which it has pounced. It eats into various parts of the body, though perhaps more often into the region of the kidney, as it is there that the kea gets the firmest stand on the back of the running sheep. This view is strengthened by the fact that the bird prefers double-fleeced sheep — that is, such as have remained a whole season unshorn, on which it obtains a firmer grip.

From Nature 29 June 1899.

50 YEARS AGO

According to Darwin the long neck of the giraffe is the result of natural selection acting through the animal's tree-feeding habit. He wrote: “the individuals which were the highest browsers and were able during dearths to reach even an inch or two above the others will often have been preserved.” There are serious objections to this argument. (1) During dearths ⃛ the recurrent wastage of young giraffes would threaten the species with extinction. (2) Under such extreme conditions of dearth the grass-eating African ungulates would also have been so short of food that it is difficult to see why more of them did not develop the leaf-eating habit and the excessively long neck. (3) Bull giraffes tend to be several inches taller than the cows, so that during each dearth males would be naturally selected at the expense of the females — another factor likely to lead to rapid extinction. An alternative theory free from these criticisms has occurred to me. ⃛ The giraffe is actively preyed upon by lions and leopards. It is reasonable, therefore, to explain the excessive length of its forelegs as the effect of natural selection acting continually through the hunter-hunted relationship. ⃛ That the neck has elongated to a degree only just sufficient to keep pace with the increasing length of the legs is suggested by the fact that the giraffe has to splay its forelimbs awkwardly to drink.

From Nature 2 July 1949.