AJSriMAL BEHAVIOR — WALKER 281 



remarkable ability to turn and twist and dodge about in the air. 

 Apparently their hearing and touch — and perhaps some other sense 

 unknown to us — are remarkably developed to aid them in locating 

 their prey. It is obvious that the expression "blind as a bat" is 

 utterly without foundation, for the most casual observation of bats 

 shows plainly that these animals can see keenly for considerable dis- 

 tances and that they are exceedingly watchful.^ No doubt their 

 eyesight is highly specialized in order that they may, while on the 

 wing, detect minute insects and successfully capture them. Since 

 insect food, when it is available at all, is generally very plentiful, 

 most bats need not lead solitary lives as do many of the animals that 

 live under conditions in which food is generally at a premium. They, 

 therefore, frequently congregate in great numbers in caves, houses, 

 hollow trees, or other convenient roosting places. Since their fingers 

 serve only to support the wing membranes bats would appear to be 

 handicapped in capturing and holding insects. However, they have 

 very successfully overcome this difficulty by developing a remark- 

 able flexibility of the neck, and an extreme dexterity of the wing. 

 Turning and twisting in the air a bat successfully follows erratic 

 insects. 



The blood-drinking bats {Desmockis and related genera), com- 

 monly known as vampires, are small animals about the size of our 

 common brown bat {Eptesicus fuscus) that have developed a won- 

 derful technique in obtaining their food. Wlien they find a warm- 

 blooded victim — horse, cow, sleeping bird, or person, as the case may 

 be — they settle on to it so gently that the victim is usually not aware 

 of their presence. With their peculiarly enlarged razor-edged in- 

 cisor teeth, they then cut off a very small thin layer of the skin, go- 

 ing just deep enough to cause the blood to flow. This is so neatly 

 done that the victim is usually unaware of the presence of the bat as 

 it quietly laps up the blood that oozes from the wound. Ordinarily 

 the amount of blood lost by the animal is not excessive. The princi- 

 pal danger from the attacks by vampires lies in the possibility of 

 infection of the small wounds. 



On the southeastern Alaskan coast I have often observed the little 

 Northwest fish crows picking up clams or mussels on the beach at 

 low tide and flying directly upward, 20 to 40 feet, then dropping the 

 shellfish on the rocks below. The birds then fly down and examine 

 the morsel. If the shell is sufficiently shattered they proceed to eat 

 the meat. If it is not broken they pick it up and drop it from a 

 greater height. 



» Experiments with bats that had been blinded disclosed that they could avoid threads 

 while flitting about In a dark room. This suggests the existence o( some other gease. 

 perhaps unknown to man, that aids them in the dark. 



