BLIND AND CAVE VERTEBRATES. 9 



THE BLIND VERTEBRATES AND CAVE VERTEBRATES OF NORTH AMERICA. 



The blind vertebrates do not belong to one class nor do those within one class 

 belong to one family. The blind fauna is very diverse in character and origin, 

 but not all families of vertebrates are represented. A certain predisposition in 

 habit and structure must be present to enable a species to dispense with light and 

 to live in caves. A large blind epigean animal might secure its food and meet its 

 mate, but it could not escape its enemies. Targe blind forms are therefore impos- 

 sible. While the size of a sun-fish (Lepomis) might not preclude it from entering 

 caves, the fact that it detects its prey by sight excludes it entirely from the possibly 

 blind. There is, on the other hand, no reason why members of the nocturnal 

 Siluridae, for instance, should not become blind. 



No large mammals are blind, nor have large mammals permanently taken up 

 their abode in caves. Bears visit caves, and raccoons, minks, and ground hogs also 

 enter them. The latter two confine their underground wanderings mostly to small 

 caves or to caves of their own making. None of these animals permanently live in 

 caves ; they are all twilight animals and depend on light for their continued exist- 

 ence ; they have normal eyes and are not otherwise modified for life in caves. 



Blatchley reports that a number of cats have established themselves in Wyan- 

 dotte Cave, where they bring forth and rear their young. Nothing is known about 

 their adaptations. They have exterminated the cave rats and are said to place 

 themselves in a narrow passage of the cave and capture bats passing through. 



Neotoma pennsylvanica, a wood rat widely distributed in eastern America, has 

 entered caves. It was formerly found in Wyandotte Cave, but has been extermi- 

 nated there. In various caves white-footed mice are found, but they are not blind. 



The common mole (Scalops aquaticus), the long- tailed mole (Parascalops 

 breweri), and the star-nosed mole {Condylura cristata) burrow in the ground and 

 are partly or entirely blind. They are not found in caves. 



Bats, which are twilight animals, but have minute eyes, do not depend on their 

 eyes to secure food; they fly at night because their food is then abroad. There 

 are in North America and the West Indies a large number of bats partly or totally 

 blind. Many, if not all of those of the temperate region, winter in caves ; a smaller 

 number spend only the day there. They do not secure much, if any, of their 

 food in caves and simply use them as shelters in a more systematic manner than 

 bears do. 



There are no blind birds, and no birds, as far as I know, permanently live in 

 caves. The phcebe utilizes the entrances as it uses all other similarly sheltered 

 places to nest. In Cuba a small owl is sometimes found in caves, but I know of 

 none that makes it a permanent home. Many owls are adjusted to existence in 

 twilight, but that they are dependent on their eyes is shown by the increase in size 

 of their eyes. Other animals, depending on their eyes but living in the dusk, 

 have similarly enlarged eyes. This is especially well shown by marine fishes liv- 

 ing at twilight depth. 



There are no cave reptiles, nor do reptiles temporarily enter caves for shelter, 

 as do mammals. One turtle found a little distance inside of one cave was evidently 

 accidental. I have never seen a snake in a cave, but once secured a copperhead 

 at the entrance to one. But there are numerous blind lizards and snakes that 



