426 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1913. 



his own burrow and immediately attacks any invader of this terri- 

 tory. His pugnacity is ever ready to show itself against his fellows 

 that swarm about him and against numerous competitors of other 

 lands that also seek to eke out an existence from the area he has 

 chosen for his own. 



The fiddler's chief competitors for the food on the beaches are 

 other species of crabs, various smaller animals such as snails and 

 worms, and some larger animals like fishes and birds. In addition 

 to honest competition the fiddler must reckon with some larger ani- 

 mals, which seek not his food but himself. Among these the rac- 

 coons, herons, snakes, skinks, frogs, toads, and fishes are most 

 important. 



The behavior of the fiddler is admirably suited to enable him to 

 gain a livelihood and at the same time escape injury or death from 

 his enemies. His aggressive attitude toward members of his own 

 genus and toward other crabs of similar size keeps enough space clear 

 about his burrow to enable him to sift his simple diet from the mud 

 in comparative safety. Furthermore, the way is thus left clear for 

 retreat to his burrow if danger threatens, and the fiddler is not slow 

 in dodging into his hole as soon as any strange or threatening object 

 moves within his field of vision. His burrow is the center of all his 

 activities, and his association for the place where it is situated is 

 very strong. Fiddlers are protected from night prowlers by their 

 diurnal habits, and they escape the fishes and snakes that hunt at 

 the edge of the advancing tide by closing the openings of their bur- 

 rows when the water threatens to inundate them. 



Although the majority of the reactions of fiddler crabs are stereo- 

 typed and appear to be instinctive, yet they are open to some modi- 

 fication. The daily life of a fiddler is more or less of a routine — to 

 dig a burrow, to seek food as long as the territory about his burrow is 

 clear, to attack small aggi'essors, to retreat from large enemies, to 

 plug the burrow when the tide comes in, to open it when the water 

 recedes, to retire during darkness, and to mate at the proper season. 

 These are his ordinary activities, and they depend largely upon 

 unvaried reactions. Some instincts are so strong that, although 

 usually advantageous, they may be harmful ; for example, place asso- 

 ciation and instinct to retire into her hole was strong enough to cause 

 a certain crab to remain for some time in danger when the burrow 

 could not be entered and she might have escaped by nmning away. 

 Nevertheless, a fiddler shows some ability to modify his reactions to 

 suit circumstances, such as departing from his usual method of car- 

 rying mud from his burrow, using different ways to plug the burrow, 

 and in some other activities, 



A fiddler crab is able to establish a place association for a certain 

 locality and to retain it for as long as three weeks. Some activities 



