CHAP. Ill BIRDS, RATS, AND LIMPETS 57 



thousands of limpets in the course of a single year. Rats are 

 exceedingly fond of limpets, whose shells are frequently found 

 in heaps at the mouth of rat holes, especially where a cliff shelves 

 gradually towards a rocky shore. A rat jerks the limpet off with 

 a sudden movement of his powerful jaw, and, judging from the 

 size of the empty shells about the holes, has no difficulty in 

 dislodging the largest specimens. ' I once landed,' relates a 

 shepherd to Mr. W. Anderson Smith,i 'on the I. of Dunstaff- 

 nage to cut grass, and it was so full of rats that I was afraid to 

 go on ; and the grass was so full of limpets that I could scarcely 

 use the scythe, and had to keep sharpening it all the time.' 

 Sometimes, however, the limpet gets the better both of bird and 

 beast. The same writer mentions the case of a rat being caught 

 by the lip by a limpet shell, which it was trying to dislodge. A 

 workman once observed ^ a bird on Plymouth breakwater flut- 

 tering in rather an extraordinary manner, and, on going to the 

 spot, found that a ring dotterel had somehow got its toe under 

 a limpet, which, in closing instantly to the rock, held it fast. 

 Similar cases of the capture of ducks by powerful bivalves are 

 not uncommon, and it is said that on some parts of the American 

 coasts, where clams abound, it is impossible to keep ducks at 

 all,^ for they are sure to be caught by the molluscs and drowned 

 by the rising tide. 



The Weekly Bulletin of San Francisco, 17th May 1893, ccfn- 

 tains an account of the trapping of a coyote, or prairie wolf, at 

 Punta Banda, San Diego Co., by a Haliotis Cracherodii. The 

 coyote had evidently been hunting for a fish breakfast, and 

 finding the Haliotis partially clinging to the rock, had inserted 

 his muzzle underneath to detach it, when the Haliotis instantly 

 closed down upon him and kept him fast prisoner. 



Rats devour the ponderous Uniones of North America. 

 When Unio moves, the foot projects half an inch or more 

 beyond the valves. If, w^hen in this condition, the valves are 

 tightly pinched, the foot is caught, and if the pinching is con- 

 tinued the animal becomes paralysed and unable to make use 

 of the adductor muscles, and consequently flies open even if the 

 pressure is relaxed. The musk-rat (^Fiher zihethicus) seizes the 

 Unio in his jaws, and by the time he reaches his hole, the Unio 



1 Loch Ci'eran, p. 102. ^ Cordeaux, Zoologist, 1873, p. 3396. 



3 A7ner. Nat. xii. p. 695 ; Science Gossip, 1865, p. 79. 



