1 8 Notes on the Haxvaiian Rat. 



lip. In one (No. 3) it will be observed the apex is gone. Popo- 

 ian rats had always completely crushed the shells of the Eulota, 

 so observations were made on the method of initial attack on this 

 species by the remaining living native rat, $ No. o. After feeding 

 one snail at a time and then interrupting the meal, it was found on 

 examining the shells that all were attacked at the last whorl, one 

 of which was also broken at the aperture. In the latter instance, 

 the body of the snail was expanded just before it was seized by 

 the rat. From the above observations and illustrations, it might 

 appear that the rats attack the portion of the shell where the mol- 

 luscan body is found. 



Many of the Hawaiian terrestrial mollusca are smaller and 

 are provided with more fragile shells than those illustrated above, 

 and may well have contributed to the diet of the native rat before 

 it was displaced by the introduced species. 



In the communications to Dr. Stone, reference was made to 

 the inability or lack of desire on the part of the Popoian rats to 

 escape by gnawing through the soft wooden lining of the cage. 

 Evidence of the ability of the common house rats, or even mice, to 

 gnaw through thick wood has been presented to most people who 

 live in wooden houses. The Popoian rats, on the other hand, have 

 made no attempt to gnaw their way out through the wood, though 

 for the first two days of captivity they tried to bite through the 

 exposed wire front. Bones and tough cartilage they do not seem 

 to make an impression on, and they were unable to bite through 

 the leg of our common rock crab, as already mentioned. 



It would thus seem that there was a comparative weakness in 

 the Hawaiian rat's gnawing system, due probably to undevelop- 

 meut in the species. Such a probability could be explained if we 

 were to take into consideration, for example, the conditions under 

 which the house varieties of the different species operated . Foreign 

 rats and mice have had, for very many of their generations, closely 

 fitting wooden walls and floors to contend with, and innumerable 

 enemies to compel them to ktep close within the shelter of such 

 wooden constructions. The Hawaiian rat shared the open life of 

 its human neighbor, with few natural enemies except the same 

 neighbor, and found the grass house walls, and loose stone founda- 

 tions and floors, places for easy hiding. 



"[268] 



