50 



NORTH AMERICAN FAUNA 68 



Molars 



The upper and lower molars have no antecedents. They erupt 

 in the late juvenile period somev^hat later than the permanent 

 canines and somewhat earlier than the permanent postcanines. 



Many young are born in the late winter-spring period. In the 

 following late winter and early spring period of stress, the food 

 intake of these large juveniles is inhibited by the eruption of the 

 permanent postcanine teeth and the accompanying loss of decidu- 

 ous teeth. In the crowded Amchitka population where food re- 

 sources are heavily exploited, such young, still dependent on their 

 mothers for much of their food, are deserted and die at this time. 

 Apparently, the mothers are unable to supply the food needs of 

 both themselves and their large young during this season of stress. 



Because poor occlusion, as described above, was observed in 

 many young otters found dead of starvation on beaches, it was 

 assumed that this condition was a factor in their failure to survive 

 (see Mortality Factors). 



Dental attrition 



The teeth of many sea otters at Amchitka Island show severe 

 tooth wear (fig. 27). In order to learn something of the nature 

 of this damage, sample skulls with worn teeth were sent to Dr. 

 David B. Scott, Chief, Laboratory of Histology and Pathology, 

 National Institute of Dental Research. After he and his associates 

 had examined the teeth they contributed information in a letter 

 of 23 May 1963. Excerpts are quoted : 



None of us feels that the pitted and worn areas have the requisite charac- 

 teristics of dental caries. The alterations are quite curious. Since we were 

 not familiar with the dentition in the otter, we removed an unerupted 

 permanent tooth and uncovered two others from under the deciduous teeth 

 of a juvenile male (KWK 59-105), and also removed one of the more interest- 

 ing atypically pitted ones from an adult female (KWK 59-11). One of the 

 former teeth split well enough for us to get an idea of the enamel thickness; 

 taken together with the appearance of the other permanent teeth in this young 

 skull the impression is gained that deep pitting is not a feature at the outset. 



The most interesting and confusing configuration in the pitting of the type 

 found in the tooth from KWK 59-11, is the tips of the cusps. As seen in the 

 sectioned tooth, the hole in the underlying dentin is actually broader than 

 the opening through the enamel, resulting in a sort of undermining. [Exami- 

 nation of many teeth indicate to me that these pits are formed when a piece 

 of hard sand is pressed into a newly formed break in the enamel. Movement 

 of the sand grain and pressure on it when food is chewed cause it to rotate 

 and create a cavity in the dentin larger than the hole through which it en- 

 tered.] This is not expected in attrition, but all of us feel that the classical 

 signs of caries are not present. There is quite a deposit of secondary dentin 



