PELAGE STUDIES 



A report "Pelage and surface topography of 

 the northern fur seal" (Scheffer, 1962)" was 

 published in February 1962. Another report 

 "Molt in the northern fur seal" (Scheffer and 

 Johnson, 1963)" contains a quantative analysis 

 of the timing of molt by age and sex. 



EYE-LENS WEIGHT AS AN INDICATOR OF 

 AGE 



The eye lens in mammals is believed to 

 grow throughout life. Since 1959, a number of 

 zoologists have published growth curves for 

 lens weight. One of the most extensive studies 

 is one on rabbits made by the Illinois Natural 

 History Survey. In 1962, a collection of lenses 

 from known-age seals (pups to age 17) was 

 saved for the purpose of testing the relation- 

 ship of age to lens weight. While the lens 

 weight method may not prove useful, a small 

 exploratory study of it will be made. 



HOOKWORM STUDIES 



Research on hookworm infection of fur seal 

 pups was carried on through a cooperative 

 agreement with Colorado State University from 

 1959 to 1962. The principal investigator, O. W. 

 Olsen also made studies on hookworms of fur 

 seals from 1951 to 1955. He was assisted by 

 graduate students C. F. Dixon in 1953-54 

 and E. T. Lyons in 1960-62. 



In each of the years 1953-55, hookworm 

 larvae were found to live over winter in the 

 soil. It seemed apparent at first that seal 

 pups were infected through their skin by 

 contact with larvae in the rookery soil. 



As a result, experimental treatment of the 

 rookery soil with salt, creosol solutions, and 

 other chemicals was tried as a way of elimi- 

 nating the larvae. The rate of infection among 



" Victor B. Scheffer. 1962. Pelage and surface top- 

 ography of the northern fur seal. U.S. Fish and Wildlife 

 Service, North American Fauna 64, 206 p. 



M Victor B. Scheffer and Ancel M. Johnson. 1963. 

 Molt in the northern fur seal. U.S. Fish and Wildlife 

 Service, Special Scientific Report--Fisheries No. 450. 

 In press. 



pups on treated areas did not differ from that 

 of pups on untreated areas. 



From 1959 to 1962 larvae apparently did 

 not live over winter but infection of pups by 

 hookworms continued much as in years when 

 the larvae did survive. If larvae are not reg- 

 ularly in the soil until August, seal pups must 

 receive their intestinal infections in some 

 other way. No evidence of prenatal infection 

 could be found in various experiments with 

 pups taken by Caesarean section. 



In 1961 several pregnant females were 

 moved and allowed to bear their pups on an 

 area isolated from hookworm infested soil. 

 Their pups became infected. The source of 

 the infection was traced to larvae in the milk. 

 These larvae develop to maturity in the in- 

 testines of pups, and eggs are passed with 

 fecal material in about 2 weeks. Free-living, 

 third-stage larvae begin hatching in late 

 August. The free-living larvae penetrate the 

 skin of seals of all ages and migrate to the 

 belly blubber. They grow slightly from the 

 time they enter the skin until they are ingested 

 with milk by a pup. Larvae in the blubber of 

 males and nonpregnant females cannot escape 

 and do not infect pups. 



Twenty of twenty- six pregnant females taken 

 at sea in Unimak Pass before they reached 

 the Pribilof Islands contained hookworm larvae 

 in their belly blubber and mammary tissue. 

 Milk samples from seven of eight pregnant 

 females contained larvae. Larvae are in the 

 milk of females for only a short time after 

 parturition; the pups are evidently infected 

 with larvae when they first nurse. The infec- 

 tion rate is very high. Superinfections are 

 possible but do not normally occur because 

 of the short period when infective larvae are 

 in the milk. The conditioning factor that causes 

 part of the larvae from the blubber of a 

 female to migrate to the milk and become 

 infective is not known. Pregnancy hormones 

 are suspected. 



Infections of fur seal pups by larvae from 

 the belly blubber of male sea lions were not 

 obtained but would not be expected in the light 

 of present knowledge. Infections of fur seal 

 pups by larvae from a pregnant female sea 



51 



