Ecology, parasitology and feeding habits of Rattus exulans Peale from the Tokelau Islands

Abstract

Eight hundred specimens of Rattus exulans, collected in eight consecutive monthly samples (Nov. 1966 - June 1967) in the Tokelau Islands, were measured, weighed and autopsied to provide information on sex-ratio, age structure and reproduction of the population. Toothwear was found to be an unreliable means of ageing and the use of various other criteria of maturity was preferred. A reproductive pattern was established using data on the condition of mammae and uteri, and prevalence of pregnancy in female rats. The food habits of Rattus exulans captured in coconut plantations, in areas adjacent to coconut plantations and in areas of human habitation, were determined from the stomach contents of 289 rodents collected in four consecutive monthly samples. The diet of R. exulans from all areas was primarily coconut meat with a small proportion of other plant material, insects and crustaceans. A comparison of the fatty acid composition of dietary fats, adipose tissue and perinephric fat of R. exulans and the laboratory white rat (R. norvegicus) was made using gas chromatography. Six parasites consisting of a cestode (Hymenolepis diminuta), four nematodes (Physaloptera muris brasiliensis, Gongylonema neoplasticum, Protospirura muricola and Metathelazia sp.) and a mite (Laelaps nuttalli) are reported here from R. exulans from the Tokelau Islands. The absence of the lungworm (Angiostrongylus cantonensis) was recorded. Prevalence of infection of H. diminuta and P. murisbrasiliensis was correlated with estimated age, weight of the rat and the season. A helminthological comparison of two populations showed no difference in faunal components or worm population levels. In both rat populations there was no difference in worm population with sex. The overall effect of the parasitic fauna upon the Polynesian rat is considered to be slight and the present parasitic fauna appears to have no medical or veterinary importance.