August 15, Rats: 1964 (cont.) Wm. Jackson--a very dense rat population. An ideal situation for extensive studies of a population at such a high density. All rats caught were Polynesian rats Traps were set out in early afternoon. (Rattus exulans). Most were inspected in the afternoon and again in early evening; about half the total catch was obtained before dark. Total catch 65. Of the females (N-27) all had perforated vaginal orifices, indicating sexual maturity. uterine scars, Only 2 lacked indicating pregnancy at a previous time, and only l was pregnant. Of the males (N-35) only 5 were not mature. were smaller than the mature individuals. These Males were, five in general, larger than the females. Possible explanations of population state: breeding season, this is the non- or population pressure has reduced reproduction. --Atrophied condition of female reproductive tract --Lack of young individuals Could support either hypothesis-~-the high prevalence of uterine scars supports the breeding season hypothesis. Three skins were prepared. preserved. Stomachs, adrenals, and lungs were No fleas or lice seen (not thoroughly checked for) but mites were found and preserved.