Studies were made on the Bush rat, Aethomys hindei in Lunyo forest (0° 5', 32° E) on the Northern shores of Lake Victoria. Rats were trapped daily (Monday-Saturday) for 47 weeks during November 1970 to November 1972 from 20–49 live traps set in a 40 by 100 m grid. In the laboratory they were examined for the condition of the external genitalia and for signs of pregnancy. Some pregnant rats were kept in the laboratory and their progeny measured at weekly intervals. The rate of growth (weight gain in g per day) was determined for both laboratory and field rats. Growth curves of laboratory rats were used to calculate the ages of young (<100 g) field rats, even though the results showed that at between 50 to 100 g field rats grew faster than laboratory rats and between 100 to 150 g, laboratory rats grew faster than field rats.
The weight distribution of rats in the field showed a clear weight difference between males and females; with some males weighing as much as 171 g while the maximum weight recorded for females was only 146 g. The weights obtained extend the weight range of these rats beyond that previously published.
Breeding (pregnancies) in the field occurred mostly in the wetter months of November- December and April whereas young animals occurred more in the drier months of December and January. Births obtained by calculation from laboratory growth curves occurred more in November.
Seasonality in the intensity of breeding was indicated although monthly breeding throughout the year was observed. The months of highest population densities were December, January and April.