280 TELFORD: MULTIMAMMATE RAT POPULATION BIOLOGY IN TANZANIA


samples (Tables 13, 14) demonstrated that mean HBL and mean weight of
female P. natalensis were greater in the critical December-February and
March-April periods of 1983-84 than at comparable times in 1981-82 and 1982-
83. This probably reflects an increased food supply despite greater population
density during the exceptionally heavy rainfall of December 1983-January 1984.
The data also could indicate survival of the larger members of the cohort, with
smaller individuals having greater mortality or being forced to emigrate from
the study areas.

 CONCLUSIONS


 The data obtained during this study suggest the following conclusions:

 1) In dry years, reproduction in either uncultivated or
 cultivated habitats begins in April and ends in August.
 Populations begin reproduction in those years at minimal
 density levels.


REPROD. I

POST-REP. El

NON-REP. D


 1982 1983 1984 1985
Figure 26. Structure of the female cohort from the university campus P. natalensis population in
fallow maize field or uncultivated grass microhabitats in January of each year, 1982-85.


TABLE 12. Average trap success forPraomys natalensis by habitat and season.

 % Positive traps in

Season Maize fields Uncultivated grass

July-December 31.2 17.1
January-April 12.7 7.3
May-June 4.0 5.4