254 TELFORD: MULTIMAMMATE RAT POPULATION BIOLOGY IN TANZANIA

of the savanna woodland association. Protected by the Division of Forestry of the university, it
has been used for experimental studies on introduced vegetation. A total of 22 sites of 1 ha. or
less in various parts of the campus were selected for sampling (Fig. 1). Selection was based upon
present or previous agricultural use, and related primarily to the cultivation of maize, which is the
major crop grown both on campus and in Morogoro Region. Study sites were classified as
follows: (1) growing maize, which sometimes had scattered beans or cassava intermixed with it;
(2) post-harvest maize, for approximately two months following the harvest, consisting of a thick,
high stubble that provides both abundant food and cover for rodents; (3) fallow field, where
evidence of maize cultivation during the previous season remained--post-harvest maize was
classed as fallow field two months following harvest; (4) old fallow field, where maize had not
been grown the preceding season, but which had supported a crop within two years; and (5) grass
habitat, which could be divided into two distinct types--that which succeeds old fallow field, and
that which had no recent record of cultivation but which was cropped regularly by machinery to
provide fodder for dairy cattle.


 RESULTS AND DISCUSSION


 Land-use cycle.-- Interpretation of the results presented here requires a
description of the land use cycle and climatic factors. The cultivation of maize
in the area depended strongly upon the timing and quantity of rainfall.
Farmers attempted to plant two crops each year, one before the "long rains"
and a second crop to take advantage of the "short rains." The long rain crop
usually was planted between February and May and represented the primary
agricultural effort of the year, furnishing about 90 percent of the annual maize
production. This crop was harvested from late June until August, and fields lay
fallow until late October. If short rains came, then planting on a considerably
reduced scale took place from late October into December. Harvest of this
crop, however, was unpredictable and generally of low yield, due both to
erratic and insufficient rainfall, and the difficulty of planting at the time of year
when rodent populations were at maximum density. Fallow fields sometimes
were burned prior to both planting periods, depending to some degree upon
the density of second growth and the availability of mechanical cultivators.
Except for the use of mechanized equipment, maize cultivation on the
university campus reflected traditional timing and practice of the Morogoro
area.

 Climatic factors.-- During the 15-year period 1970-1985, the maximum
temperature recorded at the university campus was 34.1C in December 1974,
and the minimum was 14.00C in July 1973. The recorded maximum and
minimum during the 40 months of the study were 33.7TC and 14.20C. Maxima
remained relatively constant from August through April, 28-33, but then
declined slightly until August when they rise (Fig. 2). Minima remained at 20*
or above from December until May, and varied from 14 to 20 from June to
December.