Three villages in different districts of Zambezia province,
Mozambique, were selected for involvement in the trials
based on reports from farmers indicating that rodents were
a significant pest problem, particularly after harvest when
crops are stored within the dwelling. The village of
Mutange in Namacurra district lies within a flat lowland
rice-growing area, the village of Pinda in Morrumbala
district is in a highland plateau maize-growing area and the
village of Mugaveia in Gurué district is in a mountainous
mixed forest–cropland area. Each village has approximately
400 domestic dwellings which typically consist of a
mudded timber-frame rectangle (approx. 4 . 5 m) with a
grass or palm-leaf thatched roof. The open-plan interior
contains a raised platform where food is stored, a cooking
fire and a sleeping area for approximately eight people.
Each village was divided into two portions, one half
acting as the treated area and the other as the untreated
area (experimental control). The 200 households in the
treated area were each given 10 break-back traps (big
snap-e-trap, Kness Manufacturing Ltd, USA), with all
10 traps placed in the dwellings along interior walls and
walkways, especially in places where food is usually
stored. Farmers were given individual training on the
operation of the traps and instructions to set them each
evening. Dwellings in the treated area of the three villages
were visited each morning, and the number of rodents
trapped the night before were recorded daily for the
duration of the trial (November 2000 to March 2002).
Householders in the untreated area did nothing to manage
their rodent problems over this time, and every month a
subset of 30 households was randomly selected from this
area and the occupiers set traps in the same manner as in
the treated dwellings but over three nights only. The
number of rodents caught during these three nights from
households in treated and untreated areas was recorded,
including their sex, weight, species, and whether any
females caught were observed to be pregnant. Representative
samples of each species were collected for later taxonomic
identification. The number of rodents caught
among farmers and villages was analysed by analysis of
variance (ANOVA) with a post-hoc least significant difference
(LSD) test to separate the mean values. Comparisons
between treated and untreated areas in the same village
were analysed using an independent sample T-test evaluating
the number of rodents caught and their average
weights. The potential interactions between populations of
R. rattus and M. natalensis within each village were evaluated
by linear and non-linear regression models using the
data obtained on the total number of each species caught
in each household during the trial.