Community ecology of rodents in a natural and agricultural landscape- in Western Serengeti, Tanzania
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Date
2024
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Sokoine University of Agriculture
Abstract
Rodents are beneficial ecologically as they act as food for other
organisims including humans. However, about 17% of rodent species
are problematic since they transmit zoonotic diseases, damage
properties and depredate crops. Various strategies have been
designed worldwide to control them but have proven futile due to limited
knowledge on the animals’ biology, behaviour and ecology. This
knowledge is essential for preparing integrated rodent conservation and
management strategies. Also, no one single strategy can effectively
be used to manage rodents in every part of the world, hence rodent
ecological studies in as many local areas as possible are needed.
Therefore, two ecological studies were carried out to generate
information that would contribute to the formulation of effective
strategies. The first study aimed to determine: i) spatio-temporal
community structure (species composition, age and sex structure), ii)
spatio-temporal population dynamics and breeding patterns and iii)
influence of ecological factors (vegetation attributes, soil characteristics
and seasonality) on abundance of
a dominant rodent species
M.natalensis. The second study aimed at investigating the dietary
patterns of the dominant rodent species. These are the first detailed
ecological studies in our study area.
The first study was conducted within Kijereshi Game Reserve and the
surrounding Nyamikoma village in the western Serengeti using Capture-
Mark-Recapture (CMR) technique from April 2020 to March 2022.
Sherman live traps were used to trap rodents on a 3 consecutive night’s
basis every month for twenty four months. Trapping was done in nine
70 x 70 m2 permanent grids in the wooded grassland habitat within
Kijereshi Game Reserve, and in fallow land and maize crop fields within
Nyamikoma village land. One year data collected from from 2020 April to March 2021 were used
to investigate spatio-temporal community structure of rodents in the
three habitats whereby 1,075 individuals were captured. They
comprised eight 8 rodent species and one shrew species. Mastomys
natalensis (76.6%) was the most whereas Acomys wilsoni (02%)
occurred the least abundant species across habitats and the
insectivorous animal was Crocidura cf. flavescens (11.1%). Species
richness was highest in the wooded grassland and least in maize crop
fields, probably due to mono-cultivation nature in the maize crop fields.
Fallow land had a higher diversity (1.05) while maize fields had the
lowest (0.35), suggesting presence of heterogeneity in fallow land
habitats as compared to maize crop fields. A statistical difference in
number of adults, subadults and juveniles was detected between
habitats (F2, 102 = 3.09, P=0.05), and a marginally significant
difference between seasons (F1, 102 = 3.743, p = 0.06). There were
more Juveniles in the maize crop fields than in the wooded grassland
habitat probably due to availability of food resources that favour their
reproduction. On the other hand, there was a significant difference
between numbers of females and males of M. natalensis captured
across dry and wet seasons (F1, 64 = 8.311, p = 0.005) and the three
habitats (F2, 64 = 6.9, p = 0.004). The study suggests that small scale
comparisons of the community structures of small mammals between
habitats can provide knowledge that is needed for conservation and
control of small mammal species.
A two year period data on population dynamics and breeding patterns
of M.natalensis revealed that, its abundance varied significantly across
habitats ( Chi-squared = 8.922, df = 2, p-value = 0.012) and between
seasons (W = 982.5, p-value<0.001). Females bred continuously
throughout all seasons and there was no significant difference in the
number of actively breeding females across habitats (Chi-squared =
3.52, df = 2, p-value = 0.172) and between seasons (W = 584, p-value = 0.472) probably due to presence of seeds/grains especially in maize
crop fields throughout the year. However, in most cases breeding
started to increase immediately after long rains in March/April except in
the wooded grassland where there was a lag. Numerically, the M.
natalensis abundance was higher in maize crop fields as compared to
other habitats, but densities dropped similarly in all habitats during wet
season. Nevertheless, the reasons for this is not yet clear as
substantial food resources are available especially in the maize crop
fields resulting from maize crops harvest of the second cropping
season. Although, analysis of data on several selected ecological
correlates, indicated that the latter have influence on the abundance of
M.natalensis. For example, its abundance was significantly higher
during the dry season and in farmlands than in wet season and
protected areas (χ2= 79.393, df = 2, p < 0.001). Also, the abundance
significantly associated positively with farmlands (p = 0.023) and sandy-
clay-loam soils (p = 0.007). Hence, control of the animals might be
effected between the months of November and January when densities
are low and farmers should maximize maize production during this
period which falls in their minor cropping. Also, soil type issue should
be taken into consideration during farm site selection.
The second study was conducted in the same study site as the first one,
to investigate on the dietary patterns of M.natelensis, whereby, kill traps
(Victor kill trap (1.0 x 20.3 x 30.1 cm, Animal Trap Co., Lititz Pennal)
baited with peanut butter mixed with maize bran/flour were used in
three grids of 70 x 70 m2. About 111 captured specimens were
dissected, their stomachs removed and labelled, then preserved in
containers (20 ml, glass bottle, HiSupplier_.com) containing 70%
ethanol. The analysis of stomach contents was carried out by evenly
spreading each stomach contents in a Petridish and categorised using a
binocular dissecting microscope under 25 x and 50 x magnification, into
various food categories. Overall, vegetative plant materials (41%) andinvertebrates (39.1%) dominated. During the wet season, invertebrates
dominated in the wooded grassland, followed by fallow land and maize
crop fields. On the other hand, seeds/grains were more eaten in maize
crop fields than in other habitat types. Also, in the dry season,
vegetative plant materials dominated the animal’s diet in maize crop
fields suggesting that this rodent is an opprtunistice feeder.
Description
Dissertation
Keywords
rodent- ecology, Mastomys - natalensis, Kijereshi, Nyamikoma, western -Serengeti