Population ecology of small mammals in Mount Rungwe nature forest reserve
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Date
2024
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Sokoine University of Agriculture
Abstract
Small mammals play significant ecological and economical role among
many societies. Therefore, conducting ecological assessment of small
mammals is crucial for maintaining functioning ecosystems and societal
well being. The tropical mountains are characterised by diverse
habitats, favourable environmental conditions, as well as abundant flora
and fauna, including numerous endemic species. Among tropical
mountains, Mount Rungwe Nature Forest Reserve (MRNFR) in
southwestern Tanzania stands out as the second-highest mountain in
the region, boasting its high diversity of flora and fauna, including
several important IUCN endemic species such as Rungwecerbus
kipunji, Cephalophus spadix and Galagoides sp. While there have been
various studies on small mammals in Tanzania, the studies on
mountainous small mammals remain limited, with most of them
conducted in the northern part of the country and Eastern Arc
mountains. This study aimed to understanding the ecology of small
mammals in MRNFR which is situated at the intersection of the western,
eastern and southern East Africa rift valleys. The study was conducted
between 2020 and 2022 and involved data collection along an altitudinal
gradient encompassing low-elevation, mid-elevation, and high-elevation
with habitats low and mid montane forests, montane bamboo forests,
montane bushland and montane grassland. Different methodologies
were employed based on the stated specific objectives. The total of 300
Shearman traps, 60 pitfall traps, 132 snap traps and 18 Havahart traps
were used. To determine the species composition, a combination of
Sherman traps, pitfalls and Havahart traps was used along transects
whereby five trapping nights were conducted at each elevation. Grids
measuring 70 m X 70 m were established at each elevation to examine
the influence of microhabitat parameters on small mammal abundance.
Each grid contained 49 Sherman traps which were set over three
consecutive nights. Microhabitat parameters, including vegetation and soil characteristics were collected using nested quadrant approach and
soil core method. The data on population dynamics were obtained from
permanent grids established over three consecutive days within a 24-
month period at each elevation. For the purpose of diet analysis, the
snap traps were placed in four transect lines at each elevation for six
nights during both wet and dry periods and food categories were
determined through macro-histological analysis of stomach contents. All
collected species were identified using relevant keys and confirmed by
sequencing the mitochondrial cytochrome b gene. A total of 3,183
individual small mammals comprised four families, eleven genera and
twelve species were collected. Identified small mammals were
Montemys delectorum, Crocidura luna, Lophuromys machangui,
Grammomys cometes, Cricetomy ansorgei, Dendromus nyassae,
Mysorex kihaulei, Crocidura olivieri, Hylomyscus arcimontensis,
Beamys hindei, Graphiurus sp. nov. and Mus triton. A total of nine
species were recorded during the wet season whereas ten species
were recorded during the dry season. The results revealed that habitat
characteristics and season significantly influenced small mammal
richness, composition and diversity. The mid-montane forest exhibited
the highest diversity compared to low-montane forests. Small mammal
composition varied across habitats (Est ± SE = 3.36 ± 0.032, Z= 103.8,
p < 0.001) with montane bushland showing significantly lower
composition. Season and habitat significantly influenced species
composition with montane bushland habitats having lower species
composition and diversity during the dry season. The study further
found out that small mammal abundance was influenced by elevation
and season with mid-elevation and short rain period depicting the
highest abundance. Elevation affected some species differently with P.
delectorum decreasing and Lophuromys machangui increasing with an
increase in elevation. On the contrary, Crocidura luna was not affected.
Moreover, the results revealed that microhabitat parameters influenced
abundance of individual species differently, thus indicating that altering
the microhabitat could impact small mammal assemblage and
abundance.Molecular information has revealed the presence of small mammal
species such as Graphiurus sp. which was reported for the first time in
this area. The study also demonstrated that habitat and microhabitat
types, elevation gradient and seasonal variations strongly influence
small mammal species abundance, diversity, richness and distribution
at both the population level and individual species like P. delectorum
and L. machangui. Some species such as L. machangui and P.
delectorum are distributed in Northern and Southern Highlands, thus
showing less influence from the boundaries between these two regions.
However, the distribution of other species such as Graphiurus sp. and
M. kihaulei is impacted by these boundaries. In particular, the study
revealed the presence of endangered Myosorex kihaulei in MRNFR,
which was previously believed to be endemic to Udzungwa Mountain
only. Based on genomic analysis, the study documented novel
Graphiurus sp. Such findings suggest the need to incorporate the
observed species in the management plans of Southern Highland
landscapes, particularly Rungwe Mountain, and consider the
conservation of the noted endangered species. The findings also
suggest that monitoring of species along the elevation gradient is crucial
due to a greater diversity of species in Rungwe Mountains.
Description
Dissertation
Keywords
Ecology, Small mammals, Population, Mount Rungwe