School of Science

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Browsing School of Science by Subject "Abundance"

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    The effect of habitat type on rodent, shrew and sengi species abundance, richness, diversity and composition at farm Karachas, Outjo, Namibia
    (University of Namibia, 2021) Kapala, Salmi
    Natural habitats have been fragmented by many human activities including farming, hence affecting vegetation structure. Despite being very dry, Namibia has many farms in which game, livestock and crop farming are practiced. Yet such activities affect populations of many other organisms including small mammals such as rodents, shrews and sengis. The present study investigated the effect of habitat type on rodent, shrew and sengi species abundance, richness, diversity and composition in selected open grassland habitat and woody habitats at Karachas Farm, Outjo, Namibia. Sampling at each habitat type was replicated twice. Woody plant species abundance, composition, height and percentage grass cover were determined and compared between the open grassland and woody habitats. A capture-mark-recapture (CMR) technique was employed to obtain data on rodents, shrews and sengis. Each habitat type was sampled over five consecutive nights using Sherman live traps. The result of t-, chi-square and Mann-Whitney tests, respectively, showed a statistically significant difference in the mean abundance of woody plants, plant height, and plant species richness between the open grassland and woody habitats. A Mann-Whitney test showed no statistically significant difference in the percentage grass cover between the open grassland and woody habitats. A Hierarchical Cluster Analysis (HCA) based on a Bray Curtis Similarity Index showed a low (31%) level of similarity in woody plants species composition between the open grassland and woody habitats. A total of 800 trap-nights yielded 145 individuals comprising 6 rodent red veld rat (Aethomys chrysophilus), namaqua rock mouse (Micaelamys namaquensis), bushveld gerbil (Gebilliscus leucogaster), maltimammate mouse (Mastomys natalensis), tree mouse (Thallomys paedulcus), pouched mouse (Saccostomus campestris), sengi (Elephantulus intufi) and shrew (Crocidura hirta) species. t- tests and a Mann- Whitney test, respectively, showed no statistically significant variation in rodent, shrew and sengi species abundance, richness, and diversity between the open and woody habitats. An HCA based on a Bray Curtis Similarity Index showed a high (63 %) level of similarity in rodent, shrew and sengi species composition between the open grassland and woody habitats. The present study therefore showed insufficient evidence to support the hypotheses that habitat type has an effect on rodent, shrew and sengi species abundance, richness, diversity and composition. Further studies should focus on researching the range of factors that drive rodent, shrew and sengi diversity in different habitat types of the farm. The study also recommend the use of more than one trap type when surveying rodent, shrew and sengi communities.
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    Rodent species composition, abundance, richness, and diversity amongst different habitats in two villages in the Mukwe Constituency, Kavango East region of Namibia
    (University of Namibia, 2024) Kayala, Ester N.
    Rodents are habitat bio-indicators because their population dynamics respond to changing environmental and habitat alteration such as environmental disturbances. Some rodent species such as Mastomys natalensis are agricultural pests and have caused a lot of damage to crop harvests and peoples’ belongings. Additionally, rodents serve as vectors for deadly diseases which they can transmit to humans. The aim of this study was to examine variations in the rodent species composition, abundance, richness and species diversity amongst different habitats (fallow land, less disturbed land and in the houses) in Bagani and Diyogha village, in the Mukwe Constituency. Trapping was conducted over a period of twelve months using PVC live traps, for three consecutive nights in each habitat. A total number of 285 rodent captures were recorded in 16,272 trap nights; comprising of five different rodent species, which were Mastomys natalensis, Gerbilliscus leucogaster, Thallomys paedulcus, Saccostomus campestris and Steatomys pratensis. A Kruskal-Wallis H test showed that there was no statistically significant difference in rodent species abundance amongst the three habitats in Bagani (χ2 = 1.665, df = 2, p = 0.4101), and Diyogha (χ2 = 1.715, df = 2, p = 0.3978). Whereas the same test has also revealed that there was a statistically significant difference in the rodent species richness between the fallow land (SR = 4) and the less disturbed land (SR = 2) as well as the less disturbed land (SR = 2) and houses (SR = 3) in Bagani (χ2 = 10.81, df = 35, p = 0.0026), and between the fallow land (SR = 2) and houses (SR = 3) in Diyogha (χ2 = 12.18, df = 35, P = 0.001). Additionally, the test revealed that there was no significant difference in the rodent species diversity amongst the three habitats in Bagani (χ2 = 2.551; df = 35, p = 0.147), however, there was a significant difference in the rodent diversity amongst the habitats in Diyogha (χ2 = 4.97; df = 35, p = 0.029). Dunn’s post hoc test was used for all the iii parameters to further explore the differences within the habitats. It showed that there was a significant difference in the rodent species richness between the fallow land and the less disturbed land (p = 0.006) as well as between less disturbed land and the houses (p = 0.001) in Bagani. Whereas in Diyogha, there was a significant difference in the species richness between the fallow land and the houses (p = < 0.002). Lastly, the post hoc test showed a significant difference in rodent species diversity between the fallow land and the houses (p = 0.0084). An HCA based on a Bray Curtis Similarity Index showed that there was a 30% and a 22% similarity in the rodent species composition amongst the three habitats in Bagani and Diyogha, respectively. The Spearman’s correlation (Rs) test revealed that rodent species abundance was weakly positively correlated with the rainfall (r= 0.146, n = 12, p = 0.650) and relative humidity (r = 0.403, n = 12, p = 0.193), however, the temperature (r = -0.05, n = 12, p = 0.87) had a negative influence on the rodent numbers in Bagani. Furthermore, in Diyogha, all three weather parameters had positive correlations to the rodent numbers during different seasons or months. The following study revealed that the different habitats in both villages did not influence the rodent species abundance. A similar study to the current one should be conducted for a period longer than two years in order to compare the influence climatic variables have on the rodent numbers in both Bagani and Diyogha village. However, the study should use a capture-mark-recapture (CMR) technique instead of euthanizing the rodents
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    Variations in the use of artificial waterholes by mammals at Okaukuejo and moringa in Etosha National Park, Namibia
    (University of Namibia, 2025) Mthethwa, Nomkhuleko Vangile Helen; Mfune, John K. E.
    The presence of artificial waterholes can alter local mammal biodiversity. Research on the impact of artificial waterholes on local mammal biodiversity and studies on the nocturnal patterns of water usage are limited in Namibia. In this study, large mammals that visited Okaukuejo and Moringa artificial waterholes in Etosha National Park were studied in the cool dry season in July 2022 to determine and compare their species richness, patterns of waterhole usage, duration of stay, and behaviors displayed at the waterholes. A total of 14 large mammal species were recorded at both waterholes. Species richness was significantly higher at Okaukuejo than at Moringa waterhole, with cape fox (Vulpes chama), blue wildebeest (Connochaetes taurinus), giraffe (Giraffa camelopardalis) and warthog (Phacochoerus africanus) sighted at either Moringa or Okaukuejo waterhole. Zebras (Equus quagga) and springboks (Antidorcas marsupialis) had the highest abundance at both waterholes and visited at all sampling sessions (03h00- 06h00, 07h00 10h00, 12h00-15h00, 17h00-20h00 and 22h00-01h00). This indicates more water dependence than other species and may be influenced by the diet and home ranges of these species. There was a temporal differentiation in the use of the waterholes; mammals mostly visited between 12h00-15h00 and least between 03h00-06h00. Low overlap in waterhole visitation times was observed between predators and potential prey, possibly due to predation risk. The duration of mammal stay was significantly higher at Okaukuejo than at Moringa for elephants (Loxodonta africana), springboks, and spotted hyenas (Crocuta crocuta). Duration of mammal stay was significantly higher between 22h00 01h00 at Okaukuejo, and significantly lower between 03h00-06h00 at Moringa than other sampling sessions. Black rhinos, elephants and giraffes stayed significantly longer at Okaukuejo, while black rhinos and elephants stayed significantly longer at Moringa, compared to other species. Vigilance and aggression were the most frequently observed behaviors among 13 behavior types recorded, possibly driven by the need for water, predation risk and competition for water. Behaviors occurred at a higher frequency at Okaukuejo waterhole due to higher species richness and abundance. This study provides valuable insights on the activity patterns of mammals around artificial waterholes. Repeated and seasonal observations, incorporating water quality tests at waterholes are recommended for year-round assessment of mammal waterhole use and for explaining variations in visitations, species distribution and behaviors of mammals at waterholes