General Biology

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Browsing General Biology by Subject "Abundance"

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    Certain Aspects of Ecology of Rodents in Pawe Area, Northwest of Ethiopia
    (Addis Ababa University, 2009-06) Chekol Tilahun; Balakrishnan M. (Professor)
    An ecological study dealing with species composition, distribution, relative abundance population density, biomass and habitat association of rodents was carried out in Pawe area around Almu in Ethiopia during August, 2008 − March, 2009 in natural forest, plantation, bushland, grassland and maize farm habitats. In each of the habitat types, grids were randomly selected for live-trapping and snap-trapping. Live-traps and snaptraps were set for three days twice during the wet and dry seasons. A total of 643 individuals comprising 10 species of rodents and two species of insectivores were captured. The rodents trapped were Mastomys natalensis (37.9%), Arvicanthis dembeensis (28.8%), Stenocephalemys albipes (9.2%), Mastomys erythroleucus (7.5%), Arvicanthis niloticus (4.5%), Acomys cahirinus (3.6%), Tatera robusta (2.6%), Lemniscomys striatus (1.7%), Mus musculus (0.9%) and Rattus rattus (0.3%). The two species of insectivores trapped were Crocidura flavescens (2.2%) and Crocidura fumosa (0.8%). In addition to this, Tachyorctes spledens, Hystrix cristata, Heliosciurus gambianus and Euxerus erythropus were observed in the study area. The population density ranged from 50/ha in the plantation to 311/ha in the bushland. M. natalensis was the most abundant and widely distributed species and R. rattus the least with limited in distribution in the present study area. The majority of the rodents and insectivores were associated with the bushland habitat. More number of rodents was trapped during the wet season than during the dry season. There was also significant variation in trap success among different habitat types. High cumulative average trap success of 26.2% was recorded in the bushland, whereas the lowest trap success of 4.2% was recorded in the plantation. Individuals of all age categories were present during the present study in all trapping sessions. Abundance of rodents was reduced during the dry season as a result of fire. The level of maize crop damage by rodents was 14.2 %. M. natalensis, A. dembeensis, M. erythroleucus and T. robusta were recorded as pests of maize crop in the study area. Key words/ phrases: Abundance, distribution, habitat association, Pawe, population density, rodents, species composition.
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    An Ecological Study on Rodents and Their Significance to the Ethiopian Wolf (Canis simensis, Rüppel 1838) in the Afroalpine Belt of Mt. Abune Yoseph, Ethiopia
    (Addis Ababa University, 2008-07) Damtie Teklu; Bekele Afework (Professor)
    An investigation was made on the ecological and biological attributes of rodents and their significance to the endangered Ethiopian wolf (Canis simensis Rüppell, 1835) in the afroalpine ecosystem of Mt Abune Yoseph, northeast part of Ethiopia. Investigation of small mammals was conducted by using extensive live and removal trap samplings. Livetrapping was conducted using Sherman traps. The common break back traps were used for snap trapping. Trapping was carried out in five marginally different habitats between 3650- 4102 m asl. Transect and point observations were carried out in order to collect data on wolf activity and density in relation to habitat types and rodent biomass. Sociological data was collected in the form of interviews and informal discussions to understand the attitude of the locals about the Ethiopian wolf and small mammals. A total of seven rodent species of which six endemic and one insectivore shrew (Crocidura bayileyi Osgood, 1936) were trapped in habitats sampled during the wet and dry seasons. The rodent species include Arvicanthis abyssinicus (Rüppell, 1842), Stenocephalemys griseicauda Petter, 1972, Lophuromys flavopunctatus Thomas, 1888, Otomys typus (Heuglin, 1877), Pelomys harringtoni Thomas, 1903, Dendromus lovati De Winton, 1899 and Mericulus imberbis (Rüppell, 1842). A total of 925 individuals of rodents were captured during 4212 trap nights. The rodent species were found to be varied in abundance, trap success and population density among the different habitats. Modified habitats supported less species diversity and population abundance than those with better natural vegetation cover. The abundance of rodents in barely farm was the least of all followed by over grazed alpine meadow. This indicates that habitat modification by human activities could probably cause a decline effect on small mammals. Breeding and age structure of rodent species were intimately correlated with season. The overall rodent density and biomass was lower than the records in the Bale Mountains while, they were comparable to the Simen Mountains. There were thirty nine observations on the Ethiopian wolf during the present study. There was an estimated population of one pack that includes 8-10 adult and sub adult individuals and 2-3 cubs. The local people had positive attitude towards wolf conservation, despite the mountain was the only place to graze their livestock throughout the year. Mt. Abune Yoseph harboured endemic small and large mammals, avifauna and unique vegetations. As a result, it is one among the unique biodiversity hot-spots and spectacular natural heritages. Without the proper management of small mammals and the concomitant habitat, effective conservation of the endangered Ethiopian wolf can be very difficult. At the same time, conservation of the Ethiopian wolf in the area can not be successful without the keen involvement of local communities, whose lives are strictly entwined with the wildlife and their habitats. In order to effectively conserve the Ethiopian wolf and endemic rodents in Mt. Abune Yoseph, an integrated management programme that addresses the problem of wildlife; especially habitat modification without compromising the benefits of local people is required. The unique vegetations such as the guassa grass and giant lobelias, which are currently at risk also need immediate attention. Otherwise the next generations in this area will perceive only their names and past histories through literature. Key words: Abundance, Mt. Abune Yoseph, afroalpine rodents, Ethiopian wolf, Euryopslobelia, habitat association
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    Species Composition, Abundance and Habitat Association of Rodents in Awash National Park and Metahara sugarcane Plantation
    (Addis Ababa University, 2011-02) Mengistu Solomon; Bekele Afework (Professor)
    A study on the species composition, distribution, relative abundance and habitat association of rodents species was carried out in Awash National Park and Metahara Sugarcane Plantation from August 2005 to 2007. Eight trapping grids were randomly selected based on the vegetation composition in Awash (riverine forest, Acacia woodland, Shrub bushland and grassland) and on growth stages of cane in Metahara (immature sugarcane plant, young sugarcane plant, and old sugarcane plant). An additional grid was selected from shrub bushland area outside the sugarcane plantation. A total of 1002 captures were obtained in 5880 trap nights. Of these, 309 individuals (40.98%) represented six species of rodents (Mastomys natalensis, Acomys cahirinus, Arvicanthis dembeensis, Mastomys erythroleucus, Tatera robusta and Mus musculus) in Awash and 445 (59.02%) represented eight species of rodents (M. natalensis, A. dembeensis, A. cahirinus, Mylomys albipes,Tatera robusta, M. musculus,and Rattus rattus) in Metahara. M. natalensis was the most abundant species constituting 26.5% of the total catch. A. dembeensis (17.8%), A. cahirinus (16.2%), M. erythroleucus (12.3%), T. robusta (11.8%), M. albipes (7.3%), M. musculus (5.4%), and R. rattus (2.7%) constituted the total catch. Variation in abundance among the rodent species between the two sites was significant. Most of the rodent species from Awash were trapped from shrub bushland and grassland areas. Riverine forest was the least preferred habitat by rodents in the study area. M. natalensis, A. dembeensis, A. cahirinus, M. albipes and M. erythroleucus preferred young sugarcane plants to other growth stages of the cane. T. robusta and R. rattus were trapped in more number in old sugarcane than other growth stages. M. musculus was equally abundant in both young and old sugarcane growth stages. The overall difference of the species abundance between the different stages of sugarcane plantation was significant. There was seasonal difference in the abundance of the rodent species in both Awash and Matehara. However, the overall difference in the abundance of rodents species between the two seasons was not statistically significant in Metahara. Variation in trap success in different habitats of Awash was statistically insignificant. Variation in trap success between different growth stages of the canes was statistically significant. However, there was no significant difference in trap success between the seasons. All age groups were represented in the population of most species with seasonal variation. The highest damage of sugarcane was recorded in old sugarcane plantation during both wet and dry seasons, followed by young and immature sugarcane plantations. Keywords: Abundance, Awash National Park and Metahara sugarcane plantation, habitat association of rodents, seasonal variation, species composition, trap success .