The Taxonomy and Ecology of Rodent Species Occurring in Um-Ruwaba District, North Kordofan, Sudan

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Mohamed Ali Omer Rahoum
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University of Khartoum
Abstract Following the 1986 gerbil outbreak in Um-Ruwaba Digtrict, North Kordofan, full ecological study was conducted to update knowledge about the rodent species occurring in the District and at the same time to provide basic, biological and ecological information about the dominant species (G. agag) which may help in understanding its population changes and habitat requirement for future control. The study conducted using direct observation and trapping methods revealed the Occurrence of G-eerbillus agag Thomas, G. narloillus Thomas and Hinton, Acomys cineraoeus Fitzinger and Heugl , Jaculus jaculus Thofllas, and _ferus ery'thropus Goeffroy. The karyological analysis distinguished between G. agag and G. gerbillus, and between A. oineraoeus and A. oahirinus. The histological study revealed scent glands on the belly of G. agagand A. cineraoeus males. The study on the sexual dimorphism of G. agag showed that males are larger than females in 7 out of the 21 measurements. The postnatal growth of G. agag was found to be independent of sex up and the age of puberty when males showed faster growth' rate compared to females. The post-natal growth and development showed a period of slow growth coinciding with the time when young try plant food. This suggests that the digestion of plant material is inefficient at this age. Investigation on the feeding ecology of G. agag using stomach content analysis and investigation of burrow indicated seeds as the staple and preferred plant material while insects and other plant materials were taken as, supplements when seeds were not abundant. Observation and investigation of predators revealed the occurrence of the snake, Theban Sand Boa, Eryx thebaieusus, the Spotted Eagle Owl, Bub atrioallus striped easel Poeoiliotis libyca and/or the Striped Polecat Iotonyx striates, and the domestic cat Felis domestiioa. Studies on the breeding ecology of G. agag using breeding in captivity and trapping methods showed that G. agag breed throughout the rainy and winter seasons, and ceased reproduction at the end of winter, producing about 7litters with a mean litter size of about 5 young, during, its relative long breeding season. The maximum breeding activity as recorded during November - February. Female were found dominating the population throughout the year except in June when males dominated. Studies on the population dynamics of G. agag using the burrow count method showed that G. agag population reached its maximum growth during November – February (winter), but thereafter declined to reach a very low number during June. This drastic decline of the population during June (hot dry season) was suggested to be due to mortality caused by excessive predation. The Kruskal-Wallis one way Anova test showed a significant difference between burrow numbers in different localities, different habitats and in different periods. Uncultivated lands were found to be the preferred habitat for G. agag while cultivated lands were occupied when the population expanded . The study of G. agag population changes showed, that rainfall, shelter and predation are the major factors affecting its population growth. This suggested that, the outbreak of G. agag in Um-Ruwaba District during 1986 was probably due to the long period of drought prior to the outbreak which possibly caused the drastic decline of predators while the good rainfall increased its preferred habitat. Gerbillus agag escape excessive heat during the day time by its nocturnal habitats. Burrows up 40, 45 and >50cm in depth were found to be suitable for G. agag during winter, Summer and rainy season, respectively. G. agag escape flooding during the rainy season by digging deep complicate burro in the relatively high ground sands and escape predators by burrowing and foraging in sheltered habitats, especially- those dominated by Ceahlvs spp. Further study to provide more information about the taxonomic ecology behaviour and public importance, jerbels were recommended
Ecology Rodent Um-Ruwaba District North Kordofan Zoology University of Khartoum
Mohamed Ali Omer Rahoum, The Taxonomy and Ecology of Rodent Species Occurring in Um-Ruwaba District, North Kordofan, Sudan .- Khartoum : University of Khartoum, 1991 .- illus., 28cm., Ph.D