migration corridor, satellite tracking, home range, habitat preference, population structure, elephant, Selous-Niassa
630 Landwirtschaft, Veterinärmedizin
This study assessed the status and importance of the Selous Niassa Wildlife Corridor (SNWC) in southern Tanzania as a conservation area and biological corridor for wildlife, principally the African elephant (Loxodonta africana) and other key wildlife species. The distribution and movements of elephants and other wildlife species, their population structure and population size and the potential sources of conflicts between people and wildlife were investigated by a novel combination of local knowledge of wildlife, own field observations, and advanced technology including satellite-based location and tracking of radio-collared individual elephants.
The following results emanated from this study; The SNWC harboured at least 2,400 African elephants and a globally significant population of at least 4,460 Roosevelt's sable antelope. Other key wildlife species such as eland (Taurotragus oryx), greater kudu (Tragelaphus strepsiceros), Liechtenstein's hartebeest (Alcelaphus buselaphus lichtensteinii) and African wild dogs (Lycaon pictus) were also present throughout the Corridor. However, there is also some evidence that wildlife populations have experienced declines as evidenced by fragmented distribution, and virtually disappearance of some wildlife species originally present. The SNWC contains numerous forest, bushed grassland, woodland and wetland areas that are important seasonal or year-round refuge habitats for elephants and other wildlife species.
The widely reported conflict between people and wildlife was crop damages which was claimed to be a common cause of significant reduction of crop yield. Several wildlife species were considered to be involved. Interviewed people and governmental records reported damage by elephants, hippo (Hippopotamus amphibius), buffalo (Syncerus caffer) and sable antelope. However, analysis of reports on the extent of crop damage attributed to each species and data from satellite-based tracking of radio-collared elephants indicated that only a small proportion of crop damage could be attributed to elephants. Large proportion of crop damage was attributed by weeds, crop diseases and "small pest species" such as rodents or birds.
The distribution and movements of elephants were assessed by ground observation and satellite-based telemetry of radio-collared elephants. Three major movement routes from the Ruvuma river to the centre of the Corridor, and four other routes from the centre of the Corridor towards the north were identified. Satellite-based tracking and field observations confirmed that elephants used these routes for their movements, ultimately connecting the Ruvuma River with the Selous Game Reserve at the northern end of the Corridor. The major elephant movement routes that were revealed by satellite-based tracking were known to local people.
Data from satellite-based tracking were used to determine habitat preferences and home ranges and to trace movements across international borders. Ten radio-collared elephants (2 cows and 8 bulls) were tracked for periods from 8 to 24 months. During both dry and wet season, elephants significantly preferred forests, bushed grasslands and riverine areas and avoided cultivated areas. During the dry season, elephants also preferred woodland; during the wet season they also avoided swamps. Home range sizes varied between 328 and 6,905 km2. Observed home range sizes fell into three groups: small home ranges (328 to 576 km2), medium home ranges (1494 to 3,135 km2) and large home ranges (from 4,421 to 6,905 km2). Elephants with small home ranges spent their time mostly in areas between the Selous Game Reserve and the adjoining buffer zone at the northern end of the Corridor. Elephants with medium sized home ranges stayed in the central areas of the SNWC and occasionally visited Sasawala Forestry Reserve. Elephants with large home ranges moved across the central and southern sections of the SNWC, with extensive movements between Tanzania and Mozambique, and within Mozambique. Extensive movements of elephants were reported by local interviewees to occur in the months of March and April and June and December. Satellite tracking however showed extensive movements to occur during November and December and limited mobility between March and May. Food, access to water and possibly repeated contact with people in some localities are considered to be factors likely to influence elephant movements.
Data from ground-based observations and satellite-based telemetry confirmed that elephants frequently moved across the international border between Tanzania and Mozambique along the Ruvuma River. These data support the importance of protecting the SNWC as an important elephant range and corridor, linking two of the largest protected areas in Africa, the Selous and Niassa Game Reserves in Tanzania and Mozambique, respectively.
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