09-24-2010
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کاربر خيلی فعال  
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تاریخ عضویت: Jan 2010
نوشته ها: 2,007
سپاسها: : 926
875 سپاس در 242 نوشته ایشان در یکماه اخیر
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The cheetah research project in namibia
Financed by Messerli foundation
Cheetah ( Acinonyx jubatus)
We are investigating the extent of the conflict between farmers and cheetahs as well as the behavioural ecology, reproduction biology and health status of cheetahs to provide a scientific basis for the sustainable protection of this largest remaining population of free-ranging cheetahs. We determine the diet of the cheetah, their habitat use and activity, and evaluate their reproductive health status, the sperm quality of males and the survival rate of offspring. Furthermore, we investigate mortality causes in cheetahs as well as diseases and possible ways of disease transmissions. We also determine the genetic variability, paternities and hormone levels of cheetahs. For comparative reasons, we further conduct many investigations on captive animals. These cheetahs are kept in their natural environment in large enclosures on Namibian farmland.
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In this new project the following topics are being tackled:
1. Behavioural Ecology 2. Reproduction3. Health status and causes of mortality4. Genetic und mating system5. Conservation through integration of local people
Project members
1. Behavioural Ecology
Home ranges, habitat use and activity patterns of cheetahs
The study site lies east and north-east of the Namibian capital Windhoek on commercial farmland and consists mainly of thorn-bush savannah (Fig. 1).
Fig. 1: Typical habitat in the study area
Cheetahs are equipped with VHF- or GPS-collars and located from the ground or the air (Fig. 2). The localisation data are used to determine home ranges and range overlaps of cheetahs. Their home ranges have sizes of several hundred km2 and encompass several farms (Fig. 3).
Fig. 2: Tracking of collared cheetahs Fig. 3: Home ranges of 8 cheetahs on farmland.
Black lines: Farm borders,
coloured lines: home ranges determined with the "minimum convex polygon" method Information on ranging behaviour of cheetahs is overlaid with vegetation maps using remote sensing techniques and ground-truthing in cooperation with Prof F. Siegert (Ludwig-Maximilians University Munich). This will allow us to determine the habitat preferences of cheetahs. Furthermore, we analyse daily activity patterns from GPS-collared animals in cooperation with Dr A. Berger (IZW).
Determination of cheetah diet and prey availability
The cheetah’s diet is determined by mainly two methods:
One method is based on the identification of undigested prey hairs in cheetah faeces. For this, prey hairs from cheetah faeces are extracted and imprints produced (Abb. 4). In these imprints the imbricate nucleus free cells of the epidermicula are visible, which are characteristic for each species. Imprints are then compared with hair references of prey species.
Fig. 4: Imprints of hairs of a spring hare
The other method is based on the analysis of stable isotopes, which will be done in cooperation with Dr C. Voigt (IZW). For this method the ratio of light and heavy carbon and nitrogen isotopes of different prey species are determined and compared with the respective isotope ratio of cheetahs. Since light and heavy isotopes accumulate in the tissue with each trophic level, it is possible to obtain information about the diet of cheetahs.
To determine prey preferences of cheetahs prey availability in the field has to be known. Availability of wildlife species is estimated by conducting transect counts, whereas availability of livestock is determined by consulting the farmers.
2. Reproduction
Reproductive health of female cheetahs
Previous studies on captive cheetahs indicated that captive female cheetahs suffer reduced fertility, and suggested that the low breeding success in zoos was due to the genetic monomorphism of cheetahs and/or inappropriate husbandry conditions. To investigate whether reduced fertility in zoos is due to the genetic makeup of cheetahs or to captivity itself the reproductive health of free-ranging females is compared with that of females kept in enclosures on Namibian farmland. Reproductive health of cheetahs is established in cooperation with Dr R. Hermes (IZW) on the basis of ultrasonographic investigations of immobilised cheetahs. With the ultrasonographic images females are allocated to different reproductive states. In cooperation with Dr M. Dehnhard (IZW) we additionally measure corticosteroid (‘stress hormone’) levels of both captive and free-ranging cheetahs.
Sperm quality and reproductive health of male cheetahs
Previous studies have attributed the high proportion of abnormally formed sperm known from cheetahs kept in zoos and from free-ranging cheetahs in East-Africa to the genetic monomorphism of the species. To determine the quality of sperm of both free-ranging and captive cheetah males in Namibia and investigate factors that may influence sperm quality, we obtained ejaculates from immobilised males using electro-ejaculation and estimated sperm concentration, sperm motility and proportion of abnormally formed sperm.
Sperm abnormalities frequently found in cheetah ejaculates:
Reproductive organs of free-ranging and captive males are investigated and measured using ultrasonography to determine possible differences of organ sizes.
Survival probability of juveniles
Young cheetahs are sighted from the ground or the air when their collared mothers are located. During consecutive aerial tracking flights efforts are made to regularly sight and count the offspring with a minimal possible disturbance to estimate survival probabilities and rates.
Fig. 5: Two cheetah cubs in the field
3. Health status and causes of mortality
Investigation of the general health status of cheetahs
The nutritional status, general physical condition and health status of free-ranging cheetahs are assessed by thoroughly examining immobilised cheetahs using ultrasonographic investigations of the organs and extensive laboratory analyses of a large set of samples collected during immobilisation, including blood, faeces and hairs (Fig. 6).
Fig. 6: Collection of blood samples from an immobilised cheetah
Similar investigations and sample collections are conducted from other carnivore species as well as from domestic and livestock animals to determine their health status and to identify possible disease transmitter.
Determination of mortality causes
Cheetahs found dead are dissected on site to collect samples for subsequent analysis in the lab and to determine the cause of death. Cheetahs shot as trophy or problem animals and reported to us by farmers are also dissected and sampled to determine their health status.
Identification of pathogens
Blood samples of free-ranging and captive Namibian cheetahs are tested for antibodies and antigenes of viruses relevant for free-ranging felids (Fig. 7). This work is conducted in cooperation with Prof H. Lutz (Vetsuisse-Faculty University of Zurich) und Dr T. Müller (Friedrich-Löffler-Institute Wusterhausen).
Fig. 7: Analysis of blood samples in the lab
4. Genetics and Mating System
Paternity analysis and determination of mate choice
The genetic profiles of young and their mothers as well as of males in the study area are established on the basis of microsatellite DNA fingerprinting to determine the fathers of the cubs.
Factors that might be relevant for the reproductive success of males are determined by investigating reproductive parameters such as organ sizes and sperm quality of males that fathered cubs, and ecological factors such as location and size of their home ranges.
Determination of the genetic variability of cheetahs
In the 1980s and 1990s several studies have found a low genetic variability in cheetahs. Since then molecular methods have considerably improved and more specific analyses can be conducted today. The genetic variability of the MHC (Major Histocompatibility Complex), which plays an important role in the immune response of an organism against pathogens, will be determined in cooperation with Dr S. Sommer (IZW).
5. Conservation through integration of local people
Extension and maintenance of close contacts to farmers
The regular presentation of project results during farmer meetings and the consultation with farmers in all project steps have proved to be very positive and constructive for the work on site. During these occasions the study gets new input from farmers, and additional questions are asked and included in our investigations.
Farmers with their families and guests are invited regularly to attend investigations of cheetahs. These invitations are gratefully accepted and project activities therefore get a high didactical value that can provide a basis for a slow but continuous change of attitude towards cheetahs.
Collaboration with local schools of higher education
The project maintains a close cooperation with the Polytechnic of Windhoek in Namibia. Students of the Polytechnic carry out their own short-term studies relevant for the conservation of cheetahs within the cheetah project and are supervised during the conceptual and methodological planning as well as the execution of their studies. The objective is to provide local students a basis for applied conservation in their country and to teach them how to competently investigate practical problems of conservation using a scientific approach.
6. Project members
Head of project: Dr. Bettina Wachter
PhD students: Susanne Schulze (topic: female reproduction and health status)
Johann Lonzer (topic: male reproduction and sperm quality)
Jörg Melzheimer (topic: feeding ecology and habitat use)
Assistentin: Kerstin Wilhelm
http://www.izw-berlin.de/
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ویرایش توسط Setare : 09-24-2010 در ساعت 11:38 PM
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