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Accueil du site → Doctorat → États-Unis → 1988 → ECOLOGY OF WILD SHEEP (Ovis orientalis gmelini) ON KABUDAN ISLAND, IRAN

Michigan State University (1988)


Mowlavi, Masood

Titre : ECOLOGY OF WILD SHEEP (Ovis orientalis gmelini) ON KABUDAN ISLAND, IRAN

Auteur : Mowlavi, Masood

Etablissement de soutenance : Michigan State University

Grade : Doctor of Philosophy (PhD) 1988

Ecological studies were conducted on Kabudan Island (3145 hectares) during 1982—1983 to examine habitat and population interactions of the Armenian wild sheep (Ovis orientalis gmelini). Direct population counts indicated a sex ratio of 1:1.07 among adults. The average group size on the island was 16 sheep. The population density was 0.37 individual/hectare. Survivorship data were obtained from the analysis of 151 skulls of dead sheep collected on the island. The following population parameters were also calcu lated : finite rate of increase, 1.02 ; net reproductive rate, 1.10 ; generation time, 3.0 years ; exponential rate of increase, 0.02 ; and life expectancy, 3.6 years. The Armenian wild sheep was mainly a grazer, showing slight preferences for grasses over forbs and shrubs. Of 13 plants eaten by wild sheep, Stipa barbata, Bromus danthoniae, and Aegilops triuncialis were the most-preferred food during The living biomass of wild sheep p0pulation was measu red to be 0.95 kcal/m’. In kilocalories per square meter per year the available forage, forage consumed, feces, growth, and maintenance metabolism were calculated to be 55.88, 38.96, 17.90, 0.28, and 20.76, respectively. Using these values, the efficiencies of assimilation, net production, and biomass production were calculated to be 45%, 1.3%, and 0.71%, respectively. These values for wild sheep were low as compared to those reported for other wild herbivores. Kabudan Island has been under increasingly-heavy gra— zing pressure by wild sheep. On the study area, the wild sheep population consumed about 71% of the available forage. The finding in this study further indicated that : l) the vegetative habitat is in poor condition, and 2) a downward trend in vegetative quantity and quality is evident. It is concluded that overgrazing for a long period resulted in low quantities and qualities of forage species and that this caused low energetic efficiencies in the sheep population. Recommendations are made for improving the condition of sheep population and its island ecosystem. It is believed that a reduction of at least 37% of the sheep population should be made by controlled shooting the spring and summer.


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