Thursday 28 January 2016

Ammotragus lervia: The diet of the Barbary Sheep in the Bou Hedma Mountains of Tunisia.

The Barbary Sheep (or Aoudad), Ammotragus lervia, is a wild Caprid found in North Africa, from the Mediterranean as far south as the Niger and Lake Chad, and introdiced to other parts of the world such as North America and the Canary Islands. The species is now missing from much of its original range, having suffered from habittat loss Human encroachment, overhunting and competition with domestic animals, and is considdered Vulnerable under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species. This has led to a number of recent studies of the species popuation and distribution, but other aspects of its biology have tended to be overlooked. In Tunisia the species is nearly extinct and considdered tobe Critically Endangered under the National Register of Wild Species.
In a paper published in the South African Journal of Science on 23 November 2015, Jamel Ben Mimoun and Saïd Nouira of the Laboratory of Animal Ecology at the Tunis El Manar University discuss the results of a study of the diet of the Barbary Sheep in the Bou Hedma National Park in central Tunisia.

 Barbary Sheep, Ammotragus lervia, at Oued Dekouk in Tunisia. Steve Morgan/Mammal Watching.

Ben Mimoum and Nouira examined Barbary Sheep droppings collected at monthly intervals between March 2009 and February 2010 in order to determine the proportions of different plants in the diet of the living animals. They found that two species of Grass, Stipa parviflora and Stipa tenacissima, formed the bulk of the Sheep's diet, together forming 63.2% of the plant matter consumed. However there was a strong seasonal variation in the amount of these Grasses consumed, so that they formed 69.1% of the diet in spring, 78.3% of the diet in summer, 56.6% of the diet in autumn and 34.7% of the diet in winter.

Thus Grasses form the bulk of the plant matter consumed in spring and summer (though the maximum number of different plant species were consumed in spring), In autmn browsing on trees and shrubs played a more important part in the diet, with Pistacia lentiscus comprising 7.4% of the plant matter consumed, Juniperus phoenicea 5.9% and Periploca laevigata 5.2%. Periploca laevigata remained an important part of the diet in winter, forming 5.5% of the diet. The herbaceous plant Helianthemum kahiricum was also important in autumn and winter, when it formed 13.6% and 13.0% of the diet, with two other herbaceous plants becoming important in winter; Globularia alypum, which formed 14.6% of the winter diet, and Helianthemum semiglabrum, which formed 12.1% of the winter diet.

 The current distribution of the Barbary Sheep, Ammotragus lervia, in North Africa. International Union for the Conservation of Nature's Red List of Threatened Species.

The Barbary Sheep is a highly flexible herbivore, known to be able to consume a wide range of plant species. In Texas, where it has been introduced, it has been shown to regularly consume 25 species of plants, in the Canaries 41, and in New Mexico 74 species. In Bou Hedma the species only consumed 19 identifiable species of plants, which is likely to be a result of a lack of suitable alternatives rather than a lack of willingness to consume other plants. Nevertheless the Tunisian Barbary Sheep shows a clear preference for Grasses when these are available, something which has previously been observed in Barbary Sheep in Texas and California, though other studies of the Sheep in Texas, New Mexico and Morocco have found browsing on trees and shrubs to play a more important role in the species diet. It was noted that the Tunisian Sheep showed a clear preference for open grassland during the breeding season, and that this was also the time of maximum Grass growth.

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