THE DIET OF THE BARN OWL TYTO ALBA IN THE NEGEV DESERT

Abstract

Food remains left by predators, and pellets in particular, are a good source of information about species composition in a particular area. Such information is essential for research and conservation purposes. We report here on the composition of an assemblage of barn owl (Tyto alba) pellets collected from the Holot Agur Nature Reserve located in the sand dunes in the northwestern Negev, about 10 km north of Nizzana, at 30o58′N 34o24′E. Most of the material was in compacted form, with some in the form of whole pellets. The remains were collected on 18 November 2002 from an old bus that had been abandoned in the area years before. The climate of this area is arid, with an average annual rainfall of about 100 mm, concentrated mainly between December and February (Jaffe, 1988). In the northern Negev the average mean monthly ambient temperature ranges between 11 oC in January and 26 oC in July (Jaffe, 1988). The bus was located in sand dunes where the plant community is composed mainly of low bushes of Arthemisia monosperma and Retema roetam. The area within a radius of about 1 km from the bus is devoid of trees, caves, or other potential nesting or roosting sites suitable for barn owls. Judging by the amount of material and eggshells, the bus has apparently been used for several years by barn owls. The material was brought to the lab in Tel Aviv where it was soaked for 24 hours in water, after which the bones and exoskeletons of invertebrates were separated from vegetational material and hair. Skulls and mandibles were identified using the reference collection of the Zoological Museum of Tel Aviv University. The minimum number of individuals (MNI) per species was calculated from mandibles or crania. The assemblage was composed mostly of small mammals (97%), some reptiles, and a few bones of birds in addition to some invertebrates (Table 1). It contained the remains of at least 1026 specimens, 989 of which were mammals belonging to 10 species of rodents—seven of the family Gerbillidae, two species of shrews (the common shrew and the pygmy white-toothed shrew), and an insectivorous bat. In addition, there were chameleons, geckos, and Agama lizards. The most abundant species were gerbils— Gerbillus allenbyi, G. pyramidum, and G. gerbillus (some of which may belong to G. dasyurus, whose mandibles are indistinguishable from those of G. gerbillus)—followed by the common shrew Crocidura suaveolens and the jirds Meriones crassus and M. sacramenti. All species found were known to occur in or near the area (Yom-Tov, 1988; Werner, 1988; Mendelssohn and Yom-Tov, 1999; Yom-Tov and Dayan, 1996). NOTE: