Dorcas gazelle and livestock use of trees according to size in a hyper-arid landscape O. Attum a, * , T. Mahmoud b a Department of Biology, Indiana University Southeast, 4201 Grant Line Rd., New Albany, IN 47150, USA b Wadi El Gemal National Park, Egyptian Environmental Affairs Agency, 30 Cairo-Helwan Agricultural Rd., Maadi, Cairo, Egypt article info Article history: Received 11 August 2010 Received in revised form 6 June 2011 Accepted 25 July 2011 Keywords: Acacia tortilis raddiana Acacia tortilis tortilis Balanites aegyptiaca Dung pile Latrine Midden Tamarix aphylla Tamarix nilotica abstract We examined the relationship between Dorcas gazelle and livestock use of trees according to size. Our data suggest that Dorcas gazelle use of trees differs according to species and size. Larger Acacia trees are used for territorial purposes whereas smaller trees may be visited within the course of grazing. Our data show that tree size also determines potential food availability. On shorter trees, gazelles can graze on leafy vegetation at a range of heights between ground level until the top of the tree. In contrast, leafy vegetation on taller trees is available at heights that are often too high for gazelles to reach. However, larger trees provide another food source for gazelles not found on shorter trees such as seed pods, which were only found on larger Acacia radiana trees. There was no significant difference between the size of the other tree species that were used and not used by gazelles. Goats, camels, and donkeys were typically associated with only larger trees, regardless of species. Dorcas gazelle conservation will require main- taining viable Acacia populations that are characterized by recruitment and a variation of tree sizes and ages. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The use of prominent landmarks by territorial species reduces costs associated with territoriality such as time and energy spent establishing and defending territories (LaManna and Eason, 2003). Many gazelle species use middens, sometimes referred to as latrines or dung piles, for activities related to territory maintenance, advertisement, and olfactory communication (Walther et al., 1983; Walther, 1984; Brashares and Arcese, 1999; Attum et al., 2006; Wronski and Plath, 2010). Given the investment involved in maintaining a midden, gazelles do not randomly place middens, but rather middens are likely to be placed near large landmark sized trees (Attum et al., 2006; Wronski and Plath, 2010), and concentrated along territorial boundaries (Walther et al., 1983) or within the core of an individual’s homerange (Wronski and Plath, 2010). Acacia trees are keystone species of arid ecosystems whose shade provides higher soil water content and lower soil tempera- tures beneath the tree canopy. As a result, the underneath of Acacia canopies often contains high concentrations of annual plants (Dean et al., 1999; Munzbergova and Ward, 2002), which are vital to herbivorous mammals. Animals that visit Acacias will contribute to the high soil nutrient content underneath Acacia canopies through defecation and urination that further improve soil quality (Dean et al., 1999). In addition, Acacia trees are recognized as keystone species due to their use as a refuge for many wildlife and nesting habitat by numerous bird species (Dean et al., 1999; Hollamby et al., 2006). Acacia trees are also highly valued by pastoralists as the trees are relatively drought resistant, used for firewood, charcoal production, and fodder for livestock, and the tree gum is used for medicinal purposes (Krzywinski and Pierce, 2001; Mahmoud, 2010). Livestock and feral wildlife populations often have negative consequences on native wildlife. For example, feral animals compete with native ungulates (Madhusudan, 2004), modify habitat through grazing (Zalba and Cozzani, 2004), act as a vector for disease transmission (Morgan et al., 2006), or prey on native wildlife (Fordham et al., 2006). In arid systems, livestock and feral animals may compete with native ungulates for limiting resources such as vegetation and access to waterholes (Attum, 2007; Attum et al., 2009). Gazelle populations worldwide are experiencing population declines as a result of overhunting, habitat destruction, * Corresponding author. Tel.: þ1 502 897 9955. E-mail address: oattum@ius.edu (O. Attum). Contents lists available at ScienceDirect Journal of Arid Environments journal homepage: www.elsevier.com/locate/jaridenv 0140-1963/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaridenv.2011.07.002 Journal of Arid Environments 76 (2012) 49e53