Mountain gazelle 775 Habitat fragmentation and population isolation


Natural habitats in the Mediterranean region of Israel are highly fragmented. Along the central coastal plain, where several highways cross the landscape, this is particularly problematic. Furthermore, the security fence separating the State of Israel from the Palestinian Authority greatly limits the available habitat in this region for gazelles as it runs generally north–south, 15–30 km east of the Mediterranean coast (Fig. 3). Circa 1,000 gazelles inhabit areas of low or no connectivity (Fig. 3). In central Israel there are 11 populations disconnected from any other ga- zelles, living in de facto enclosures, and a further six pop- ulations have partial connectivity (Fig. 3; Supplementary Table 2). Continuous monitoring of these enclaved popu- lations is needed to understand the nature and effects of fragmentation. Fragmentation and isolation have long been noted to have severe negative effects on wild populations (Caughley, 1994). These include, among others, the detri- mental effects of demographic and environmental stochas- ticity, genetic effects of small populations and the Allee effect (Simberloff, 1988).


Collisions with cars


The Israel Nature and Parks Authority database includes re- cords of a total of 467 gazelles found dead or wounded on or next to roads during 2009–2017. These numbers increased significantly from 14 to 86 per annum during this period (linear regression; R2 = 0.83, F1,7 = 34.50,P = 0.0006). This increase can be attributed to increases in the length and width of the roads, and traffic volume. However, greater awareness of Israel Nature and Parks Authority rangers dur- ing this period and an increase in some gazelle populations could have also contributed to the increase in collisions. During 2006–2014 c. 300 mountain gazelles were brought to the Hospital for Wild Animals, a third of which were vic- tims of car accidents (i.e. an annual mean of c. 10). We view this as the lower boundary of the true toll of roads on ga- zelles as many may perish by the side of the road without being attended or recorded. Effects of collisions with cars can be particularly great along the central coastal plain of Israel, where gazelle populations are smaller and more frag- mented, and road traffic is greater (Fig. 3).


Fragmentation constraints on behaviour


Fragmentation may prevent animals from behaving natu- rally. Gazelles exploit so-called green waves (sensu Merkle et al., 2016),moving seasonally according to food availability along mountain slopes or other gradients to track high quality forage (Geva, 1980). For example, in the Naftali Mountains in northern Israel, gazelles forage during winter on herbs at 250–450 m above sea level, predominantly in


Batha habitats. As these herbs dry with the approach of summer, the gazelles move to lower elevations and forage on the green leaves of bushes and trees that grow in garrigue and maquis habitats (Geva, 1980). Increased fragmentation deprives gazelles of the opportunity of freely tracking food sources as these become available seasonally.


Predation


Predators affect prey either directly by killing individuals or indirectly by modifying the behaviour of the prey species (Lima, 1998). In Israel the main natural predators of gazelles, the wolf and golden jackal, are predominantly sustained by rubbish and agricultural products, complemented by wild- life such as rodents, hares Lepus capensis and partridges Alectoris chukar, but also by gazelle fawns and sometimes adult gazelles (Gingold et al., 2009). This has pronounced effects on some gazelle populations. For example, the popu- lation in the Golan Heights has probably become stagnant because of high predation pressure (Dolev et al., 2018). In addition to their natural predators, gazelles are


predated by the increasing population of the feral domes- tic dog Canis familiaris. The Israel Nature and Parks Authority estimates that tens of thousands of feral dogs roam Israel, often in packs of 4–8 that hunt and disturb wild animals, and have a detrimental effect on mountain ga- zelles (Manor & Saltz, 2004). Dog packs hunt gazelle fawns and significantly reduce gazelle breeding success via harass- ment of adults (Manor & Saltz, 2004; Gingold et al., 2009). The former practice of culling feral dogs has almost halted as a result of pressure from animal rights groups, and feral dog numbers are increasing (Y. Shkedy, pers. comm., 2019). As a result of the high human population density in the Mediterranean region of Israel, feral and domestic dogs can travel from settlements into neighbouring natural or semi-natural regions (Knesset Research and Data Center, 2015). Fragmentation further exacerbates the effects of pre- dators. During their first month after birth young gazelles lie on the ground for most of the day while their mothers watch from a distance. Higher predator density increases the prob- ability of fawns being discovered and killed by predators (possibly including wild boar Sus scrofa) during this period (Mendelssohn, 1974). Detection and predation of young gazelles may further increase in regions with intense cattle grazing, where there is less vegetation cover (Shamoon et al., 2017). Furthermore, predators have learned to chase gazelles towards fences and other barriers; frightened gazelles often collide with them, and die or fall stunned, making them easy prey (Yom-Tov, 2016). Predation pres- sure may further increase as gazelles are driven to be more nocturnal, to minimize contact with people, increasing their overlap in activity period with their principal nocturnal natural predators (Shamoon et al., 2018).


Oryx, 2021, 55(5), 771–778 © The Author(s), 2020. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S003060531900108X


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