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عنوان فارسی مقاله:
نتایج خشکسالی طولانی مدت در گرسنگی فیل های آفریقایی (AFRICANA Loxodonta)
عنوان انگلیسی مقاله:
Prolonged drought results in starvation of African elephant (Loxodonta africana)
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
Human-induced climate change is threatening wildlife communities globally (Thuiller et al., 2006). For example, incidents of drought occur more frequently globally and, particularly, in Africa over the last 25 years (Collier et al., 2008). Recent studies predict that failure of long rains in East Africa may become a frequent occurrence in the future (Yang et al., 2014). Although drought is an integral part of arid and semi-arid systems, prolonged periods without rainfall may result in mass die-offs of wildlife (Knight, 1995). To prevent mass wildlife dieoffs due to the predicted increase in drought periods, there is a need to better understand the causes of drought-induced mortality. In this paper, we aim to unravel the drought-related causes of mortality of the African elephant (Loxodonta africana). Although some studies have investigated elephant mortalities as a result of drought (Caughley et al., 1985; Moss, 2001; Foley et al., 2008), and the effect of environmental factors such as spatial and temporal variability in drinking water, food distribution (extrinsic drivers) and local population density (intrinsic driver) (Young and Van Aarde, 2010), few studies have focussed on long-term drought events, particularly on adult elephant mortality. This is because elephant mortality data were mainly from unpredictable, opportunistic single-drought events, whereas long-term, consistent records of elephant mortality are rare (Dudley et al., 2001, Foley et al., 2008, but see Aleper and Moe, 2006). Continent-wide declines in African elephant populations are attributed largely to elephant poaching for ivory (Prins et al., 1994; Kahindi et al., 2010; Bouche et al., 2011; Burn et al., 2011; Maingi et al., 2012; Wittemyer et al., 2014) and loss of habitat associated with increased human population (Douglas-Hamilton, 1987; de Boer et al., 2013), but rarely to abiotic factors such as rainfall variability. Given the predicted increase in drought periods, the mortality of wildlife will likely rise, especially for species that are relatively more water dependent than others and those that require large amounts of daily food (Okello et al., 2015). For instance, in Kenya's Amboseli National Park, the droughts of 2007 and 2009 drastically reduced the population of large mammals, and species such as wildebeest (Connochaetes taurinus) declined by over50% (Okello et al., 2015). Elephant mortality as result of drought over the past few decades remains unprecedented (Corfield, 1973; Dudley et al., 2001; Walker et al., 1987; Foley et al., 2008). For example, drought is suspected to have contributed substantially to the elephant population drop in Tsavo from 35,000 elephants in 1974 (Cobb, 1976; Blanc et al., 2007) to below 12,000 elephants in 2011 (Ngene et al., 2011). Given their large body size and long generation time, survival of an adult elephant may be buffered against temporal variation in limiting resources (Gaillard et al., 1998; Gaillard et al., 2000; Prins and Van Langevelde, 2008; Moss and Lee, 2011). In the dry season, for instance, elephants shift their diet from a predominance of grass towards increasing amounts of woody browse (Lindsay, 1994; Moss et al., 2011; Kohi et al., 2011). This diet shift enables elephants to cope with prolonged drought. However, elephant feeding requirements and the patchy distribution of resources in savannas may cause heterogenous elephant aggregation across the landscape (Wittemyer et al., 2007; Chamaillé-Jammes et al., 2008). Consequently, at high densities, elephant may deplete local forage resources, often in the proximity of waterholes and rivers, particularly during the dry season (De Beer et al., 2006; Chamaillé-Jammes et al., 2008). Several previous studies identified distance to water as the primary environmental factor influencing the density of elephant during the dry season (Verlinden and Gavorv, 1998; Maingi et al., 2012), but the relationships between adult elephant mortality and both high local elephant density and forage availability close to water during dry periods remain unexplored. This study therefore investigates whether elephant natural mortality varies seasonally, whether elephant carcasses are clustered around water points, and what are the relationships between observed patterns of elephant mortality and precipitation, distance to water, forage and local elephant density? Water is scarce in arid and semi-arid savannas and most seasonal rivers and water holes dry up during prolonged drought. Consequently, elephant, especially the breeding herds, are constrained to close proximity of the remaining permanent water sources (O'Connor et al., 2007; Young and Van Aarde, 2010). We therefore hypothesize that elephant mortality will be higher: a) when dry periods are longer, b) closer to water points, and c) in areas with higher local elephant density.
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کلمات کلیدی:
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