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Ganswindt A.,University of Pretoria | Munscher S.,University of Pretoria | Henley M.,University of South Africa | Henley M.,Transboundary Elephant Research Programme | And 3 more authors.
Wildlife Biology | Year: 2010

Free-ranging African elephants Loxodonta africana use their front feet frequently during the process of foraging and this could be the reason for the high prevalence of physical injuries to these parts of the body. Although the occurrence of severe lameness caused by foot lesions in adult elephants has already been investigated and the clinical and pathological findings have been reported, the effect of foot injuries on glucocorticoid levels as a potential physiological stress response has not been examined. Given the practical difficulties involved in monitoring unpredictable events in free-ranging animals, like the occurrence of foot injuries in elephants, it is not surprising that information regarding the endocrine correlates of physical injury is still limited for elephants. In our study we investigated the effects of foot injuries on concentrations of faecal glucocorticoid metabolites (GCM), body condition score (BCS) and reproductive behaviour in two GPS/radio-collared elephant bulls in the Kruger National Park, South Africa. We monitored the bulls aged 40 (Bull 1) and 30 (Bull 2) 2-3 times per week for 13 months starting in June 2007 and frequently collected faecal samples for non-invasive hormone monitoring. Faecal samples were lyophilised, extracted and assayed with an enzyme immunoassay which detects GCM with a 3α-hydroxy-11-oxo-structure. Both bulls acquired foot injuries (right-front), which caused temporary lameness, but the effect of injury on GCM concentration differed between bulls (P < 0.001). In Bull 1 the injury lasted ± 250 days and was associated with an up to four-fold increase in GCM concentrations (P < 0.001) and his BCS reduced from 'good' to 'very thin' by the end of the injury period. In Bull 2 the injury lasted 65 days and was associated with a smaller increase in GCM concentrations (P = 0.03) together with a reduced loss in condition when compared to Bull 1. Following recovery, the condition of both bulls improved progressively and faecal GCM returned to baseline concentrations. Collectively, the data clearly underlined the value of non-invasive hormone measurements as a tool to provide information on the level of stress experienced by elephants. Thus, monitoring GCM levels could help improve the assessment of an elephant's state of health. © 2010 Wildlife Biology, NKV. Source

Vogel S.M.,Wageningen University | Henley M.D.,University of South Africa | Henley M.D.,Transboundary Elephant Research Programme | Rode S.C.,University of South Africa | And 4 more authors.
African Journal of Ecology | Year: 2014

Negative influences on the establishment and persistence of large trees used by tree-nesting birds as nesting sites represent a potential threat to vultures and raptors. We monitored large trees and their surrounding vegetation and analysed whether trees with nesting sites are at risk due to elephant impact. Trees with nests did not differ in elephant impact from control trees without nests, and the survival rates of trees with nests and the actual nests within the trees showed that nests decreased at a faster rate than the trees themselves. Elephant damage did not affect the persistence of nests over the 5-year monitoring period. However, the presence of insects and fungus on large trees was negatively related to tree survival, thereby indicating that elephant impact could indirectly facilitate insect and fungus attack and shorten the lifespan of a tree. © 2014 John Wiley & Sons Ltd. Source

Marshal J.P.,University of Witwatersrand | Rajah A.,University of Witwatersrand | Parrini F.,University of Witwatersrand | Henley M.,University of South Africa | And 4 more authors.
European Journal of Wildlife Research | Year: 2011

Foraging behaviour and habitat selection occur as hierarchical processes. Understanding the factors that govern foraging and habitat selection thus requires investigation of those processes over the scales at which they occur. We investigated patterns of habitat use by African elephants (Loxodonta africana) in relation to vegetation greenness to investigate the scale at which that landscape attribute was most closely related to distribution of elephant locations. We analysed Global Positioning System radio-collar locations for 15 individuals, using the Normalized Difference Vegetation Index as a representation of vegetation greenness in a Geographic Information Systems framework. We compared the importance of vegetation greenness at three spatial scales: the total home range, the seasonal home range and the 16-day home range. During the wet season, seasonal home ranges for both sexes were associated with intermediate greenness within the total home range; there was no evidence of selection based on greenness at finer scales. During the dry season, the strongest associations were within the 16-day home range: individual locations for males tended to be in areas of intermediate greenness, and those for females were in areas of intermediate and high greenness. Our findings suggest that the role of vegetation greenness varies with the scale of analysis, likely reflecting the hierarchical processes involved in habitat selection by elephants. © 2010 Springer-Verlag. Source

Ganswindt A.,University of Pretoria | Ganswindt A.,Reproductive Biology Unit | Muenscher S.,University of Pretoria | Henley M.,University of South Africa | And 7 more authors.
Hormones and Behavior | Year: 2010

Sexual activity in mature male African elephants is predominantly associated with the occurrence of musth, a state or condition which refers to a set of physical, physiological and behavioral characteristics, including an elevation in androgen levels. Although musth appears to be energetically costly, the degree to which it is associated with changes in adrenal endocrine function (e.g., glucocorticoid output) is still unclear. To investigate the possible effect of musth on adrenocortical function, and the impact of socioecological changes on androgen and glucocorticoid levels, six adult African elephant bulls were followed for 13. months in the Kruger National Park, South Africa, and observations and fecal sample collection for endocrine monitoring was carried out about twice weekly. Our data showed that the occurrence of musth was associated with reduced glucocorticoid output, suggesting that musth does not represent a physiological stress mediated by the hypothalamic-pituitary-adrenal axis. This confirms previous findings in captive-housed animals, providing evidence for a suppressive effect of the musth condition on adrenocortical activity. Furthermore, a seasonal effect on androgen and glucocorticoid levels was found, which appears to vary depending on the reproductive status of the animal. The results also indicate a relationship between the presence or absence of social partners and changes in testicular and adrenal endocrine activity. Finally, the data confirm previous findings in captive-housed elephants, that an elevation in androgen concentrations usually occurs before the onset of physical musth signs, and therefore support the idea that the change in androgen levels represents the initial stimulus for the musth condition. © 2010 Elsevier Inc. Source

De Knegt H.J.,Wageningen University | Van Langevelde F.,Wageningen University | Skidmore A.K.,University of Twente | Delsink A.,University of KwaZulu - Natal | And 18 more authors.
Journal of Animal Ecology | Year: 2011

Understanding and accurately predicting the spatial patterns of habitat use by organisms is important for ecological research, biodiversity conservation and ecosystem management. However, this understanding is complicated by the effects of spatial scale, because the scale of analysis affects the quantification of species-environment relationships. We therefore assessed the influence of environmental context (i.e. the characteristics of the landscape surrounding a site), varied over a large range of scales (i.e. ambit radii around focal sites), on the analysis and prediction of habitat selection by African elephants in Kruger National Park, South Africa. We focused on the spatial scaling of the elephants' response to their main resources, forage and water, and found that the quantification of habitat selection strongly depended on the scales at which environmental context was considered. Moreover, the inclusion of environmental context at characteristic scales (i.e. those at which habitat selectivity was maximized) increased the predictive capacity of habitat suitability models. The elephants responded to their environment in a scale-dependent and perhaps hierarchical manner, with forage characteristics driving habitat selection at coarse spatial scales, and surface water at fine spatial scales. Furthermore, the elephants exhibited sexual habitat segregation, mainly in relation to vegetation characteristics. Male elephants preferred areas with high tree cover and low herbaceous biomass, whereas this pattern was reversed for female elephants. We show that the spatial distribution of elephants can be better understood and predicted when scale-dependent species-environment relationships are explicitly considered. This demonstrates the importance of considering the influence of spatial scale on the analysis of spatial patterning in ecological phenomena. © 2010 The Authors. Journal compilation © 2010 British Ecological Society. Source

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