Browsing by Author "Von Dürckheim, Katharina EM"

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    Olfaction and scent discrimination in African elephants (Loxodonta africana)
    (Stellenbosch : Stellenbosch University, 2021-04) Von Dürckheim, Katharina EM; Leslie, Alison J.; Hoffman, Louwrens C.; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: As an endangered mammal, novel research into the African elephant’s ethochemistry will assist ethologists, conservation biologists and wildlife managers in understanding odour signals in elephant exudates, and how they impact elephant behaviour in captivity and in the wild. Analytical methods combining genetics, statistics with SPME GC_MS and innovative metabolomics visualisation software are a useful first step in unlocking odours salient to elephant reproduction, breeding and behaviour. Mammals, such as the African elephant, which live in sophisticated, fission-fusion, social systems marked by linear dominance hierarchies and ritualized greeting ceremonies, require an effective means of communication in order to maintain social cohesion. A number of acoustic, olfactory and visual signals have been described. Within a group context, individuals need to discriminate between members of their group and foreign conspecifics in order to avoid inbreeding and to identify recipients of nepotistic behaviour. Such olfactory group/herd/clan/colony identity signals have been described in a number of mammals such as beavers, bats, naked mole rats, rabbits, fur seals, lemurs and hyena but are lacking in the iconic African elephant. It is to date not clear what fixed and variable information is encoded in African elephant urine, temporal gland secretions (TGS), genital and buccal secretions, and whether an olfactory signal for herd membership exists, although scientists have long expected this to be the case. Specifically, African elephant TGS, buccal and genital secretions in adult females have not been described in a free-ranging population. The overall objective of this research was to augment scientific understanding of African elephant olfactory behaviour in a multi-disciplinary way, combining behavioural observation and experimental trials of African elephants in sanctuaries in South Africa, with genetic and chemical data sampled from a free-ranging African elephant population during a translocation event in Malawi. The research first assesses olfactory acuity and scent discrimination ability in African elephants through novel behavioural bioassays. Subsequently, this study examines whether chemical signals in urine, TGS, buccal and genital secretions encode for age, sex and identity, and explores whether odour is correlated with genetic relatedness. For the first time, the chemistry in TGS, buccal and genital secretions is characterised in wild African elephant adult females (n=40). Elephants were found to be highly adept at scent-discriminating between humans, and scent- tracking a target human across various substrates, including distractor trails. Results suggest that elephants may utilise olfaction to discriminate between individual conspecifics. This was tested using behavioural bioassays, which concluded that African elephants can discriminate between unfamiliar and familiar conspecifics from both urine and dung. Urine elicited the most interest, and was used for further detailed analysis using the comprehensive metabolomics tool XCMS online. TGS, buccal and genital secretions from wild-sampled elephants (n=113) were found to encode individual identity in African elephants. TGS and buccal secretions encoded for age, and TGS and genital secretions tended towards significance for sex. Genetic relatedness was not correlated with odour in TGS, buccal and genital secretions at the herd level. However in all three odours, Similarity Percentage Analysis (SIMPER) identified “herd” as a highly significant factor in explaining chemical differences between herds. This suggests that group odour in African elephants is not correlated to genetic relatedness at the population, herd and individual level, and allows for the possibility that bacteria may be involved in group odour. The biomarkers alkan-2-ones and alkan-2-ols previously published in association with elephant male urinary microbial communities, were identified in adult female buccal and labial secretions. SIMPER analyses further extracted a number of short-chain fatty acids significant to chemical differences between groups (notably acetic acid, pentanoic acid, hexanoic acid, decanoic acid, dodecanoic acid and tetradecanoic acid). These and other compounds have been identified in similar studies as key volatile compounds from bacterial fermentation in clan-living hyenas and colonially-living meerkats, further supporting this possibility. The frequent affiliative social behaviour of African elephants is posited as a likely mechanism for bacterial transmission. Conservation objectives can be supported by an improved understanding of how chemical communication in social mammals like elephants influences mate choice, establishing social relationships, courting, mating and the use of scent for establishing territories. In African elephants, an improved understanding of elephant semiochemistry and eliciting behaviour could shed light on scent manipulation for elephant translocation and reintroductions, captive breeding, welfare and enrichment protocols, human elephant conflict (HEC), elephant reintroductions, social behaviour and habitat selection.