HILL, S. P. (2004)

Verhaltensbiologische und physiologische Untersuchungen zum Wohlbefinden von Westlichen Flachlandgorillas (Gorilla gorilla gorilla) in menschlicher Obhut.

Behavioural and physiological investigations of welfare in captive western lowland gorillas (Gorilla gorilla gorilla).

Dr. med. vet. Dissertation

312 Seite

Department of Veterinary Science,  University of Cambridge, England
Leitung: Prof. Dr. Don Broon
Zoo Duisburg, Leipzig Zoo, Howletts Zoo/England, Port Lympne Zoo/England, Paignton Zoo/England, Lissabon Zoo/Portugal


Four studies were conducted to investigate behavioural and physiological indicators of welfare in western lowland gorillas (Gorilla gorilla gorilla) housed at six European zoos. In the first two studies, behavioural responses of gorillas to changes in housing were measured, namely relocations to new enclosures (Study 1) and feeding-related environmental enrichment efforts (Study 2). As enrichment efforts do not necessarily equate with successful enrichment, I hypothesised that these housing changes would have either an enriching, aversive or neutral effect on animals. The results of Study 1 have shown that the behavioural repertoire of most individuals did not change across the entire post-relocation period compared with the baseline. Greater behavioural responses were observed month-by-month and, for some individuals, conclusions can be drawn about changes in welfare. In Study 2, behavioural data were collected before, during and after the provision of feeding-related environmental enrichment efforts designed to provide a more complex feeding environment. For most individuals, these efforts were associated with a reduction in time spent performing behaviours that indicate poorer welfare, compared with during the baseline. Faecal samples collected opportunistically during Studies 1 and 2 were used in Study 3 for glucocorticoid metabolite analyses. The results of a validation procedure showed that an enzyme immunoassay (EIA) measuring 5β-3α,11β-diol corticoid metabolites was likely to have practical applications for this purpose. Gorillas’ adrenal responses to the housing changes suggested that there has been an enriching effect overall. Results of a storage experiment showed that faecal samples can be left at environmental temperature (25 ºC) for up to 8 hours after defecation with no significant effect of bacterial enzymes on metabolite concentrations. In Study 4, acidity of regurgitated food produced during an abnormal behaviour, regurgitation and reingestion, was measured and compared with acidity of food originally consumed. Results showed that regurgitated food was more acidic than was the original food ingested and so regurgitated food contains stomach acids. Such behaviour is therefore potentially injurious, as in the similar human condition, rumination syndrome, and another human eating disorder, bulimia nervosa.



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