THE PHYSIOLOGICAL IMPACT OF CAPTURE: STRATEGIES FOR IMPROVING IMMOBILIZATION OF WILD EAST AFRICAN MESO- AND MEGA-HERBIVORES

East African meso- and mega-herbivores have been a key part of the Earth’s ecosystem for millions of years, but are now at risk of disappearing. To ensure their conservation, operations that involve veterinary immobilization are becoming essential for wild populations. However, capture morbidity remains high, with both short- and longer-term physiological alterations that can result in acute or delayed death. In large-sized herbivores, the size and unique anatomy and physiology contribute to the high susceptibility to capture stress, drugs adverse effects and alterations due to recumbency. On top of this, the limited knowledge in the species-specific physiological response to immobilization and, as a result, the obliged practice of extrapolating drug doses and protocols from similar species, enhances the risk of complications. Improvement in capture methods and drug protocols are advocated, and as such, in order to develop targeted strategies, it is essential to gain a better understanding of the species-specific physiological impact of capture. The general objective of this thesis is to advance the knowledge of the physiological mechanism of capture morbidity, and evaluate strategies for the prevention, detection and treatment of complications arising from opioid-based immobilization of selected species of East African megaherbivores, the giraffe (Giraffa camelopardalis ssp. tippelskirchi and reticulata) and the black rhinoceros (Diceros bicornis ssp. michaeli), and in a large mesoherbivore, the African buffalo (Syncerus caffer). A key factor of this study was the collection of data through an opportunistic approach, whereas the research design was shaped for each of the study species based on targeted needs, thus different specific objectives were pursued for each species. In free-ranging Masai giraffes that were immobilized for a translocation, a combination of etorphine and azaperone was evaluated for physiological and handling safety. Early opioid antagonization – a common procedure performed to reduce etorphine’s respiratory depression – was performed at low doses to assess if it would result in smoother restraint and transport. The protocol produced safe inductions, but variable opioid-related excitement occurred and accounted for metabolic derangement. On the other hand, early antagonization with low dose naltrexone allowed calm restraints, a stable physiological function during the recumbency, and enabled smooth recoveries and loading into the chariot with resulting uneventful transport. No delayed complications or resedation were observed during a two-week post-capture boma monitoring. Although the protocol allowed safe immobilization and transport, the study highlighted that further research on techniques that reduce induction-induced excitement, which poses severe health risks in giraffe capture, is advocated. Building up on the study performed in Masai giraffe, the physiological mechanism of capture morbidity occurring in both vehicle and helicopter darted reticulated giraffes, immobilized with an etorphine-azaperone combination, was investigated in order to detect the predisposing factors for homeostatic alterations and to define and guide prevention strategies. Trends over time in blood gases, selected biochemistry variables and cardio-respiratory function were analyzed following early opioid antagonization, and the use of a non-invasive nasal capnometer was investigated. In the helicopter darted giraffes, severe metabolic alterations were observed as a result of an intense startle response, whereas in vehicle darted giraffes, these were moderate and mainly a result of etorphine-induced excitement. Intense excitement occurred when lower doses of etorphine were administered, whereas higher doses resulted in respiratory depression, severe respiratory acidosis and hypoxemia. Early antagonization produced an improvement over time of gas exchanges, but not of the acid-base status, and resulted in poor immobilization quality. Nasal capnometry proved to be a useful non-invasive monitoring tool for field ventilatory function in giraffes. The severe alterations observed suggest that advances in giraffe immobilization should focus on reducing both opioid-respiratory depression and excitement, and onto providing adequate sedation and analgesia during field immobilizations. In Eastern black rhinoceroses, two intra-anesthetic treatments, butorphanol and oxygen, or doxapram, butorphanol and oxygen - which are routinely administered to improve gas exchanges, but which efficacy has not been investigated yet in the species - were evaluated. The mechanism of physiological alterations resulting from capture was investigated, and nasal capnometry was evaluated for its accuracy in monitoring carbon dioxide. Hypoxemia and severe lactic acidosis, proportional to more intense pre-dart chase, occurred. After the administration of doxapram and butorphanol, the initial hypoxemia and acidosis improved, presumably as a result of increase in ventilation mediated by doxapram; whereas the same values worsened when butorphanol only was administered. This might suggest that, different to other rhinoceroses, increased oxygen consumption is not the primary mechanism of hypoxemia in black rhinoceros. Nasal capnometry was efficient in monitoring carbon dioxide trends, but not accurate in predicting absolute values. Although intra-anesthetic treatment with doxapram partially improved gas exchanges, and post-capture complications did not occur for at least nine months, the severe metabolic and respiratory alterations observed highlight the need of advances in black rhinoceros capture methods that focus on preventing the origin of physiological alterations. The physiological safety of two immobilization protocols, etorphine-azaperone and etorphine- medetomidine-azaperone combinations, was compared in free-ranging African buffalos. The aim was to evaluate if medetomidine’s sparing effect would have allowed to safely decrease etorphine doses, and its adverse respiratory effects, without increasing the risk of excitement or poor immobilization quality. The addition of a low dose of medetomidine allowed to decrease etorphine dose by 30 %, and resulted in quicker and smoother inductions, and significantly improved immobilization quality. Medetomidine reduced the occurrence of tachycardia and respiratory acidosis, but not of hypoxemia. Etorphine-medetomidine-azaperone combination is recommended for buffalo immobilization as it provides greater physiological and handling safety, and can help to reduce the onset of capture stress. The new knowledge acquired within the different studies of this thesis has allowed to detect and evaluate species-specific strategies for the prevention (through knowledge of factors influencing capture morbidity, and improved immobilization protocols), detection (through clinical monitoring) or treatment (intra-anesthetic drugs) of capture and drug complications in large-sized herbivores. Species- specific and intra-specific variation of physiological response to capture stress and drugs were individuated, and hence a species-specific approach needs to be endorsed when capturing large-sized herbivores. Furthermore, based on the new information gained in this thesis, further studies can now specifically focus towards targeting solutions for the specific detected physiological alterations. The advances on immobilization methods resulting from this thesis represents a first step towards the improvement of the safety of immobilization of giraffes, black rhinoceroses and buffalos, and by reducing the risk of occurrence of delayed morbidity, it also contributes to the conservation of these East African large-sized herbivores.