Abstract
Conservation management interventions for the critically endangered black rhinoceros (Diceros bicornis) require immobilization, which offer opportunities for semen collection and cryopreservation to establish genetic reservoirs. In free-ranging rhinoceroses, a combination of the potent opioid etorphine and the tranquilizer azaperone is routinely used for chemical immobilization but is associated with muscle rigidity and severe cardiopulmonary changes. Additionally, azaperone inhibits semen emission. Seven free-ranging, male, sexually mature black rhinoceroses were immobilized with an alternative protocol consisting of 4.5 mg etorphine, 5 mg medetomidine, 50 mg midazolam and 2,500 IU hyaluronidase delivered remotely by darting from a helicopter. During the immobilization, electro-ejaculation was performed with a portable electro-ejaculator, and a species-specific rectal probe. Animals were observed for muscle tremors. Longitudinal changes in respiratory rate, heart rate and peripheral oxyhemoglobin saturation, measured at 5 min intervals, were assessed using a general mixed model. Non-invasive oscillometric blood pressure and arterial blood gas variables were measured at first handling and before reversal and compared using the Wilcoxon rank sum test. All animals were successfully immobilized, showed no muscle tremors, presented with normal heart rates and lactate concentration (<5 mmol/L), recovered uneventfully, but experienced acidemia, hypoxemia and hypercapnia. Induction time and total time in recumbency were 4.2 ± 0.41 and 38.4 ± 6.9 min, respectively. Electro-stimulation commenced after 11.7 ± 3.98 min and completed after 24.3 ± 6.65 min. Semen-rich fractions were successfully collected from six animals. Our observations indicate that etorphine-medetomidine-midazolam provides a promising immobilization protocol for free-ranging black rhinoceroses, that allows for successful electro-ejaculation.
Highlights
IntroductionAs the numbers of individuals in the wild decrease, the preservation of gametes and their use in assisted reproductive technologies is gaining importance as additional conservation tools [3]
In a recent assessment of the black rhinoceros population [1], the species was again classified as “critically endangered” by the International Union for Conservation of Nature (IUCN) with just over 3000 individuals in the wild—a result of the extensive poaching for horn [2].As the numbers of individuals in the wild decrease, the preservation of gametes and their use in assisted reproductive technologies is gaining importance as additional conservation tools [3]
Electro-ejaculation (EE) as the most commonly used method for semen collection in wildlife species has been criticized to have animal welfare implications when used in conscious domestic animal patients
Summary
As the numbers of individuals in the wild decrease, the preservation of gametes and their use in assisted reproductive technologies is gaining importance as additional conservation tools [3]. Semen collection and cryopreservation allow to effectively preserve viable gametes in large numbers for future use in artificial insemination or ovum pick-up and embryo transfer by minimally invasive techniques and can be performed opportunistically during chemical immobilization for other management purposes [4]. Electro-ejaculation (EE) as the most commonly used method for semen collection in wildlife species has been criticized to have animal welfare implications when used in conscious domestic animal patients. In wildlife species chemical immobilization is required for this procedure [4]. Heart rates and serum cortisol levels were significantly lower in anesthetized domestic animals compared to conscious animals during and following EE [5]
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