A+ A-

Understanding the intricacies of rhino immobilisation

The reality of rhino poaching has made us all too aware of the fragility of the species. It is with growing frequency that veterinary professionals are required to work on these animals in an attempt to save them. Intervention varies from conducting the necessary steps to make a translocation possible, to efforts to save an animal that has sustained a poaching attack, to other veterinary procedures like dehorning.

Rhinos' response to immobilisation (anaesthesia) has proved to have complications, but Prof Leith Meyer from the Department of Paraclinical Sciences in the Faculty of Veterinary Science at the University of Pretoria, is constantly working to better understand how these iconic animals respond to immobilisation. Thus far, Meyer's research has isolated the drugs that work best to stabilise white rhino and found ways to improve blood oxygen levels in the immobilised animal.

When immobilised, rhino – particularly white rhino – experience tremors that are sometimes so severe that it is very difficult to work on them. The cause of these tremors was not clear until Meyer and his team set out to understand them and whether cardiorespiratory supportive interventions alter their intensity. The study looked at the possible mechanisms that lead to muscle tremors and physiological responses during etorphine–azaperone immobilisation in eight boma-held and 14 free-living sub-adult male white rhino in the Kruger National Park. The reason for the two groups was to test whether the interventions that worked best on boma-held rhino had similar results in the free-living rhino. Sub-adults were chosen because they would not yet have become territorial, and by removing them temporarily from the wild, the social structures of other rhino would not be affected.

One of the objectives of the study was to develop a model that grades the severity of these tremors. Tremors were measured using a tremor scale and activity loggers which were able to measure even the slightest movements. Loggers were attached to the shoulder and leg of each animal to monitor tremors and the differences in readings – often the leg logger picked up too much movement, which is not always a result of the tremors, but rather general movement of the leg.

Meyer's research has proven that white rhino are particularly sensitive to the drugs used during immobilisation. These drugs tend to depress their breathing and also have metabolic effects which cause the sedated animals to burn up oxygen more quickly. Because they are not breathing properly while under the drugs, they are not able to supplement the deficit. 'Arterial blood that goes to the tissues ends up being very low in oxygen, resulting in the animal becoming severely hypoxic,' explains Meyer. Furthermore, these drugs cause high levels of carbon dioxide and increase the acidity of the blood. During times of hypoxia and acidaemia, oxygen deprivation causes the body to go into survival mode, releasing stress hormones (catecholamines), such as adrenaline, into the blood. Just as in humans after getting a big fright, the body begins to shake.

Meyer correlates the severity of the tremors to the level of stress rhino are under during the capture process (being chased by the helicopter), together with the effects of the drugs that cause them to become hypoxic and acidaemic, releasing adrenaline into the blood stream.

The stress from the helicopter chase is likely to also cause the rhino to produce more heat than it dissipates, which can lead to hyperthermia. The increased heat produced from the tremors, can worsen the hypoxia and acidaemia, causing severe respiratory and metabolic consequences.

While it is imperative to react to the tremors, they do serve as a useful tool to monitor how the animal is doing. Severe tremors serve as a warning sign that something is physiologically wrong, and suggest that the animal is compromised.

Intervention to reduce the intensity of the tremors is necessary. Oxygen levels need to be restored and carbon dioxide needs to be expelled to improve the pH level of the blood. The drug butorphanol improves the flow of gases in the blood and reduces the severity of tremors. 'By providing oxygen intranasally, oxygen levels can be brought back to normal, which slows the tremors significantly, even stopping them completely,' says Meyer. Administering intravenous butorphanol is a simple, readily available technique that will significantly improve oxygenation, thereby reducing tremors and improving the safety of white rhino immobilisation in general.

Meyer is continuously trying to understand all possible scenarios to reduce the risks to rhino when immobilised. 'We have to do these tests now while we still have many rhino, because if they do get to the stage where they become critically endangered, if we do not understand how they react to anaesthesia, we may have a very serious problem.' He aims to make anaesthesia as safe as possible for rhino.


Banner and cover photo by Joel Alves, a veterinary student in the Faculty of Veterinary Science


Privacy Policy

The University is firmly committed to protecting the privacy of users of the website. No personal information about users of this website will be disclosed to a third party without the prior consent thereto by the user. (Personal information shall at all times be dealt with in accordance with the provisions of the Protection of Personal Information Act, 2013 (Act 4 of 2013).)

The University reserves the right to automatically collect information on users' usage of the website (for example, via cookies) in order to improve users' browsing and interaction with the University and for non-personal statistical purposes.

Changes to this privacy policy

The University reserves the right to change, amend, or update this privacy policy periodically.

Modifications to the website

The University reserves the right to modify, change, amend or discontinue the website (or any part thereof) temporarily or permanently, without prior notice.


The University may provide links to other websites or resources. This does not imply the University's endorsement of such sites. The University does not have any control over these websites and will, therefore, not be liable for any damages whatsoever arising from the utilisation of these websites by users.

The University does not prohibit third-party sites to link to publicly visible content on this website. However, it is expressly prohibited for any third party to frame any page on this website in any way whatsoever without the prior written approval of the University.

University of Pretoria proprietary rights

The copyright and other intellectual property rights (which include the University’s brand and logo), which are owned by or licensed to the University, existing in and attaching to this website, are the property of the University. These include but are not limited to text, content, design, layout, graphics, organisation, digital conversion and other information related to the website.

Users are granted a non-exclusive, non-transferable, revocable licence to:

  • access and use this website strictly in accordance with these terms;
  • use this website solely for personal, non-commercial purposes; and
  • download or print out or distribute content from the website, or any part thereof, solely for personal, non-commercial purposes, provided that all copyright and other intellectual property notices therein are unchanged.

Any reproduction of the content of this website, or a portion thereof, must include the following copyright notice: ©University of Pretoria. Users who wish to use the content from this website for commercial purposes may only do so with prior written permission from the University.


This website is for information purposes only. No representations or warranties are given by the University of Pretoria (hereafter referred to as the University) regarding the accuracy of the information this website contains, any material this website provides for or any part of this website. Any reliance by the user on any information this website contains, any material this website provides for or any part of this website, is at the user’s own risk and the University shall not be liable in any way whatsoever in respect of the user or any other person, directly or indirectly, arising from the utilisation of the information this website contains, any material this website provides for or any part of this website.

The user hereby agrees that in the event of any dispute arising from the utilisation of this website in any manner, form or substance whatsoever, the relevant South African law will apply and the appropriate courts of South Africa will have jurisdiction.

Terms & Conditions

By accessing this website, the user hereby agrees to the following:

The use of this website is at the user’s sole risk. This website is provided on an "as is" and "as available" basis. The University gives no warranty that (i) the information posted on this website will meet the user’s requirements; (ii) the information posted on this website will be uninterrupted, timely, secure, virus free or error free; and (iii) the information posted on this website will be accurate or reliable.

Any material downloaded from or otherwise obtained through this website is utilised at the user’s own risk, and the user will, therefore, be liable for any and all damages of any nature whatsoever arising from such utilisation of the website.

Limitation of liability

The user expressly understands and agrees that the University shall not be liable for any damages (subject to the provisions of Chapter 2 of the Consumer Protection Act, 2008 (Act 68 of 2008) (even if the University has been advised of the possibility of such damages) resulting from: (i) the use or the inability to use the website; (ii) the cost of procurement of substitute goods and services resulting from any data, information or services obtained or messages received or transactions entered into through the website; (iii) unauthorised access to or alteration of the user’s transmissions or data; (iv) statements or conduct of any third party on the website; or (v) any other matter relating to the website.