Chemical Immobilization for Lions
Many procedures that are regularly carried out in domestic animals with minimal restraint require sedation or anesthesia for the safety of the exotic animal, the veterinarian and support staff. This is true whether the exotic animal is captive (in a zoo setting) or in the wild. Generically, the chemical immobilization of exotic animals is veterinary anesthesia conducted under substantially more difficult circumstances than one typically finds in the veterinary clinic.1 In general, wild felids respond to anesthetic agents in a manner similar to that of domestic cats.2 While the physiological responses between domestic and wild felids during maintenance of anesthesia are similar, successful anesthetic procedures require significantly more knowledge and skill than is demanded in the typical small animal veterinary practice.
Given the speed of decline in lion populations in Africa and Asia (43% between 1993 and 2014),3 programs directed towards protecting habitat for wild lions must continue to be the mainstay of conservation efforts in areas where these animals still roam free. A thousand years ago, lions roamed as far afield as southern Europe, the Middle East and Asia, but they are now found mainly in Africa and are generally restricted to the bigger game reserves. According to the International Union for Conservation of Nature (IUCN), the lion population in the wild is now facing a threat that exceeds those of rhino and elephant in terms of the percentage of the population disappearing.
Habits and Habitats
African lions are very large animals, with males weighing up to 225kg and females up to 150kg. In the wild, the lion's average lifespan is approximately 15 years. They are the biggest and most social of the African wild cats, and live communally in prides. Pride leadership can shift between several individual animals both male and female, but the social structure of the pride hinges around the bond between related lionesses, who collaborate in all tasks, from raising cubs to hunting.4 In the wild, male lions can be adopted or driven from the pride in spectacular territorial battles over territory or individual dominance, but the pride’s structure remains unaffected, firmly under control of the dominant lioness.
Lions prefer open woodlands and thick scrub. This type of landscape allows them to get as close to their prey as possible without being seen. More often than not, lions can usually be sighted in areas where big game herds frequent. In most cases, lions hunt at night and rest during the day, but have been known to hunt at dawn, dusk and on cooler days.3 During the day, they can usually be found resting near thorn thickets, or by water holes. Generally, lions feed every three to four days. On average, they require between 5kg and 7kg of meat a day, but can go without food for more than a week and then stock up, eating up to 50kg of meat at one sitting.3
Lions hunt both collaboratively and by singularly. Collaborative hunting usually involves males approaching the intended prey upwind with the intention of driving it towards lionesses hiding in the bush downwind.2,3 Lions are not as fast as most of their prey so they rely heavily on the element of surprise when hunting. The lions will usually attempt to get to within 30 meters of their prey before they spring. Lions don't have the stamina for long chases, and thus will not pursue their prey very far if a first attack fails.
Should they reach their prey, the target is knocked off balance, dragged down and subsequently killed with a bite to the back of the neck or the throat. The dominant male lion will eat first, followed by other members of the pride. Lionesses feed themselves next, with cubs getting the leftovers.3
Lions have a broad diet with over two dozen animal species on the menu, including ostriches, quelea nestlings, tortoises and small crocodiles. Their preference is for waterbuck, buffalo, giraffe, zebra and wildebeest among the bigger animals, and porcupine and warthog as smaller game. It is believed that male and female lions may have different prey preferences, with males being more disposed towards hunting buffalo, while lionesses prefer zebra or wildebeest.3 Lions will also occasionally scavenge, sometimes chasing smaller predators such as cheetah away from their kills. In some instances, up to 50% of a lion's diet can come from scavenging rather than hunting live prey.
Immobilization Protocols
African lions (Panthera leo) are often immobilized for routine procedures such as microchipping, collaring, disease prevention and medical treatment. Asiatic lions (Panthera Leo Persica) and hybrid lions are often subjected to chemical immobilization and anesthesia for various measures related to conservation and elective and emergency surgical procedures by veterinarians.2 Management of long-term anesthesia is generally carried out under using injectable anesthetics and ancillary drugs which can pose problems due to changes in depth of anesthesia and alterations in homeostasis which lead to stress-related complications.
Ideally, the drugs used for the immobilization of wild or captive exotic felids should rapidly induce reliable and reversible immobilization. Numerous drugs and drug combinations have been employed for the immobilization of free-ranging lions, including phencyclidine, ketamine-xylazine, tiletamine-zolazepam and medetomidine-ketamine.3 In large felids, tiletamine-zolazepam has been the drug combination of choice for immobilization by many wildlife veterinarians. This combination has a wide safety margin and few cardiopulmonary or thermoregulatory side effects, but as a result of the long elimination half-life of tiletamine and the lack of an antagonist, recoveries are often prolonged. In combination with medetomidine, however, the effective dose of tiletamine-zolazepam can be reduced by as much as 75% in wild felids and the recovery time thereby significantly shortened by antagonizing the effects of medetomidine with atipamezole.2,3
The Handbook of Wildlife Chemical Immobilization (Arnemo & Kreeger, 2018) lists the combination of ketamine (2.5 mg/kg) plus medetomidine (0.07 mg/kg) for the immobilization of lions. For reversal, the authors recommend atipamezole (0.35 mg/kg). Alternatively, tiletamine-zolazepam (2 mg/kg) plus medetomidine (0.07 mg/kg) may be used and antagonized with atipamezole (0.35 mg/kg).5
Chemical Immobilization of Wild and Exotic Animals. (Nielsen, 1999) offers a unique protocol that is often used for the capture and immobilization of wild African lions. Since lions and hyena (Crocuta crocuta) are mortal enemies, tape recordings of hyena vocalizations and lions feeding can be used to draw lions to bait. Additionally, an oral neuroleptic in the bait can aid in sedation and make for easy darting.1 For immobilization, the author recommends:
- Ketamine in doses of 5 to 20 mg/kg, with or without 0.5 to 4 mg/kg of xylazine,
- Telazol® in doses of 1.5 to 40 mg/kg, or
- Medetomidine in doses of 0.04 to 0.10 mg.kg with 2 to 3.5 mg/kg of ketamine.1
Atipamezole (0.35 mg/kg) may be used effectively as a reversal agent for the above listed drugs.
1Nielsen L. Chemical immobilization of wild and exotic animals. Iowa: Iowa State University Press, 1999; 227-281.
2Morris P.J. Chemical immobilization of felids, ursids, and small ungulates. Vet Clin North Am Exot Anim Pract 2001; 4:267-98.
4Jacquier, M., et. al. Reversible Immobilization of Free-ranging African Lions (Panthera leo) with Medetomidine-tiletamine-zolazepam and Atipamezole. Journal of Wildlife Diseases, 42(2), 2006, pp. 432–436.
5Arnemo, J., Kreeger, T. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed.
About NexGen Pharmaceuticals
NexGen Pharmaceuticals is an industry-leading veterinary compounding pharmacy, offering sterile and non-sterile compounding services nationwide. Unlike other veterinary compounding pharmacies, NexGen focuses on drugs that are difficult to find or are no longer available due to manufacturer discontinuance or have yet to be offered commercially for veterinary applications, but which still serve a critical need for our customers. We also specialize in wildlife pharmaceuticals, including sedatives and their antagonists, offering many unique options to serve a wide array of zoo animal and wildlife immobilization and anesthesia requirements.
Our pharmacists are also encouraged to develop strong working relationships with our veterinarians in order to better care for veterinary patients. Such relationships foster an ever-increasing knowledge base upon which pharmacists and veterinarians can draw, making both significantly more effective in their professional roles.
Disclaimer
The information contained in this blog post is general in nature and is intended for use as an informational aid. It does not cover all possible uses, actions, precautions, side effects, or interactions of the medications shown, nor is the information intended as medical advice or diagnosis for individual health problems or for making an evaluation as to the risks and benefits of using a particular medication. You should consult your veterinarian about diagnosis and treatment of any health problems. Information and statements have not been evaluated by the Food and Drug Administration ("FDA"), nor has the FDA approved the medications to diagnose, cure or prevent disease. Medications compounded by NexGen Pharmaceuticals are prepared at the direction of a veterinarian. NexGen Pharmaceuticals compounded veterinary preparations are not intended for use in food and food-producing animals.
NexGen Pharmaceuticals, LLC does not recommend, endorse or make any representation about the efficacy, appropriateness or suitability of any specific dosing, products, procedures, treatments, services, opinions, veterinary care providers or other information that may be contained in this blog post. NEXGEN PHARMACEUTICALS, LLC IS NOT RESPONSIBLE NOR LIABLE FOR ANY ADVICE, COURSE OF TREATMENT, DIAGNOSIS OR ANY OTHER INFORMATION, SERVICES OR PRODUCTS THAT YOU OBTAIN THROUGH THIS BLOG POST.