Chemical Immobilization for Leopards

The Leopard (Panthera pardus) is the most widely distributed large wild cat, and occupies a broad variety of habitats, ranging from rainforests to deserts and from the fringes of urban areas to remote mountain ranges.1 The Indian subspecies, Pantherapardus fusca, is found all across India, except for desert areas and above the timberline in the Himalayas. Despite being protected under India’s Wildlife Protection Act of 1972, it is still threatened due to poaching.2

The severe threat of extinction of wildlife species has alarmed wildlife biologists and conservationists for several decades. Many conservation efforts are being attempted focusing on wild animals and their ecosystems. These conservation and management programs often rely on methodologies (e.g., radio-collaring, procurement of biomedical samples for research purposes, translocation of the animals to another area, management purposes in captivity) that require the handling of animals.

Methods of Restraint: Which is Best?

Restraint is often required in the manipulation and handling procedures performed on wild animals. This can include routine veterinary care, surgical intervention, vaccination, hormonal implantation or sterilization, assisted reproductive techniques, blood collection for genetic health analysis or for conservation and management purposes. Thus, the capture and handling of wild animals plays an important role in wildlife conservation and management.

Although physical restraint is straightforward in theory and usually poses minimal risk to animals, it has several limitations and many times it is impractical. In such cases, chemical restraint is the most reliable alternative to restraining wildlife species when required; as such, it has become a valuable tool in wildlife conservation research and management. Great care must be taken when anaesthetizing wildlife species to keep within the safety margin of anesthetics, whether employing neuromuscular blockers, single drugs or drug combinations.

With the advancement of the last few decades, chemical restraint of zoo and wildlife species has improved with safer and efficient drugs, portable monitoring equipment, and precise methods of drug delivery. Modern immobilizing protocols have drastically reduced side-effects of drugs and the attendant causalities. Furthermore, the use of antagonists for anesthetic agents helps to avoid undesirable and harmful effects of drugs, and for the speedy recovery of highly valuable wildlife species. In recent years, chemical restraint has been successfully employed by wildlife veterinarians to treat or relocate animals in captivity as well as in the wild. Advanced procedures have become increasingly more popular and are gradually being adopted by zoos around the world for the safer handling of wild animals. Modern capture methods call for a relatively high degree of expertise and experience, as well as basic knowledge of anatomy, physiology and behavior of the animals to be captured. Unfortunately, many zoo veterinarians and wildlife managers lack such expertise and experience. The ultimate success of the wildlife capture, transport and re-establishment of animals is determined not merely by the success in capture of the animals but more often evaluated in terms of how the animals are handled, transported and kept after capture and whether they adapt and breed successfully in their new environment.²

Chemical Restraint for Wild and Captive Leopards

Chemical restraint is a safe and effective capture method when applied correctly and with the proper precautions. It is advantageous over physical capture because it allows examining and treating sick and injured animals, or animals caught in poachers’ snares or traps. Chemical restraint enables the restraint of aggressive animals within a group, and the equipment required for chemical restraint is easily transported in the field.

A variety of drugs have been used for chemical restraint of zoo and wild animals, including leopards. While there is no “perfect” drug or an anesthetic that will suit all wild species, an ideal drug should have the following properties:

• Readily available
• Economical
• Readily soluble in water
• Stable in solution with long shelf life
• High therapeutic index
• Potent (required dose delivered in small volume)
• Fast-acting
• Smooth onset of induction
• Minimum excitement
• Non-irritating upon administration via IV or IM routes
• Good muscle relaxation
• Minimum depression of physiological variables (heart rate, breathing)
• Sufficient analgesia at subanesthetic doses
• Retention of reflexes such as swallowing
• Effective antidote (reversal agent) with minimal side effects
• Rapid degradation to inactive, non-toxic metabolites
• Safe to use in pregnant animals
• Safe for humans upon accidental exposure

Drugs for the Chemical Immobilization of Leopards

In the immobilization of wild leopards, anesthetic drugs are generally administered by remote darting systems. Pole syringes may be used to inject animals that are in captivity, or in close proximity (such as animals in squeeze cages, crates or crush passageways). Drugs can also be injected with ordinary syringes after the animals have been captured in nets or by other mechanical means.¹

The preferred sites of darting in the leopard are the shoulder and hindquarters. The muscles of the shoulder, the biceps and triceps, are among the best places for remote injection in ungulates. It is better to avoid the upper part of the shoulder because the dart needle may become embedded in the cartilage or scapula. In light-muscled animals, the hindquarters are usually a preferable site for darting.

Nielsen’s Chemical Immobilization of Wild and Exotic Animals recommends that wild leopards be trapped in a cage or with staked bait, after which they may be remotely darted. Recommended drugs for the immobilization of leopards include:

• 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.³

These drugs and dosages are largely supported by other researchers and available sedation protocols.

Uncontrolled recoveries due to prolonged sedation are a serious concern in wildlife research, since the sedated free-ranging animals can be easily injured (or preyed upon, in the case of prey animals). It is therefore important to determine a suitable antagonist for the speedy recovery of anaesthetized leopards. α-2 adrenergic antagonists such as yohimbine, tolazoline and atipamezole have been used effectively in leopards for antagonizing the anesthetic effects of ketamine, xylazine and medetomidine.⁴