Many studies require individual animals to be marked for identification. Marking techniques can cause effects ranging from short-term discomfort, to long-term influences on breeding and survival. It is essential, for the welfare of the animal and the integrity of the research results, that the marking procedure not adversely affect the normal behaviour, physiology, ecology or survival of individuals. In choosing an acceptable marking technique, the investigator must consider the nature and duration of the restraint that is required for its application, the amount of tissue that is removed or damaged, the amount of momentary or prolonged pain that is involved and the potential risk for infection. In many cases it has been possible to reduce the harmful effects of the mark by careful design, with special consideration to colour, attachment position, mass and the season in which it is applied.
In general, investigators should not assume that marking procedures will have no adverse effects on their study subjects and should make efforts to evaluate any such influences. Where possible, investigators should assess the effects of new marking procedures on captive individuals before incorporating them into field studies.
It is desirable for the scientific community to encourage ancillary research that specifically addresses the effects of marks and devices. Preferably, such research, which makes comparisons between marked individuals and controls, can be initiated in association with current studies. Because of the difficulty of providing appropriate controls, there are few systematic studies that assess the potential adverse effects of marking procedures. Many of the cautions mentioned here are based on unpublished observations.
In general, for a marking procedure to be effective, it should meet as many of the following criteria as possible:
Hot branding has been used in a number of instances to imprint identification numbers on the horns and skin of wild mammals. This method produces third-degree burns which lead to the production of visible scar tissue. Because of the pain associated with this procedure, this method is not commonly recommended.
Freeze branding (cyro-branding) appears to be more acceptable than hot branding for marking wildlife because it is less painful and the possibility of infection is minimized. This technique, which was originally developed for the identification of livestock, has been used with varying results in several wildlife species.
Tattooing is a common method of identification and has been used successfully in many species. Tattoos have been applied to the inside of the lip, the ear, and the thinly-haired area of the groin. The location and proper application of the tattoo will influence its future readability. In most cases, the animal must be recaptured or examined after death in order to read this type of mark.
Techniques that involve the removal or damage of tissue, such as toe, tail, or ear clipping are forms of mutilation. These procedures may have adverse effects on the behaviour and survival of wild animals and their use in marking free ranging wild species cannot generally be condoned. It is strongly recommended that alternative marking techniques be used in field research. However, in those few instances where removal of tissue is not judged to impair the normal activities and survivability of the marked animal and does not cause bone damage, pain or severe blood loss (e.g. ear notchings of small rodents), these marking techniques can be utilized. When toe or tail clipping are felt to be the only methods that can meet the requirements of a particular study, their use should be appropriately reviewed and approved by a review or animal care committee before implementation.
The removal of toes must never be performed on animals that use them for activities such as burrowing (ground squirrels) or climbing (red squirrels), or on animals where important bone structures have to be removed. When toe clipping is used is used as a marking technique, no more than one toe per foot should be removed.
Ear tags are used to mark many different mammalian species and are usually made of plastic, aluminum, or plated steel. These tags are available commercially in a variety of materials, sizes, configurations and colours. Care must be exercised so that a tag of appropriate size is applied. This will help to reduce potential problems, including heat loss as a result of increased temperature conductance through a metal tag or snagging of excessively large tags. By tagging both ears the researcher will help to reduce the chances of a lost identity in the event that one tag is torn out. Application of ear tags during fly seasons or using unhygienic techniques may predispose to localized infections. Researchers should understand the ear anatomy to avoid blood vessels and the appropriate application technique before use.
Consideration should be given to the size of the bat and the type of material used in the band in order to minimize the risk of injury. Tattoo needles have been used to mark wing membranes of bats as an alternative to banding, however, these marks were not always visible after five months. The researcher should contact active bat researchers and/or the literature for the most appropriate marking techniques.
Adjustable and/or expandable neck collars or bands, in a variety of materials with visible colour bands and numbers, are a common method of identifying wild mammals in field studies. These have been used successfully to mark bighorn sheep, deer, elk, moose, bison, and antelope. The size of the collar must be carefully selected in order to allow for normal growth and activity of the study animal.
Modifications to neck bands have been introduced in order to improve their visibility in the field. These alterations include the addition of vinyl coated nylon flags, bells, and battery operated neon lights or light emitting diodes which allow for night observations of species such as deer and beaver. Because these modifications may attract predators and interfere with the normal behaviour and social interactions of the marked animal, their use is justifiably limited.
Tetracycline, a fluorescent marker, has been administered orally or as an injectable to permanently label bones and teeth of several species. Other fluorescent or dye markers have been used in oral baits to temporarily identify the individual animals which consume them.
The use of radioisotopes as markers in natural systems may be valuable. However the application of these agents should only be undertaken with caution. Researchers are required by law to have special training and to observe certain precautions. In addition, a licence is required which outlines the safety procedures, the disposal of waste material, and the release of isotopes into natural systems. The potential use of these agents must be evaluated with consideration to the possible deleterious effects that these agents may have on the study animal, its predators and the public.
Radioisotopes have been injected into captured mammals prior to their release. This method has allowed researchers to estimate population size by counting radioactive droppings.
A chemoluminescent tag, using Cyalume® injected into hollow glass spheres as a light source, has been cemented to the mid-ventral fur of bats allowing their flight to be tracked at night. The light resulting from this tag lasts from two to three hours and is visible from a distance of 200 m.
Beta lights are another light source useful in tracking small fossorial mammals. They consist of glass capsules coated with phosphor and filled with tritium gas. Beta lights last up to 20 years and can be seen up to 400 m. However, their use must be approved by radiation authorities.
Dyes have been used to colour the hairs in numerous species of mammals, including bears, elk, deer, mountain goats, wolves, ground squirrels, bighorn and Dall sheep, peccary, and snowshoe hares. Some of the dyes used are Nyanzol A, Nyanzol D, blackpowder, clothing dyes, human hair dyes, red and orange aniline dyes, and picric acid. The method of application of these materials has varied from simply painting the dye on the animal to the use of compressed air sprays or paint balls. They have been administered from the ground, helicopter carried paint ball guns or from aircraft rigged with crop spraying devices. Care must be taken to use non-toxic dyes.
Paint has been used to mark horns of bighorn sheep and bison and has also been sprayed directly on the hide. A commercial paint pistol is available that can propel paint pellets up to 15 m. Coloured plastic adhesive tape has been successfully used as a temporary mark on the horns of bighorn sheep. This material is durable and it is easily applied to immobilized animals. Horns have also been permanently marked with heat branding or the insertion of metal pins.
Coloured ear streamers and ear switches are temporary markers that have been used on larger mammals. The most durable material appears to be vinyl coated nylon. Streamers are usually attached through slits in the ear or by metal tags. The same criticism and limitations to the acceptability of this method exists as for neck bands. In addition, consideration must be given to the behavioural effects of streamers. In general, ear switches have not been found to be any more valuable than ear tags.
Passive integrated transponders or microchips have been used to mark study animals permanently and can be used as an ancillary method of identification. These devices are implanted subcutaneously or intraperitoneally with complications reported rarely. However, animals must be recaptured and special equipment used to identify marked individuals. In addition, the transponders may migrate if applied subcutaneously, and this can make reading them more difficult in larger species. Microchips are most frequently used for the identification of individual animals where external marking is not desired (i.e., anti-poaching projects).
The attachment of small radio transmitters to free-roaming mammals has become a routine method of monitoring the location and movement of individuals, and is used successfully in a wide variety of mammalian species. There is little direct evidence that when transmitters are of appropriate size, and are properly attached, they adversely affect research subjects. Transmitters are applied most frequently to the larger species, but with the development of units weighing less than 2 g, they also have applications in the study of smaller species such as bats and rodents.
A wide variety of attachment methods for transmitters are currently in use. The methods for attaching transmitters to a wide variety of taxa are reported in the literature. It is mandatory that investigators who are intending to utilize telemetry in their investigations access those sources which are relevant to their study species. A review of the pertinent literature will help to identify any potentially adverse effects that transmitters may have upon the behaviour, survival and well-being of their study animals. It is strongly recommended that prior to being used in the field, new attachment techniques are reviewed and, if appropriate, evaluated on captive individuals.
Radio transmitters vary in size, longevity and range characteristics, and are available from several commercial suppliers. The researcher should choose a transmitter and method of attachment that harmonizes with the anatomy and behaviour of the study animal. Neck collars are the most common method of attachment in larger mammals.
The addition of an external mass to an animal's body can have an adverse effect on its energetics. Therefore, it is recommended that the combined weight of the transmitter and neck collar does not exceed 4 % of the animal's body weight. Special consideration must be given to the attachment of neck collars in those individuals who will undergo significant musculoskeletal growth and in those species that have marked seasonal fluctuations in body condition.
Proper collar width is also critical. If the collar is too narrow excessive undue pressure is applied to the animal's neck, resulting in abrasion and pressure necrosis. If too wide, the animal's neck movements may be impeded. Rubber-impregnated nylon webbing (machine belting) and non-impregnated seatbelt type webbing are materials that are most often used for neck collars. Plastics are often used for smaller species, but their durability and flexibility are affected by temperature and age. The use of collars with protruding or whip antennae is avoided in species which chew on them, such as carnivores. Inserts of degradable material which allow collar drop-off are strongly advised. Consideration should be given to the recapture and removal of collars at the end of the study period.
Special attention must be given to the attachment of transmitters in fossorial and arboreal species. Surgically implanted radios have been used on medium sized mammals such as marmots, furbearers and ground squirrels with similar neck and head width where collars are easily removed. General anaesthesia and veterinary assistance is recommended for the implantation of abdominal transmitters. These devices may have a limited range and short battery life, but if properly installed can be successful. In bats, transmitters have been successfully attached to the fur. As a general rule, this type of transmitter should not exceed 4% of the bat's total weight.
Solar operated ear tag mounted transmitters and subcutaneous transmitters have recently become available for larger mammals in situations where collars are undesirable for esthetic reasons (wildlife viewing).
For more information on this topic, consult the RIC (Resources Inventory Committee) manual entitled Wildlife Radio-telemetry, Standards for Components of British Columbia's Biodiversity No. 5.
It may be necessary to transport animals as part of an experimental protocol or to move them from capture sites to holding facilities. Transport containers and methods of shipping animals will vary widely from species to species. The live traps that are used for capture are usually adequate for transport over short distances. However, if the animals are large or are to be confined for a longer period, these traps may not be suitable. In general, the containers used in transportation must protect the occupants from injury and allow the individual sufficient space so that it can assume a normal posture and engage in comfort and maintenance activities unimpeded by conspecifics. In most cases, animals should be separated. Containers should be padded in those instances where excitable animals or species with delicate bone structures are to be shipped. Adequate ventilation must be provided. For longer journeys, water and food should be provided. The inside of containers should be as dark as possible, while still allowing them good ventilation, to find food or water, and to move about. It is recommended that transport vehicles be equipped so that the transported animals are not exposed to excessive noise, movement or temperature extremes. Proper arrangements should be made to ensure that animals arrive at destinations during normal working hours, rather than on weekends or holidays. Further information and regulations on animal transport and appropriate caging are available from Transport Canada and Canadian Food Inspection Agency.
Wild animals used in captive studies should be as healthy and free of trauma as possible. Some exceptions to this rule include investigations into the effects of environmental stress and disease. Housing standards should follow CCAC guidelines and/or institutional animal care standards.