Copyright © 1998 Province of British Columbia
Published by the Resources Inventory Committee
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There are many different ways to physically attach transmitters to wildlife. Some species such as grizzly bears or wolverines require very sturdily-built transmitters and attachment systems. Special consideration is also needed for transmitters fitted to prey species. While a snowshoe hare may not be particularly hard on a transmitter, a lynx which captures the hare may damage the transmitter so that the researcher may be unable to locate it. Researchers studying species which spend a lot of time in the water (e.g., beaver) must ensure that transmitters and their attachment system will stand up to frequent immersion. The best attachment option for a particular study must be chosen on the basis of the body type, shape, size and lifestyle of the study species and the type of data required by the researcher. Provincial standards for Wild Animal Capture & Handling must be consulted prior to any capture, restraint, or transmitter attachment.
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Researchers are strongly urged to follow these recommendations with regard to attachment of radio tags (after Bertram 1980 and White & Garrott 1990):
Rules for wildlife transmitter attachment
1. Always carry a spare tag, to replace a dying tag or to test receiving equipment.
2. Routinely record the signal pulse rate of tags, to detect the slowing which precedes cell failure.
3. Tag more than one animal in a social group, in case one tag fails.
4. Treat all animals with the utmost respect.
5. Use the smallest possible transmitter package when instrumenting any animal. Although it may vary for some species, generally no tag should exceed 5% of an animal's body weight. For some animals, such as bats, 4% may be a more appropriate proportion.
6. Transmitter packages which are placed on animals which are dependent on cryptic coloration should be as inconspicuous as possible.
7. Transmitters and their attachments should be tested on captive animals before they are tested on free-ranging animals. Test animals should be the same sex and age as the intended wild animals, and researchers must anticipate potential difficulties due to changes in an animal's size, morphology, or behaviour over the course of its life.
8. Transmitters should always be tested both before and after attachment to ensure that they are working correctly and that the magnets have been removed.
9. Allow several days or up to one week for newly instrumented animals to acclimate to a transmitter before collecting data about "normal" behaviour.
10. Whenever possible, avoid instrumenting animals during their reproductive period, as many species appear to be particularly sensitive to disturbance at this time.
11. Seriously reconsider placing a transmitter on any animal that appears to be in poor body condition or impaired in some other way, unless it is particularly meaningful to the study to follow that specific individual. Recaptured animals showing adverse effects from transmitters should not be retagged. Researchers should not sacrifice the individual for the sake of a larger sample size
Once transmitter attachment is complete, the animal should be carefully observed before release. Short-term behaviours such as scratching at the collar or attempting to shake off a tag will generally cease when the animal becomes accustomed to carrying the transmitter. These behaviours should be distinguished from more serious effects such as improper balance, impeded movement or shifting harnesses which will require intervention. It is an unfortunate reality that many of these problems and behaviours will not be apparent or manifest until the animal is actually released and is difficult to recapture. This only serves to emphasize the importance of thorough research, preparation and testing beforehand.
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Collars are the most common form of transmitter attachment for mammals. Collars should be made of materials which :
Common collar materials are butyl belting, urethane belting, flat nylon webbing, tubular materials, metal ball-chains, PVC plastic, brass or copper wire and cable ties.
The transmitter package may be situated either under the animal's neck or on top of it. Collars must be properly fitted for the comfort and safety of the animal. A collar should fit snugly to prevent it coming off or chafing the animal as it moves, but it must also be sufficiently loose as to be comfortable and not interfere with swallowing or panting. To reduce the risk of chafing on the neck, collars should generally be fastened at the side, with any metal fittings covered or smoothed on the inside surface of the collar. Neck circumference will vary according to species, age, sex and sometimes the season. Transmitter manufacturers usually have records of collar sizes previously used for various species.
Collar thickness and width are important considerations. Width of the collar will affect how the transmitter sits on the animal's neck. Some researchers prefer narrower collars because there is less surface area in contact with the animal. Others prefer wider collars for better weight distribution (Burger 1989c). One of the most important considerations should be the possibility of the collar getting caught up in vegetation. This is a particularly important consideration with small mammals (especially those that burrow).
Expandable collars and harnesses are mandatory in those cases where it is necessary to allow for growth in young animals or for species which undergo neck swelling (e.g., male ungulates in rut) (Hölzenbein 1992). Braided nylon over surgical tubing and nylon web with elastic folds are offered as expandable collars by one company. Expandable collars should not be used unless they are well tested, as poorly designed collars can be very problematic. In the past, certain collars have stretched prematurely as a result of social interactions or behaviours such as neck rubbing. As a result, there is always the possibility of transmitter loss, icing up in winter, or of the collar becoming snagged by branches or even the animal's own legs.
Breakaway or "rot-away" collars are strongly recommended in cases where the researcher does not intend to recapture the animal and remove the collar. Breakaway collars or harnesses incorporate a link of material which is designed to break away and allow the transmitter to drop off after a pre-determined interval. Breakaway links should be environmentally degradable material or electronic links controlled by timers or radio receivers. Environmentally degradable materials which have been used for this purpose include cotton thread and sections of cotton fire hose or cotton spacers on large mammal collars (Karl and Clout 1987; Hellgren et al. 1988). These weak links may also function to break and free the animal if the collar/harness is snagged on a branch. However, it is important to consider that the breakaway collar or harness does not impair the movement or activities of the animal during the period in which it is being shed. For example, a breakaway bird body harness could easily impair wing movement as it is lost and result in mortality. Radio and timer-controlled breakaways may be jammed by freezing or dirt, and also add to the size, weight and complexity of the transmitter package.
Where appropriate, it is recommended that collars and harnesses be marked in order to enhance their visibility. Paint or non-metallic reflective materials may be sewn or glued to collars and harnesses; however, this is likely not appropriate for cryptic species. Metallic tape or foils should not be used as they will detune the transmitting antenna. Adhesive tapes should also not be used as they are not very durable and may foul fur or feathers. For game species or urban studies it may also be helpful to mark a contact phone number on the collar. Colour-coded collars are also available from telemetry equipment manufacturers.
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As it is not possible to establish detailed protocols for all methods of attachment, this section presents a selection of commonly used methods and some key considerations surrounding successful deployment.
Tail Mounts are attached to the tail feathers of a bird. In different studies, they have been glued (including wax) or sewn to a bird's rectrices or attached to them with cable ties or alligator clips (Bray and Corner 1972; Kenward 1987).
Transmitters attached to tail feathers are lost when the bird moults. Rectrices should be handled gently while the transmitter is being attached as stresses to the base of the feather may result in its being moulted prematurely. Considerations should be made with respect to the organism's life history. Depending on how an animal uses its tail, a tail mount may be inappropriate (e.g., woodpeckers - antenna may snag in bark of a tree).
Implantable transmitters are best suited for species:
They are also used for certain biotelemetry applications (especially body temperature). Implants are sealed with neutral (biologically inert) epoxy, resin, or wax, and implanted into the body cavity or under the skin. The antenna may be left external to the body, implanted under the skin or it may be contained entirely within the implant unit.
Despite the initially invasive nature of this technique, one of the key advantages of implants is that they may be much less irritating (if implanted correctly) to the animal than an external tag. Implanted transmitters have a fairly limited range. Those with an implanted antenna will have an even shorter range, but will be less subject to damage or infection than transmitters with external antennas. Transmitters are also expensive to implant as they generally require that researchers employ a qualified veterinarian. Animals may also need to be held for a protracted period in order to recover from the effects of a general anaesthetic.
Backpack modules are attached to the animal by a harness, which is often run through tubular passageways on the transmitter pack (Nicholls and Warner 1968; Jackson et al. 1985; Ward and Flint 1995). Harnesses may be made from soft Teflon ribbon, plastic-coated wire, metal beads, plastic beads, surgical tubing or polyester soft stretch elastic.
The style of harness used depends on the study species, and it is generally necessary to test a harness style on captive specimens before using it in the field. Some manufacturers offer ready-made harnesses to fit the more common species. Elastic harnesses will eventually degrade and free the animal from the transmitter and biodegradeable sutures can be used to release harnesses from aquatic animals. Kenward (1987) states that it is best to avoid the use of harnesses for a species that can be tagged any other way, as the animal may potentially wear the harness for the duration of its life, and even the best-fitting harnesses may eventually snag.
Adhesive transmitters may be glued onto an animal's body, often its back, with cyanoacrylate glue, false eyelash cement, surgical bond (skin cement) or other glue-like substances. Titan Seabird Glue is used by one researcher to attach tags to Dunlin (P. Shepherd, Simon Fraser Univ., Burnaby, B.C., pers. comm.). In birds, the area is usually prepared by trimming feathers to 2 to 5 mm in length. Carapace mounts are typical with turtles while other reptiles have had tags taped to their tales. Mammals can have them glued directly to the fur (e.g., bats, voles) or sometimes the fur is removed before attachment. Typically the whip antenna runs dorsally and caudally to the long axis of the body.
Depending on the type of adhesive used, the tag will generally detach itself. Preparation of an attachment site on the animal may require clipping/shaving which may induce additional stress and potential physiologic problems, such as interference with thermoregulation or flight. Aggressive grooming of adhesive transmitters may shorten their active life further than limits imposed by the power supply.
Necklace packs are often used on upland game birds. These packages simply hang down on the breast of the bird, supported by light flexible cable or cord around its neck. The cord is run through a sleeve to protect the bird's neck.
This system is probably the easiest and quickest to mount, resulting in shorter bird-handling time. Necklace must be long enough to allow the animal to swallow large food items without choking.
Although originally designed for use on polar bears, eartag transmitters have since been used on other species of bear and ungulates (Telonics). They are particularly favoured for large animals with changing neck girth (e.g., juveniles, male cervids). A round design and foreshortened antenna allow the transmitter to rotate freely while remaining in place.
This type of transmitter can range over 3 km given ideal conditions (flat landscape, open vegetation, dry environment). Long antennas should be avoided as they can annoy the animal.
Numerous other techniques have been used to attach transmitters to animals. For example, meshwork vests with transmitters attached have been used on birds (Lawson et al. 1976). Numerous other examples can be found in Chapter 7.
If an attachment design is new, it is critical to test it adequately, preferably on animals in enclosures before conducting a study in the wild. It is important to keep in mind, however, that a captive animal may not have the same physical demands as a free-ranging one. For example, a captive raptor may tolerate a certain attachment technique, but a wild bird will have to fly and hunt with it.
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Copyright © 1998 Province of British Columbia
Published by the Resources Inventory Committee