10-12-2012, 12:07 PM
Wildlife Radio-telemetry
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INTRODUCTION
Wildlife radio-telemetry may be defined as the transmission of information from
a transmitter on a free-ranging wild animal to a receiver. Wildlife-related
telemetry is also known as radio tagging, radio-tracking or simply ‘tagging’ or
‘tracking’. Advances in the field of wildlife telemetry have made it possible to
acquire detailed data on many aspects of wildlife biology, including habitat use,
home range size, mortality and survivorship, and migration timing and routes.
Since many wildlife species are secretive and difficult to observe, radiotelemetry
has provided a valuable tool to learn more about their respective lifehistories.
As a result, radio-telemetry studies are very common throughout the
current wildlife literature (see Bibliography).
Despite its popularity, radio-telemetry is inappropriate under many
circumstances. It is an expensive and time-consuming technique which has
proven to be unsuitable for use in some species (due to the animal’s size or lifehistory
traits). Despite the frequency with which radio collars and other
transmitters are attached to research animals, surprisingly little is known about
their effects on the behaviour and survivorship of the species in question.
Certain First Nations groups strongly believe that collars and even ear tags
influence behaviour and therefore actively oppose the use of these devices on
game animals. The potential for modified behaviour and differential survival of
radio tagged animals may introduce additional bias and error which could be
reflected in study results. Quite clearly it can also be detrimental to the animal
wearing the tag. The placement of a radio tag on an animal represents a
commitment by the researcher, and there is the possibility that it is done at the
expense of the animal it is placed on. Thus, transmitters should only be attached
when project funding guara
Ethical Considerations
In British Columbia, it is strongly recommended that all studies involving radiotelemetry
of terrestrial wildlife undergo peer and veterinary review prior to
commencement. This review should include examination of inventory
objectives and methods, evaluation of expected ecological impacts, and
provision of permits by the proponent (e.g., telemetry amendment to banding
permit). In addition, experienced reviewers can provide valuable guidance
regarding transmitter weight, attachment method and capture protocol, helping
to avoid problems which have already been solved by other professionals.
Because of the invasive nature of telemetry projects, researchers should be
particularly diligent that proper field procedures are followed. Apart from the
obvious humane considerations, animals which are unduly stressed or
influenced by the capture technique and/or radio tag will not be representative
of normal behaviour for the species. In extreme cases, injury and mortality may
be the end result.
Permits and Licenses
Both the federal and provincial governments have responsibilities for wildlife in
British Columbia. It is useful to have an understanding of the jurisdictions of
these different agencies to appreciate the licensing requirements for telemetry
projects of different species.
The Department of Fisheries and Oceans is responsible for all marine mammals
in British Columbia. These will not be covered in this manual.
The B.C. Ministry of Environment, Lands and Parks has sole jurisdiction over
all reptiles, amphibians, and terrestrial mammals in the province. The Ministry
issues sundry permits to biologists who will be capturing, handling and/or
collecting wildlife in the province.
The Ministry also protects the province’s birds, and has sole jurisdiction for a
portion of these, including all raptorial birds, cormorants and pelicans, upland
game birds, kingfishers, corvids, blackbirds, grackles and cowbirds. The
Ministry is responsible for issuing sundry permits for activities involving these
bird groups.
TRANSMITTERS
Conventional transmitters consist of an antenna, a power source and a
transmitter unit. Although this combination is fairly fundamental, the specific
components chosen may vary between projects. In light of this, rather than
attempt to recommend a particular type of transmitter, it is likely more useful to
the researcher to describe the basic equipment options which are currently
available for transmitters.
Transmitters
Transmitters (tags) are available as complete units (including attachment
options such as collars) or as components which are assembled and finished by
the researcher. (Note: transmitters which are not assembled commercially may
be subject to additional testing and certification requirements through Industry
Canada.) Manufacturers generally package transmitter units in a metal can
and/or cover them in an acrylic or epoxy resin coating to protect them from the
elements (e.g., salt water) and from being damaged by the teeth, beak or claws
of the animal.
One-stage and Two-stage Transmitters
Transmitters are available as one- or two-stage circuits. One-stage transmitters
are useful for many applications due to their simple design and consequent low
weight (as low as 0.5 g or less). Two-stage transmitters consist of a basic
oscillator plus an amplifier, and must be powered by a minimum of 2.4 volts.
Two-stage transmitters are larger, more complex and often more powerful than
single-stage units. Functionally speaking, choosing between a one- or two-stage
transmitter has several implications (Table 2).
General Protocols
Ideally, transmitters should be stored on a wooden shelf with at least 2.5 cm
distance between magnets on different collars to ensure that the magnets do not
cancel one another out and activate the transmitters (Decker 1988). A stored
transmitter should also be exercised 2 to 3 days/month in order to prevent the
build-up of a ‘passivation layer’ on the battery electrodes. A receiver should be
used to check that all magnets are in place and all transmitters are turned off.
Small transmitter tester units are also available from several suppliers.
A detailed log should be kept of each transmitter unit (including those in
storage) giving receipt dates, storage times, testing and results, deployment date,
number of relocations and any notes on unusual signal characteristics or animal
behaviour (see Appendix for sample). If the transmitter fails, the log is
invaluable when the failure is analysed by the manufacturer.
Transmitters may be refurbished (replacing the battery, canister, antenna and
attachment and testing all components) or retrofitted by re-working a transmitter
to new specifications, (e.g., changing a deer tag to a moose tag; Decker 1988b).
Both of these procedures are best done by the company from which the
transmitter was originally ordered.
TRANSMITTER ATTACHMENT
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.
Protocols - Removal & Recovery
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.