Geoscience Reference
In-Depth Information
with paint, the technique is discouraged for use on amphibian skin, for which
nontoxic stains and dyes should be used. In cases where toxicity is unknown,
laboratory trials should be undertaken before any field use. Few guidelines are
provided for the use of brands, dyes, or paints with birds and mammals.
Radiotransmitters
Most professional zoological societies address the issue of radiotransmitters
specifically. Many fish, reptile, and amphibian species are not suitable for
radiotelemetry because of their small size. However, for species that are
amenable to telemetry, stomach implants and internally mounted transmitters
should be small and coated with a biologically inert coating, and not interfere
with physiology and behavior. Externally mounted transmitters should be
shaped and attached to reduce chances of entanglement, irritation, or con-
striction. In the case of large birds, it is suggested that radiotransmitters weigh
less than 1 percent of body mass to reduce negative effects on biomechanical
performance. For smaller birds transmitters should not exceed 5 or 10 percent
of body mass. Before use in the field, biologists should observe individuals in
captivity to evaluate effects of radiomarking on behavior. For reptiles, amphib-
ians, and most mammals, it is recommended that transmitters not exceed 10
percent of body mass.
CRITIQUE OF GUIDELINES AVAILABLE FOR CHOOSING MARKERS
In general, the guidelines provided by zoological societies are too general for
choosing a specific marker for a given study objective or species. Some recom-
mendations made by professional societies even appear to ignore the findings
of previous marker evaluation studies. For instance, fin removal is recom-
mended by several fish societies as an appropriate method of marking many
species, despite numerous instances in which the technique has been shown to
affect fish biology (table 2.1). Also, it is recommended that mass of transmit-
ters never exceed 10 percent of body mass of vertebrates, even though some
transmitters weighing less than this have been shown to produce negative
effects. Given that, at least for birds, the effect on flight power increases with
body mass, the 10 percent threshold is clearly an arbitrary construct that does
not apply to all species. Furthermore, a given mass or drag has different effects
depending on the type of flight (e.g., soaring, flapping, sprint; Pennycuick and
Fuller 1987; Pennycuick 1989; Pennycuick et al. 1989). Therefore, general
guidelines (e.g., 10 percent, 5 percent, or 3 percent) can be misleading.
