Geoscience Reference
In-Depth Information
Chapter 2
A Critical Review of the Effects of Marking on the
Biology of Vertebrates
DENNIS L. MURRAY AND MARK R. FULLER
Vertebrates often are marked to facilitate identification of free-ranging indi-
vidual animals or groups for studies of behavior, population biology, and phys-
iology. Marked animals provided data for many of the topics discussed in this
volume, including home range use, resource selection, social behavior, and
population estimation. Markers can be classified into three general categories:
mutilations, tags and bands, and radiotransmitters. The appropriate marking
technique for a study depends on several considerations, including study ob-
jectives, target species, marker cost, marker efficacy, and marker effects on the
animals (Day et al. 1980; Nietfeld et al. 1994).
Studies using marked animals are characterized by the assumption that
marking does not affect animals or that negative effects are not important
(Ricker 1956; Day et al. 1980; Nietfeld et al. 1994). The assumption of no
significant marking effects is critical because it is the basis for generalizing data
collected from marked individuals to unmarked animals and populations.
However, the assumption has not been tested rigorously for most marker types
or animal species, despite the often necessary use of seemingly invasive mark-
ing techniques. The general paucity of marker evaluation studies apparently is
related to the difficulties associated with conducting such tests in the field, as
well as the belief that marker evaluation is tangential to most study objectives
and therefore of minor importance to the researcher. In addition, studies that
evaluate marker effects often suffer from small samples, thus leading to quali-
tative conclusions or weak statistical inference (White and Garrott 1990). As a
result, researchers tend to choose markers that intuitively seem least likely to
induce abnormal behavior or survival, even though data supporting that asser-
tion usually are weak or lacking. However, if the assumption of no marking
