Geoscience Reference
In-Depth Information
marking (Baupre 1995; Brawn et al. 1995; Christian and Bedford 1995; Riley
et al. 1995). Subjective evaluation of potential marking effects is a good first
step, but whenever possible quantitative measurements of the biology of
marked versus unmarked animals (Vekasy et al. 1996) or comparisons of pre-
and postmarking behavior of individuals should be included.
When markers were suspected of exerting short-term effects on animals,
researchers excluded data obtained during an arbitrary period (2-14 days after
marking; Baupre 1995; Bloomer et al. 1995; Roberts et al. 1995; Migoya and
Baldassarre 1995; Miller et al. 1995). However, this practice can result in data
bias if marking causes subsequent increases in mortality of young or frail ani-
mals; the result would be an inflation of survival estimates. Two studies (Cot-
ter and Gratto 1995; Cucco and Malacarne 1995) evaluated the effect of one
marker type using an alternatively marked cohort as control, without validat-
ing that negative effects of the alternative marker did not occur.
We found no indication from our survey that authors addressed potential
long-term effects of markers, although one study (Booth 1995) inferred from
the lack of external damage in study animals that long-term tagging mortality
was absent or negligible. In another case (Höglung et al. 1995) marked and
unmarked animals were monitored and data from both cohorts were appar-
ently pooled, but no mention was made of trying to evaluate possible marker
effects. It is also notable that almost all (more than 90 percent,
n
= 16)
instances in which authors addressed marking effects the studies involved ani-
mals that were marked with radiotransmitters. This implies that various forms
of mutilation and tagging or banding are either assumed by researchers to have
little or no effect or else not afforded the same scrutiny in the editorial process.
To summarize, our review of ecological studies found that in general
authors tended to overlook or not acknowledge potential marking effects. In
few cases potential marking effects were addressed, but usually only in a super-
ficial manner or one that could produce bias in the resulting data.
Future Approaches
j
This review clearly indicates that there are a large number of reported marking
effects from commonly used markers, there is a lack of thorough guidance
from zoological societies in choosing a marker, and there is a common failure
to address potential marking effects in the ecological literature. Thus, we pro-
vide the following recommendations for using markers and for additional
research into the effects of marking wildlife.
