Geoscience Reference
In-Depth Information
low rates of seroma and infection (Harms et al. 1997). One constraint with
transmitter implants is that transmission distance is reduced when the antenna
is implanted in the abdominal cavity, although some researchers (Korschgen et
al. 1995; Petersen et al. 1995; Korschgen et al. 1996a, 1996b) have developed
a technique to exit the antenna from the body, thereby augmenting transmis-
sion distance.
Since the mid-1980s several investigators have considered the effects of
radiomarking on bird energetics. This issue is important for birds because
radiomarking compounds the increase in energy required to carry additional
mass by adding aerodynamic or hydrodynamic drag (Pennycuick 1975; Wil-
son et al. 1986; Culik and Wilson 1991). Streamlining of transmitters reduces
aerodynamic drag and therefore minimizes their negative effects (Obrecht et
al. 1988). Although some researchers failed to detect effects of transmitters
weighing less than 4 percent of body mass (Sedinger et al. 1990; Gessaman et
al. 1991b; Bakken et al. 1996), others (Pennycuick and Fuller 1987; Gessaman
and Nagy 1988; Pennycuick et al. 1988, 1990, 1994; Gessaman et al. 1991a;
Wilson and Culik 1992) indicate that, either for different species or larger
transmitters, radiomarking can affect bird metabolism. This may be particu-
larly important for large birds because they have proportionally less surplus
power than smaller birds (Caccamise and Hedin 1985).
Mammals
TAGGING
Although studies of mammals often involve marking, marker ef-
fects have been evaluated in few instances (Leuze 1980; Kenward 1982; White
and Garrott 1990). This appears to be particularly true for externally mounted
metal or plastic tags, with few studies evaluating effects of such markers (table
2.4) despite their widespread use. Internal PIT tags have been used in several
species of mammals and evaluation tests (Fagerstone and Johns 1987;
Schooley et al. 1993) so far have failed to detect significant negative effects.
MUTILATION
Toe clipping is a widely used tool for marking small mam-
mals, and many studies have evaluated the effects of this technique on survival
and body condition (table 2.4). Several studies have detected effects of toe
clipping, but similar numbers of studies have failed to observe negative effects.
In one case, different studies on the same species provided conflicting results
(Ambrose 1972; Pavone and Boonstra 1985), suggesting that study methodol-
ogy can influence outcome of marker evaluation studies. In two cases (Pavone
and Boonstra 1985; Wood and Slade 1990), significant effects of toe clipping
