Biology Reference
In-Depth Information
removal of egg masses in the spring may serve as a more effective means of
population control. This notion has yet to be field tested.
Control efforts against
Bufo marinus
in Australia have largely been devoted
toward public education; research to identify effective means of long-term control;
and preventing establishment of new populations on offshore islands, at the south-
ern end of its range in New South Wales, and at the western end of its range in
Northern Territory and Western Australia. Much of the border-control activity
relies on volunteer labor (R. Taylor and Edwards, 2005; Boulter et al., 2006;
Sawyer, 2006).
Attempts at localized removal of populations of
Trachemys scripta
are being
made in France (Dupré et al., 2006), but details on operational efforts are lacking.
These turtles have been removed from some populations using floating basking
traps (Gianaroli et al., 1999), submersible traps (Spinks et al., 2003), and shooting
(Mosimann and Cadi, 2004), but these activities were apparently not part of sus-
tained control operations. Eradication of an established population of
T. scripta
in
Queensland, Australia is being attempted using traps for basking adults and trained
dogs to detect nests (O'Keefe, 2005). Infested ponds have also been filled in and
compacted or drained, desilted, and fenced to prevent re-colonization. The success
of this project is not yet certain.
Management Limitations
As can be seen from these several examples, prevention and eradication programs
against invasive reptiles and amphibians have been sparse. This probably results
from the still-common perception that these species do not, by and large, pose suf-
ficient ecological problems that they merit the effort. Just as important, such control
operations as have been attempted have met with relatively little success. That
result stands in contrast, for example, to the situation for many mammals and
plants, where control methods and successful eradication operations are becoming
fairly routine (see, e.g., Veitch and Clout, 2002; Nogales et al., 2004; K. Campbell
and Donlan, 2005; Howald et al., 2007). There are a variety of reasons, both bio-
logical and social, for this poor rate of engagement and success, and these are worth
reviewing so as to determine whether and how this currently mediocre record might
be improved.
Control operations against alien reptiles and amphibians will very often have to
overcome three biological obstacles posed by the alien species themselves: crypsis,
high reproductive rates, and high population densities. All three may not be opera-
tive in each individual invasion, but they will be for many, and one or two of them
are likely to apply in almost all invasions. Crypsis merely refers to the fact that most
reptiles and amphibians are difficult to locate. Most species are of small size and
get by in life to a large extent by hiding from predators, including land managers
and biologists. Even species of moderate or considerable size - such as most snakes -
are remarkably effective at hiding. It has been remarked, for example, that one can
