Biology Reference
In-Depth Information
and had a far more lasting effect on this invasion. I know of no other instance in
which this social factor has yet served as a barrier to herpetological control efforts,
but the fact that “animal-rights” groups have even opposed eradication efforts
directed against rats (Howald et al., 2005; Towns et al., 2006) suggests that it is only
a matter of time before such opposition becomes relevant for other herpetological
invasions too. Even without organized opposition to removing alien herpetofauna,
area residents often like these animals and oppose their removal (e.g., Enge et al.,
2004a). The same can be true for members of the scientific research community
(e.g., Holden, 2003).
Control methods effective against invasive reptiles and amphibians, as a group,
have been barely researched or applied. As previously noted, considerable research
in this direction has been expended against brown treesnakes on Guam. Some of
these methodologies are likely to have application against other invasive reptile
species, but unmodified transferral is by no means certain and seems unlikely in
many cases. For example, traps have proven quite effective at reducing brown tree-
snake populations in sensitive port areas on Guam, but those traps are biased toward
capturing large animals, trap design took many years of careful research to opti-
mize, and the design is sufficiently particular to brown treesnakes that it cannot
automatically be applied against other snake populations, such as pythons or water
snakes. Indeed, an attempted application of brown treesnake traps to control
Lycodon aulicus
in the Mascarene Islands failed (Rodda et al., 2002). This is not to
suggest that knowledge gained for controlling brown treesnakes is irrelevant to
other species, only that additional research will often be required to shape that
knowledge to create an effective tool to use against the biological peculiarities of
the next focal species. Similarly, identification of concentrated caffeine (Campbell
and Kraus, 2002) and citric-acid solutions as effective sprays for killing coqui is
likely to have application to some other frog invasions, even though the need for de
novo development of these techniques in Hawaii helped delay operations against
coqui until such point as total eradication was impossible. Recent work in devising
control methods for cane toads has focused on development of traps, attractants,
toxins, exclosures, biocontrol, and sterile-male release methods (R. Taylor and
Edwards, 2005; Molloy and Henderson, 2006; Schwarzkopf and Alford, 2007).
None of these techniques is yet perfected for that species, but should they be, they
may prove useful against other anuran invaders as well.
The prospect of using parasites as biological control agents against certain
herpetological pests - in particular, brown treesnakes and cane toads - has been
considered (e.g., Whittier et al., 1997; Whittier and O'Donoghue, 1998; Holzman,
1999; Telford, 1999; Caudell et al., 2002; T. Robinson et al., 2005) but has not
progressed very far. This likely reflects the difficulty of guaranteeing host specifi-
city, vector availability, and demographic significance of biocontrol enemies for
most vertebrate species (Howarth, 1999; T. Robinson et al., 2005; Rodda and
Savidge, 2007). Indeed, even clinical effects may be lacking in heavily parasitized
animals (e.g., Caudell et al., 2002; Jakes et al., 2003), and it remains to be determined
to what extent reptile and amphibian populations may be ecologically limited by
parasitism. All this makes use of biocontrol against invasive herpetofauna highly
