Biology Reference
In-Depth Information
risky, success uncertain, research costs high, and funding difficult to justify (e.g.,
Colvin et al., 2005). It remains to be seen whether such approaches will ever be
relevant to control of reptiles and amphibians, but skepticism is justified.
For most invasive reptile and amphibian species we are in a similar position to
where we were in the early 1990s with brown treesnakes or in the late 1990s with
coqui - effective control methods have yet to be investigated or even identified.
This makes it difficult for managers to respond to reptile and amphibian invasions
even when they have the desire to do so. Paucity of management tools is likely to
remain a serious roadblock for effective action against invasive reptiles and amphib-
ians for many years to come.
Many of these identified biological and social constraints have been relevant to
each of the species against which control operations have so far been attempted
(Table 4.1), and this concatenation of constraints has undoubtedly been important
in generating the poor record of control success to date. These same limitations will
undoubtedly pertain across a wide variety of additional herpetological invasions not
yet engaged with. Generally stated, the problem is that the high reproductive rates
and high densities formed by many reptiles and amphibians enforce a narrow
window of opportunity during which eradication can potentially succeed. Failure to
act before this window closes means that most species will rapidly become so dense
and widespread that effective action is soon impossible. Running counter to this
biologically driven need for a rapid response is the fact that crypsis and the four
social constraints - especially entrenched disbelief and undeveloped control
Table 4.1
Constraints operative in control operations already attempted against reptile and
amphibian species. + indicates the constraint is operative, − indicates it is not. Number of symbols
is my rough estimate of the relative degree to which the constraint applies. Crypsis likely applies
to all of these species at one stage of their life cycle or another, but I use the symbols to indicate
the degree to which it hinders effective control operations
Constraint
High rate
of repro-
duction
Opposition
to killing
species
Lack of
control
methods
High
density
Disbelief
in problem
Support for
invasion
Species
Crypsis
Bufo marinus
+
+++
+
−
−
−
−
Bufo gargarizans
+
+++
+
−
−
−
−
Eleutherodactylus
coqui
−
+
+
++
+
+
++
Limnodynastes
dumerilii
+
+++
?
−
−
−
−
Rana catesbeiana
+
+++
+
−
−
−
+
Varanus niloticus
−
+
−
−
−
−
++
Boiga irregularis
++
−
+
+
−
−
++
Python molurus
++
+
?
+
−
−
++
Trachemys scripta
−
−
−
?
?
?
−
