Biology Reference
In-Depth Information
logistical difficulties for most turtle fanciers, being decidedly less easy to arrange
than the release of a large number of small frogs or lizards. Conversely, the large
number of releases of single or few pet turtles is not logistically burdensome and
is correspondingly larger.
One may also upend this matrix of relationships to examine pathway importance
for each herpetological taxon (Fig. 2.13). This confirms that crocodilians have been
introduced entirely deliberately, that the same is virtually true for salamanders, and
that the other taxa have been introduced for a greater diversity of reasons. Frogs and
lizards have been introduced via all six pathways, with lizards having a slightly
more balanced distribution of introductions across the six pathways than do frogs.
Introductions of snakes have involved all pathways except food, and turtles have
been introduced mainly through the pet trade and “intentional” pathways, but intro-
ductions for food have also been important.
It is of considerable importance to stress that establishment success rates vary
across pathways, a result hinted at by contrasting the relative histogram heights in
Fig. 2.8 vs. Fig. 2.10 or Fig. 2.9 vs. Fig. 2.11. Examined directly, introductions via
the nursery trade, biocontrol, and food pathways have had a higher establishment
success rate than those arriving via the “intentional”, cargo, or pet trade pathways
(Fig. 2.14). As pointed out earlier (Kraus, 2003c), this is unsurprising because the
two deliberate pathways of biocontrol and food have often involved well-funded
programs supported by scientific or agency personnel and have often resulted in the
coordinated release of many individual animals. This focused, scientifically
informed effort with large numbers of propagules has no doubt contributed to
making these pathways more likely to lead to population establishment than the
other deliberate pathways involving the pet trade and private “intentional” introductions
Fig. 2.13
Relative pathway importance for each reptile and amphibian taxon. Biocontrol = dark
blue, cargo = red, food = yellow, nursery trade = blue, pet trade = brown, and “intentional” =
green
