Environmental Engineering Reference
In-Depth Information
species richness and functional redundancy are low, and propagule pressure can be
high (Denslow 2003, Daehler 2006). Indeed, native ant species are uncommon on
most oceanic islands (Wilson and Taylor 1967) and even some large archipelagos,
like New Zealand (Valentine and Walker 1991).
h e perceived vulnerability of island ecosystems to invasion and impact by inva-
sive alien species has led some natural resource managers to consider the protection
and restoration of insular environments as impossible (Reaser
et al
. 2007). h is
pessimism is probably related to both the attributes of islands and island species
(e.g. limited ranges), and the particular operational di culties of managing islands
including isolation, the ongoing lack of su cient resources, lack of operational
capacity, and high rates of staff turnover, all of which lead to loss of morale and
institutional memory. However, numerous successes in invasive species manage-
ment on islands belie these obstacles, making for renewed optimism (Simberloff
2002; Veitch and Clout 2002).
We have four straightforward aims in this chapter. First, since documented case
histories of control programmes for invasive invertebrates are few, especially in
natural areas and on islands, we describe the evolution of the control campaign
against the yellow crazy ant
Anoplolepis gracilipes
in rainforest on Christmas Island
(Indian Ocean). Second, we crystallize the key ingredients that led to the climax
of the operational programme in an aerial baiting operation. h ird, because every
control programme operates under unique circumstances, we illustrate the com-
plexities of the actual response against generic integrated response frameworks.
Fourth, and perhaps most importantly, we evaluate the campaign to produce a list
of issues and lessons that apply not only to ongoing eff orts to suppress this invasive
ant on Christmas Island, but that might also resonate with, and inform eff orts to,
manage other intractable invasive invertebrates.
The yellow crazy ant (
Anoplolepis gracilipes
, hereafter YCA;
Fig. 11.2a), is one of
the world's 100 worst invaders (Lowe
et al
. 2000). Its area of origin is obscure, but
is typically cited as Africa where all other congeneric species are found (Wilson and
Taylor 1967). This generalist consumer has invaded many oceanic islands across
the tropics, and continents including Australia and North America (Lowe
et al
.
2000). Propagule pressure (estimated by interception rates at Australian and New
Zealand ports) and vector diversity are both high, and source regions are diverse
(Commonwealth of Australia 2006; Ward
et al
. 2006).
As in other important invasive ant species, kinship and intraspecifi c aggres-
sion in the yellow crazy ant are negatively correlated, suggesting that relatedness
facilitates supercolony formation (Drescher
et al
. 2007). Extensive, polygynous
supercolonies can form where worker ants are sustained at high densities. Given
its numerical abundance, rapid recruitment to food resources, and aggressive
