Environmental Engineering Reference
In-Depth Information
100
80
60
40
20
0
0
20
40
60
80
100
Pre-treatment YCA activity (ants card
-1
30s
-1
)
Fig. 11.5
The knock-down effect of Presto
®
01 ant bait on the activity of
the yellow crazy ant at 44 waypoints, 1 month before, 1 month after aerial
broadcast of Presto 01. X axis is the number of ants running across a 100 cm
2
card in 30 s, averaged across 11 cards placed on the soil surface along a
transect at each waypoint. Note that over the entire range of ant activity,
knockdown was consistent, i.e. density independent.
error, mostly as the result of occasional overshoots on baiting runs. A total of 9 ha
were missed, including a 6 ha in the north-west of the island which could not be
baited because of the high density of fl ying seabirds.
Pre- and post-baiting surveys of ant activity were conducted at 44 waypoints
in supercolonies from the IWS to measure e
cacy of control. At each waypoint,
card counts of YCA were used as per the IWS and the aerial baiting trial. Ant activ-
ity at each site was assessed once 1 month before and 1 month after waypoints
were treated. YCA activity declined precipitously following aerial treatment
(Fig. 11.5). Ant activity fell from 21.6
±
18.7 ants/30s (SD) prior to treatment,
±
to 0.13
0.50 ants/30s after treatment, an average decline of 99.4%. h e decline
>
was
97% at 40 of 44 waypoints, and 100% at 77% of waypoints. h is met the
target of 99% knockdown set by the steering committee prior to the aerial baiting
operation.
11.3.2.7 Non-target impacts
Aerial broadcasting of tonnes of toxic bait in the National Park had the potential
to cause serious impacts to non-target species of special conservation signifi cance.
These included endemic reptiles, several endemic land birds, an endemic seabird,
and an unknown number of endemic invertebrates.
Although fi pronil is toxic to crabs, the risk posed to the red crab population by
the aerial baiting campaign was considered minimal because resident red crabs
were already annihilated within supercolonies. Furthermore, live crabs near the
