Suchergebnisse

The current experiment aimed to determine the proportion of wild-caught
possums from previously poisoned and non-poisoned populations that developed
aversions to 1080 baits. In addition, we aimed to identify the bait
characteristics mediating the ongoing aversions. In an initial test, animals
from areas previously exposed to a 1080 control-operation avoided 1080 baits
(60–80%), whereas few naive animals (0–20%) avoided
these baits. The baits comprised a green-dyed, cinnamon-lured cereal loaded
with 0.08% 1080. As a result of the exposure to the toxic baits, over
80% of the naive animals subsequently developed aversions to those
baits. Sixty-nine of these averse animals were allocated to one of 16
bait-treatment groups in a factorial design balanced for population, sex, age
and bodyweight. Each bait was characterised by four factors: (a) presence or
absence of 1080, (b) presence or absence of green dye, (c) lure type (cinnamon
or orange), and (d) bait type (No. 7 or carrot). The presence or absence of
1080 or green dye did not influence the degree of bait avoidance. Lure type
had a significant effect on consumption, with 53% of possums avoiding
an orange bait compared with 73% for cinnamon baits. Bait type also had
a significant effect on avoidance rates, with carrot baits being avoided by
42% of possums compared with 83% for No. 7 baits. Changing the
bait type would appear to hold the greatest promise for overcoming aversions
by possums to cereal bait.

Brodifacoum is a second-generation anticoagulant rodenticide used widely for controlling brushtail possums (Trichosurus vulpecula) in New Zealand. We determined its toxic effects on possums to make inferences about the welfare of brodifacoum-poisoned possums. Caged possums were fed a lethal dose of brodifacoum in cereal baits then either bled and killed 4, 8, 12, 16 or 20 days later to establish the effects on blood-clotting, or observed for behavioural changes until death. Blood-clotting time was prolonged 8 days after possums first began ingesting brodifacoum and time to death was 20.7 ± 1.7 days (mean ± s.e.m.). Clinical signs of poisoning, including changed appearance, pale noses and external bleeding, appeared from 14 days after initial poisoning (7 days before death). Possums gradually became inactive and lethargic, typically crouching and lying in abnormal postures for 6 days before death. Feed intake reduced concurrently, resulting in significant loss of body weight of 5.9 ± 2.1%. All possums had widespread, usually severe, haemorrhaging. Internal haemorrhages first appeared in all possums 8 days after initial ingestion. These haemorrhages, and consequent blood loss, may cause distress, pain, weakness or sickness, and this is supported by evidence from humans and other animals. Reduced feed intake, inactivity, lethargy and the display of abnormal postures suggest that possums do experience distress for at least 6 days before death.