Environmental Engineering Reference
In-Depth Information
such negative beliefs about owls, as part of their research, these authors asked farmers about their
use of pesticides (since they could pose an obvious threat to owls feeding on farm pests, particu-
larly rodents). Although they reported that agricultural pests posed the most serious threat to their
livelihoods, only 28% of farmers stated that they used pesticides to control vertebrate pests such as
rodents and mousebirds (Collidae), which feed on their crops. Of these, 45% admitted using Furadan
to poison rodents and to a lesser extent, mousebirds.
The (mainly poor) farmers interviewed stated that they used Furadan, due to its high toxicity
(and hence its effectiveness), its affordability and its widespread availability. Field observations
confi rmed largely unsuccessful attempts at poisoning rodents and mousebirds by slicing open a ripe
tomato still attached to the plant and smearing a layer of Furadan on its surface (a practice also car-
ried out in Croatia, see Chapter 5) in anticipation that the pests would feed on it and die. The authors
received anecdotal reports from fi eld workers that a number of mousebirds poisoned by ingesting
Furadan were later consumed, presumably while in an incapacitated state, by a Mackinder's eagle
owl (
Bubo capensis mackinderi
) that itself died.
3.5.2 Effects of Furadan on vulture populations in Kenya
Of all the wildlife species in Kenya, vultures have suffered disproportionate declines due to Furadan
poisoning, more than any other non-target species. Although lions have likely been hardest hit in
terms of their overall population declines, vultures are hands down the largest unintentional victims
of poisoning due to their reliance on carrion for almost their entire diet (Mundy, Butchart, Ledger
et al. 1992). In addition, vultures are extremely vulnerable to poisoning because they forage commu-
nally, often in very large numbers, which means hundreds can be killed at a single poisoned carcass.
Reports of mass vulture deaths in Africa due to poisoning are numerous (e.g., Borello 1985; Allen
1989; Anderson 1984; Simmons 1995). In April 2004, S. Thomsett witnessed the after effects that
one carcass baited with Furadan can have on the scavenger community. In this incident, 187 vultures
of three species perished alongside a number of spotted hyenas (
Crocuta crocuta
) in the Athi River.
Vulture samples collected and analysed by the Government Chemist tested positive for residues of
carbofuran (Government chemist, unnamed, personal communication, 2004).
Since 2007, conservationists in Kenya have recorded the deaths of 366 vultures due to poison-
ing (J. Clark, unpublished data) and this number is likely an underestimate of the actual total. Not
included in this amount are other well-known scavenging birds including bateleurs (
Terathopius
ecaudatus
), tawny eagles (
Aquila rapax
), Steppe eagles (
Aquila nipalensis
), fan-tailed ravens
(
Corvus rhipidurus
), and Marabou storks (
Leptoptilos crumeniferus
), many of which have perished
from consuming baited carcasses (J. Clark, unpublished data). Though the majority of poisoning
cases (as supported by laboratory tests or strong anecdotal evidence) are linked to Furadan, other
pesticides have also been used to poison wildlife, including amitraz (an antiparasitic agent/acari-
cide), cyhalothrin (a pyrethroid insecticide) and Marshal (carbosulfan, another carbamate whose
chemistry is briefl y detailed in Chapter 1).
Because they travel long distances to fi nd carcasses and reproduce slowly, vulture populations
can be extremely hard hit by wide-scale poisoning and their populations are slow to recover, if at all.
A decade ago, none of the vultures found in Kenya were listed on the IUCN Red List of Threatened
Species. At present, fi ve out of eight species are Red-listed and populations continue to decline
(Ogada, Torchin, Ezenra et al., in review). In fact, no other functional group of birds has faced such
a heightened threat of extinction within the last decade.
Two recent studies confi rm that Kenya's vultures are declining rapidly. Virani and colleagues
(2010) documented large declines of vultures and other scavenging birds in and around the Masai
Mara National Reserve over the last 30 years. Staggering declines in abundance were recorded
for seven of eight scavenging species. Signifi cant declines were recorded for Egyptian (
100%),
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