Les hommes ont oublié cette vérité. Mais tu ne dois pas l'oublier, dit le renard. Tu deviens responsable pour toujours de ce que tu as apprivoisé.
Le Petit Prince, chap. 21

Sunday 17 November 2013

Secondary poisoning of feral cats in NZ

Three papers analyse different effect of secondary poisoning on feral cats.

Alterio, N. (1996). Secondary poisoning of stoats (Mustela erminea), feral ferrets (Mustela furo), and feral house cats (Felis catus) by the anticoagulant poison, brodifacoum. New Zealand Journal of Zoology, 23(4), 331-338.

A poisoning operation using Talon 20P™, active ingredient brodifacoum, targeting rabbits (Oryctolagus cuniculus) in coastal grasslands on the Otago Peninsula, New Zealand, also killed stoats (Mustela erminea), ferrets (Mustela furo), cats (Felis catus), and mice (Mus musculus) and probably possums (Trichosurus vulpecula), hedgehogs (Erinaceus europaeus), rats (Rattus rattus), hares (Lepus europaeus occidentalis), and chaffinches (Fringilla coelebs). A new immigrant ferret also died 41 days after poisoning. If repeated in other habitats such as tussock grasslands and forests this method could greatly assist in restoration of mainland ecosystems and mitigation of bovine tuberculosis (Mycobacterium bovis) by controlling a variety of pests/ Tb carriers in one operation. The removal of small mammalian predators following poisoning operations could decrease immediate predation pressure on native wildlife. However, the efficacy of this multi‐species pest control method and unwanted side‐effects must be researched before its routine use. This research also demonstrates the potential threat of second‐generation anticoagulantpoisons such as brodifacoum to small mammalian carnivores with high conservation value in their native countries.

Heyward, R. P., & Norbury, G. L. (1999). Secondary poisoning of ferrets and cats after 1080 rabbit poisoning. Wildlife Research26(1), 75-80.

The incidence of secondary poisoning was determined by using radio-telemetry to assess the survival of 68 ferrets and 21 cats on two treatment sites and one control site in the dry tussock grasslands of New Zealand. The treatment sites were aerially poisoned with 1080-coated carrot baits (0.02% wt/wt) to control rabbits. The control site was not poisoned. Ferrets and cats were monitored at two-weekly intervals for at least 1 month before, and 2 months after the poison operations. Muscle samples from ferrets and cats that died within 50 days of poisoning on the treatment sites were assayed for 1080. In all, 7–11% (n = 28) of ferrets on one site and 8–15% (n = 26) of ferrets at the other site apparently died of secondary 1080 poisoning. Natural mortality rates of ferrets were 46–81% per annum. While we have evidence that secondary poisoning of cats does occur, we monitored insufficient numbers of cats to reliably estimate mortality rates.

Declines in predator numbers are commonly observed after rabbit poisoning. This study indicates that secondary poisoning contributes to these declines.

Gillies, C. A., & Pierce, R. J. (1999). Secondary poisoning of mammalian predators during possum and rodent control operations at Trounson Kauri Park, Northland, New Zealand. New Zealand Journal of Ecology23(2), 183-192.

A poison baiting operation at Trounson Kauri Park in Northland, New Zealand using first 1080 and then brodifacoum targeted possums (Trichosurus vulpecula) and rodents (Rattus rattusRattus norvegicus and Mus musculus). Predatory mammals were monitored by radio telemetry during the operation. All six feral cats (Felis catus), the single stoat (Mustela erminea) and the single ferret (Mustela furo) being monitored at the beginning of the operation died of secondary poisoning following the 1080 operation. A further two cats and four stoats were monitored through the ongoing poisoning campaign using brodifacoum in a continuous baiting regime. None of these radio tagged carnivores died of secondary poisoning. However, tissue analysis of additional carnivores trapped at Trounson found that cats, weasels (Mustela nivalis) and, to a lesser extent, stoats did contain brodifacoum residues. The duration that the radio-tagged predators were alive in and around Trounson Kauri Park suggests that the secondary poisoning effect was much reduced under the continuous baiting strategy compared to the initial 1080 poison operation.

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