Gemmeke (1995) Investigation of the hazard of secondary poisoning of hedgehogs by mataldehyde ingested by slugs on arable land

Title: Investigation of the hazard of secondary poisoning of hedgehogs (Erinaceous europaeus L.) by metaldehyde ingested by slugs on arable land, A Deutsche Pflanzenschutzdienst Publication. 1995

Authors: H. Gemmeke

Country: Germany

Background to study

A controlled experiment using wild captured hedgehogs to identify whether hedgehogs eat metaldehyde-poisoned slugs and whether ingestion causes them to exhibit symptoms of poisoning.

Method

• 20 hedgehogs were captured in the wild using a hand-held sight and kept in captivity being fed cat food for one week to acclimatise.
• Six of the hedgehogs were kept as control (3 males and 3 females) and six others that were observed eating dead slugs provided in addition to cat food after the acclimatisation were retained as test animals.
• Slugs were poisoned with Lonza AG slug pellets with 5.88% metaldehyde active ingredient and after 2-4 hours were removed and refrigerated prior to the trials.
• Slugs showing symptoms of poisoning were presented to the test animals in batches of 200 and observations on the feeding of slugs and behaviour following ingestion were undertaken for 3 days.
• Hedgehogs were recuperated for a period of one week prior to release back into the wild.

Key results

• Four hedgehogs ate 0, 12, 196 and 198 of the 200 slugs provided and the remaining two at all 200 of the slugs offered suggesting that there is variation between individuals in their choice to eat dead slugs.
• None of the test animals showed any adverse symptoms, behavioural differences or signs of poisoning when compared with the control animals.

Key messages to landowners and managers derived from these results

• There was no evidence to suggest that slugs poisoned with metaldehyde are fatal to hedgehogs, however there is evidence elsewhere to suggest that ingestion of metaldehyde pellets by hedgehogs can be fatal.
• Commercial retailers and producers of metaldehyde slug pellets should provide clear guidance on the risks of using slug pellets in both domestic gardens and in agricultural areas on hedgehogs.
• Consumption of fatal doses of slug pellets by hedgehogs may be avoided by scattering pellets rather than leaving them in piles as these may be mistaken for anthropogenic food sources which have been found elsewhere to attract hedgehog foraging and density in urban areas.