Hedgehog (Photo By Gibe, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2 9948)

Dear Readers, my Zoological Society of London magazine this month had a rather troubling article about hedgehogs. Vets who were looking at dead hedgehogs sent in by members of the public for the Garden Wildlife Health project, collected between 2012 and 2020,  found that 62 percent of hedgehogs from across England had been exposed to rodenticides, such as warfarin. A quarter had pesticide residues in their livers at such high levels that it would have killed a bird of prey.

Normally, rodenticides cause internal bleeding – most of the poisons act as anticoagulants, which means that the mice and rats haemorrhage internally. However, the hedgehogs, most of whom had been killed in road accidents, didn’t show such symptoms. Scientists are scratching their heads as to what effect, if any, the rodenticides have on the hedgehogs, especially as rodent poisons are becoming more toxic  because many mice and rats now have immunity to traditional doses. The assumption is that ingesting the toxins at levels that would kill other animals can’t be good for the hedgehogs.

How are the hedgehogs picking up the rodenticides in the first place? They are more omnivorous than most people (including me) used to think, so they might be eating the dead rodents directly. They could also be eating the various invertebrates who feed on carrion, and the poisons could also leach into the soil during decay and be picked up by earthworms etc. All in all, rodenticides are causing a fair amount of havoc, not just in birds of prey and owls, but also in foxes and other predatory mammals, including domestic dogs and cats. It feels way past time that we found other ways of controlling rodent infestations, and only used these chemicals as a last resort.

I’d like to also give a shout out to the Garden Wildlife Health Project, which collates information from all over Britain in an attempt to get a picture of disease threats to our wildlife. If a creature dies in your garden, you can report it online, and will sometimes be asked if you’re happy to send off the dead animal for a post mortem. The website also has lots of very interesting advice on animal diseases, how to identify them  and what to do if a sick animal is spotted in  your garden. Well worth a look!