Medicinal leech conservation breeding programme

As we face global declines in biodiversity, the Royal Zoological Society of Scotland (RZSS) has pledged to reverse the decline of at least 50 species by 2030. In Britain, medicinal leeches are currently restricted to a handful of sites (In Scotland there are just three known sites) and the species has also become rare across its European range. To help boost the wild population in Scotland, our charity is undertaking a conservation breeding programme for the species.

Medicinal leeches are a type or worm, but unlike land-dwelling earthworms, they spend the majority of their time in water. They have two suckers, a posterior sucker, used as leverage to move, and an anterior sucker, used for feeding.

This species of leech can grow up to 20cm and are very colourful, with clear stripes on their back and highly variable speckled patterns on their underside. Medicinal leeches in Scotland tend to have a darker colouration that their relatives in England, which can make the stripes harder to see.

Medicinal leeches get their name from a time when they were heavily used for bloodletting in medicine. Unfortunately, overharvesting of leeches for medical purposes, combined with habitat loss and freshwater pollution has result in a decline of the species, which is now extinct in much of its former range, with the IUCN categorising it as globally Near Threatened. The purpose of our new breeding programme is to breed enough medicinal leeches to be able to release them into new sites in Scotland, safeguarding the species against extinction.

To help us achieve this, we have constructed a bespoke facility at Highland Wildlife Park to give the medicinal leeches the best possible chance of successfully breeding and producing more leeches for release into suitable habitats. Our expert team will draw on knowledge from years of experience delivering breeding and release programmes for other invertebrates like pine hoverflies and dark bordered beauty moths. Close monitoring of the species will also provide opportunities for us to learn more about them.

This work is in collaboration with Buglife Scotland and Species on the Edge.

This project is also supported by the Nature Restoration Fund and Species on the Edge.