Medicinal leech

Invertebrates play crucial roles in keeping ecosystems healthy and functional. From pollination to waste recycling, to filling crucial links in food webs, invertebrates do it all! If we want to save big, fluffy species, we need to conserve wee beasties too – even bloodsuckers like the medicinal leech (Hirudo medicinalis).  

This species is a type of worm, but unlike their land-dwelling earthworm cousins, medicinal leeches spend most of their time in water and feed exclusively on blood. They have two suckers, a posterior (back) sucker, used as leverage to move and an anterior (front) sucker, used for feeding.

These fascinating animals were historically used at a massive scale in medicine around the world. Overharvesting of leeches for medical purposes, combined with habitat loss and freshwater pollution has resulted in a decline of the species. Medicinal leeches are found in just three locations in Scotland and are classed as Near Threatened globally by the IUCN.  

To boost the population of medicinal leeches in Scotland, in 2023 RZSS started a conservation breeding programme for the species in a specially designed facility at Highland Wildlife Park. Working in partnership with Buglife as part of the Species on the Edge Initiative, we aim to breed enough leeches to start new populations in suitable lochs around the country.