Edible contraceptive shows promise for management of grey squirrels in the wild. A method of managing populations of grey squirrels has taken a significant step forward, aided by Roslin expertise.A contraceptive designed for use in the animals has been shown to be effective in rats, in a key step towards its application in squirrel habitats.Experts are now focused on increasing the scale and longevity of the treatment, so that it may be used in the wild. This would help to manage the threat posed by grey squirrels, which can spread disease to the endangered native red population, as well as taking over habitats. Immune response The research, led by the UK Government’s Animal and Plant Health Agency (APHA), found that rats in a lab setting were rendered infertile by ingesting a contraceptive in the form of a vaccine. The treatment triggers an immune response that causes the body to produce antibodies against reproductive hormones, interfering with the reproductive system and causing infertility.The vaccine is contained in a capsule, made from plant pollen spores by Sporomex, which is designed to have minimal environmental impact, and can be added to food bait.These vaccines have also been shown to have an effect on captive grey squirrels, and studies are ongoing. For this final, crucial part of the work, APHA is collaborating with experts from the Roslin Institute and MV Diagnostics to increase the scale and duration of these vaccines suitable for taking into the wild.Roslin experts have provided advice on immune response measurements in research towards the treatment, which aims to offer a safer, more ethical method of population control compared with traditional methods.Parallel efforts are ongoing to develop a feeding station that is accessible only to grey squirrels, with options including a weight-sensitive door enabling access to bait.Together the initiative should enable an effective, non-lethal and low-maintenance option for managing a widespread invasive species. The research is funded by the UKSA, a partnership of 45 signatories, and the UK Squirrel accord. Red squirrel populations face threat of disease and loss of habitat from grey squirrels. We are pleased to be involved in this exciting project that could enable the development of a manageable, humane solution for control of populations such as grey squirrels. Professor Jayne Hope Roslin Institute I’m really encouraged by the progress we’ve made in our research so far as part of this important partnership project. These breakthroughs are a positive step forward towards a grey squirrel management tool that will mean so much for our UK woodlands. Bex Pinkham Animal and Plant Health Agency We are excited to be involved in this groundbreaking research. Developing an immuno-contraceptive that could be used in this way has major implications for the ethical control of wildlife pests. Spokesperson, MV Diagnostics The Roslin Institute receives strategic investment funding from the Biotechnology and Biological Sciences Research Council and it is part of the University of Edinburgh’s Royal (Dick) School of Veterinary Studies. Related links The UK Squirrel Accord Publication date 25 Sep, 2025
