Two 13-year-old girls from Devon have spearheaded an ambitious project to boost the population of harvest mice, Britain's smallest rodent, which is threatened by modern farming practices. Eva Wishart and Emily Smith, best friends and devoted naturalists, released 250 of the tiny mice into a nature reserve near Wishart's home this week.
The pair were inspired to act after learning about the species' decline due to pesticide use, multiple annual cropping, and combine harvesters. Over two years, they bred dozens of mice in 27 tanks set up in their garages, using plants like honeysuckle and hazel from Wishart's garden to create suitable habitats. The project was funded by £4,000 raised through crowdfunding, boosted by a social media share from naturalist Chris Packham.
Harvest mice are just 70 millimetres long, with sandy fur and a prehensile tail—the only UK mammal with this trait. They are important prey for larger animals and predators of agricultural pests. The release was carefully managed with a soft-release enclosure built by a carpenter, featuring tiny holes to allow mice to exit while keeping out snakes and rats.
Wishart described the mice as 'my little babies' and expressed pride in their release, while Smith admitted she would miss the responsibility. Packham, who attended the release, praised the practical project amid the biodiversity crisis. The girls plan to survey the area for nests next September and hope to release more mice in spring.
Wishart noted that the daily commitment to care for the mice is minimal—just 10 minutes—and contrasted it with peers' screen time. Her first attempt at breeding mice faced a setback when a neighbour's cat ate three of four mice, but the fourth survived and gave birth. For her next project, Wishart aims to release common lizards into the same reserve.
