If you were down at Penns Place a few Saturdays ago, you might have noticed a little black spaniel in a bright orange vest.

A little black cocker spaniel looks at the camera expectant. Next to him is a woman in orange high vis jacket and a baseball cap. she smiles proudly. — River and handler, Lucy Wilde are the only detection dog and conservationist duo in the UK working on signal crayfish

River is unique: the only conservation dog in the UK trained to find signal crayfish (Pacifastacus leniusculus), an American invasive species that was farmed as a delicacy in the UK in the 1960s and escaped into the wild.

The signal crayfish is a well equipped predator and will eat vegetation, small invertebrates and fish, including young native crayfish. If they’re hungry, they will turn on each other. They grow up to 18cm and burrow up to two metres deep into waterway banks, damaging habitat and leaving canals vulnerable to collapse.

a small black working cocker spaniel holds its nose to the high sandy river bank. — River indicates with a freeze when she detects the presence of a signal crayfish. Photo: Lucy Wilde

As if this weren’t enough, they also carry “crayfish plague”, a fungal disease, which is fatal to the UK’s native white-clawed crayfish. The native crayfish has declined drastically to the point of extinction. The situation is akin to that of the invasive grey and native red squirrel.

River’s handler, Lucy Wilde explains to Dogs with Jobs presenter, Kate Fairweather, how River has ended up with this specialised role, and what her working life looks like. Huge thanks to Lucy for stopping by Petersfield to give a demo.