Hopes for the Tansy beetle at the Canal and River Trust’s Naburn Lock near York

The tiny, iridescent Tansy beetle, or Chrysolina graminis, is listed in the UK as an endangered species.

Yet, like Yorkshire folk who know God’s own county is the only place to live, it seems the Tansy beetle agrees.

It almost exclusively resides on a short 30-mile ‘corridor’ of the River Ouse, from Linton-on-Ouse in the north to Selby in the south (though two much smaller colonies have in recent years been rediscovered in the Cambridgeshire Fens).

The Ouse population is thriving. Annual surveys undertaken for more than a decade by the Tansy Beetle Action Group (TBAG) - a partnership of local and national organisations working together to conserve the Tansy beetle - show that while numbers fluctuate along this corridor, 40,000 beetles were estimated at its peak in 2016.

The presence of tansy beetles fluctuates according to the prevalence of clumps of Tansy plants; as well as being this leaf beetle’s primary food source, it’s also where this beetle deposits its eggs and its larvae grow.

The Tansy beetle population isn’t evenly spread, with some Ouse colonies boasting a denser population than others. And sometimes the beetles need a bit of help to move between Tansy clumps along this corridor, as, unlike some other species, they prefer to walk rather than fly.

This is one reason a new colony has been introduced at Canal and River Trust’s Naburn Lock by one of the charities ecologists, Phillippa Baron, and Dr Geoff Oxford, Honorary Fellow in the Biology Department at the University of York who, along with his wife Roma, has been investigating the biology of the Tansy beetle for more than three decades.

“Creating safe havens, where beetle populations can be protected from summer flood, is important to preserve beetle numbers,” explains Geoff.

“The Tansy plant naturally thrives at Naburn and with the many visitors to Naburn Lock, it’s an ideal site for an ‘educational’ population of the beetle to be established, where families can take their children to have a look for the beetle and learn more about it.”

Geoff and Phillippa chose a Tansy clump in a quiet, elevated spot on the site and worked with City of York Council on an information board, so people can read all about the beetles and their habitat.

Geoff collected the 40-plus beetles for release at Naburn from a colony further up the river at Nun Monkton, which he and Phillippa released in June. This gave the population time to establish and breed before the adults die in July and the larvae go underground to pupate, reappearing above ground again in August as fully grown adults, before going back underground in autumn to over winter, avoiding the worst of the flooding season.

“We really hope this colony thrives – the population we introduced on the Selby Canal is successful and has expanded and grown,” adds Phillippa.

“Nature and wildlife conservation along our canals and riverbanks is an important part of Canal & River Trust’s work and we know that nature and wildlife attract people to visit our rivers and canals.

So, it’s great that we can work with partners to educate people about a rare and endangered species such as the Tansy beetle.”

Naburn Locks were once busy with barges transporting goods to and from near by York and Hull.

The first lock at Naburn was built in 1757 – one of the earliest examples of canal engineering in the country- and in Victorian times, a larger lock was built alongside the original one to allow large freight barges to pass through. It was opened Queen Victoria’s grandson, Prince Albert Victor.

The Trust was launched in 2012, taking over the guardianship of British Waterways’ canals, rivers, reservoirs and docks in England and Wales.

It creates new routes for people to work and places to enjoy, while also helping thousands of people young and old develop their confidence and learn new skills.

For more information, visit: canalrivertrust.org.uk