Rare insects found during North Yorkshire bat survey point to climate change

Sounds of animals were recorded at more than 140 locations along the river. Though primarily a project for surveying bat species and numbers in the area, the project picked up a number of other mammals as well as insects, including a species of cricket never before recorded by the survey.

Of the 390,000 recordings of bats between May and September, at least eight different species of bat were confirmed, with the Common Pipistrelle responsible for more than 200,000 recordings.

The project has run since 2020 and relies on the contributions of dedicated volunteers and citizen scientists to conduct bat monitoring. Anybody can sign up to collect the equipment and set it up in a pre-arranged location where it is left for four nights. The devices are triggered when they detect ultrasound, such as the echolocation calls of bats, but also noises from certain other animals, including shrews, rats, moths and crickets.

Incidental recordings of other species are analysed by researchers who run the survey, and provide clues to changes over time.

Toby Panter, Ryevitalise Conservation Field Officer said: “This year has been our biggest survey to date, covering 141 different locations in the River Rye catchment and recording over 144 different nights between May and September. It’s great to see strong results for species such as the distinctive brown long-eared bat and for Daubenton's bat – known as the water bat due to its preference for hunting insects over rivers.

“As well as bats we recorded two different shrew species, and making its debut this year was Roesel’s bush-cricket, which was heard in not just one, but four locations and across eight different nights.”

The Long-winged Conehead was the first cricket recorded by the survey, last year. It was recorded again in 2023 alongside two more cricket species, which suggests significant changes in the national distribution of these insects.

Data from the North York Moors National Park supports other studies which report cricket populations spreading northwards.

Roesel’s Bush-cricket was only found at a small number of marshy sites in the east of England up to the 1980s, however it has since spread inland in all directions. Meanwhile, the Long-winged Conehead was previously featured on the Red Data List because it was considered so rare in Britain, although it has since become common in southern and eastern England.

Climate change is widely accepted by ecologists to be behind the successful spread of the invertebrates, although an increase in uncut road verges and grasslands may also have contributed.

“The only slight disappointment,” Toby continues, “is that we didn’t hear our rarest species, the Alcathoe bat this year, but they’re very much known for being an elusive and mysterious species. There’s always an element of luck required in these surveys, and we hope to hear it again in 2024.”