- The rare moth is limited to just one location in England—Strensall Common, a protected area of lowland heath close to the city of York.
- But moth numbers are declining by an average of 30-35 percent per year.
- The moths’ rapid decline is most likely being driven by a reduction in its host plant—the Creeping Willow, researchers say.
The dark bordered beauty moth is heading towards extinction at its last known site in England, a new study has found.
The rare moth (Epione vespertaria) is found in just a handful of locations. Scotland, for example, hosts a few small populations of the moth. In England, the rare moth was previously found at Newham Bog in Northumberland, but is now considered extinct there. Now, the tiny insect is limited to just one English site — Strensall Common, a protected area of lowland heath close to the city of York. And this last English population is declining rapidly, according to the study published Wednesday in PLoS ONE.
“The Dark Bordered Beauty is a very special and charismatic moth, which has been observed and admired at Strensall Common for well over a century,” co-author Terry Crawford of the University of York, said in a statement. “It has long been part of the natural history heritage of England and of Yorkshire. Because of the loss of populations elsewhere in England, the loss of the population at Strensall Common would mean extinction of the moth in England as a whole.”
Prior to 2007, about 500 to 1,000 dark bordered beauty adults were thought to occur in Strensall Common. But when scientists monitored the northern part of the Common between 2007 and 2014, they found that adult moth numbers were declining by an average of 30-35 percent per year, indicating that there might be fewer than 100 individuals remaining.
The moths’ rapid decline is most likely being driven by a reduction in its host plant — the Creeping Willow (Salix repens), the researchers say.
Previous studies have shown that the moths tend to concentrate in a few hotspots at the Common that have large, healthy Creeping Willow patches at high densities. One of these areas was destroyed in a fire in 2009. Additionally, increased sheep grazing and damage due to frost may have caused a decline in suitable host plant patches, the study speculates.
Female dark bordered beauty moths prefer to lay eggs on tall, healthy Creeping Willow plants. The researchers think that the shortening of plants due to grazing and damage due to frost could have resulted in a decline in moth numbers.
So grazing, which is currently used as a management strategy at the Common to prevent the habitat from becoming overgrown with trees and taller shrubs, may be pushing the rare moths towards extinction, the authors write.
“Our study indicates the potential conflict between generic habitat management and bespoke management for species,” co-author Peter Mayhew, also from the University of York, said in the statement. “It is vital that monitoring programmes are integrated into site management so we can increase our knowledge of rare species that rely on such habitats in a specific way. We must also not be complacent when species are restricted to a single site, even if their population at first appears healthy.”
- Baker D, Barrett S, Beale CM, Crawford TJ, Ellis S, Gullett T, et al. (2016) Decline of a Rare Moth at Its Last Known English Site: Causes and Lessons for Conservation. PLoS ONE 11(6): e0157423. doi:10.1371/journal.pone.0157423