Moths play a key role in terrestrial ecosystems, providing crucial ecosystem services such as pollination and pest control. They are also a vital source of food for amphibians, birds and bats who rely on moths and caterpillars for survival.  

Each species, (both adult moths and larval forms) rely on different plants for feeding and pupating. Therefore, recording individuals of specific species can indicate what plants are growing in the area, and thus influencing habitat management. Moths respond quickly to environmental changes, for example the number of generations they can produce, species movements, species diversity and increase or decreases in species richness. Because of their species diversity and ability to respond to environmental change they are an excellent indicator for the health of habitats. Many species of moths will readily come to light traps for identification which makes moth trapping an easy way to survey the species, further adding to the suitability of using moths as ecosystem indicators.  

Moth trapping

Moth trapping is the most common way to record moth species. Moths are attracted to the light on the trap. As they enter, they get stuck, taking refuge in egg boxes inside the trap. Most moths cannot escape and will stay hidden in the boxes until first light. Recorders can then look at the moths for identification. They are then safely released. The most well used traps are Skinner, Robinson and Heath. Typically, the bulbs favoured by moth trappers are the MV bulb and attanic. These bulbs can attract moths from great distances, giving species rich and diverse yields. Whereas this can be beneficial for recording over large areas or on migratory hotspots, it does not give an accurate result for species present in very localised areas.

NB. Mercury Vapour bulbs are now banned in the UK, they can no longer be bought or sold. Any existing bulbs can still be used but must be disposed of safely.  

Westhay Moor

RoAM (Recorders of the Avalon Marshes) and Bristol university have been working to create a new kind of moth trap over the last two years. These traps are lightweight, and battery powered, meaning they can be deployed in ‘wilder’ places. They use LED lights that have been specifically designed to match the wavelength of the widest range of moth species. Having multiple small traps using LED lights gives a more detailed and reliable result.

Previous studies of Moths on Westhay Moor have been irregular and with the use of high intensity lights. Results from these traps cannot be confirmed as resident to the specific site as the distance travelled by moths to reach the trap is unknown.  

Westhay Moor is the pilot for high resolution moth monitoring, with the idea to have consistent and ongoing monitoring through April-September.  Results gathered from the traps will provide an insight into what species are resident to the site and help to monitor these populations in the future. Information from population trends will help indicate how species are responding to environmental changes and understand how this can affect the wider ecosystem. This can help to better understand the habitat we are managing at Somerset Wildlife Trust and how management techniques can help our wildlife thrive.  

Thanks to Somerset Wildlife Trust moth trappers, there is now baseline moth data that is local to not just the reserve as a whole, but a specific area. The focus area for species monitoring over the last couple of years has been the Mire at Westhay, following the peatland restoration work, it will be interesting to see how moth populations adjust and change with the environment.  

Eight moth counts were conducted through spring/summer 2024 on the Mire at Westhay Moor, on areas that had not yet been cell bunded as part of the peatland restoration work. A total of 163 moths were recorded with 51 different species identified. These results are the start of a valuable long term data set that could be used in the future to indicate how moth populations could be changing at Westhay Moor, post restoration and in relation to climate change.