Chasing Northern Wings
Our guest writer Sophie unveils the climate effects on Scotland’s rarest butterflies
This summer I’ve been all over Scotland, from the coastlines at Carrick Sands and Fife, to the mountains in the highlands and the Cairngorms, and to the islands of Arran, Mull and Skye, in pursuit of one thing: butterflies. Specifically, three species of butterfly, the Northern Brown Argus, Mountain Ringlet and Scotch Argus.
These three butterfly species all share one thing in common, in the UK they are only found in the north, in northern England and Scotland. They are also all considered the most vulnerable of all the butterflies in the UK to climate change.
I’m interested in these northern butterfly species in particular because they are adapted to living in colder climates. Research suggests that species living in colder environments are likely to be particularly vulnerable to climate change, and disproportionate population losses and range contractions have already been reported. The research I’m doing as part of my PhD at Lancaster University focusses on trying to understand how vulnerable these northern butterflies are to climate change. To do this, I’m looking at how well they can control their own body temperatures, as this will affect the temperatures that they actually experience day to day as the climate changes.
Butterflies are small, cold-blooded insects, and can’t control their temperature metabolically like humans, and other warm-blooded species, can. Instead, they can control their temperature using their behaviour. Even simple behaviours like changing the angle of the wings can have a big effect on the body temperatures of a butterfly. Research done using infra-red cameras has shown that different wing angles can change the body temperature of large white butterflies by over seven degrees Celsius! The angle of the wings affects how much heat from the sun that the butterfly’s body is exposed to. There are many different behaviours that butterflies can use to control their temperature, from facing towards the sun or away from the wind, moving into tall shady plants to cool down or basking on the warm, bare ground.
How well butterflies can control their temperature differs between species. Previous research has shown that the Mountain Ringlet butterfly, a small brown butterfly with orange spots that only lives high up in the mountains in the Lake District and the Highlands, is not very good at controlling its body temperature. At high temperatures, the Mountain Ringlet doesn’t seem to try and cool down. We therefore think that they may be particularly prone to overheating at high temperatures, which will become more frequent with climate change. My research looks at whether this is likely to be the case for all the other species cold adapted butterflies in the UK.
But how do you work out how well a butterfly can control its body temperature? The method I use is rather simple: measure the body temperature of the butterflies. To do this, I use a fancy thermometer, which has a thin wire attached to it. The end of the wire measures temperature, so I just have to touch the end of the wire onto the butterfly and I get a temperature reading. It’s an effective method, and means that all the butterflies I catch only have to be in the net for a few minutes, and can then be released completely unharmed. Comparing the body temperatures of the butterflies across different air temperatures lets me assess how well they can control their temperatures.
Over the last couple of summers, I’ve caught hundreds of butterflies and recorded their temperatures in this way. As part of this fieldwork, I spent a few gloriously sunny days in Skye at the start of September, staying in the Torrin bunkhouse, which is managed by High Life Highland Countryside Ranger service.
It proved to be the ideal location, as on the opposite side of Loch Slapin, Scotch Argus butterflies were flying in abundance. The Scotch Argus is a small, deep brown butterfly with orange markings, and black and white spots. On Skye, we could drive along and see them flying along the roadside verges. In England, the Scotch Argus is limited to a few populations, mostly in nature reserves and I’m used to parking up and walking to specific grid references where I’ve been told I’ll be able to find them, so being able to see them unexpectedly whilst driving along was a novelty to me!
After a busy summer, intensely watching weather forecasts (butterflies only fly on warm, sunny days which weren’t that common this summer!) and catching butterflies, I now have lots of data on the temperatures of our northern butterflies. I’ve got a lot of data analysis to crack on with, but my research should hopefully help to understand how vulnerable our northern butterflies are to climate change. From there, I’m hoping we can make more informed decisions on the best ways to conserve these beautiful butterflies.
Sophie Mowbray is a PhD student at the University of Lancaster, with a keen interest in ecology and conservation. As well as studying butterflies for her work, she also spends her spare time photographing and sharing the different butterfly species she comes across on her instagram account summerofbutterflies. She loves anything that gets her outside in nature, especially hiking long distance trails, and walks along her local canal.
Moving North
Many of us have been doing the big butterfly count this year, which carries on next week and until 4th August - if you haven’t had a look yet - here is the link. It can be completed on an app - so very simple really.
Thanks for sharing the photos and information about these beautiful butterflies.
Wow, you’ve got good at catching butterflies!