Spanish butterflies are better than British species at regulating their body temperature – but may be at greater risk of extinction, warns new research.
An international study, led by the University of Cambridge and the Institut de Biologia Evolutiva, has found that different butterflies use different methods to regulate their internal body temperature.
Butterflies in Catalonia in northern Spain angle their wings towards the sun, while butterflies in the UK rely on finding microclimates – a technique which can sometimes be less effective. However, as climate change sees global temperatures increase, both populations will face new challenges.
Butterflies switch from heat-seeking to heat-avoiding behavior once air temperatures reach approximately 22° C (71.60 °F) , meaning British butterflies, used to colder environments, may initially benefit from the hotter climates. However, they will still be threatened by possible habitat loss caused by global warming.
Spanish butterflies, on the other hand, already existing in warmer weather, may find themselves in more immediate danger – with extinction a possibility if they do not adapt quickly enough to climate change.
“Like all insects, butterflies are ‘cold-blooded’ and use their environment to regulate their internal temperature. We found that, on a community level, butterflies in Catalonia were better at regulating, or buffering, their body temperature than butterflies in the UK,” said lead author Eric Toro-Delgado.
“This could be because butterflies in Spain have more thermal options available to them, whereas many landscapes in the UK do not provide a sufficient diversity of thermal options such as alternating areas of shade and sun,” he added.
“However, as temperatures rise, butterfly populations in Catalonia may be at greater risk since they are already near their optimum body temperature – meaning they could be in danger of overheating. Meanwhile, as the UK’s climate becomes more like Spain’s, British butterflies may initially benefit,” he continued.
In the long term though, British butterflies will be at risk too as they rely on different habitats for body regulation – habitats that may be destroyed as temperatures rise.
“Species that rely mostly on sun to warm up and shade to keep cool are at the greatest risk of population decline, due to climate change causing a loss of biodiversity and habitats,” explained Dr Andrew Bladon, the study’s senior author.
“So, if we can provide butterflies with biodiverse road verges, more wildflowers, more trees, and longer grass, they may be able to more easily move through the landscape, helping them find their preferred temperatures so they can thrive,” he added.
He added that initiatives such as ‘no-mow May’ could further counter habitat loss – helping butterflies survive. The study, published in the Journal of Animal Ecology, was conducted by measuring the body temperature, air temperature, and perch temperature of almost 800 adult butterflies from 23 different species in Spain.
These results were then compared with similar data collected from butterflies in the UK in 2020. In addition to the findings about differences in thermoregulation, the research team also discovered that the size of a butterfly’s wings was more important in the UK than in Spain.
“This is likely because in a warm country like Spain, the ability to avoid heat is preferable, and wing size may play a less relevant role in this than in warming up,” said Toro-Delgado.
Toro-Delgado also warned about the other dangers butterflies may face as a result of climate change – such as associated impacts like droughts and heatwaves. These extreme weather events can not only push butterflies past their body temperature limits but can also kill the plants that their caterpillars rely on.
“Climate change is a two-pronged attack that can take out both adult butterflies and their caterpillars. Climate change and biodiversity loss go hand-in-hand, and we urgently need to address both if we’re going to protect important species like butterflies,” he said.
Produced in association with SWNS Talker
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