The importance of temperature for rare butterfly

Exeter University research investigates the importance of temperature for rare butterfly.
2019 is proving to be a year of climatic extremes. Hot, sunny weather back in February saw the mercury hitting 20°C in some parts of the country, while in July the UK’s all-time maximum recorded temperature was exceed with a new record of 38.7 °C. Current research at the University of Exeter is helping to uncover how temperature affects our wildlife, with a special focus on one of the Lizard’s threatened species butterfly.

A male Silver-studded Blue butterfly

The Silver-studded Blue is a scarce butterfly in Britain, that can be found on the heaths and coastal grasslands of the Lizard. Elsewhere in Cornwall, it also occurs on sand dunes and some of the former mining sites in the region. This butterfly has a rather unusual lifecycle in that it has a special relationship with certain species of ant. The caterpillars produce a sweet, sugary liquid to reward ants, which in return protect it from predators and even let it live inside their nest. Because of this close association between butterfly and ant, Silver-studded Blues can only be found in places where the right species of ant occurs at high enough densities.

A black Lasius ant – the host species associated with Silver-studded Blues

Our research is investigating how both habitat conditions and temperature constrains the distribution of the butterfly and its associated ants. Temperature can vary greatly on a scale of centimetres or metres due to the influence of topography and vegetation. For small, cold-blooded insects, this fine-scale variation in “microclimate” can be very important in determining where they can and can’t live. We are studying this relationship with temperature at sites across Cornwall, looking at where the Silver-studded Blue and its host ants can be found, and what the habitat and microclimate conditions are like in these locations. One such site is the National Trust’s Penrose estate, where we are also looking at how the activity of Silver-studded Blues varies with different weather conditions and the time of day. This should help to give us a more mechanistic understanding about how environmental conditions directly affect the butterfly. By better understanding the factors important for allowing species to persistence within landscapes, we can improve our ability to predict how these species are likely to respond to future environmental changes.

Published: Sept 2019
Author: Marcus Rhodes (Exeter University)

Blame the jet stream

What a strange and capricious place the Lizard can be. At this time of year, I usually go and camp at Tenerife Campsite outside Mullion. It is a National Trust campsite characterised by its tranquility, calm and beautiful starry skies visible at night because the light pollution is at a minimum.This year, I chose a week that was bookended by two big low pressure systems sweeping in from the Atlantic, with a more modest yet sufficiently wet and windy mini-storm in the middle. Between these unseasonable weather events the sun shone, a gentle breeze ruffled grass, hair and dog fur, and all was well with the world. I arrived on the Monday, when the worst of the first storm had already slipped away east, its magnitude only evidenced by the soggy ground and my brother's diminishing stock pile of tent tape, to mend the rips forced open by 60mph gusts.On Tuesday we mooched over to Kennack Sands (the easterly, dog-friendly beach) and sat with our backs against the wall, marvelling at the rich colbalt sea and pretty fluffy clouds while Treacle snoozed with her nose in the sand. But higher up, beyond the benign cotton wool clouds, I could see higher, fast moving clouds, and I knew the balmy weather wouldn't last. Sure enough, Wednesday night treated us to a dowsing, with a soggy start to the morning.

Do not disturb! The growing threat to our seals

For local residents and the many visitors to The Lizard, the chance to see our seals swimming and diving, or hauled out on the rocks is one of the many wildlife delights. Seals are however very vulnerable to disturbance – you should always give them space and observe from a distance – use binoculars if you can - and keep dogs on a leash when you spot seals.
The dangers are highlighted in a new report released in July - ‘Please Do Not Disturb! – The Growing Threat of Seal Disturbance in the United Kingdom’ – which sets out the growing and harmful impact that human activity is having on our globally rare and important seal populations. Funded by the Seal Protection Action Group (SPAG) and the Cornwall Seal Group Research Trust (CSGRT) for The Seal Alliance, the report documents case studies around the British coast – including here in Cornwall – where our protected seal populations are suffering chronic disturbances from human activities, often causing serious injury and with potentially fatal consequences.

Link to the report  https://www.cornwallsealgroup.co.uk/wp-content/uploads/2019/07/2019-07-DO-NOT-DISTURB-public-report-for-release.pdf]

As the summer holidays begin, millions of British and international visitors flock to popular coastal destinations around the British Isles. The increasing popularity of ‘staycations’ and higher numbers of visitors from overseas, crowding around our coasts adds huge pressure onto our wildlife, especially seals. The South West of England, including Cornwall and our own Lizard peninsula, is a key area that these beautiful and intelligent marine mammals use for resting, socialising, breeding and moulting.
The researchers found compelling evidence that our seal population is suffering chronic disturbance issues from human intrusion through recreational activities as well as expanding tourism.