Observations on the coming season and the importance of Collard Hill
How the weather can affect populations of the butterfly
One of the main challenges for wildlife over the coming years is how will it cope with the regular, extreme weather events which seem to becoming common place. Over the course of the last two years, the Large Blue in theUKhas had to navigate hot and very dry springs and wet, cool flight periods.
Droughty conditions during the first third of the year are far from ideal for the Large Blue’s host ant Myrmica sabuleti, which whilst being a heat-loving insect, tends to stay in the nest when it is both hot and dry. A reduction in foraging means there is less food being brought for ant grubs which in turn results in fewer and smaller grubs for the caterpillar to eat: during a prolonged drought the ants will even eat their own grubs together with any Large Blue caterpillars in the nest.
Wet weather during the flight period is of less concern provided it is interspersed with some sunny spells when mating and egg-laying can take place: in 2011, despite the regular rainy days the number of eggs laid on Collard was up by over 30%, testament to its excellent management. So far during this flight period the opportunity for females to fly has been extremely limited and I’m keeping my fingers crossed for a distinct improvement in the weather. Although still early in the season, (I’m writing this on 11/6/12), it is apparent that we will have an excellent population of Large Blues emerging on Collard and I believe thousands of eggs will be laid over the coming month.
Planning for the future
There are two ways in which the future for the Large Blue in theUKcan be enhanced, firstly by managing sites well so that populations can grow and secondly by ensuring that there are new sites in good condition where the existing populations can migrate to and form new colonies. Working with Butterfly Conservation and all their partners, (National Trust, Somerset Wildlife Trust, South Somerset District Council, the Clark Trust, CEH, Oxford University and several private landowners), Funding was secured from the SITA Trust for three years to expand the Large Blue landscape in the Polden Hills. Over the course of last winter, scrub clearance was carried out on many sites, including Collard Hill, by both contractors and volunteers from the thriving Large Blue Poldens Action Group. The ants and distribution of foodplants on each site have been surveyed and, where necessary, propagated plants of Wild Thyme have begun to be planted. We will hopefully end up with more sites, with varying aspects, supporting larger populations of Large Blues in an extended landscape.
Collard is now a very important core site and produces so many Large Blues that it is used as a donor population to start new colonies in other regions. Later in the month my colleague Sarah Meredith and I will be collecting eggs to rear into caterpillars which will be released onto sites in the Cotswolds.
After six highly successful years in post, Rob Holden (NT Area Ranger) moved to a new job and I have been delighted to meet his replacement Ian Clemmett who I am sure, together with Hayley Dorrington, will build upon the wonderful legacy that Rob left behind at Collard.
It gives me enormous pleasure that so many people are interested in Large Blues and visit Collard each year and I would urge you to come and enjoy, not only Large Blues, but many other butterflies, wildflowers and the stunning views. Once again we are lucky to have another excellent warden in Lottie Faulkner who, with her helpers, will help you to enjoy your visit and to see this iconic butterfly. Please bring some sunshine with you!
Project Officer for the Large Blue Butterfly Project
(David is a freelance ecologist who has worked on Large Blues for nearly 30 years. He is funded by the Centre for Ecology and Hydrology and Butterfly Conservation).