Natural history adventures sailing the culinary seas...

Friday, 1 July 2011

Orange-tip chasing

Mrs Teacup spent April and May in deepest Scotland chasing Orange-tips polewards with a UEA research group, investigating the responses of range-expanding butterflies to climate changes. In comparing populations from the core and margins of the species’ distribution, we hoped to quantify increased dispersal in margin populations, and establish whether a correlation with morphological characteristics (wing lengths) could be detected. We expected margin populations to be flying further and straighter, with a longer wingspan, to aid their dispersal to new thermally suitable habitats. Sciency stuff aside, what a glorious species to eye up for 8 weeks! The challenge commenced in what was forecast to be the hottest April on record – an amazing stroke of luck.

Admiring these insects was a joy - characteristic bright males and the more understated females, both with gorgeous green mottled underwings aiding flawless camouflage. This species has a huge amount of charm. It is no surprise then, that the males were chosen as a pin-up in a public awareness campaign in 1990s for range-expanding species, adorning the front of thousands of postcards sent to the public asking them to report sightings in Scotland. Over 1000 sightings were reported and even today inquisitive members of the public all agree, “there’s a lot more of them around this year”. And lots we found, over 300 individuals were tracked in 23 days, in Carlisle and Kilmarnock.

Northern populations of Anthocharis cardamines like damp habitats, which required much chasing along rivers and streams with wet feet! Upon catching the critters (along with many Green-veined whites), individuals were cooled in a glorified picnic cool-bag to calm them down, before being marked, sexed and assessed for condition. We then released them on food plant (Cuckooflower - Cardamines pratensis, or Garlic mustard - Alliaria petiolata), or a nectar source, and waited for take off. On warm days, tracking with a GPS antenna attached to our backs (no laughing please) was quite an exhausting exercise – these orangey wonderments fly almost 2 metres a second, often through high swards, across brambles and nettle beds – chasing them was a high risk activity, filled with lots of comedy moments launching ourselves head-first into nettle beds as a patrolling male glides away across the river!

On cold days, the waiting game often took 20 to 30 minutes – what a wonderful opportunity to watch this species at close range, basking, nectaring, and even some ovipositing occurred, not to mention a lot of Orange-tip loving! Males often swoop on a hostile female who curves her abdomen out of reach despite repeated attempts to mate. Watching females on host plant was glorious, flitting from plant to plant, nectaring like mad – if butterflies could smile I'm certain there’d be a lot of smiling faces in the sunny meadows of central Scotland J. All in all, a fantastic few months in the field; birds singing and butterflies meandering, through bluebells, red campion, herb robert, wild pansy, daisies and lots of forget-me-not. Forget it? I will certainly not.

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