Katy Malone is a Conservation Officer with the Bumblebee Conservation Trust and has a special interest in the great yellow bumblebee. Here she explains why, and reveals some of the steps being taken to try and halt the decline of this distinctive insect.

Think of a wild creature, an icon of Highland wildlife. What springs to mind for you? I would imagine the first things are probably large, furry, charismatic animals such as red deer, wildcat, pine marten, and red squirrel? I’d like to make a case for a rather smaller, equally furry, brightly coloured creature – the Great yellow bumblebee.

Going, going, gone?

In the UK, the Great yellow is only found in the Scottish Highlands and Islands, associated with flower-rich machair and grasslands around the far north coasts and outer islands. It has been a UK Biodiversity Action Plan (BAP) Species since 1997, becoming a UK BAP Priority Species in 2007.

But it wasn’t always so. Fifty years ago it was widespread throughout the UK in both inland and coastal areas, though never in great numbers (due to its specialist niche – more on this later). It may always have been more associated with coastal areas however.

Its name in German, ‘Deichhummel’, means dyke (seawall) bumblebee. In contrast to many rare species which are pushed south, the distribution of the Great yellow has actually moved northwards instead, and the best places to find it are the Uists, Orkney and the far north coast of the mainland between Caithness and Kinlochbervie.

Great yellow on clover, Gordon Mackie (Caithness)

Bumblebees are thought to have originated in the Himalayas around 30 million years ago and most of the 250-odd species worldwide are similarly cold-adapted². Of the 24 species of British bumblebees, Great yellows are the largest and hairiest, which may go some way towards explaining why it seems to dislike the hotter climate of our southern neighbours.

I mentioned that they occupy a rather specialist niche. They are most often found in open grassland, such as extensive flower-rich meadows, rarely visiting gardens except where there is suitable grassland close by.

Changes in our agricultural landscape over the last 75 years have hit them particularly hard. We have lost 98% of our wildflower meadows on which bees depend. Since the 1940s, two species have become extinct and it is thought that one third of our social bumblebee species have declined by more than 70%³. Note though that accurate data is limited to distribution rather than abundance – a key gap in our knowledge that the Bumblebee Conservation Trust (BBCT) is plugging through our BeeWalk⁴ survey scheme. The Great yellow is now one of the two rarest bumblebees in the UK.

Great yellow on Clover, Gordon Mackie (Caithness)

Secondly, Great yellows emerge from hibernation quite late, generally in late May/early June, so need flowers that bloom late into autumn in order to complete their annual lifecycle. A nest that does not produce new queens and males at the end of its life has failed. A Great yellow must have a supply of nectar well into September/October, such as that provided by greater knapweed and devils-bit scabious.

Thirdly, bumblebees can be broadly categorised as short tongued or long tongued. This determines the type of flowers they prefer to feed on – deep flowers have lots of nectar but need a long tongue to reach them, while open shallow flowers are easy to access but tend to have relatively little nectar by comparison. Great yellows have a very long tongue. They feed predominantly on the tube-like florets of red clover and other members of the pea/vetch family.

So the Great yellow needs (1) open grassland, (2) long flowers, (3) late flowers, and lots of them. Traditionally-crofted machair is perfect, but this type of management is not widespread, and flower-rich habitat remains vulnerable to changes in grazing regimes and cropping.

One of the ways BBCT is currently addressing this is through an innovative new project based in Caithness, called Thurso: Gateway to the Great Yellow, or T:GGY for short⁵. With funding from the Heritage Lottery, SNH, the People’s Postcode Lottery and the Caithness and North Sutherland Development Fund, T:GGY is an exciting and timely community-focused project and call to action. It is designed to engage and encourage local people living in Caithness to do something positive to help protect our bumblebees and other pollinating insects. Although focussed on Thurso, the main town in Caithness, the benefits of habitat work and community engagement will be spread right across this county which is so crucial to the survival of the rare Great yellow bumblebee in mainland Britain.

We are working in partnership with the University of the Highlands and Islands, Forestry Commission and Learning through Landscape to involve communities in active conservation work to safeguard, restore and create valuable bumblebee habitats. Supporting volunteers through training, and setting up long-term monitoring of bumblebee populations through our national survey/monitoring programme, BeeWalk, is a key element of the project and one of BBCT’s long term strategic aims. If you would like to know more, have a look at our website link below, or keep an eye on the local press.

References

1. National Biodiversity Network Gateway (NBN) (2013) http://data.nbn.org.uk/gridMap/gridMap.jsp#topOfMap (Accessed 11/01/2013)
2. Hines HM (2008) Historical biogeography, divergence times, and diversification patterns of bumble bees (Hymenoptera: Apidae: Bombus). Syst. Biol. 57, 58–75
3. Burns F, Eaton MA, Gregory RD, Al Fulaij N, August TA, Biggs J, Bladwell S, Brereton T, Brooks DR,Clubbe C, Dawson J, Dunn E, Edwards B, Falk SJ, Gent T, Gibbons DW, Gurney M, Haysom KA, Henshaw S, Hodgetts NG, Isaac NJB, McLaughlin M, Musgrove AJ, Noble DG, O’Mahony E, Pacheco M, Roy DB, Sears J, Shardlow M, Stringer C, Taylor A, Thompson P, Walker KJ, Walton P, Willing MJ, Wilson J and Wynde R (2013). State of Nature report.The State of Nature partnership.
4. http://bumblebeeconservation.org/get-involved/surveys/beewalk/
5. http://bumblebeeconservation.org/news/thurso-gateway-to-the-great-yellow-wins-heritage-lottery-fund-support