Glasgow & SW Scotland Butterflies

Glasgow & SW Scotland Branch Website

February 27, 2011

Light Trapping for Rannoch Sprawler at Loch Rannoch in 2012

Filed under: Moths — Andrew Masterman @ 1:14 pm
UPDATE 2012: Further survey work is planned for the weekend of 23-25 March 2012 to search for Rannoch Sprawler along the south-east quadrant of Loch Rannoch and to do some further survey work on the north side further away from the road and behind the MacDonald Loch Rannoch Hotel. If you would like to get involved, please email andrewmasterman@hotmail.com
 
RESULTS 2012: A total of 77 Rannoch Sprawler were obtained in 2012 during four nights trapping. The map below shows the trapping results for 2011.
In 2011, the result of the four nights light trapping at 19 different points was a total of 33 Rannoch Sprawler which were caught in seven different 1 km squares five of which were new.

In 2012, the result of four nights trapping at 29 different points was a total of 77 Rannoch Sprawler in eight different 1 km squares four of which were new.
 
These results show that Rannoch Sprawler occurs in at least 12 different 1 km squares at Loch Rannoch and sometimes occurs in large numbers. These are very positive results.
 
 
The first British specimen of Rannoch Sprawler was taken at Rannoch in the spring of 1854 and it is currently known from four different areas of Scotland: the Rannoch area; near Braemar; on Speyside; and in Glens Affric and Moriston.
Distribution of Rannoch Sprawler in Scotland
Distribution of Rannoch Sprawler in Scotland
The Rannoch Spawler is a large and impressive noctuid which occurs in two forms: a grey Speyside form and a reddy Rannoch form.
Grey Speyside form of Rannoch Sprawler on left and red Rannoch form on right. Credit John Knowler.
Grey Speyside form of Rannoch Sprawler on left and red Rannoch form on right. Credit John Knowler.
Butterfly Conservation commissioned survey work in 2010 on rare moths in the Rannoch area as part of the Moths Count project funded by the Heritage Lottery Fund and many other partner organisations. The results for Rannoch Sprawler are presented below.
The flight period of the Rannoch Sprawler is from March to mid-April when it can be caught using light traps or you can search for adults on the south side of the trunks of large birch trees during the day. Waring & Townsend Moths Field Guide suggests it can take as long as six hours to find one Rannoch Sprawler using this daytime search method. Daytime searches for Rannoch Sprawler on the south sides of the trunks of large birch trees were unsuccessful in 2010. While some distinguished Scottish Lepidopterists have been heard to lament the loss of traditional Lepidoptera methods such as searching the trunks of trees for moths during the daytime, there is such a thing as being a Luddite! In the case of Rannoch Sprawler, using a light trap is a much more efficient method than daytime searches of birch trunks and therefore the author is using this method in 2011 to confirm that Rannoch Sprawler is present in the areas of suitable habitat which were identified in 2010.
The habitat of the Rannoch Sprawler is mature open birch woodland with large trees. Waring & Townsend suggest that both downy and silver birch are used and that downy birch is used at Rannoch. However, the surveys in 2010 revealed that silver birch and not downy birch occurs at the sites of the historical records. The photos below show such silver birch habitat on the north side of Loch Rannoch and a close-up of the trunk of one silver birch tree which has large crevices and knobbly bits at the bottom.
Birch Woodland occupied by Rannoch Sprawler on north side of Loch Rannoch
Birch Woodland occupied by Rannoch Sprawler on north side of Loch Rannoch
Close-up of Silver birch trunk in woodland occupied by Rannoch Sprawler
Close-up of Silver birch trunk in woodland occupied by Rannoch Sprawler
The map below shows the areas around Loch Rannoch which were identified as containing suitable habitat for Rannoch Sprawler in 2010 plus the sparse historical Rannoch Sprawler records. The areas of apparently suitable habitat are large and light trapping across these areas is required in 2011 to confirm that Rannoch Sprawer is present. Click here for a Word document file containing this map which can be printed out and taken into the field.
Distribution of Rannoch Sprawler records around Loch Rannoch and areas of habitat.
Distribution of Rannoch Sprawler records around Loch Rannoch and areas of habitat.
Permission to use light traps in the shaded areas on the north side of Loch Rannoch has been obtained so there is an opportunity here to catch a very rare and spectacular moth if you have not already had the priviledge of recording this large majestic noctuid! If anyone is keen to bag the red ‘Rannoch’ form of the Rannoch Sprawler during the latter half of March when I plan to trap there over 2 or 3 nights, please email andrewmasterman@hotmail.com .
You can get a budget room for £43 a night for a mid-week stay at the Loch Rannoch Hotel , Kinloch Rannoch if you book online, or there are very scenic wild camping spots at the east end of Loch Rannoch at Kinloch Rannoch.
RESULTS Posted 1 April 2011
Trapping took place on the nights of 21, 22, 23 & 28 March 2011. Heath traps were placed at a total of 19 different points and Rannoch Spawler found at 12( 63%) of these random sites within suitable habitat. A total of 33 Rannoch Sprawler were caught in seven different 1 km squares, five of which were new 1 km squares for Rannoch Sprawler.
Eight and nine individual Rannoch Sprawler were caught in two traps on the 28 March 2011 suggesting that Rannoch Sprawler is very numerous at these sites around Loch Rannoch. However, the two squares above Kinloch Rannoch, NN6559 & NN6659 had both Silver & Downy Birch whereas the squares further west were dominated by Silver Birch. The habitat in these two squares seemed less good with fewer old Silver Birch trees and this was confirmed by the absence of Rannoch Sprawler at four trapping sites in NN6559 and at one of the trapping sites in NN6659. But overall, there is certainly large areas of suitable habitat for Rannoch Sprawler as well as large populations of the moth which is shown by the large trap totals at some sites.
Many thanks to Greg & Andy Fitchett for trapping over two nights with four Heath Traps and to Stan Campbell for attending.
Results of trapping for Rannoch Sprawler in 2011
Three Rannoch Sprawler caught in a Heath trap & placed on a Birch trunk
Three Rannoch Sprawler caught in a Heath trap & placed on a Birch trunk

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