Adding a bit of structure: moth monitoring and the Garden Moth Scheme

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Last Sunday I attended the excellent annual conference of the Garden Moth Scheme, which was well-attended, informative and enjoyable. And most importantly it showed how valuable it can be to record in a slightly more standardised way that we might otherwise do. Read on for more on the benefits of structured recording, and how you can join in with GMS.

Lots of people record moths and send their records in to their county moth recorder, which is an excellent way of finding out which species are where and contributing to the National Moth Recording Scheme. However, using this data for monitoring purposes is not straightforward, as there are so many variations in how, where and when people record their moths. To get good data on population trends for moths a more structured approach is needed.

Mean annual catches of the longest running RIS trap (Barnfield), in 3 year categories, compared with average values for RIS arable and grassland sites.

Mean annual catches of the longest running RIS trap (Barnfield), in 3 year categories, compared with average values for RIS arable and grassland sites.

The largest-scale example of structured moth recording is the Rothamsted Insect Survey (RIS), which celebrated its 50th anniversary in 2014. One of the RIS projects gathers data from Rothamsted moth traps positioned around Britain and Ireland. The first of these traps was used in the 1930s and 1940s, and following a gap in the 1950s an extensive network has been developed since the 1960s. This has provided an unparalleled set of long-term monitoring data for moths, and unfortunately what the data tell us is not very good news: the one trap that was running before the second world war was producing a lot more moths than traps have done subsequently, suggesting that there was a major decline in moth abundance in the 1950s (see graph on right). And the declines have continued: Rothamsted data was used in a joint project with Butterfly Conservation to assess the State of Britain’s moths over the last 40 years, from which the headline news was that two-thirds of widespread moths have undergone a significant decline, especially in southern Britain.

The Rothamsted moth traps are run by a network of volunteers, and new volunteers are welcome, but it is quite a big commitment. You have to have space to install the trap, and you have to commit to running it every night of the year for at least five years. Many of the Rothamsted traps are situated in places such as Field Studies Centres or research institutes.

GmsBut there is another moth monitoring scheme that you can join in with much more easily. The Garden Moth Scheme asks its participants to run a moth trap once a week (on the same night each week if at all possible) and to record the numbers of a suite of common species (you can of course record all the species you see if you wish, but the GMS focuses on a main list of around 220 species). Even if the weather is unpromising it’s still important to run your trap, and if you have a night where you record no moths that is still useful data! It is this regular pattern of recording once a week whatever the weather that helps give this survey its structured data, and allows for robust analysis of the results.

The GMS is an entirely volunteer-led project that has been running nationally since 2007, and the data it has collected is building up into a major resource. A recently published paper uses GMS data to show that gardens containing more diverse habitats have more moths, gardens near the coast have more on average than inland gardens, and gardens in urban areas have fewer moths on average than non-urban areas. These results are not perhaps very surprising, but the GMS data allows the trends to be quantified and investigated further. The full paper is open-access, see: Bates, A.J., et al. 2014. Garden and Landscape-Scale Correlates of Moths of Differing Conservation Status: Significant Effects of Urbanization and Habitat Diversity. PLoS ONE 9(1): e86925. doi: 10.1371/journal.pone.0086925.

A previous paper looked at the effects of different designs of moth trap and different bulb types to compare the catches of each (Bates, A.J., et al. 2013. Assessing the value of the Garden Moth Scheme citizen science dataset: how does light trap type affect catch?. Entomologia Experimentalis et Applicata, 146: 386–397. doi: 10.1111/eea.12038 – unfortunately this one isn’t open-access), and members of the GMS are busy looking at the data in various ways to pick out trends and report back to the participants via regular newsletters and annual reports. Over time the data will become ever more useful and will allow for further research.

Moth trap in my former garden in Berkshire, and the best garden I've ever had for moths - sadly, where I live now is much less good!

Moth trap in my former garden in Berkshire – sadly, where I live now is much less productive for moths!

All in all the GMS is an excellent way for moth recorders to add an element of structured monitoring to their recording, without doing anything other than running a moth-trap in the garden, the sort of thing that moth-recorders love to do anyway! If you want to join in for the 2015 you need to be quick – recording is due to start this coming Friday 6 March (although at a push you can start a week or two later if you miss that first deadline), so head straight over to the GMS Getting involved page. I’m going to give it a go this year, and I look forward to seeing how my results fit in with everyone else’s.

If you do take part in GMS, please remember to copy your results (along with all your non-GMS moth records) to your county moth recorder as well.

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Lightness falls

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New research suggests that light pollution can reduce mating success in Winter Moths

Light pollution map from CPRE's Dark Skies project

Light pollution map from CPRE’s Dark Skies project

Moths are in trouble – evidence is accumulating (see Butterfly Conservation and Conrad et al. 2006) to show that many moth species are in decline, especially in the southern half of Britain. But what are the causes? Research is showing that a combination of factors is likely to be involved (Fox et al. 2014), with habitat change or loss and climate change likely to be a large part of the story. But another factor that could be impacting on moths is ‘light pollution’, the tendency for humans to want their own habitat to be lit up at night, so we can work, play and feel safe walking the streets. The night-time glow of towns and cities is visible from miles away, and even in rural areas roads, shops and houses may be illuminated.

Could all this light be affecting the lives of nocturnal creatures such as moths? It seems plausible, but it’s hard to prove, not least because the way most of us go out and look for moths is by putting bright lights out to attract them. How to find out what light pollution does to moths when they’re hard to observe in the dark?

Mating Winter Moths by F. Lamiot via Wikimedia Commons

A newly published paper (“Artificial light at night inhibits mating in a Geometrid moth” Van Geffen et al. 2015) has used an ingeniously simple method to investigate this, and the results suggest that we should indeed be worried about what light is doing to moths. Koert van Geffen and colleagues carried out their study in the Netherlands, and chose Winter Moth as their subject. Why Winter Moth? One reason why they make good study subjects is that their habits are a bit more predictable than for many moths: female Winter Moths are flightless, and one they emerge from their cocoons under ground they ascend the nearest oak tree and wait for the males to find them. And there is an established method for trapping them, by setting up ‘funnel traps’ that steer the females into a container once they climb far enough up the oak tree.

So Winter Moths are going to be climbing their oak trees, and if you shine a light on the tree the females can’t fly away. The Dutch team set up a series of different lighting regimes directed at oak trees, using green, white and red light, plus unlit trees for comparison. They counted the females on each tree, and checked them to see if they had mated. The results seem to me to be quite dramatic.

Mean number of female Winter Moths caught per night on trees with different light treatments, from Van Geffen et al. 2015

Mean number of female Winter Moths caught per night on trees with different light treatments, from Van Geffen et al. 2015

By far the greatest number of female moths were caught from the unlit trees. Of the illuminated trees, white had fewer than red, and green fewest of all. All lit trees had more moths on the shaded side than the lit side, but only under red light did even the shaded side produce anywhere near as many moths as the unlit trees. And there was a big difference in mating success: 53% of females caught from the unlit trees had mated, but only 28% of the females under red illumination, 16% under white, and 13% under green.

Van Geffen et al. also studied male moths using pheromone traps positioned under different lights. The differences here were less dramatic but still apparent, with fewest males caught under red light, more under white, more again under green, and the greatest number from unlit traps.

This is of course just one study of one moth species, but it showed that in this instance artificial light reduces the activity of female moths, and also reduces the male response to female pheromones, resulting in decreased mating success. The lights used in the experiment were LEDs with a light intensity of 10 lux – street lighting can be much brighter than this, up to 60 lux (Gaston et al. 2012).

Relatively simple and effective research, providing more evidence of the pressures on moth populations. Can we do anything to reduce the effects of light pollution? Gaston et al. 2012 review possible ways of preventing too much light escaping into the wider environment. Further useful information and advice is available from Buglife’s research and Campaign to Protect Rural England’s “Dark Skies” pages. For instance, we can reduce the intensity of artificial lighting, direct it more precisely so there is less overspill, and leave lights on for shorter periods so that they are only illuminated when they are actually needed. This not only has the potential to help wildlife, but to reduce energy use and costs as well – moving lighting in this direction has got to be a no-brainer.

By taking action at home and encouraging local authorities and businesses to do likewise we can all help shed some darkness and take moths out of the spotlight.

funding for work experience with invertebrates and mammals

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The People’s Trust for Endangered Species is awarding funding for students/recent graduates who wish to gain experience by taking up an internship with conservation or research organisations – details available here.

For work with invertebrates, two internships are available this year, deadline for applications is 15 June 2009. Mammal internships have been allocated for 2009 but will be available again in 2010 (I see that there are seven mammal internships available, which is a bit unbalanced given the relative number of species to choose from, but far be it from me to criticise funding for worthwhile causes!).

(I’m indebted to the Amateur Entomologists’ Society for information on these awards, via the AES Twitter feed.)

Evolving snails: launch of Evolution Megalab

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Continuing today’s snail theme, today is the official launch of the Evolution Megalab, a project being run by the Open University where people can contribute to evolution research by surveying the Brown-lipped Banded Snail Cepaea nemoralis. There’s been quite a lot of publicity about it today, and it is part of the OU’s celebration of Darwin 200.

Anyone can take part in the survey, and the Megalab site has full instructions, along with associated videos (see below) and an identification quiz you can take to rate yourself as a Cepaea identifier. Cepaea snails have a long history as evolutionary study subjects, and the Megalab gives you the chance to add to this body of work. You can also see what historical records are held for your area.

For those with mixed feelings about snails, there is no need to hate Cepaea snails! They prefer dead or decaying vegetation and although they can be common in gardens they don’t do much if any damage.