Task 11

Nocturnal creatures

For this task I have been asked to report on sampling and ID strategies for moths and bats, based on sessions as part of the course. Then I present an experimental design to address a question relating to an environmental gradient (using both moths and bats in the study).

As part of the course, I attended a presentation and practical session at Oxford Brookes University on 8th April 2024, presented by Dr Matthew Bulbert (Senior Lecturer in Conservation Ecology).

Moths

Presentation

The presentation explained some of the issues around moth populations, such as the large decline in abundance, their conservation value including for education and awareness building, as well as their use as indicators of environmental change due to their sensitivity (Bulbert, 2024). It then covered sampling methods:

Light traps: A light is used which disorients the moths (a paper by Fabian et al. (2024) suggests they use the light to orient themselves as to what is up or down), they then fly into a surface and fall into the box through a funnel and are trapped. The box has egg cartons inside to give them somewhere to rest and hide during the day, which is soft on the wings. These are typically stacked in a spiral arrangement. In the session I saw a heath-trap, which is a small, contained, light trap. It allows connection to a portable battery and has a light sensor, so that it will only turn on when it is dark. The light source produces the same wavelength as sunlight and the box has a hole at the bottom with a funnel to drain any rainwater that gets in. It is advisable if setting up multiple light traps to ensure they are out of the line-of-site of one another.

Heath trap

Heath trap with light sensor covered so the light turns on.

Malaise traps: Using light and then a screen to intercept the moths. As the moths are on a screen it may be possible to film/photograph and potentially use image recognition to categorise and identify them.

Wire roping: Some moths may not be attracted to the light so other methods such as this can be used. Rags are dipped in wine and hung out to attract them.

Pheromone traps: It is possible to use species-specific pheromone traps to attract males to the trap.

Finally, the presentation covered an introduction to identification of moths, with tools that could be used to aid identification e.g. What’s flying tonight? (Butterfly Conservation, Centre for Ecology & Hydrology and UKMoths, no date), inaturalist SEEK (iNaturalist, 2023) and field guides.

For identification, we can follow these steps:

1. Is it Macro or Micro? Macro > 10mm (mostly), micro < 10mm (mostly)

2. Habitat/Phenology: This is where tools such as What’s flying tonight? are useful, as well as iNaturalist for recent sightings

3. Is it Nocturnal or Diurnal?

4. What is its wing position? Arrow, parallel, spread, tail or tent? This can help determining the family (see below)

5. What is its wing pattern? Essentially pattern matching against photos/illustrations in the field guides.

6. Physical features – mainly for taxonomical classification e.g. dissection/genitalia

Some typical characteristics of moth families:

• Drepanidae – typically not complex patterning at wing tip, angular edges

• Erebidae – mostly arrowhead, except for footman shaped like a sole

• Geometridae – slender bodies, typically spread wings, some arrowhead

• Hepialidae – tent like with ‘boa feather scarf’

• Noctuidae – shallow tent, tendency to have patterning with stigma, spots, waves

• Notodontidae – medium sized, steep tents

• Sphingidae – including hawkmoths, much larger than other families

Practical identification

For the practical session we were to look at specimens collected from a heath trap deployed on the university campus. However, overzealous security had removed it! Luckily, Dr Bulbert had deployed one in his garden as a back-up, so we were able to view and identify some specimens.

For checking the heath-trap in the field, it is important to check the ground around the sides of the box (in case any moths are there), then carefully lift the funnel to check. It is best to do this just after sunrise before the moths have had time to warm up (this should really by done before 10am). The best conditions for sampling are when it is warm, with cloud cover and no wind. When the sampling for this session was done it was windy, so this was not ideal!

Egg boxes with moths resting

I then took some photos of the moths and proceeded to use the available tools to identify them. I used What’s flying tonight? (Butterfly Conservation, Centre for Ecology & Hydrology and UKMoths, no date) in conjunction with the British and Irish moths field guide (Manley, 2021). For the last moth I used iRecord (Biological Records Centre, 2024) and the auto-id function to check.

Brindled Beauty Lycia hirtaria

From Manley (2021, p.318): Family Geometridae, this is a common species and found in ‘woods, parks and gardens’ which fits (trap was in a garden). The photo in the book matches the specimen in terms of wing shape and patterning.

Brindled Beauty Lycia hirtaria

Streamer Anticlea derivate

From Manley (2021, p.288): Family Geometridae, this is a common species found in ‘Open woods and margins, hedges, gardens’, which fits (trap was in a garden). It also says that it ‘has a purple tinge when fresh’, which we can see from my photo. Specimen’s wing shape and pattern match the image in the book.

Streamer Anticlea derivate

Common Quaker Orthosia cerasi

From Manley (2021, p. 398): Family Noctuidae, this is a common species found to be ‘frequent in lowland woods’. Its feeding plant is listed as ‘broadleaved trees’, so feasibly can be found in gardens. It states that it usually has ‘well-defined oval and kidney marks and outer cross-line’, which are evident in my photo (highlighted) and where the specimen matches the photos in the field guide.

Common Quaker Orthosia cerasi showing defined oval and kidney marks, and outer cross-line

Hebrew Character Orthosia gothica

From Manley (2021, p. 398): Family Noctuidae, this is a species that is ‘common absolutely everywhere’. It is named after the ‘dark saddle mark’ which looks like ‘the 14th letter of the Hebrew alphabet’.

This specimen was harder for me to identify. From the photo you can see that the character is not as obvious on the right. Wing scales may come off and so these visible characters become harder to see. There were photos in the field guide which showed variation in how this species looked, which made me think it could be that. I used iRecord to see what the auto-ID function recommended, and it picked the same.

Hebrew Character Orthosia gothica

As the traps didn’t have many specimens, I then proceeded to identify moths from images that had been shared by using the same tools. In the photo below I am identifying a Water Carpet Lampropteryx suffumata, family Geometridae. You can just see the page open in Manley (2021, p. 294) showing matching images for comparison.

Using a field guide to identify a Water Carpet Lampropteryx suffumata from a photo.

As part of the course, I attended a lecture given by Daniel Bardey on the Bats of Britain. This was followed up with a quiz that tested my identification skills using photos, videos of roosting bats and analysing calls using spectrograms.

Bats

Presentation

The presentation covered lots of areas of bat ecology, identification and legislation (Bardey, 2024). There are 7 genera of bats in Britain: Horseshoe, Noctule, Serotine, Pipistrelle, Long-eared, Myotis and Barbestelle; with 17 species. They are probably one of the most protected animals in the UK, with 3 separate pieces of legislation ensuring their protection:

• Wildlife and Countryside Act 1981

• Countryside and Rights of Way Act 2000

• The Conservation of Habitats and Species Regulations 2017

This means that for surveying work this must be considered and licencing is needed to disturb them. For identification in the hand (where a licence needs to be obtained) there are 4 key identification features: the ear shape, nose shape, tragus shape (the tragus is a piece of skin bats have in front of the ear canal) and the calcar shape (which is a cartilage spur on the back foot). There are keys that allow identification of bats in the hand using these characters e.g. if the bat has a leaf-shaped nose then it will belong to the Horseshoe genus; if the base of the ears are joined (next to each other) then it will belong to either the Long-eared or Barbastelle genera.

Looking for signs of bats, or where bats might be, rather than that bats themselves is an important strategy. For example, there are crevice dwellers e.g. serotines and pipistrelles, and void dwellers e.g. brown long-eared and horseshoes (who will hang upside down, like a plum!). Noctules, for example, live in woodpecker holes. Interestingly, I learnt here that as there are no woodpeckers in Ireland there are no noctules! A tool to help determine what sort of bat might be in a particular roosting site is the bat tree habitat key (Bat Conservation Trust, 2024) which provides a useful spreadsheet that shows what types of sites bats have been found in. Additionally, look out for field signs such as moth wings and bat droppings. It was explained that bat droppings will crumble in your fingers as they are very dry, unlike mouse droppings which will be hard. As part of the presentation a jar of brown long-eared Plecotus auritus bat droppings was passed around, so I was able to crumble it between my fingers to feel what it was like – not something I was expecting to do!

The use of bat call structures (echolocation calls) was covered. The structure, peak frequency and intervals vary between each of the UK species so this can be used to identify them e.g. Noctule Nyctalus noctula have echolocation frequency of around 20-25kHz whereas the soprano pipistrelle Pipistrellus pygmaeus is at about 55kHz. The echolocation call corresponds to the bats’ foraging habitat. Those calls that are of a more constant frequency provide information over a greater distance e.g. when hunting in open areas whereas those that are over a higher frequency range (but shorter time) provide more detail but over less distance e.g. when hunting in closed canopy habitats.

Practical identification

For this quiz the first questions tested identification of photos of bats to use their physical characters to determine ID. I used the notes from the lecture slides (Bardey, 2024) and other material such as the UK Bat Key (Bardey, 2022) that were provided.

For the example above, following the key:

Leaf-shaped nose: NO (so not a horseshoe)

Do the ears meet in the middle of the head? NO (so not a brown long-eared)

Is there a post calcarial lobe? Can’t see from the photo, so need to use a different character. It has very long ears and the tragus is also long, which checking in Walker (no date) indicates it is a Bechsteins myotis and NOT a common pipistrelle.

Quiz question from photo: Bechsteins Myotis

Other aspects of the quiz involved watching a video taken from an endoscope camera inserted into a roost (in trees) – also something that needs a license. As the camera is only inserted briefly, so as to not disturb the bat too much, it is very hard from a glimpse of a bat to determine what species it is. Even though I was able to pause the video and didn’t have to do it ‘live’, I found this part a lot harder than the clear photo images to get correct.

Quiz question from video: Natterers

The final set of questions was taking an audio recording (.wav files) and then using the sound analysis tool kaleidoscope lite (Wildlife Acoustics Inc., no date-a) to analyse the call. For the audio file below, I have highlighted part of the call to analyse. It shows that the frequency with the highest (peak) energy in the selection is 20.419kHz (highlighted in red rectangle below) and that there are 4 calls within 1 second, which matches what is expected from a noctule.

This quiz gave me an appreciation of the techniques used for identifying bats and the difficulties involved in it. I have also attended the Discover your local bats and Bat walk sessions, so I have some further experience including hands-on use of bat detectors.

Call analysis of a noctule, in Kaleidoscope Lite. Fppeak highlighted.

Experiment

Research question: Are organic farming practices beneficial for wildlife compared with methods using pesticides?

This experiment will assess biodiversity of moth and bat populations across a gradient of pesticide use. Sites will be identified that have high/medium/low/no use of pesticides applied to them, with other factors selected to ensure appropriate replication i.e. comparable geographic locations, crop type, surrounding habitat etc. Moths and bats have been selected as good bioindicators due to their sensitivity to stressors.

To measure bat biodiversity, an initial survey will determine if there are any habitat features that may present as good bat roosting sites to inform whether sites can be used as replicates. Surveying will be performed from May through September as this is the recommended time for automated/static ground-level bat activity surveys (Collins, 2023, p. 20). This will involve positioning a number of static automated bat detectors in the field, such as the Song Meter SM4Bat FS Ultrasonic Recorder (Wildlife Acoustics Inc., no date-b) to record bat activity. The data from these recordings can be analysed to determine the presence of bats, species composition and relative abundance of calls which can give insight into the activity of the bats; note that this method cannot count the number of bats as it will only be possible to count the number of passes made. This method has been chosen as it is less intrusive/disturbing than harp/mist netting and identifying in the hand, yet there is evidence that it is valuable method for monitoring variation in the relative abundance of bat calls (within species) and species richness (Thomas and Davison, 2022).

To assess the biodiversity of the moth populations at each site, light traps are to be used that can be attached to portable batteries. It is important that these are positioned such that the lights are out of line-of-sight of one another. Another consideration is that having lights on may affect the bat population, so this surveying must be done either on different nights to the bat surveys, whilst ensuring the weather/temperature is similar (to stop these factors confounding the results), or on an area of the site that is sufficiently far enough away (out of sight) of the light traps. Traps will be examined the following morning and observed species richness and abundance will be recorded.

The study will determine if there is any correlation between the amount of pesticide used on the farm sites and the measures of biodiversity of moth and bats. My expectation of the results is that there would be a negative correlation shown i.e. the more pesticide used, the lower the measures of moth abundances and species richness, and the lower the activity (bat calls). However, I wouldn’t expect to see much difference in species richness recorded for bats, as there are unlikely to be high numbers of bat species in one area/habitat.

Further consideration may be given to using additional, complimentary, survey methods such as:

• The use of automated call analysis for bat ID, due to the large amount of audio data that will be generated.

• The use of video recordings (e.g. night-vision camera) of the bats. If a roost is identified a count of bats emerging/re-entering could be used.

• The use of a malaise trap for moths, with photo/video of the sheet with an auto-ID developed for detection of species and counting.

References

Bardey, D. 2022. A Guide to British Bats.

Bardey, D. (2024) ‘Bats of Britain’ [Presentation]. BIOL7001: Taxonomy and Identification. Oxford Brookes University. 22 April.

Bat Conservation Trust (2024) Bat Tree Habitat Key. Available at: http://battreehabitatkey.co.uk/?page_id=18 (Accessed: 14 May 2024).

Biological Records Centre (2024) iRecord. Available at: https://irecord.org.uk/ (Accessed: 14 May 2024).

Bulbert, M. (2024) ‘Moths’ [Presentation]. BIOL7001: Taxonomy and Identification. Oxford Brookes University. 08 April.

Butterfly Conservation, Centre for Ecology & Hydrology and UKMoths (no date) Whats flying tonight. Available at: https://connect-apps.ceh.ac.uk/whats_flying_tonight/ (Accessed: 14 May 2024).

Collins, J. (2023) Bat surveys for professional ecologists: Good practice guidelines. 4th edn. London: Bat Conservation Trust.

Fabian, S. T., Sondhi, Y., Allen, P. E., Theobald, J. C. and Lin, H.-T. (2024) 'Why flying insects gather at artificial light', Nature Communications, 15(1), pp. 689. Available at: https://doi.org/10.1038/s41467-024-44785-3.

iNaturalist (2023) Seek by iNaturalist. iNaturalist Available at: https://www.inaturalist.org/pages/seek_app (Accessed: 07 June 2024).

Manley, C. (2021) British and Irish moths: third edition: A photographic guide. 3rd edn. London: Bloomsbury Wildlife. Bloomsbury Naturalist.

Thomas, R. J. and Davison, S. P. (2022) 'Seasonal swarming behavior of Myotis bats revealed by integrated monitoring, involving passive acoustic monitoring with automated analysis, trapping, and video monitoring', Ecology and Evolution, 12(9), pp. e9344. Available at: https://doi.org/https://doi.org/10.1002/ece3.9344.

Walker, M. (no date) Identification of British Bats. South Nottinghamshire Bat Group.

Wildlife Acoustics Inc. (no date-a) Kaleidoscope Lite. Available at: https://www.wildlifeacoustics.com/products/kaleidoscope/kaleidoscope-lite (Accessed: 07 June 2024).

Wildlife Acoustics Inc. (no date-b) Song Meter SM4Bat FS Ultrasonic Recorder. Available at: https://www.wildlifeacoustics.com/products/song-meter-sm4bat (Accessed: 07 June 2024).