By Dan Moule, BSc Conservation Biology student
|Dan Moule, doing |
The aim of the study was to measure the catches of moths and other night flying invertebrates over time in relation to three different light bulb sizes. Conducted at three sites on the farm platform between the hours of midnight and 4am on alternate nights (weather permitting), we spent six weeks alone in the dark with only the moths, flies and other assorted Dartmoor wildlife for company. If the commotion of the nocturnal wildlife, freezing cold (only a slight exaggeration) or biting midges weren’t enough to keep us awake, our beepers were primed and ready to stir us every fifteen minutes to change our sample jars.
During the study we stayed in one of the four cottages provided for scientists working at the farm platform. We conducted our first night’s study after induction on arrival at site and caught a first glimpse of some of the fascinating creatures we would become very familiar with during ID work in the lab the next day. Species that we couldn’t identify to family were allocated a letter of the alphabet as a name and photographed. At the end of the first day, we had already gone through the alphabet and had to add numerical values to the names (and by the end of the study we had gone through the alphabet more than ten times!).
We were made very welcome on our second night by a massive dinner party hosted by some of the other students and scientists who were working there. And then it rained—for over a week without pause. Unable to get out and study, we soon got to know the staff and guests at the institute who were always friendly and willing to help/gossip. That was just as well, as we were isolated miles away from the nearest civilisation, such as a pub. The complex had a generously stocked games room and so we became quite good at table tennis in the first rainy week, even discussing joining the table tennis society when we got back (that hasn’t been mentioned since).
|"Homer Fly" or "Species Z", |
a lesser dung fly.
The alarm system of the research centre is possessed, possibly by the ghosts that reputedly haunt the medieval manor house located at the institute, and every now and then the tranquillity of night was interrupted by the ringing of alarms accidently set off by night cleaners (at least we weren’t the only ones sleep-deprived). I saw a quite rare meteorological event called a ‘bolt from the blue’ one clear night, which was amazing. On another occasion, a duck flew out of the darkness directly into my face when I was walking across the field at night.
Moths get drunk on light—that’s the only way to describe it. They go crazy for it, they lose control of themselves. One night I caught a (drunk) mating pair of large yellow underwings, (Noctua pronuba). This was a great opportunity to compare a known male and female specimen of the same species.
|Some moths from our study site.|
|The light trap.|
The farm had planned to put bullocks back into my field (aptly named ‘The Great Field’) and, not expecting us to have been rained off so much earlier on, thought we would have probably completed our study at that point. Unfortunately, we were still there. And that meant I had to share my field that last week with 40+ inquisitive bullocks. One consequence was that I had to go back to generator power (in case the bullocks managed to electrocute themselves from my mains cable—with bullocks, anything is possible). This meant my mains cable had to be removed from my field and installed in one of the other sites. The cable was 150 m long and weighed 70 kg and it was tangled by the time we got it to the other field. We spent an hour and needed the space of the entire field to untangle it.
I was a little apprehensive about how the bullocks might take to me as I jangled my jars across the field to my light trap in the dark (which had now become a cage due to the fact we had to install 2 m fences around it to protect the equipment from the beasts). When I entered the dark field that first night and started to cross I kept track of where they were by the reflection of light from their eyes. Being careful not to shine my headlamp directly in their face, in case they got alarmed and went mental, I scanned around the field to see where they all were. Unfortunately they were all sitting around in the void between me and my trap. They all stared straight at me, motionless as I navigated through them, but it was only when I was facing them that they behaved in that way. As soon as I had passed them, as soon as my back was turned, they began to approach me. By the time I had locked myself in the cage and started the generator, they had surrounded me totally. It was surreal.
The second issue I had with those bullocks was their tendency towards mindless vandalism. When I arrived at my light trap for the following night’s study (again, closely followed by the whole herd), I discovered that the bullocks had broken a chain, lifted a latch, opened the gate and ransacked my cage. They had knocked the light trap and generator over but worst of all, they had defecated all over the place. I had to spend the night in there! Luckily nothing was broken and I managed to lock them out by tying the gates together with a bootlace, reassembled the trap and, with barely seconds until midnight, I was ready to begin. I have to confess that I did use some pretty strong language and shout at them at that point. They were surrounding me and so I was operating in a fly storm again. After I had told them off a bit they left me alone earlier than they had done the previous night. Every single one of them disappeared into the darkness. Maybe a minute had passed before I heard a deafening thudding of hoofs, the herd was charging directly at my cage. As they ran towards the cage they stared straight at me and only at the last moment did they fan off to either side, before circling me a couple of times before running off into the darkness. They did this once more and then left me alone for the night. Animal behaviour wasn’t one of my strongest modules last year so I can’t offer an official explanation for that behaviour, but I guess I’d surmise that maybe they took offence to my telling them off and wanted to reiterate that a herd of half-tonne bullocks can be a lot more intimidating than a small ape shouting from the safety of a 2 m cage…
After I’d finished that night, I secured the cage once again. I made that cage a fortress, tying down the latch and making it (I thought) impossible for them to break in again. You can’t underestimate the tenacity of a horde of inquisitive bullocks it seems, for when I visited my generator the next day, they had broken in again, and this time they actually had destroyed the light trap (and defecated a bit more).
So to conclude, don’t underestimate the intelligence or strength of these creatures, and you probably shouldn’t shout at them either. They watched craftily from a distance as we surveyed the damage and realised our study had prematurely come to an end. One of them even came over to gloat as we packed up.
Despite the rain, and technical hitches, and unruly bullocks – we had managed to complete four full replicates of our lattice square experimental design and met some fascinating species along the way. We have yet to finish the ID work and analyse the data, but the North Wyke light trap study will always be remembered fondly in my mind.