Phenomenon

 

PHENOMENON: strictly “..any event that is observable.” (Wikipedia)

Common usage “..most commonly used to refer to occurrences that at first defy explanation or baffle the observer.” (Wikipedia)

Keen natural historians go through life observing the wonders of nature. Day by day we see “life” happening before us; the passing of the seasons; life cycles of animals and plants; the feeding; the mating; the changes of form or size. We find wonder and enjoyment in all the changes as they occur. Some of it we understand; much of it is still a mystery.

But every now and again, something happens which takes us completely by surprise. Something which we have never seen before; possibly never heard of; possibly heard of but never witnessed. Some “event” which we may have guessed at, or realised must take place but never seen. A “natural phenomenon”!

Some years ago Mary and I were on a conducted birding holiday in Romania and part of the trip was living on a boat and cruising the waterways of the Danube delta.                           

One afternoon as we cruised from one lake to another along a narrow tree-lined waterway we ran into a veritable snowstorm of hatching Mayflies. They were locally so thick, the visibility was poor. As we cruised slowly through them they were alighting on us and everything they touched.

They were lifting off the surface and just hovering, up to about 3m off the water. Males were mobbing females, and rafts of mating insects covered the water. Within 200m they were gone, and within a few hours they would all be dead. An insect which may have been living as a larva in the river for months, even years, had hatched into an adult, flown, mated, laid eggs, then died within a brief afternoon; the phenomenon of a mass, synchronous hatching. Our Romanian guide had been brought up living on one of the islands in the Delta, and in his forty odd years had never seen it although he was a professional wildlife guide. For this one species of Mayfly it was just the right place, at the right time, for somebody to witness and record it.

 

Nowadays, with widespread dissemination by the media, many natural history phenomena are well known. Like the mass migration of Monarch Butterflies across the Americas. Or the beaching of shoals of spawning fish. But I know of two such occurrences which are not so widely known.

I used to be a commercial fisherman (trawling and dredging). We spent a lot of time bottom trawling about twelve miles off Looe in south Cornwall. The aim was to catch bottom-dwelling fish like Lemon Sole, Plaice, etc., but along with them we were scraping up a lot of other sea life which was not marketable, like sea urchins, starfish and seaweed encrusted small stones. It was usual to tow for about three hours. That allowed sufficient time for the ‘catch’ to accrue, without collecting too much ‘debris’ which would weigh the cod end down and so chafe it out on the seabed. Normally we would fish day and night until we had collected a good catch or run out of ice.

                                        A bag of mixed fish and "trash".
And each “bag” would drop about 500kg of mixed fish and debris on deck.
But on one occasion, when we hauled we had about a tonne in the bag, and when we opened the cod end we found it was mostly composed of Brittle Stars (Five-fingers Starfish). This had caused quite a lot of chafe, so when we shot the trawl again we towed off in the opposite direction. But after a couple of hours we appeared to be slowing down, so we hauled again, and found, once again we were gagged up with these delicate feathery brown starfish. So we steamed off for a couple of miles and found some ground that wasn’t full of unwanted catch. It was the first time in 10 years of fishing that I had come across such an accumulation. It is apparently associated with their breeding cycle.

We had a similar experience with Queen Scallops. These are the smaller, bi-convex relations of the Scallop (which is flat on one side and convex on the other). Whereas the Scallop is mainly bottom dwelling and moves infrequently (by swimming), the Queenies are always much cleaner looking, which suggest they spend less time inert on the bottom. They are more free swimmers, rising quite high off the bottom at times to filter feed as they swim. (We often found them caught in the net of the top cover of our box-trawls at probably 2m off the bottom.) At times and in certain areas we caught quite a lot as by-catch (We later concentrated on catching them for market.) But on one occasion we found that while fishing in our favourite area for Lemon Soles we were getting “gagged-up” with Queens. The tow which includes sunset (the dimpsey haul – the first haul after dark) is usually a bit better than all the other hauls in twenty-four hours, other factors aside. But on this occasion it was away and above what we expected. We had over a tonne bag, mostly Queens. It was a surprise, but then fishing is full of surprises, so we shot away again, and the next tow was almost as bad. Not only does the extra weight cause chafe to the belly of the trawl, but it creates a lot more work for the crew to sort through by hand to find something saleable, and then shovel the rest over the side. We continued through the night with little better results, but by next day we were back to the normal catch. And the following night the same thing happened. So after the dimpsey haul we steamed off before shooting again. And the same thing happened. So we gave up for the night and ran into Mevagissey for a night's sleep. I think we did this for three or four nights before we found we were clear of the extra Queens at the dimpsey haul. So again, a mass gathering of a creature we had no idea did such things. And again, to do with their breeding cycle.

I now know that Spider Crabs do a similar sort of thing when they congregate to moult their shells.

But those are instances of things which are not really in our world. We are creatures of the air and the land. So perhaps it is understandable that we don’t know about them. But the same sorts of “occurrences” happen in our world.

Cockchafer.

May Bugs (Cockchafers) suddenly appear in May. We start catching them by the dozen in moth traps. But what I didn't know was that Noctule Bats are tuned in to their hatching from pupa in the grass. I don’t know if they are so alert to what is going on that as soon as the May Bugs start to hatch they find them, or whether experience has taught them to look out for this every May. Whatever, a friend once told me that he knew when the bugs were hatching because at dusk he saw the Noctule bats swarming over his lawns. It must be a very short feeding season for the bats on these beetles, but anyway, they have cottoned on to it. But one would have to be in the right place at the right time, and in the right conditions to ever witness this “phenomenon”.

Female (above) and male (below) Ghost Moths "in-cop"

    .
Mary and I are invited to a friend’s “wildlife farm” open-days every year to run a moth trap as part of the attraction of the place to raise funds. Our first year, as we were walking down across his wonderful flower meadows to start the moth trap up, we noticed that there were many silvery-white male Ghost Moths hovering just above the tops of the grasses and flowers, looking for females roosting in the foliage. We watched the spectacle for a moment before I thought of taking a photo, or even a video clip. So I hurried back up to our camper-van to get my camera, but by the time I got back, less than five minutes later, they were all gone! They’d all found a mate and were settled in the grass ‘in-cop.’ But it is so ephemeral; it only lasts a matter of 20 minutes as the light fades, over a few nights a year. Chances of observing this are slim. Again, right place, right time, and an observant naturalist. Next morning I walked the mown paths around these flower rich meadows and picked up many Ghost Moth wings that the Noctule Bats had discarded from their previous evening’s foraging.

I’ve never seen  a bat mating swarm,  but apparently at some hibernation sites male and female bats of some species congregate, and mating takes place. This starts about October and extends into the winter months. Studies have shown that females join these “swarming” parties flying either at the entrance to, or within a hibernation site, only once. Whereas males repeatedly, over several nights, will join the throng. Presumably a female, once mated is content with that single coupling. Males on the other hand can maximise the distribution of their genes by mating with several females. All this takes place during the night; not at dusk or dawn, when bats frequently “swarm” at the entrance to a roosting site before re-entering.

                                        A Crow Butterfly.
While we were touring Australia on one of our trips we came across a mass aestivation of Crow Butterflies. Quite a lot of creatures “aestivate”. It is almost the opposite of hibernation, except that those creatures which do it pass the time resting through the heat of summer or a prolonged draught. In this case, we had walked into the bush in Northern Australia at a wind-pump, pumping up water for stock. Coming to a very dense clump of trees, we found thousands of Crow Butterflies aestivating. They were hanging thickly off the lower branches.

                                                Crow Butterflies aestivating.
Over the area of a tennis court there must have been millions. Most were at rest, but some were restless and flitting around disturbing others. Why they congregate, making them such big targets for predation, puzzles me. But perhaps it is strength in numbers.

In the early 70's we visited Lopwell Dam, the head of the tidal River Tavy. The “Dam” is a weir about 1.5m high, with a sluice-gate and a water take-off structure alongside it at one end. Almost as soon as we arrived I spotted a Mink apparently eating the moss at the side of the sluice.

But realising that Mink wouldn’t be eating moss, I took off my shoes and socks and waded over to see what it had been feeding on, and I found elvers (those 10cm. long, almost transparent young eels) by the hundreds, wriggling up the wet moss at the sides of the slope. So rummaging in a waste bin in the car park I found a poly-bag which didn't leak, and I scooped up some of these fragile eels and took them back to show the others (and to populate our garden pond). I had heard of elver runs, but associated them with the big rivers like the Wye and the Parrett. But of course, they will also “run”, at certain states of the tide and the moon up any river. But one needs to know when and where to observe this. Because it only happens on a few tides in any year. And we had chanced on seeing it.

Elvers "bagged" from below the dam at Lopwell.

         
Mary keeps prompting me with more and more instances of mass gatherings from our travels. Great eruptions of flying ants on the headland near our daughter’s house, with consequent swirling masses of hirondines and gulls following them high into the sky and out over the sea. 

                                            Swarming Locusts.
In Queensland we found ourselves overtaken by vast numbers of locusts. They flew, their wings rustling, from tree to tree, devouring every leaf before flying on.

Notice at entrance to National Park, in New South Wales.

 Huge numbers of Bogong Moths migrate from Queensland to the southern end of the Great Dividing Range, to hibernate among the rocks in winter. Traditionally the local indigenous people would celebrate this nutritious bush-tucker and collect the moths in bulk.

  A Bogong Moth.

                                   

It is a slow process by which we learn the behaviour of plants and animals. When it is so rarely seen we tend to call it a phenomenon. But to the participants it is just part of their lives! For my part I find it fascinating. I never cease to feel amazed at the ingenuity of nature!

(The infrequency of observing these phenomena means that much of my phtographic evidence goes back to the days of slides. Hence the poor quality of some of these pictures!)