In praise of craneflies

Here are some curious creatures from Hauxley last week. Scott spotted the left hand one as it lay, elegantly submerged, just beneath the surface of a pool. At the hind end a corona of short tails clad in a dense fur of water repellent hairs breaks the surface tension and allows the creature to replenish its air supply. The other two maggots turned up later in the week, at first glance apparently the same species but the middle one has tails festooned with wispy tufts, whilst, on the right, the larva ends with delicate lobes and what look like two eye spots but are the opening plates leading into the trachae breathing tubes that ramify the length of the body. That left hand one is substantial: 3cm of ominous twitching, a small head reaching back and forth, the jaws gnashing. The other two are not so big but, again, you can see the retractable dark head and mandibles. All three are larvae of craneflies (the family of flies called Tipulidae). Cranefly maggots thrive in damp soils, swamps and ponds, shredding leaves and other detritus with those tough jaws. They are not glamourous insects. There is not a Cranefly equivalent of the British Dragonfly Society or Balfour Browne Club (a sort of train-spotting club for water beetle enthusiasts. I should know, I've been a beetle train-spotter for 30 years). I do not know precisely which species these craneflies are (I don't know imprecisely either, to be precise), nor much about what they do, the habitats they prefer or why they should turn up this year but not last. The larger one was widespread in the Hauxley ponds this week and grown fat on what they offer. When the behaviours of pond invertebrates have been observed in detail they commonly show complex and nuanced natural histories, with precise behaviours and tolerances: for example, where water boatment will or will not lay eggs or damselflies changing behaviours in response to different predators and water beetles sensitive to changing structural densities of weed beds. These cranefly maggots are probably just as particular in their ecologies but remain mysterious.

The heron and the fast flatworm

January’s blog  highlighted the striking ability of pondweeds to get to unexpected places, considering that they can neither fly, walk nor swim under their own power (12^th and 19^th Jan). Here is another neat example of colonisation from Hauxley Nature Reserve. A few weeks ago we dug out some brand new ponds amongst the older experimental ponds from which I’ve recorded the invertebrates since 1994. The new ponds look raw: in the left hand photograph you can appreciate the unlovely bare mud, sheer sided and often clouded with muddy water. But look closely in the bottom left and there are the elegant prints of a heron which has deigned to wade through, and, amongst the heron’s tracks the dark, gliding oblongs of flatworms (right hand picture). They are species of Polycelis, either tenuis or nigra but hard to tell which without dissecting their reproductive organs and this is not that sort of blog. Polycelis are hunters, which suggests that there is something to hunt. Small Hydroporus water beetles and Crangonyx freshwater shrimps were also evident. All these creatures and numerous in the pools around about and have moved into this new home readily. The original ponds from 1994 also colonised very quickly but with a slightly different fauna of pea shrimps and water fleas. This new round of ecological succession may be different because the adjacent older ponds, spring boards for colonisation, harbour a more varied fauna.

The liver-sausage slicer

More core try-outs. Here are Pete and Dave experimenting with the new, hand welded, Dave designed corer (unveiled on the 5th April blog). The metal core tube has a plunger allowing us to gently push out the sediment samples, the plunger handle calibrated to measure out 1cm sections which are then sliced off. The sections from this core were strikingly similar to liver-sausage, a kind of processed meat that seemed to dominate 1970s Sunday tea-times, with its distinctive grey-blue-brown patina and deeply savoury taste. I had assumed liver-sausage had become extinct now that our supermarkets are full of rustic treats from across the whole of Europe but Pete assures me it was all he ate in the second year of being a student. We can now cut up the cores immediately in the field rather than bringing them back to the lab and struggling to detach them from tubes. This core came out of a pond that lingers along the headland of an arable field at Blakemoor Farm towards the south end of Druridge Bay. The fine sediment gets ploughed and driven through occasionally and the pond lacks the dense swards of swamp plants that seem to be associated with the darker, organics rich mud. We suspect these arable field ponds are much less effective at trapping carbon, although the surface of the mud can often be a vivid mosaic of green algae bubbling out oxygen on sunny days. Over April we hope to core a range of pond types to characterise the organic carbon that has buitl up in their sediments. Dave's corer looks the business.

The engineer and the Harrod's toilet brush

Newcastle upon Tyne, where we are based, has proud tradition of engineering. There is a lingering scatter of ship yards along the Tyne now used to pamper North sea oil and gas rigs and, over in the west end of the city, a massive workshop constructing armoured vehicles where once lord Armstrong's yards supplied battleships to the world. The heyday of engineering has largely gone nowadays, leaving a strange flotsam in the Discovery Museum which has galleries of shining engines, pistons, motors, winders, winches and mills. In the days of digital the knack of manufacture still has its place and research often brings out the best. We have been struggling with how to take a core of sediment from the ponds. We need to be able to drive down into the thickest mud, sometimes through mats of roots, pull out the whole core and not lose the gloop at the top. Dave has lovingly designed our very own corer, all the state of the art standard ones having proved a failure. Hand welded is resembles a hydrid between a bazooka and broadsword. We tried it out in the sudden sunshine up at Blakemoor farm on Thursday. The substantial metal pushes into the mud with satisfying substance, unlike some of the flexing and buckled plastic tubes we have tried. Dave laments the absence of foot braces to help push down but I’m sure they can be added. The metal tube has a cunning, calibrated plunger to push out the core. The only thing we need is something to clean out the inside of the tube between cores. Dave has the answer: a toilet brush from Harrods. This is the charm of research. Here we are struggling to pull out plugs of mud, accurately and precisely to measure weights and volumes and this has required a craftsman’s eye for design and an inexplicable bit of top quality bathroom shopping.

The ponds' Antiques Road Show

The month of March may have been cold but there has also been little rain. No wonder many of the shallow field flashes have dried out since November. The ponds of south east Northumberland have changed over the decades too. Here are some simple data from a talk I gave last week to the north-east branch of the Institute of Ecology and Environmental Management. Always glad to have people turn up; I still fret that ponds don't quite have the allure of the Large Hadron Collider even though ponds are especially rich in wildlife compared to the large lakes and rivers that dominate the imaginations of policy makers. The data are for the south east corner of Northumberland, in a triangle roughly from Amble, at the north end of Druridge Bay, south to Newcastle inland and Tynenouth, the latter at the coast. I counted all the ponds (...and moats, troughs, tanks and the like) I could find on 1:10,00 Ordnance Survey maps across all the historic editions. "Survey" in the table above shows the survey edition dates when maps were revised. Okay, it is not a complete pond census, only an audit of ponds that appear on maps but those Victorians in the Nineteenth Century were very detailed map-makers, capturing features down to 4 metre diameter. The overall number of ponds has not changed much, but the turnover of individuals ponds has been considerable, with an conspicuous late surge led by golf courses. The general increase in recent years matches data from the UK countryside Survey and recent audits by Pond Conservation. Which should be good news, unless all those old ponds were superb wildlife hotspots compared to these new sites.

"....til the wild geese have flown"

Shakespeare’s King Lear reckoned winter lasted until at least their departure. The cold has kept us indoors but Druridge Bay is exquisite in winter. Thursday morning I was up at Blakemoor and Ellington, the pastures still empty of ewes and lambs, the arable fields with bedraggled winter wheat rotting away. The North Sea has been churned all weak into a deep iron blue. Theatrical sheets of snow whipped in, the sort of snow dry as polystyrene bobbles, bouncing off jackets and hats. The easterly blast blew in some surpirses; a taxidermist asking me if i'd seen his friend who he'd lost searching for the wreck of puffins that has been washing up all week. The final snow wall was trailed by a barn owl, drifting in on the eddies behind the snow front. I was out doing the first complete census check of ponds. As usual there were surprises, many of the shallower sites dried out but many of the tiny pools and ruts in gateways more conspicuous. the number and extent of ponds chnages significantly with season and year, which begs some tricky questions for surveys which rely on just one snap-shot visit in one year. A few dollops of frog spawn wallowed unconvincingly. We are keen to get out and collect a full range of sediment cores from across the range of pond types, but have been waiting for some new corers after our experiments with open sided screw-cores out of which the runnier top sediments dribbled (see 1st March blog). This has left Scott and Pete largely stuck in front of computer screens. However Dave Cooke has been welding and forging a new design. If the wild geese ever leave we will soon be back out.

Wrong place, wrong time

The deluge and floods of 2012 have barely receeded, both from memory or the landscape and winter has lingered on into early March. Here is a stiking recollection from last summer; the scatter of silver shards are a shoal of sticklebacks marooned and doomed on the path to the hides at Druridge Pools. The water had overwhelmed drains and ditches, creating a single washland from the Pools across to the dune tracks. These sticklebacks had ventured out beyond their orginal home, as all species have to, at least some individuals (see blog 19th November for flying molluscs, 12th Jan for airborne pondweed) . This swarm's bad luck left them in trackway puddles as the high water receeded. Reminds me of those fossil fish beds in museums, which conjure up a picture of ancient pools and their floundering inhabitants. I quite often splash through scattering shoals on other paths and tracks around the Bay; adventurous sticklebacks seem ubiquitous. Others will have made it to new pools, their good fortune a curse for many of the invertebrates which are vulnerable to these voracious mini-hunters.