Nigel Grist
is a biologist with a ‘deep well’ of information and knowledge, a result of his interests in moor, marine and avian life. Additionally, he is an accomplished photographer and artist. His presentation this Monday, on the ‘natural and un-natural history’ of Dartmoor combined his knowledge and photographic skills in a most interesting, entertaining and memorable way. His photographs were beautiful; pictures in themselves
His post-graduate work started in Durham working on Kittiwakes, was followed by a research job in Hull and later he set up his own consultancy. Using his skill in building a database he created a master diagram of Dartmoor, identifying 379 tors and hills, with the target of walking to them all. He did this in 11 months, reckoning he and his hound covered 1,200 Km in doing so. He noted that a large number of the tors and hills are named after creatures: Crow tor, Cuckoo rock, Doe tor, Dunnagoat tor, Feather tor, Fox tor, Gnat’s Head, Hare tor, Hen tor, many of which he saw and photographed
The presentation was divided into sections, starting with Dartmoor’s geology, through witches’ hair and mossy beds, flesh eating plants, problem plants, bottomless bogs, dark woods, damsels and dragons, small hairy things, beasts on the air, serpents and toads, and other beasts to human, ancient and modern and our impact on the moor
Dartmoor is an enormous batholith, extending down 5 – 6 Km of granite, a mixture of felspar, mica, tourmaline and quartz. In places the tors appear like layers of pancakes, for example, Chat tor (Grid Ref. SX 555852) and Branscombe’s Loaf (SX 554892). This formation has resulted from a decrease in pressure on the granite as the thick overlying deposits became eroded. In several places pit depressions, erosion pits arising from repeated freeze-melt, such as on Heltor Rock (SX 799871) and the Devil’s Frying Pan (SX 562769) near Great Mis tor, can be found. It is not yet agreed whether Dartmoor was fully glaciated on not. The hummocks on the north side of Cox tor (SX 531761), and the ‘ribbons’ of granite on Great Staple tor (SX 842760), are evidence of glaciation from the last ice age.
Dartmoor Wildlife
- Clean air on Dartmoor has led to there being at least 354 species of lichen on Dartmoor, some having Dartmoor as their only known place. On Blackinstone Rock (SX 787856) alone there are 90 species of lichens and mosses. The Victorians even built steps up the rock so as to enable them to see them better. Lichens at the top of many rocks can differ from those lower down, due to birds perching and defecating on the top, so providing different nutrient conditions. Tiny, colourful lichens can be found on Dartmoor, such as Devil’s Matchsticks (Pilophorus acicularis), with bright red heads and a tiny yellow lichen, that breaks down rush and sphagnum moss. Some lichens are edible, but did not come recommended for their taste, such as ‘Rock Tripe’(Umbilicaria sp). A bright yellow parasitic fungus, ‘Witches Butter’(Tremella mesenterica), found on gorse, is parasitic on another fungus that lives on the gorse
Dartmoor Plant life
- The gorses are counted as a ‘problem plant’ and are routinely burnt. Sheep and ponies can eat the soft new growth. Bracken continues to be another problem. It can be discouraged by flattening it using heavy horses dragging sleepers over a period of 5 to 6 years. Now mechanisation is used to achieve the same end
Around the damp areas sundews, some with elongated leaves and some with round, and butterwort can be widely found. Both many headed and single headed cotton grass (Eriophorum) and yellow bog asphodel (Narthecium ossifragum) flourish in the many mires, such as Fox Tor Mire (SX 620710) and Emsworthy Mire to the west of Saddle tor (SX 751764). ‘Ossifragum’, the botanical name of the bog asphodel, might be associated with its effect on sheep, since it is thought that sheep which eat it can become doddery and fall, so breaking their legs. Marsh St. John’s Wort (Hypericum elodes) can also be found in the mires, being a good food for damselflies. Around the mires, wheatears, and stone chats can be found. The mires are dangerous, sheep and ponies meeting their death in them. Nigel showed us a photograph of one pony up to its shoulders in a mire that he and companions were able to haul out
Dartmoor has one of the main concentrations of upland oakwood in the UK, Wistman’s Wood (SX 770613) and Black Tor Copse (SX 563896), are the best known. Piles Copse (SX 643621) on the River Erme is another. Wagtails, dippers and kingfishers thrive there. These ancient woods are rich in epiphytic growth, with planus lichens and ferns on the branches flourishing
Nigel’s close-up photographs of damsels and dragonflies
were particularly beautiful. He had captured golden ringed dragonflies, red darters, skimmers, a large red damsel and finally a dazzling blue Demoiselle, that, he pointed out is only found by running water. He specifically mentioned Red Lakes (SX 641665) as a place to find Black Darters
People have had an impact on Dartmoor
from ancient times. The Neolithic monuments are apparent right across the moor. Examples were given of barrows and burial chambers (SX 668592) and stone rows, double rows (SX 651611 and 555748) and the long line of at least 1,000 stones still visible, running north above Ivybridge (SX 655575). Neanderthal flint tools have been found in a dig near Hay Tor (SX 757771). There are 400 Km of Reaves that 1,500 years ago divided the territory in to workable areas, suggesting a sophisticated social system and the muscle power necessary to create these 2 metre-wide low banks. Holne Moor is the best known (SX 66995)
.
Rowan trees often give a clue that you are near a tin working, tin mines being found all over the moor. Some are open work and deep, as is Hexworthy Mines (SX 654728). Around the River Plym the tin spoils at 90 Degrees to the river are very clear (SX 605675). Now the tin spoils have become a fine place for mosses and lichens to grow. Leats conveying water were constructed over Dartmoor, some to create power for the stamps that crushed the ore and the bellows for the furnaces. Many are still there
The tin miners were bound to have come across the distinctive adders, the grass snakes with the cream spots on its neck, and lizards. All are common. Maybe Stingers Hill (SX631660), near to a tin mine, was named following a number of unpleasant encounters. Rabbit keeping was an important industry, with hundreds of thousands being sent as meat to Plymouth and for fur to London. Huntington’s Warren by the River Avon (SX 660670) only ceased in the 1950s. The warrens were constructed on a south slope, cigar shaped and often 4 metres long. The spoil from the surrounding drainage ditch was placed centrally and turfed over with, at times, a granite slab over the ditch to enable access. A good example is Ditsworthy Warren (SX 585664) which shows a good number of these all in one place, clear drainage channels and the River Avon downhill and a leat on the upland so constraining the rabbits’ movements
It was an excellent presentation. This was a well-attended meeting (51 people) with several members of the Kingsbridge Camera Club
attending as well as our usual members. It was good to see them
Juliet Morton