Invasive Aliens. Dan Eatherley

Ages for the paucity of written records, is vague. Roads and other imperial infrastructure disintegrated, vibrant towns and cities decayed, and trade declined, all slowing the influx and spread of new species. Yet, this was a period of great human churn as populations from Ireland, Scotland and other outlying regions of the British Isles moved into undefended territory, joined by continental immigrants, particularly from Scandinavia, the Netherlands and Germany. These movements of Angles, Saxons, Jutes and other peoples would have instigated fresh introductions, deliberate and accidental, but for now the details are lost in time.

      The elite are always keen to improve upon what nature has provided and, when it comes to reshaping and enhancing the landscape, few matched the enthusiasm of the Norman invaders of 1066. With a mania for hunting, Britain’s newest overlords depopulated large tracts of territory in the interests of blood sport. Dozens of hunting grounds, or ‘forests’, were designated, encompassing not just wooded areas but moorland, cultivated fields, and even whole villages, from which the occupants were banished under ‘forest law’. Any animals which could jeopardise the chase were also dealt with with ruthless efficiency: sheep and goats, whose grazing could damage the forest vegetation, were removed, and unwanted dogs hobbled in a procedure known as ‘lawing’, which saw the claws from one foot lopped off with mallet and chisel. The Anglo-Saxon Chronicle for 1087 implies that William the Conqueror’s focus was native game: ‘Whoever slew a hart or a hind [male or female red deer] was to be blinded. He forbade the killing of boars even as the killing of harts. He loved the harts as dearly as though he had been their father. Hares, also, he decreed should go free.’ Yet, William and his successors seemed happy to bring in, and protect, foreign quarry species.

      This included the fallow deer. Like the indigenous red deer, fallow offered fabulous sport for the mounted hunter and hound by galloping away across the countryside. (The roe, Britain’s other native deer, was far more skittish and a bit of a killjoy: its instinct was to hunker down in thick undergrowth at the least sign of danger, and it could even die of fright.) As discussed, small numbers of fallow deer may already have been present in Britain before the Normans; certainly, by the beginning of the twelfth century the species is known to have been well established. There’s also a possible Sicilian connection here.

      After a 30-year campaign, the Normans completed their capture of this Mediterranean island from the Arabs in 1091. Perhaps impressed by the parks of wild animals, including fallow deer, kept by Sicily’s previous rulers, in 1129 King Henry I had 11 kilometres of wall built around his own estate at Woodstock, Oxfordshire, to which he introduced lions, leopards, camels and a porcupine. And fallow deer. According to the archaeologist Naomi Sykes, ‘This collection, which is the direct ancestor of London Zoo, was not simply a frivolity; it was a metaphor for the Norman Empire, a statement that the Norman kings had power not only over the wild creatures in their possession but also over the countries from which the animals derived.’ In addition to being far more manageable than red and roe – their scientific name Dama comes from the Persian for ‘tame’ – fallow thrived on poor quality land, so proved an immediate hit. By the 1300s, the deer had been stocked in some 3,000 parks across Britain; in England alone, these enclosures covered the equivalent of 2 per cent of the entire land area. The modern distribution of fallow deer, whose UK population probably exceeds 200,000 individuals, matches that of the medieval parks from which they escaped. (According to Charles Smith-Jones of the British Deer Society, fallow are remarkably loyal to their home areas and seem inclined to heft strongly to them.) Like other deer species – both native and introduced – the fallow is today regarded as a crop pest, an unwitting cause of vehicle collisions, and a potential carrier of disease from bovine tuberculosis to foot-and-mouth.

      The common pheasant was already successful before its introduction to Britain, having colonised a swathe of Eurasia from the western Caspian region to Japan. As discussed, in Britain its bones first turn up at Roman sites, and historical documents – most of them written after the fact – indicate that pheasants were sometimes eaten as a luxury prior to the Norman invasion. For instance, in 1059, King Harold is said to have offered the bird as a privilege to the canons of Waltham Abbey in Essex, a gift deemed equivalent in value to a brace of partridges or a dozen blackbirds. In 1098, Radulfus, the Prior of Rochester, dispatched to his monks 16 pheasants (along with 1,000 lampreys, 300 hens, 30 geese, 1,000 eggs, 4 salmon and 6 bundles of wheat). A contemporary and perhaps more dependable record – a bursar’s roll at Durham Priory dated to the reign of the Saxon king Edward the Confessor (1042–1066) – includes a purchase of one pheasant and 26 partridge. Pheasants may first have been kept in royal parks and forests, along with fallow deer, and their increasing prominence on banquet menus from the late twelfth century implies that they had by then naturalised. In 1251, Henry III ordered 290 of them for his Christmas feast, and by the late 1400s, pheasants warranted legal protection from the Crown. These early imports were in fact the ‘Old English’, or colchicus, subspecies from the Caucasus and lacked the distinctive white neck ring of the torquatus race, originating in China, which is these days released for shooting.

      The pheasant is something of an outlier from this period in retaining a certain aristocratic association. The best explanation is that these poorly camouflaged, clumsy fliers have so far failed to get along in the British countryside, despite repeated reintroduction. Of an estimated 20 million poults (young birds) loosed annually, 90 per cent perish within the year. And not just from the shooting: most evade the guns only to be picked off by foxes or end up as roadkill.

      Although pheasants might one day naturalise in Britain, there’s precious little evidence for that so far. The same can’t be said for what is without doubt the most impactful of all medieval introductions.

      ‘It’s quite a massive hill here, this site,’ I said. ‘And that’s all just made for the rabbits, this big mound?’

      ‘Well, no. The hill, I think, is natural. It’s just that rectangular mound there that’s made for them,’ responded David patiently.

      ‘Sorry. I was thinking the whole hill was a warren!’

      ‘Oh. That would make it the world’s biggest pillow mound, yeah.’

      The aroma of wood smoke wafted in the chilly morning air. A distant chainsaw whined. We were standing at the foot of a steep grassy hillock, almost 100 metres high, upon which was broodingly perched a three-storey tower of limestone. Known these days as the Bruton ‘dovecote’ for its later repurposing by pigeon-fanciers, the original function of the pale-yellowish structure, which dates back to the 1500s, is a mystery. One theory has it as the prospect tower for the nearby Bruton Abbey – long since demolished on the orders of Henry VIII during his dissolution of the monasteries – offering the local aristocracy a grandstand view of the abbey’s deer park. But neither doves nor deer, nor indeed the pair of Friesian cows munching contentedly near the base of the tower, had drawn me to South Somerset today.

      No, I was interested in rabbits and in particular how and why these shy burrowing mammals from southwest Europe had been introduced to Britain, and then run amok. An important clue was offered by the pillow mound, a characteristic earthwork which to the trained eye shouts ‘rabbit’. Clearly, my eye wasn’t trained because Dr David Gould, a landscape archaeologist from the University of Exeter who had agreed to show me some, needed to point out the example that was right in front of us.

      ‘You see that ridge coming down the hill?’ he said. ‘That’s one.’

      The British population of the European rabbit today numbers in the tens of millions and the species is now regarded as a worldwide menace. Yet the original bunnies were an ineffectual lot, hardly a patch on their vigorous descendants and quite unable to excavate their own burrows. This is where the pillow mounds came in. Created by piling up soil in long, low heaps, and encircled by ditches, possibly to deflect any floodwaters, these artificial structures provided a dry, soft and well-ventilated substrate into which the rabbits could dig. Some even incorporated stone-lined tunnels making life easier still for their feeble tenants. At the same time, pillow mounds concentrated the rabbits in one place for ‘hunting’. If you could call it that. The phrase ‘shooting fish in a barrel’ comes to mind.

      The pillow mound was a hallmark of the artificial rabbit warren, or ‘coneygarth’, from the Middle