Dr Terry Mabbett writes on the hidden benefits of Oryctolagus cuniculus.
I was recently talking to Kevin Ross, a woodsman who has featured in Forestry Journal before for his steadfast management and guardianship of Tunstall Common in East Suffolk, as a forestry contractor running a thriving local woodfuel/bespoke sawmilling operation. With his extensive knowledge covering forestry, agriculture and wildlife, I often consult Kevin on a wide range of subjects. This time it was about sallow and the wood-burning profile of this native willow. However, we strayed onto wild rabbits (Oryctolagus cuniculus) when I recalled how my grandfather had fed green sallow stems to his domestic rabbits.
It was Kevin who first alerted me to rabbit haemorrhagic disease (RHD) during a visit to Suffolk and how it was impacting heavily on the local wild rabbit population there. Scientists at the University of East Anglia subsequently reported how RHD, caused by a calcivirus (strain RHDV 2), had moved into the wild brown hare (Lepus europaeus) population and how they now feared for this native lagomorph.
Rabbits are notorious pests of young forest stands and agricultural crops, so at first sight RHD may appear to be a positive development, but like most things in nature it’s a matter of moderation. Kevin fears the RHD pandemic in wild rabbits will deprive Suffolk’s top-end mammalian and avian predators of a major food source, with major implications for other wildlife, game birds and domestic fowl.
ROAMING REYNARD AND SCENT-STALKING STOATS
Red fox (Vulpes vulpes) is a prime example, says Kevin, because wild rabbits are a major food source for this canine predator. If rabbits disappear, foxes will make more of a meal of another popular food source, the eggs and nestlings of ground-nesting wild birds, game birds and domestic poultry, as well as placing more pressure on mice and voles, thus reducing the food supply for owls. Among this alternative prey and especially pertinent to East Anglia is the nightjar, a flagship avian species of lowland heathland which is very much on the contemporary land use agenda in Suffolk. “And on past experience, even domestic cats might not be safe if the red fox population is deprived of its mainstream wild prey,” said Kevin.
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Stories about the stoat (Mustela erminea), a mustelid predator also called short-tailed weasel or ermine are even more fascinating. “Stoats stalk their prey by sight as well as scent,” said Kevin, adding how “the stoat’s relentless and near-perfect pursuit, including down the rabbit’s burrow, may end up with the stoat staring the rabbit into submission.
“And like foxes, stoats deprived of rabbits as mainstream prey will almost certainly increase predation of bird’s eggs and nestlings. Stoats are big egg eaters, with the additional advantage of being able to climb hedges and trees, which means songbirds like blackbirds, thrushes and robins will suffer more than they already do.”
Kevin described the stoat as a ‘precision predator’ immobilising rabbits by puncturing the skin below the skull at the back of the neck. Stoats stand accused of surplus killing of rabbits, drinking the blood but leaving most of the carcass. However, others claim lack of blood on the scene is due to the shallow incision not being able to reach the artery, while leaving carcasses on the landscape is a form of food storage and obesity avoidance, with stoats returning later to consume the kill.
Stoats appear to be surrounded by more fable and folklore than any other native mammalian predator. In addition to blood-sucking is the infamous ‘weasel war-dance’, a dervish-like dance used to mesmerise rabbit prey. And there are reports that stoats hunt in packs, although these are possibly confused by stoats’ habit of playing in family groups.
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How much of this is firm fact or myth is anyone’s guess. However, history shows Kevin Ross is absolutely right about rapid reductions in rabbit numbers having impacts on ecosystems and the environment, with myxomatosis caused by a poxvirus a classic case in point.
IBERIAN LYNX AND EUROPEAN RABBIT
An early point of reference is the Iberian Peninsula (Spain and Portugal), native home of the European rabbit, where the arrival of myxomatosis in the 1950s wiped out 95 per cent of the population and was credited with kick-starting a rapid decline of the Iberian Lynx (Lynx pardinus). With its distinctive facial beard, Iberian lynx was reliant on rabbits for 75 per cent of its prey, and was unable to adapt to alternative prey like the red fox did. The rabbit population recovered over the next three decades, but the arrival of RHD in 1988 caused a second wave of destruction (up to 80 per cent) and sent the Iberian Lynx into a further tailspin. Its decline was finally arrested and stabilised by various programmes including the controlled release of 100,000 rabbits into the wild to multiply and reach equilibrium with the feline predator population.
The latest reports from the coalition of conservationists striving to rescue Iberian lynx from extinction is upbeat, with a population of over 1,000 predicted for 2021. A key member of the coalition is Ramon Perez de Ayala of the World Wildlife Fund, Spain, who says the Iberian lynx may not be completely ‘out of the woods’, but has certainly reached a milestone having slumped to just 100 animals two decades ago. The availability of wild rabbits for the lynx to prey on is clearly the key to success. Ramon Perez de Ayala said: “I know how to create lynx populations, but it is rabbits that are my biggest headache.”
It should come as no surprise that wild rabbits are the main prey of Iberian lynx. Both predator and prey are native to the Iberian Peninsula and have clearly co-evolved over many millennia. Spain takes its name from the Carthaginians who called it ‘Ispania’, meaning ‘land of the rabbits’. It appears the European rabbit has saved the Iberian lynx.
The situation in Australia, where both European rabbit and red fox are alien invasive species, is even more complex. In 2017, RHD was purposely released into the Australian environment as a biocontrol agent against a highly damaging rabbit population. However, there are already fears that red fox, increasingly deprived of a dietary staple, will turn its attention to Australian native mammals, many of which are on the danger list – more so after the horrendous bushfires of 2019/2020.
GAME BIRDS AND BUZZARDS IN BRITAIN
But back to birds’ eggs in Britain and how much more risk there will be from predators like red foxes and stoats if the rabbit population takes a dive. I asked Kevin Ross about the implications for pheasant rearing and the game bird industry in general.
“Game bird rearing is not so much at risk at the egg stage given the nature of modern breeding methods,” he said. “Incubation of pheasants’ eggs, for instance, is carried out by estates on a large scale and in secure premises using ‘bought-in eggs’, with many imported from Europe. As such, these predators will generally not get the chance to damage the game bird industry at the egg incubation stage.”
Between 1 May 2018 and 31 April 2019 over 25 million hatching pheasants’ eggs were imported from four EU countries – France, Poland, Portugal and Spain.
“Enhanced risk for pheasants is at the poult stage and especially from common buzzards, for which wild rabbits feature prominently as natural prey,” said Kevin. Though now stable and increasing in many places, common buzzards were once a rarity on the landscape with availability of wild rabbits playing an important part in the raptor’s ups and downs. History shows common buzzard persecuted to extinction in many parts of the British Isles by gamekeepers during the 19th century. The birds made a significant comeback during WWI when gamekeepers were in France and Belgium firing guns at the Kaiser’s army instead of shooting buzzards and other predators.
The same relaxations on buzzard persecution would have happened during WWII, but within a few years common buzzards, along with other birds of prey like the peregrine falcon, were hit by the toxic effects of organochlorine insecticides like DDT, aldrin and dieldrin, which at that time were mainstream pesticides to protect arable crops against insects like leatherjackets and chafer grubs. Being fat-soluble, these highly toxic insecticides, which act on the nervous system, accumulated at the very top of the food chain in birds of prey. However, the common buzzard suffered a double whammy during the 1950s when myxomatosis almost wiped out the wild rabbit population.
Indeed, I had never seen a common buzzard until a possible sighting in 1963 when a friend and I observed a pair of large raptors apparently with a nest at the top of a lone Scots pine. I was gobsmacked, having never seen anything like it before. Kestrels, sparrowhawks and, of course, peregrine falcons at that time had already been decimated by chemical pesticides and were virtually absent from south Hertfordshire and Middlesex. However, my friend Mike Robinson had recently relocated from Newton Le Willows in Lancashire and had seen common buzzards while on holiday in North Wales. He was sure we had stumbled upon a pair of these raptors. There was at least one animal carcass at the nest which looked like a wild rabbit or a brown hare.
This land is now the Hertfordshire and Middlesex Wildlife Trust’s Fir and Pond Woods. The site is adjacent to land owned by the London Borough of Enfield, soon to become one of the biggest tree-planting projects in the area, comprising 38,000 trees, both broadleaves and conifers, with 70 per cent of productive species harvestable for timber.
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We did not report the sighting due to other, more preoccupying things, like GCE exams just a couple of months away. However, I do recall carrying out research many years later to find that it would have been the first report of common buzzards nesting in Hertfordshire for close to a century. Ironically, the nest would have then been in Middlesex, not Hertfordshire, because Greater London Council and all the associated boundary changes, including disappearance of the ancient County of Middlesex, were still two years away.
I got to see my buzzards two years later (1965) in Cardiganshire, West Wales (now Ceredigion) while studying at University College Wales, Aberystwyth (now Aberystwyth University). I remember standing on the university hockey pitch at Plas Gogerddan watching in amazement as buzzards swirled in the grey skies above the hills. Not a sensible thing to do when you are centre-half and a ‘hot-shot’ from University College South Wales, Swansea is steaming down the pitch, ball at stick.
According to Kevin Ross, the common buzzard is quite partial to pheasant poults, especially when its more usual and natural prey, the wild rabbit, is in decline. “Not only does the common buzzard prey on wild rabbits but it is frequently encountered eating rabbit roadkill,” he said. Pheasant poults in the release pens are easy prey for buzzards, which sit on the adjacent trees and swoop down to pick them off. And it appears there are plenty to go round, with almost 16 million pheasant poults imported from France alone in 2018.
Densely canopied woodland with no understorey of shrub, small tree or brambles makes an ideal habitat for avian predators to strike, by easily picking off the poults as soon as they are released onto the bare woodland floor. Apparently the perfect pheasant pen comprises a mix of small trees like thorns (hawthorn and blackthorn) as well as elder to provide low-roosting opportunities; large trees for the birds to spend the night in once they have been in the pheasant pen for a few weeks; shrub and herb species (e.g. grasses and nettles) to offer daytime cover; and finally some hard cover like bramble and bracken where birds can hide if they feel threatened by raptors.
RABBIT ACTIVITY PROTECTS USEFUL PLANTS AND BUTTERFLIES
Rabbits are not native to the British Isles and were most likely introduced during the 11th century by the Normans. However, wild rabbits have been on these islands for almost 1,000 years, with ample time to co-evolve with other species. It is therefore inappropriate to regard this lagomorph as an alien invasive pest species with no benefits for the environment. More appropriate is ‘honorary native’, in the same way that sweet chestnut of the tree world is treated.
Rabbits do cause a lot of damage to young trees, but this can be avoided by installing solid-wall tree shelters of the appropriate height. Ironically the beneficial microclimate and enhanced growth and establishment aspects of these modern tree shelters were accidentally arrived at during trials aimed at protecting newly planted trees against herbivory, mainly by rabbits, by using tree guards which evolved into tree shelters.
So be careful what you wish for with myxomatosis, RHD and other pathogenic microbes which have the potential to wipe out wild rabbits. Collateral damage may include destruction of flagship ground-nesting birds of lowland heathland such as nightjar and woodlark by increasingly hungry foxes and stoats, together with an increasingly big hit on game birds like pheasants from raptors like the common buzzard deprived of its mainstream meal of rabbit meat.
No one should go away believing wild rabbits only benefit predators further up the food chain, because burrowing and grazing activities of rabbits benefit other fauna too (and, notably, the rare stone curlew, now confined to a few hundred pairs on Norfolk Breckland and the South Downs in Hampshire). Patches of sandy soil created by rabbit activity warm up quickly in the spring sunshine to provide ideal places for stone curlews to bask or site their nests on. According to experts, flint stones excavated by rabbits help to camouflage eggs laid in a scrape-nest on bare ground lined with small stones, shells and – wait for it – rabbit droppings. What’s more, a surfeit of rabbits on such sites means predators like stoats and foxes are less likely to feast on stone curlew eggs and chicks.
The supreme irony is that the European rabbit as an introduced mammal, blamed for the worst excesses of herbivory, can assist the conservation of useful wild plants, along with insects (sometimes rare) which rely on these plants. Dr Roderick Robinson of North Yorkshire, with an interest in bracken and its associated flora and dependent butterflies, has an interesting story to tell.
“Rabbit activity including burrowing, scratching and grazing on open sites helps to keep down the growth of grass and allow proliferation of broad-leaved (dicotyledonous) plants like violets, and many other spring-flowering plants like ground ivy (Glechoma hederacea) and bugle from which these early season butterflies can derive nectar,” he said.
Be careful what you wish for with a complete lack of goodwill towards rabbits.
AUTHOR’S NOTE:
Herbivory: the consumption of plant material by animals.
Lagomorph: any placental mammal belonging to the order Lagomorpha and characterised by having two pairs of upper incisor teeth which are specialised for gnawing; includes rabbits and hares.
Mustelid: a mammal belonging to the weasel family (Mustelidae) and distinguished by a long body, short legs, and musky scent glands under the tail. Other native mustelids include weasels, badgers and beavers.
Raptor: Not an altogether clear name for the birds of prey which it is meant to describe. The word ‘raptor’ is derived from the Latin ‘rapere’ meaning ‘to seize’. Raptor generally describes birds of prey feeding on live, captured prey or on carrion, and where the prey is large relative to the predator. Bird enthusiasts may limit its use to birds of prey which hunt during the day and are distinct from classic, nocturnal avian predators like barn owls.
Tunstall Common: A 36.6 hectare biological Site of Special Scientific Interest east of Tunstall in Suffolk. It is part of the Sandlings Special Protection Area under the European Union Directive on the Conservation of Wild Birds, and the Suffolk Coast and Heaths Area of Outstanding Natural Beauty.
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