The Dangerous Wild Animals Act 1976 prohibits the introduction of wild boar into the project, so our Tamworth pigs have taken on the role of their indigenous forebear. An old breed, renowned for their hardiness, they have long legs and snouts, narrow backs, long bristles and a surprising ability to sprint for short distances as fast as a horse - very much like the wild boar.
Registered as a breed in the early 19th century on the statesman Sir Robert Peel’s estate at Tamworth in Staffordshire, they have lost out to fast-growing, large-littering modern breeds specifically designed for intensive farming. The Rare Breeds Survival Trust estimates fewer than 300 registered breeding Tamworth females in the UK.
The pigs graze throughout the summer and in the autumn gorge on fallen acorns, plentiful in our landscape of open-grown oaks. When the ground is soft, from autumn through to late spring, they rootle, turning over clods of turf with their snouts, in search of roots and rhizomes, earthworms and other invertebrates. Pigs are particularly partial to the deep, strong roots of docks and thistles.
They will also eat carcasses, grinding up bones with their powerful jaws, serving a role as Europe’s hyena. They can even hold their breath underwater, foraging for rhizomes, submerged acorns and freshwater mussels.
The pigs’ disturbance has resulted in numerous trophic surprises. Rootling exposes bare soil, allowing pioneer plants like sallow (hybridised willow) to colonise. Sallow is the food source of the purple emperor butterfly. Before rewilding there were no purple emperors on Knepp. Now we have the largest breeding population in the UK.
Soil exposed by rootling is swiftly colonised by solitary bees, and the over-turned clods of earth kick-start the creation of anthills which, in turn, provide food for our burgeoning population of green woodpeckers.
Rootling also provides opportunities for so-called ‘weed’ species such as chickweed, scarlet pimpernel, vetchlings, common fumitory, knotgrass and red fescue - food source of the critically endangered turtle dove. Before we began rewilding we had no turtle doves at Knepp. By 2017 we had at least 14 purring males, and in 2020 we recorded 23. Turtle doves are, according to the RSPB, the most likely bird to go extinct within our shores in the next few decades. Knepp is the only place in the country where turtle dove numbers are increasing. Could the turtle doves’ success here be a consequence, at least in part, of our rootling pigs?
Pigs may also have a positive effect in the battle against climate change. A recent study shows that rootling, or ‘bioturbation’, by wild boar/pigs in closed canopy woodland – mixing up leaf litter and organic matter on the forest floor with the mineral soil – increases the stability and storage of carbon in the soil.