#12 Beaver by Cath Bashforth
Meet Cath Bashforth, ecologist for Forestry England!
As an ecologist for Forestry England, Cath is involved in the management of the natural heritage of the Forestry England land holding in Yorkshire Forest District. She works to ensure our forests are managed sensitively for wildlife and looks for opportunities to improve biodiversity where possible. She also works on projects for specific species such as Pine Marten, Water Vole, Turtle Dove, and Eurasian Beaver. Cath can be contacted via email at cath.bashforth@forestryengland.uk.
Cath’s chosen species is the Eurasian Beaver Castor fiber. Weighing between 20 and 30kg, Eurasian Beavers are the largest rodent species in Europe and the second largest in the world. Beavers are completely adapted to a semi-aquatic lifestyle with webbed hind feet, a flattened rudder like tail and a waterproof pelt. They have other adaptations too including nostrils which shut to keep out water while Beavers are submerged, and a see-through second eyelid which acts as goggles. They also have a second set of lips which close behind their front teeth, allowing them to transport building materials and food without swallowing water. The long, strong claws of the front limbs enable them to dig and to manipulate objects. Their tooth enamel contains iron, which makes them very strong and orange in colour. Because the orange enamel on the front of their teeth wears away more slowly than the white dentin on the back, they are always sharp. In fact, the front teeth of Beavers are so strong and sharp that Neolithic and Iron Age people used them as woodworking tools - gold mounted Beaver teeth have been found in Anglo-Saxon burial mounds.
Beavers are monogamous, with adult pairs typically producing 2-4 “kits”, each year. They live in family groups comprising an adult pair, the kits of the current year and the young from the previous year.
Beaver (c) Leigh Foster
Totally herbivorous, their diet consists of herbaceous vegetation such as grasses, sedges and other aquatic plants. Beavers also fell trees to eat their bark, twigs and leaves. Native riparian tree species are attuned to this activity and will rapidly regenerate - through coppicing, suckering or growth from dispersed cuttings - in response to Beaver cutting. Most Beaver activity is confined to 20-30m of a watercourse. On large rivers and water bodies with easily accessible food resources, Beavers do not build dams and live instead in a series of bank-side burrows. These burrow systems have an underwater entrance and a living chamber at the end of a tunnel set above normal water level, and can be wholly or partially reinforced with timber. They extend their feeding zones and territories by excavating ‘canals’ in flatter landscapes. Beaver lodges are constructed where burrowing is difficult.
True ‘ecosystem engineers’, European Beavers build dams of sticks, logs, stones, leaves, silt, and mud in sub-optimal habitat to create an environment which suits their living purposes – aiming to create water depths of over 80cm. Other than man, it is the only other species to significantly manipulate the environment for its own purpose. This structural change in the environment enables them to move about their territory to food sources via water as much as possible; Beavers move more efficiently and feel less threatened from predation whilst in water. Beaver dams can also play a role in slowing water run-off during periods of flooding by increasing water retention times. The Beaver dams can also act as a filter capturing silts and pollution resulting in an increase in water quality downstream.
“Other than man, Beavers are the only other species to significantly manipulate the environment for its own purpose.”
Beavers are known as a “keystone species” – this is an organism that helps define an entire ecosystem. Without its keystone species, the ecosystem would be dramatically different or cease to exist altogether. Beavers’ niche as wetland engineers has a significant, positive impact on the natural landscape. Wetland habitats with intermittent tree canopies which are formed by Beavers provide both a greater expanse and variety of living opportunities. These are readily exploited by a wide range of plant species which in turn increase the feeding and breeding opportunities for insects. Greater standing and submerged dead wood habitat further enhances this process and invertebrate densities can rise in Beaver generated wetlands by up to 80%. This cycle provides a greater food resource for fish, amphibian and invertebrate predators whose densities rise in response. Carnivores such as Otter also exist at greater densities in Beaver generated wetlands due to greatly enhanced food resource.
Cath and part of a Beaver dam, for scale!
No one's sure exactly when the Beaver went extinct in Britain. The species was hunted to extinction by man as it was highly valued for its fur, meat and medicinal glands. The last written record is noted by archaeologist Professor Bryony Coles as a record of a bounty of two pence paid for "a beaver's head" by the churchwarden at Bolton Percy, a village on the lower River Wharfe in south Yorkshire, at the incredibly late date of 1789. Professor Coles has suggested they may have clung on perhaps even as late as 1800, believing the animals may have survived unobserved on the Humberhead Levels.
After an absence of several centuries the Eurasian Beaver returned to the English countryside in the early 2000s, having been released into outdoor fenced enclosures at 25 sites. Escapees from these enclosures, as well as illegal releases, have demonstrated the capacity of Beavers to thrive in England’s highly modified landscapes. Populations of wild-living and breeding Beavers are now present in as many as six separate geographical locations in southern England. There may also be additional, as yet unidentified, wild-living populations. The wild-living English beaver population is likely to exceed 60 territories and total as many as 400 individual Beavers.
In North Yorkshire, one of these enclosed Beaver trials has been underway since 2019, when 2 Beavers from Tayside were released into a 10ha enclosure in Cropton Forest, North Yorkshire as part of a 5-year trial licensed by Natural England. The pair had 2 kits in 2019, 2 kits in 2020 and 4 kits in 2021, bringing the current Yorkshire Beaver population to 10! Cath and her team plan to relocate the 2 oldest juveniles to another project this winter. Working on this trial, and subsequently bringing the Beaver back to Yorkshire, has been the highlight of Cath’s career:
‘To be closely involved in bringing the beaver back to Yorkshire for the first time in several hundred years has been incredible. Watching the changes that the species have made to the site in the short period they have been there has been amazing. The site has changed beyond recognition to a real ‘wild’ and ‘natural’ landscape and initial results have proved that the beavers are having a positive affect on the biodiversity of the site with increased numbers of amphibians, dragonflies and damselflies. Bat numbers have increased and Otter, Heron, Kingfisher visits to the site are also increasing due to the increasing water storage and associated food resource.’
There is also some evidence to suggest that the Beaver activity may be slowing the speed that water travels through the site in times of heavy rainfall, but it is too early to be conclusive on this front. The future of the Cropton family will depend on the outcome of the government’s consultation on the Beaver as a free-living species in England.
Cath and her team releasing two of the project’s beavers in North Yorkshire.
Monitoring
The beavers in the North Yorkshire project are monitored by trail camera. Other biological monitoring for a range of other species including amphibians, small mammals, birds, butterflies, bats, fresh water invertebrates, botany, fungi, fish, damselflies and dragonflies were carried out as a baseline before the beavers were released and will be undertaken periodically throughout the trial to get and understanding of beavers’ impact on biodiversity.
Further information and acknowledgements
NEYEDC would like to thank Cath for her time and expertise in helping to create this blog. If you’d be interested in contributing a piece for the series, contact Lucy at lucy.baldwin@neyedc.co.uk. To find out more about biological recording, see the Naturalists page on our website.
Beaver caught on trail cam in the North Yorkshire enclosure.