Tag Archives: ecology

Object of the Month – February 2021

Water voles are probably best known from the character ‘Ratty’ from The Wind in the Willows. Recently described as “Britain’s fastest, declining mammal”, they are making a comeback thanks to careful wildlife management and the return of a locally extinct predator – the polecat.

Water vole © Saffron Walden Museum.

Water voles are about the same size as a brown rat, but with a furry, much shorter tail, and small ears. Today, they are a semi-aquatic mammal, relying heavily on streams and rivers for food and shelter – they use their teeth to dig burrows into steep banks to shelter and raise their young.

Do water voles need water?

But it wasn’t always this way. They don’t show any of the usual adaptations for a water-based mammal, such as webbed feet and a ‘keeled’ tail (flattened sideways but taller top-to-bottom), both of which make otters very strong swimmers.
In the 1500s, rewards for hunting ‘rats’ may actually have referred to ‘water voles’ that lived entirely on land. Their burrowing habits and herbivorous diet would have made them an agricultural pest, which would explain the rewards paid for hunting them. Modern water voles are always found on waterways, so any hunting must have succeeded in wiping out fully-terrestrial water voles.

A population vole-ercoaster

In the 1990s and early 2000s, the number of water voles in the UK plummeted, making them Britain’s fastest-declining mammal. Surveys of water vole territories in Essex showed that  81% of recent territories were still occupied in 1990, but by 2005, only 7.5% of territories were still occupied in certain areas.
Such a drastic decline couldn’t just be down to habitat loss, and they are resistant to pollution – water vole colonies live in the banks of streams which run from landfill sites along the Thames estuary, and on rubbish-choked streams near Rainham.

Studies by Essex Wildlife Trust showed that crashes in water vole numbers closely followed local increases in the number the invasive American mink. These animals are not native to the UK, and became established after escaping or being released from fur farms from the 1950s onwards. Mink will hunt water voles in their burrows and in water, and a female can destroy a water vole colony in one breeding season. The water vole’s usual predators only hunt on land, and are too big to fit in their burrows.

American mink. © Saffron Walden Museum.

Essex Wildlife Trust began work in 2007 to control mink numbers in key water vole strongholds, allowing water voles to recover, and spread. In 2012, more areas were put under mink control, and water vole colonies were relocated from sites destroyed by development along the Thames and M25. Surveys in 2013 showed that these colonies had survived and spread, with several new colonies established along the river Colne and its tributaries.

Ratty’s new best friends

Since 2000, wildlife surveys have found an ever-increasing number of polecats, a native predator which had been extinct in Essex for over 100 years. Polecats were hunted to near extinction across the UK by gamekeepers, who treated them as dangerous vermin, and they were also easily caught and killed in rabbit traps, which fell out of use in the 1950s. Polecats have probably spread into Essex from a targeted release in Hertfordshire in 1982-3.

Natural Sciences Officer, James Lumbard, with the skin of a recenltly-mounted polecat. The polecat was brought to the Museum after being found dead at the roadside. Image © Saffron Walden Museum.

Otter © Saffron Waledn Museum. This otter is on view in the Victorian Museum Workroom display when the Musuem is open.

Informal tracking and recording also suggests that the return of polecats may be helping water voles spread and recover more quickly, by reducing mink numbers. The same is true for otters, which are now returning to Essex, after being declared locally extinct in 1986. Both of these animals are native predators that rarely hunt water voles, but will compete with the American mink for food and territory, and are also big enough to hunt or kill mink. There are no studies to confirm it yet, but it could be very good news for water voles, and wildlife-lovers across Essex.

References

Are the otter and ​polecat combining to reduce mink numbers? East Anglian Daily Times, first published 31 March, 2019. Accessed 29.1.2021: https://www.eadt.co.uk/news/business/rise-in-polecats-and-otters-hit-mink-2562736

Mammals of Essex by John Dobson and Darren Tansley, 2014.

Object of the Month – October 2020

New Zealand Kiwi

We’ve been busy over the last few weeks moving the bird taxidermy from a temporary home back to their usual store. October’s object of the month is a mounted kiwi skin, probably of a little spotted kiwi (Apteryx owenii), the smallest of the five kiwi species.

A stuffed Little spotted kiwi sking, facing left, mounted on a 'naturalistic' base.

The little spotted kiwi in Saffron Walden Museum. © SWM

With strong, heavy legs and no wings, kiwis have evolved for life on the ground. They are nocturnal, dig burrows to nest in, and have stiff, hair-like outer feathers to withstand pushing through leaves and twigs. Unlike most birds they have keen hearing and a good sense of smell to help them find food, mostly earthworms and insects.

A page from a book with drawings showing the head, wing and strong feet of a kiwi.

Kiwis have ‘whiskers’ around their beak, stiff feathers and tiny wings, and strong feet for digging.
[Internet Archive Book Images / No restrictions]

Kiwi numbers have plummeted since Europeans arrived in New Zealand, bringing rats, stoats, pigs, cats, dogs, trophy hunting and habitat destruction. Kiwis grow and reproduce slowly and only thrive today on protected reserves, with intensive work to remove these threats. The indigenous Maori regard the kiwi as a taonga (treasure), and actively protect the birds across 230,000 hectares of land, about the same area as the national government’s Department of Conservation. Altogether, an area of land bigger than Essex is managed for kiwi conservation.

Coloured map of New Zealand showing distribution of kiwis at present day and before European colonisation.

Light green, current location of kiwis; Dark green, location of kiwis before European colonisation; Dark grey, kiwis never known here. [© New Zealand Department of Conservation]

Map with numbers and letters showing locations of Little spotted kiwi populations across New Zealand.

Little spotted kiwi reserves – Predator-free islands: 1, Hen Island; 2, Tiritiri Matangi; 3. Red Mercury Island; 4, Motuihe Island; 5, Kapiti Island; 6, Long Island; 7, Anchor Island; 8, Chalky Island
Mainland: A, Shakespear Open Sanctuary; B, Cape Sanctuary; C, Zealandia.
Michal Klajban / CC BY-SA 4.0

See the little spotted kiwi and find out more about kiwi species in our Object of the Month display when the museum re-opens soon.

More information
New Zealand Department of Conservation (DoC) –  Facts about kiwi: https://www.doc.govt.nz/nature/native-animals/birds/birds-a-z/kiwi/facts/
New Zealand DoC – Little Spotted Kiwi: https://www.doc.govt.nz/nature/native-animals/birds/birds-a-z/kiwi/little-spotted-kiwi/
New Zealand DoC – Kiwi: https://www.doc.govt.nz/nature/native-animals/birds/birds-a-z/kiwi/
Science Learning Hub – Conserving our native kiwi: https://www.sciencelearn.org.nz/resources/2784-conserving-our-native-kiwi
WWF New Zealand – Kiwi: https://www.wwf.org.nz/what_we_do/species/kiwi/

References

Internet Archive Book Images. ‘Features of kiwis’ Transactions and proceedings of the New Zealand Institute (1870). Internet Archive Book Images / No restrictions. Available from commons.wikimedia.org [Accessed 29.9.2020]

Michal Klajban. ‘Apteryx owenii – distribution map. CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0). Available from commons.wikimedia.org [Accessed 29.2.2020]

New Zealand Department of Conservation. Kiwi Recovery Plan Summary Document 2018-2028. New Zealand Government, 2018. Available from https://www.doc.govt.nz/nature/native-animals/birds/birds-a-z/kiwi/docs-work/ [Accessed 29.9.2020]