Hedgehogs in hibernation: what are their chances of survival?

Studies suggests hedgehogs are in decline across Europe – by 50% over the last 10 years in open countryside, and about 30% in urban areas – and there could be fewer than one million left in the UK.

Now, a research team led by Hartpury University’s resident hedgehog expert Lucy Bearman-Brown has uncovered fresh evidence about the impact of hibernation and the environment on the survival on rural populations.

The new study, which has been published in the Animals online journal, found that hedgehogs living in rural environments appear to be more at risk immediately before and after the winter hibernation period than during the hibernation period itself.

Lucy, the lead author of the report, carried out the research with Dr Philip Baker and Dr Luke Evans from the University of Reading, Professor Dawn Scott from Keele University, and Dr Richard Yarnell and Dr Antonio Uzal from Nottingham Trent University, and was funded by the People’s Trust for Endangered Species (PTES) and the British Hedgehog Preservation Society.

“Hedgehogs have declined markedly in the UK in recent decades and one key stage that could affect their population dynamics is the annual winter hibernation period,” said Lucy, Senior Lecturer in the Animal Department at Hartpury University.

“Despite its potential importance and given the wide range of ways in which human activities could affect this phase, little research has been conducted on the hibernation behaviour of hedgehogs in Britain in the last 40 years.

“Therefore, we radio-tracked 33 hedgehogs from two contrasting rural populations in England – at Hartpury and Nottingham Trent University’s campus near Southwell in Nottinghamshire – to examine patterns of winter nest use, body mass changes and survival during hibernation.

“None of the hedgehogs that we monitored died during hibernation, which might be surprising. In fact, all deaths occurred prior to or after the hibernation period, mainly from predation or vehicle collisions.”

Nida Al-Fulaij, Grants Manager for PTES, added, “Lucy’s research is really important. We can now focus our efforts on investigating what farm management practices, particularly of hedgerows and scrubby areas, can help give our rural hedgehogs the best chances of surviving hibernation.

“Ensuring hedgehogs and other wildlife have access to plenty of secure foraging and nesting areas is going to be critical.”

Lucy explained that during hibernation, which typically lasts from November to April in the UK, hedgehogs face many specific challenges, including the need to have accumulated sufficient fat reserves to survive for many months with limited food.

They need to find enough appropriate building material, such as the leaves of broadleaved trees, to construct a hibernaculum that will maintain an appropriate temperature within the nest.

The local area must also be sufficiently diverse that it offers a variety of nesting locations close to one another so that hedgehogs can relocate safely if they are disturbed by humans, predators or a change in conditions, such as flooding.

Changes in temperature patterns throughout winter may also cause hedgehogs to rouse from hibernation when natural food availability is limited, which can make them vulnerable to starvation.

Lucy said: “Hibernation success is dependent on several factors, all of which may be negatively affected by agricultural intensification and/or climate change.

“Our research found that hedgehogs consistently nested close to some habitats, including hedgerows and woodlands but avoided others, such as pasture fields.

“Our data suggests that hibernation was not a period of significant mortality for individuals that had reached a sufficient weight in autumn, but that habitat composition did affect where nests were built.

“Therefore, land management practices – both historic and current – that provide hedgehogs with access to vegetated areas is likely to positively influence hibernation success and the survival chances of hedgehogs.”

Lucy added: “For our study, data could only be reliably collected from radio-tagged individuals and radio-tags can only be fitted to animals weighing more than 600g for welfare reasons.

“Current guidance is that hedgehogs weighing less than 450g by October are unlikely to survive hibernation and may need help, which can be provided by wildlife hospitals.

When asked what members of the public can do to care for hedgehogs in their gardens over winter she said: “Providing nesting places, such as bushes, shrubs and wild areas, leaving leaf litter around and offering fresh water and food such as cat biscuits can all really help.

“Connecting your garden to neighbours’ will allow them to move around safely to find new nesting places. There are also a range of hedgehog houses on the market which can provide suitable nest sites.”

Lucy’s other research includes helping to train a special ‘detection dog’ to sniff out hedgehogs so they can be protected or moved out of harm’s way in land development projects.

Richard Yarnell, Associate Professor in Ecology said, “This research suggests that hedgehogs are relatively safe while hibernating in their winter nests, but face greater risks of mortality when they are active from human causes such as road traffic accidents.

“Further research is required to understand if predicted milder and wetter winters from climate change will impact hedgehogs over-winter survival. During warm winters hedgehogs are less likely to hibernate, increasing their chances of being killed while active in the countryside, adding further pressure on already declining hedgehog populations”.