Dormice whiskers aid tree-climbing
Dormice use their whiskers to help them climb trees, researchers say.
By twitching them upwards, outwards and straight ahead up to 25 times a second, they sense where they are going, a University of Sheffield team has found.
The process, called whisking, is used by some other rodents, and by whiskered mammals including seals and walruses.
Dr Robyn Grant, from the university's Active Touch Laboratory says whisking is "a parallel sense to our sense of touch".
She says hazel dormice (Muscardinus avellanarius) use their whiskers, or vibrissae, in a similar way to how people use their eyes - scanning to recognise what is in front of them.
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- Dormice may spend up to 75% of their life asleep
- Hazel dormice (Muscardinus avellanarius) numbers dropped by about 50% in the 20th Century
- Hazel dormice live for up to five years, hibernating on the ground in the winter
- They build their summer nests in tree holes or thick bramble and stay living in trees while it's warm
- The species is vulnerable to changes in habitat such as loss of hedgerows, altered farming practices and fragmentation of woodlands.
"Because of the uneven surface on branches, they vibrate them to find where to put their feet, as well as to work out where there's a gap and where to change branches," says Dr Grant.
Dormice are endangered in the UK and hibernate most of the year in small nests on the ground, but in the summer they live in trees.
Dr Grant says that they can also use the sensory nodes in their whisker follicles, which respond to the vibrations of their whiskers. This helps them to locate and determine the size, shape and quality of a food item, or to sense their way home.
The research by the team at the Active Touch Laboratory (ATL@S) is working to compare how a number animals, including opossums, seals and other rodents, move and use their whiskers in a sensory way.
Dr Grant says there are differences in how each species moves its whiskers. Different animals twitch at a different frequency, for example, and most rodents generally whisk their whiskers just backwards and forwards.
"We really want to try to classify strategies common between different animals, looking at whether all climbers use whiskers this way," says Dr says Prof Grant.
"And [we want to] use their different experiences in whisking to try and explore the evolution of their sensing systems."
By using an infrared lightbox, they were able to film nocturnal animals in the dark.
The team recorded the movements of whiskers using a high-speed video camera, which films at 500 frames per second, enabling the researchers to play back the whiskers' movements in slow-motion.
Using this high-speed digital videography, the team has examined whisker movements of nine species of British rodent.
They studied wood, harvest, yellow-necked and house mice; field, bank and water voles; brown rats; hazel dormice and one non-rodent - the water shrew.
The team then used "automatic whisker tracker" computer software to analyse the movements recorded on the video, and obtain data that they could compare.
Dr Grant says the rodents all showed whisking that was similar to rats and mice, but the water shrew did not. This indicated that the dormouse family (Gliridae) shared a common ancestor with other rodents.
She added that previous "whisker research" may have involved animals' whiskers being trimmed off. Without whiskers dormice cannot walk well; they fall off ledges and cannot cross gaps.
See more on BBC Two's Springwatch at 20:00 BST on Tuesday, 29 May.