Badgers are opportunistic animals and take advantage of many sources of food. At Kew Gardens this includes the autumn crop of yew berries that fall onto the ground near their setts. Indeed, the badgers seem to relish this delicacy so much that they have been seen standing on their hind legs to reach the berries on the lower branches of yew bushes. Evidence of the badgers’ nightly feast can be seen by visitors to the Gardens in the badgers dung pits, which in the autumn contain faeces full of the bright red remains of the yew berries.
Yew 'berries' contain a poisonous seed surrounded by a bright red, fleshy aril (Image: Geoffrey Kite)
Yew (Taxus baccata) is a deadly poisonous plant. Kew scientists have been called upon several times to help with the investigation of human and livestock deaths suspected as being caused by yew consumption. Usually this involves investigating the stomach contents of the victim to find evidence of yew leaves. An analytical method has also been developed at Kew to detect the toxic taxine alkaloids from yew should microscopic examination be inconclusive, and this was published in the scientific journal Veterinary and Human Toxicology.
The yew ‘berry’ is not a berry at all in the strict botanical sense but a naked seed sitting on a fleshy, sweet, red-coloured mucilaginous appendage called an aril. The aril lacks toxic alkaloids but high concentrations of the alkaloids are present in the seed. The badgers at Kew were observed eating entire fruits, including the seeds, and seeds were found in the badgers faeces. So how do the badgers survive this potentially deadly meal?
John Lees, a Biology student from Manchester University who was working at Kew on his industrial placement year, was receiving training in the methods to used detect yew alkaloids in poisoning cases. Thus the ‘badger problem’ seemed an excellent opportunity to develop his skills.
John gathered yew seeds from badger dung and from fruits on yew trees and performed analyses to compare the levels of alkaloids in both samples. He found that seeds that had passed through a badger’s gut contained a similar level of alkaloids to those that had not, indicating no major loss of alkaloids from the seeds.
This opportunistic observation, published in Mammal News, suggests that badgers can eat yew berries with impunity, with most of the toxic alkaloids being retained in the unbroken seeds protected from even a badger’s sharp teeth by its mucilaginous aril.
Item from Dr Peter Gasson (Micromorphologist, Kew) and Dr Geoffrey Kite (Phytochemist, Sustainable Uses Group, Kew)
Gasson, P., Lees, J., & Kite, G. (2010). How do badgers eat yew ‘berries’ without being poisoned? Mammal News 157: 12–13. Also available at Mammal Notes.
Kite G.C., Lawrence T.J. & Dauncey E.A. (2000). Detecting Taxus poisoning in horses using liquid chromatography/mass spectrometry. Veterinary and Human Toxicology 42: 151–1544.
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