My dog, a 4-year-old whippet called Merlin, occasionally seems to select and eat goosegrass (Galium aparine) from a hedgerow, carefully pulling out stalks and ignoring the other plants surrounding it. Is he self-medicating, and if so, how does he know which plant to eat?
鈥� As the owner of a 4-year-old whippet that shows no interest in goosegrass, I was curious to find out what may be stimulating Merlin鈥檚 predilection.
Goosegrass, also known as cleavers, contains many chemicals that may have a biological effect, including asperuloside, caffeine and phenolic compounds. It has been used as a tea by herbalists and is said to act as a diuretic and 鈥渓ymphatic鈥�.
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Its appeal to dogs is noted on the online Gundog Training Forum, where a number of contributors report that their dogs actively seek it out.
The effects of goosegrass are obviously open to question. There is an unverified report that it lowers blood pressure in dogs without affecting their hearts or producing unwanted effects. But I doubt any dog would either be aware of its own blood pressure or actively seek to lower it.
Because goosegrass belongs to the same family as coffee, could it be that it gives dogs the equivalent of their owner鈥檚 mid-morning caffeine boost?
As for how yourcorrespondent鈥檚 dog finds the goosegrass, we all know that dogs can distinguish smells way beyond our imagining (see 鈥淭he nose knows鈥�, New 杏吧原创, 4 July, p 35). Phenols have a very strong scent that even humans can detect, so it is probably very easy for dogs to find, even if the phenols are present in small quantities.
Still, as the Gundog Training Forum points out, there is no substitute for visiting a vet to check whether this behaviour should be encouraged. Just because something is eaten without apparent harm does not mean it is good for you.
As one vet said to me about a substance now widely recognised as being harmful to dogs: 鈥淗ave you ever seen a dog refuse chocolate?鈥�
The apparently self-medicating behaviour of animals is known as zoopharmacognosy, and your dog is probably eating the goosegrass to induce vomiting in response to a mild stomach irritation. My cat does the same thing, often selecting specific species of grass. She did this both in the UK and now in Hong Kong, so the species seems irrelevant, beyond individual preference.
Goosegrass is so called because geese like to eat it, purportedly because it helps to eradicate worms from their digestive tract 鈥� which folk tales explain by suggesting the plant鈥檚 tiny hooks catch worms and carry them from their bodies.
Peter Sims, Hong Kong
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This article appeared in print under the headline 鈥淢erlin鈥檚 magic鈥�