What can animals teach us about staying healthy? A great deal, argues Cindy Engel. Animals, she says, are constantly self-medicating, eating anything from charcoal to leaves to ward off illness and to treat sickness. An animal behaviourist at the Open University, Engel came upon the new science of animal health while searching for a cure for her own illness. Now she has brought together all the knowledge of the field in a book. She tells Maggie McDonald a few secrets from the animal world-such as what leads sheep in the Shetlands to bite the heads off live Arctic tern chicks.
How did you get so interested in the health of animals?
I had chronic fatigue syndrome for four years from 1990. Doctors couldn鈥檛 do anything for me, so I had to help myself. I started getting interested in diet, in nutritional and herbal medicine, and in adjusting my lifestyle and stress levels. While reading about traditional herbal medicines I came upon this folklore about animal self-medication. I knew from my background studying animal behaviour that a lot of it was completely ridiculous. But some examples were intriguing and highly likely. I wanted to know if there were scientists working on this. I discovered that there was a young science called zoopharmacognosy, which started in 1994 when a small group of scientists from around the world got together for their first conference to share their work on animal self-medication.
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How did it help you?
I realised that animals do not just rely on their immune systems to remain healthy. They have to take an active role in maintaining their health. They pay constant attention to health maintenance. The only reason I have recovered is because I took personal responsibility for my health. Instead of living on high energy and fast foods, I changed to a more sustainable diet of fruit and vegetables and concentrated on keeping in tune with my body. I had to acknowledge something that the doctors could not see: how my behaviour was contributing to my illness.
You seem to have used this approach both to cure your illness and to keep it at bay. What are animals doing?
Some scientists have tried to discriminate between preventive and curative self-medication in animals. The problem is that often you can鈥檛 know the distinction. Take a rat, for example, which because it cannot vomit will seek out clay whenever it feels sick. The clay binds to toxins and deactivates them. The rat will eat clay if it starts to feel slightly nauseous, though we cannot tell that the rat is ill. What looks like preventive medicine to us can be curative to the animal. I believe animals, like people, self-medicate unconsciously. People sometimes find something that makes them feel better even when they haven鈥檛 made a conscious diagnosis. Patients suffering from schizophrenia, for example, smoke on average three times as much as other people. If you ask them why they smoke a lot, they just say that they like it. Pharmacologically, however, nicotine reduces the symptoms of schizophrenia.
How crucial is self-medication to the survival and evolutionary fitness of animals?
My own illness and how I dealt with it made it clear to me that this is a really undervalued aspect of animal behaviour. Fitness measures how well an organism is adapted to its environment, which in turn determines its survival. Although it鈥檚 something that interests all biologists, they haven鈥檛 taken note that health maintenance is the way animals improve fitness. An animal doesn鈥檛 just have to survive, it has to be as healthy as possible in order to successfully compete with others.
How do they acquire this knowledge? Is it cultural?
This area is so under-researched. My aim is to promote health maintenance as a new way of looking at animal behaviour. We need to find out more. There are some intriguing snippets. For example, Thomas Struhsaker of Duke University has been studying red colobus monkeys in Zanzibar that eat charcoal to deactivate toxins in the plants they eat. He noticed that the young learn this habit from their mothers, just by watching them. Mike Huffman at the University of Kyoto is looking at chimpanzees that fold up hairy leaves and swallow them as a scour for intestinal parasites to see how much of this 鈥渓eaf-swallowing behaviour鈥� is learned through experience.
How do animals match an illness to a medicine?
Early on in this field, other scientists thought we were proposing that an animal knew exactly which herbs to use for which ills, and they had a problem with that. But that is very much not the case. When you bring all these examples together, what becomes really obvious is that animals are highly flexible in their self-medication. Apes seem to swallow any rough-surfaced leaf they can find to clear parasites. They use more than 30 different leaves. It鈥檚 not just great apes. Bears and geese use these mechanical scours, too. I suspect that鈥檚 why dogs and cats eat grass. I heard from a traditional herbalist in Suffolk that one of the old ways of getting rid of worms in horses was to cut off a piece of the horse鈥檚 tail hair and coat it in honey to make the horse swallow it. It鈥檚 exactly the same principle: they鈥檙e using the indigestible hair as a mechanical scour. What I found interesting is that traditional herbalists have been using the same general broad-acting strategies that you find in the wild.
Do domesticated animals self-medicate?
There are still remnants of self-medication behaviour in domesticated species. Cattle sometimes eat clay, for example. I talked to lots of farmers who said their cattle are always digging down and licking at the soil. They had always assumed that they were digging for minerals, and some of them had even done blood tests to find out which mineral they were lacking. But observation of free-range cattle in Venezuela shows that they are digging for the clay itself. Clay when given to cattle binds viruses that cause diarrhoea and gastrointestinal illness. It absorbs bacterial toxins too. Where this information has been picked up it鈥檚 been used, and it increases by up to 20 per cent the efficiency with which cattle turn food into muscle.
Is this wise, bearing in mind how antibiotics were overused on farms to enhance growth and productivity?
No one wants farmers to force clay into their cattle through their feed, but I am trying to encourage a change in mindset whereby farmers will allow their animals to self-medicate when necessary. Clay can be harmful in excess, so it鈥檚 safer to allow them to self-medicate anyway. When it comes to broiler chicks, I鈥檓 fighting a losing battle trying to get the industry concerned about levels of discomfort in their stock because their chickens generally live only 28 days. But if farmers helped their animals to self-medicate against pain-which experiments have shown them capable of doing-that could help the agricultural industry regain public approval.
What else can we learn from animals about our own health?
The most important dietary change we might make is to acknowledge the importance of non-nutrients that are sometimes thought of as toxins. Many of these medicinal compounds taste bitter or astringent, so we have gone to great lengths to avoid them or breed them out of our food plants. But they may be essential to health. The Masai, for example, get up to 60 per cent of their protein from animal products, yet suffer nowhere near the amount of heart disease that is attributed to such a diet in the West. The trick is that they still use bitter herbs in their daily food that are high in antioxidants that counteract the negative effects of animal fats. We assume that we can improve on traditional diets. We have replaced many herbs with artificial flavourings and preservatives, but we didn鈥檛 know that we were losing all the medicinal non-nutrients that herbs contain. We haven鈥檛 got those in our diet any more.
Why do animals cover up their dead?
Some species go to great lengths to bury their dead. Elephants are well known for doing it, less well known are badgers. There鈥檚 a strong possibility that gorillas do. Bees embalm in antibacterial wax anything that dies in their hive. I put it down to hygiene, another aspect of health maintenance. I spoke to a couple of forensic scientists who told me that even a light covering of soil would dramatically improve the rate of decay and colonisation by flies.
Is there an animal version of drug abuse?
Certain species seem to return again and again to fermented fruit as if they were actually enjoying the inebriation. Therein lies the difficulty: are they doing it for fun or are they doing it for the high calorie content? It could be both.
Isn鈥檛 this work of huge interest to pharmaceuticals companies?
Yes, and some people have gone down this route. For example, Eloy Rodriguez, one of the co-founders of zoopharmacognosy, hopes that animals will reveal valid or new drugs for human medicines. This must seem attractive to some pharmaceuticals companies. They would not have to worry about being accused of stealing traditional medicines from people. However, I have my doubts that animals are going to show us many 鈥渕agic bullet鈥� medicines, because a lot of the methods animals use are non-chemical-the use of clay, for example. Animal medicines are not easily patentable.
Does it matter that you are a generalist in a field of specialists?
Several publishers didn鈥檛 like the interdisciplinary nature of the book. It鈥檚 now rare to come across interdisciplinary science. One of the reasons why I work for the Open University is that there you do need to be flexible. But there鈥檚 a great deal of interest in animal self-medication from scientists in lots of different disciplines, from chemical ecology to botany and ethnoveterinary medicine. I鈥檝e been talking to vets at Bristol University who are interested in how farm animals and pets can self-medicate their pain. I鈥檝e been talking to entomologists in Germany who investigate how insects self-medicate against our attempts at biological pest control. And anthropologists such as Richard Wrangham at Harvard are interested in the evolutionary and cultural aspects of primate self-medication. My aim is to bring together all the published research and all the interesting anecdotal stories from the field and just say, 鈥淭his is a new way of looking at animal behaviour.鈥�
What animal behaviours have amazed you?
The thing that surprised me most was discovering that sheep on the Isle of Foula in the Shetlands extract and eat the bones of live Arctic tern chicks. They bite off their legs and heads, leaving their decapitated bodies lying around. The sheep do this in their quest for minerals that are not found in their grazing grounds. I found that pretty horrific.