Sarah Duguid
Humans have long known the healing properties of different plant species. From pounding roots and berries into cures, to using plant extracts in powerful pharmaceuticals, we have harnessed the power of nature to our own advantage. We are, some of us neurotically, aware of what we put into our bodies and how we are going to be affected by it. But what about species in the wild do they care about what they eat?
This is a question that has long interested Lyn Phillips. A bush guide in the Eastern Cape, she is hoping that by taking groups to look at animals and the plants that they eat, she will stimulate some scientific enquiry. Why is it, she asks, that many animals in the wild don’t get sick and why is it that scientists aren’t looking into the role that diet plays in the generally good health of African domestic wildlife?
Phillips has begun a series of night drives in a bid to get people into the bush and observing the behavior of wild animals. So far, according to Phillips, no scientific study has been done in Eastern Cape valley bushveld to assess the role that plants might play in maintaining animal health. Perhaps, she suggests, the reason many wild animals don’t get sick is because they get all the nutritional requirements they need for natural preventive medicine from the diversity in their diet. But research is needed and Phillips hopes that research could mean a significant step forwards in conserving the veld.
She takes groups out in the late afternoon, when they make their way to a hide overlooking an old, dry dam. And here they wait for night to fall.
There are no promises as to what the guests will see but the big thrill, she says, is just to be out in the bush under the stars waiting for a pair of eyes to get caught in the spotlight. And in between waiting for animals there is the chance to look at some of the more unusual plant species.
By noting what the creatures of the valley bush like to eat and by relating that to the medicinal value that many of these plants hold for humans, it would be possible to draw conclusions about why the animals choose their diet as they do. The bush is home to a pharmacopoeia but nobody knows whether and how it is applicable to wild animals. Even if animals do not consciously seek out plants to cure ailments there is a latent set of decisions that drives them towards certain plant species.
Food can be scarce and animals cannot afford to devote too much energy to finding the most nutrient-rich food. Their choices have to be based on a few simple sensory cues that serve as predictors for the likely nutritional value. A clever eater might be defined as “a short-term maximiser for nutrient intake alone” that “selects a diet that maximises the intake rate of nutrients during foraging periods”. The animals live in a harsh environment and they need to get the greatest benefit from what they eat while expending the least effort on eating.
But findings have begun to show that “real ungulates select a much more varied diet than that predicted on the basis of optimal foraging theory”. At the crux of the matter is what makes a plant acceptable and tasty to the animals. So far studies have shown that even if there is plenty of a particular plant species along an animal’s foraging path, they don’t necessarily eat them.
The animals’ choice of forage has been found to be based on a variety of criteria. Animals have been found to select plants high in soluble carbohydrate content. Soluble carbohydrates act as a ready supply of energy to the animal. But animals are also limited by how difficult and time-consuming some foliage is to digest. The value of a food plant to the animal is influenced by the relationship between the structure of the plant, its leaf size, the existence of thorns and the bite dimensions of the animal.
The bush willow, for example, is palatable for kudus, which are able, with one bite from their relatively large mouths, to get plenty of nutrients. Even though the wag ‘n bietjie tree has a higher protein content, its leaves are smaller and armed with thorns so the kudu can’t get as many nutrients with one bite. Thorns mean that animals can’t take big bites, and this reduces the speed at which they can eat, and therefore the rate that they take nutrients into their systems. Big mouthfuls meant that they are optimising the use of their energy.
But there are many questions that need to be answered, says Phillips. Some animals naturally go for a balanced diet as a survival strategy and humans need to find out more, if we are to be able to create areas that will protect our wildlife.
Lyn Phillips will be offering night game drives as a special extra at the SciFest