Driving through large stands of beautiful grassland in some of our reserves and not seeing any or very few animals, you must have asked yourself “Where are all the animals?” Well, there might be good and obvious reasons for not seeing any of the grazers on that apparently appetising grassveld, reasons that we as human beings do not always consider or even understand as we prefer not to eat grass!
Just as trees and other plants have evolved various means to protect themselves against browsers (leaf feeders), so have grasses developed methods to reduce grazing and protect themselves against grazers (grass feeders). Although grasses and grazers have evolved and coexisted for millions of years, their relationship is not one of compliance and acceptance, but rather of tolerance and adaptation. Grasses are constantly evolving new strategies to reduce over-utilization by grazers while grazers develop new approaches to deal with grass ingenuity.
Grasses are considered palatable when they taste nice, have a high protein value, produce a lot of leaves and are digestible. By changing these factors through structural and chemical adaptations, grasses can reduce their palatability and become less acceptable to grazers.
Structurally grasses defend themselves by becoming very fibrous, especially towards the end of the growth season, which make them less digestible. Most grasses contain microscopic silica crystals within the leaves, which effectively wear down the teeth of grazers. It’s like chewing bubblegum containing minute sand grains. In order to overcome this problem grazers have all developed high crowned teeth. The presence of hairs on the grass stem and leaves is another effective deterrent against insect grazers such as locust. To these “goggas” those hairs on a grass plant are what the thorns of a thorn tree are like to mammal browsers.
Chemical defense relies on the production of aromatic oils and other bad tasting chemicals that grazers, especially mammal grazers, find unacceptable. Good examples are Pinhole grass, Stinking grass and Turpentine grass.
Other important factors to consider are the structure and composition of the grassveld. Just as we like variation in what we eat, so do animals and for that matter grazers. Monocultures (large grass stands of a single grass species) are not favoured by animals and they tend to avoid it even if the grass species is palatable. Animals are also very vulnerable to predation in tall grasslands and they spend as little time as possible in these areas.
So, next time you drive through those grass plains in one of our beautiful nature reserves not seeing any game, have a good look at the grasses while considering all the factors mentioned above. It just might give you an idea where else to go looking for those elusive Tsessebe, Red Hartebeest or Blue Wildebeest.