adminThe term “partitioning” can be used interchangeably with divide, separate and split, hence food partitioning means dividing a resource such that each individual or species gets a share or portion of the resource. Time is also partitioned between mammals with similar traits and characteristics although overlaps may also be observed.
The Livingstone Sango Gallery exhibition aims to show emphasis on how food is partitioned by herbivores in the savanna when food is more abundant. The migrations in the Serengeti are an example of how food is partitioned. This has been observed with three species; zebras, blue wildebeest and the Thomson’s Gazelle, hence there are tens of thousands of these herbivores that migrate in those plains.
All these three populations have significant local and full scale movements, for zebras some can cover up to 100-200km. Most migrations take place between winter and summer and they take place in well defined paths, the animals moving in a single file and these movements are often before water supplies are depleted. Hence these result in a succession of waves where herbivores graze on different plant species in turn but in aggregation.
In other parts of the savanna during the wet season grass biomass is very high and food is not a problem for all herbivores, even more so the grass is high in protein content, as most of the grasses are short as they would have just re-sprouted due to the rains. Then in the dry season food becomes scarce and the herbivores tend to migrate to areas where there is food.
In these areas grasses are often tall as they are not disturbed by grazing after their re-sprouting following the rains, they are therefore high in fibre than protein hence are less nutritious. This is when the food partitioning really starts. Zebras move in, and munch in first as they can utilise the tall grasses despite their low protein and high fibre content as they are hind-gut fermenters.
Their extraction and breakdown of protein is less efficient than that of ruminants and they obtain sufficient protein only because the passage of food through the alimentary canal is about twice as fast as in ruminants. As a result, zebra must ingest much more grass than other herbivores like the wildebeest, even though it is of lower quality.
Antelopes such as the impala and Thomson’s Gazelle need a diet with low cellulose and fibre concentration, for adequate nutritional benefits. Zebras can therefore feed on grasses that are above 10-15cm from ground level without any complications, though like other herbivores they prefer to forage on shorter grass.
The zebras will therefore use their strong, sensitive, mobile upper lip to push the herbage between their incisor teeth with which they then cut the grass free. The long grass is therefore shortened to lower heights and also because zebras, the grass is also trampled and is modified.
These two disturbances (that is grazing and trampling) lead to new shoots sprouting and these are more nutritious and high in protein than fibre hence favouring the wildebeest that come next as they are ruminants.
Wildebeest prefer grasses that range between 10-15 cm and their muzzles or snouts have evolved to eat short grassland and they are less successful in dealing with taller types from which the leaves have to be selected and stripped. The leaves from these grasses are also higher in protein than fibre and cellulose hence are nutritious. This is good for the wildebeest as less time is taken trying to digest fibrous materials and more time is taken in ingesting hence more nutrients are taken up by the animal.
Following in the wave are antelopes which require less of the food required by wildebeest with an estimate of about a fifth of that for wildebeest.
For example the Thomson’s Gazelle prefers grasses that are 5-10cm in height and these are also high in protein. Even though the grass is too short they complement it with fruits and dicotyledonous plants in order to obtain more proteins as they need more proteins than wildebeest.
In summary this shows how herbivores divide food within themselves to ensure existence of the other species. The presence of zebras in this case facilitates the feeding of the smaller herbivores that are less adapted to digesting fibrous foods.
This may seem to be an advantage only for the smaller herbivores but the zebras benefit from the high forage intake and because of their digestion system they also get enough nutrients to sustain themselves.
We hope that the public will be able to join us as we unveil this exhibition on 16 May 2012 at 1715hrs. Museums in a changing world, New Challenges, New Inspirations!
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