Migration and Resource Allocation in Loxodonta africana
Introduction
Each year, multiple times a year,
African elephants, or Loxodonta africana,
migrate across vast spaces in the continent of Africa. These elephants travel in herds that can be
very large in size. The migrations they
endure could happen for any number of reasons, including avoiding enemies,
climate change, changes in resource availability, or a combination of all of
these factors. A null hypothesis to
explain these movements could be that the movement is random, and that there is
no scientific explanation for why the elephants migrate, and that at any random
moment in time, there are an equal number of elephants on the land. One alternative hypothesis is that they are
migrating to better allocate resources. Once
the resources are depleting where they currently are, they move to a more
resource-rich location. Another
alternative hypothesis could include that they are straying away from human
activity. Human activity is increasing
everywhere globally, compromising the habitats and ecosystems of organisms
around the world, including African elephants.
During my search for information, I researched all of these
possibilities.
Materials, Methods, and Study System
I completed a lot of research put in
many hours researching this topic. I
found that the library proved to be the best place for research due to the
quiet, focused environment around me. For
my primary resources, I used the Western Michigan University library database
systems. I first used the library
homepage to search for plausible databases. At the library homepage, I clicked
on “Research” and under that heading clicked on the sub-heading of “Subject
Guides.” I then clicked on “Biological
Sciences.” It then gave me two different
databases I could use: Web of Science and Biosis Preview. When using Biosis Preview, I used multiple
keyword searches such as “African Elephant,” “Migration Patterns,” and
“Distribution,” but I did not find any articles that related to my search topic
that would help research my thesis. I
then used the Web of Science database. I
found many more helpful, related articles here.
Because authors were irrelevant to me at the beginning of my search, I
used simply key words to find articles related to my thesis. For my first search, I searched for “African
Elephant” and “Migration Pattern” and came up with 6 hits, of which I used
information from 3. My next search was
“African Elephant” and “Migration,” and that turned up 17 articles, 6 of which
I could use. My third search turned out
to be the one where I found the most information. I searched “African Elephant” and “Resources”
and received 91 article hits. Some of
them were overlap from previous searches but I found 8 articles that were
directly related to my thesis. I found
that searching with too many or too refined of key words did not help with
finding articles for my thesis because it was too narrow of a search and I was
looking to find direct answers for my hypotheses instead of searching for related
articles and putting the information together myself. I spent about 6 hours just doing research and
reading articles related to my thesis.
There were so many articles to choose from and so much to read that I
felt I needed to read many of them to acquire adequate knowledge to write my
thesis paper.
Results
The null
hypothesis stated said that elephant movement is random, and that there is no
scientific explanation for why the elephants move from place to place, and that
at any random moment in time, there are an equal number of elephants on the
land. After researching the two possible
alternative hypotheses, I have found an adequate conclusion to the migration of
elephants.
Allocation of Resources
One
alternative hypothesis stated that elephants migrate to where resources are
more readily available than where they currently are. It is no secret that elephants consume mass
amounts of water. In such a hot
environment, drinking water is one way that the elephants stay cool. In one conducted study, researchers noticed
that when they made artificial watering holes around where the elephants
migrated, the elephants migrated directly to those spots. When the water would start to run out in that
particular area, they migrated to another watering hole (Loarie). The matriarch of the herd is the one who
leads and when she started to leave, the rest of the herd would follow
suit. In areas of southern Africa, there
appears to be two reasons for elephants to migrate for resource
allocation. During the wet season, the
elephants had smaller home ranges because of the seasonal productivity of the
plants. They had smaller home ranges
because the seasonal productivity of the plants was limited to a smaller area
rather than during the dry season, which is when the home ranges were larger
because of the wide distribution of the plants they use for food (Young). The nutrition in the plants is what the
elephants are after. Because salt helps
with water retention and elephants consume a lot of water, one of the main
nutrients that they search for is sodium.
This helps to explain the migration patterns of elephants; they follow
the plants that are the highest in sodium content (Rode). One common myth and misconception about
African elephants is that they cause a lot of destruction wherever they go and
destroy the plants. This is not the case
because elephants tend to use the same migration routes every year, and they
wouldn’t be able to do this if they destroyed the plants. One element that is important in an
elephant’s diet is nitrogen. In one
conducted study, researchers observed the nutrient content of trees in patches
that elephants frequented. They noticed
that the elephants tended to “save” the trees that were higher in nitrogen
content and the only damaging effects were on the trees that had little to no
nutritional value to them. The elephants
also use an effect called coppicing of the trees. This happens when the elephants strip the
trees of their leaves and nutritional value but don’t kill the tree. The tree then recovers in the following years
and the elephants are able to use the new stems from the same trees again
(Pretorius). In another study, it was
shown that the top five (5) woody plants most eaten by African elephants, all 5
of them showed high coppicing capabilities.
In the following years after the coppicing takes place, the elephants
return to eat the coppices. This shows
how the plant cycles continue to partially dictate when and where the elephants
migrate to (Chira). This is not to say
that elephants do not impact the vegetation in their environment. The average African elephant eats between 300
and 500 pounds of food per day. In a
simple conducted study, with a control site and an experiment site with aloe
plants, which is a staple in the diet of elephants, the experiment site had
much more damage on the plants than the control site without elephants (Parker). Elephants migrate because their resources
are used up at a quicker rate than other organisms who do not eat as much. However this combined with the coppicing
technique they use, African elephants are able to use the same migration route
year after year because they know that the resources in these areas will be
available to them.
Human Interference
Another
alternative hypothesis as to why elephants migrate is because of human
interference. They are moving to either
get away from human activity or human activity has caused them to change their
migration routes because the resources they once had are no longer there anymore
and new resources are put there instead.
In one simple study it was shown how separate populations in the wild
and in captivity or a protected area differed.
The populations that were protected had flourishing numbers while the
populations out in the wild suffered decreasing numbers (Loarie). However, it is impossible to be able to move
every elephant to a protected area. But
there is something to be learned about their migration patterns, though. Because they use the same migration patterns
every year, human interference can be limited because of this knowledge. In one particular study, researchers studied
how the social relationships among seven (7) different elephant families
influenced their special segregation and seasonal movements. Their data showed that dominant families
prefer the same habitats and areas, which, unless humans interfere, would limit
their interactions with humans because they use the same migration routes
(Wittemyer). One such human interaction
that is causing controversy is how the elephants raid the crops of
farmers. Their migration routes are
interrupted by farms that are being built.
In a study that observed crop raiding behavior, results showed that
elephants are raiding crops that are high in sodium (Rode). This is actually something the elephants seek
out because they need large amounts of sodium in their diet. With this new knowledge of resource location,
they alter their migration routes and this increases the amount of
human/elephant interference, which is causing a problem because farmers are
losing money because of this behavior. This
example shows how elephants will change their migration patterns in response to
a substation of resources. But they will
also change their migration patterns to stray away from human activity. In a study conducted to test stress levels in
elephants due to human activity, researchers observed the concentrations of glucocorticoid
metabolites in the fecal matter of elephants that lived near Gabon, Africa,
where petroleum operations were taking place.
The results showed that the elephants living near the oil operations had
higher concentrations of glucocorticoid metabolites, which means they had
higher stress levels than those living away from the commotion
(Munshi-South). The increased amount of
human activities is having a negative impact on the populations of African
elephants. Elephants will adjust their
migration routes, but it is only so long before they do not have anywhere to
move to. Researchers have observed that
there is a direct correlation between the increase in human population and
activity and the decrease of elephant populations. This happens when the amount of land
transformed into human-use land, such as for agriculture or housing, becomes
much more dominant than the natural habitats of the elephants (Hoare). Human interactions are affecting elephant
migrations and allocation of resources in a negative way because the elephants
are no longer able to reach the resources they need, so they interfere with
humans and their crops.
Discussion and Conclusion
The null hypothesis stated that
elephant movement is random, and that there is no scientific explanation for
why the elephants migrate, and that at any random moment in time, there are an
equal number of elephants on the land.
However, after much research, it has been proven that this is not the
case. African elephants have migration
patterns that they use in relationship to space, time, and resources, and human
interactions influence the elephants’ migration and allocation of
resources. Human interactions can change
an elephant’s migration route due to crops or due to increased industrial
activity. It’s not random. African elephants migrate towards their
resources in need, and use the same migration patterns because it leads them to
the same resources.
Sources Cited
Chira,
R.M., and J. I. Kinyamario. 2009. Growth response of woody species to elephant
foraging in Mwea National Reserve, Kenya. African Journal of
Ecology 47: 598-605.
Hoare,
R.E., and J.T. Du Toit. 2001. Coexistence between people and elephants in
African
Savannahs. Conservation Biology 13: 633-639.
Loarie,
S., R. Van Aarde, and S. Pimm. 2009. Fences and artificial water affect African
savannah
elephant movement patterns. Biological Conservation 142: 3086-3098.
Munshi-South, J., L. Tchignoumba, J.
Brown, N. Abbondanza, J.E. Maldanado, A.
Henderson, and A.
Alonso. 2008. Physiological indicators of stress in African forest elephants
(Loxodonta africana cyclotis) in relation to petroleum operations in Gabon,
Central Africa. Diversity and Distributions: A Journal of Conservation
Biogeography 14: 995-1003.
Young,
K.D., S.M. Ferreira, and R. J. Van Aarde. 2009. The influence of increasing population
size and vegetation productivity on elephant distribution in
the Kruger National Park.
Austral Ecology: A Journal of Ecology in the Southern
Hemisphere 34: 329-342.
Young,
K.D., S.M. Ferreira, and R. J. Van Aarde. 2009. Elephant spatial use in wet and
dry
savannas of southern Africa. Journal of Zoology 278: 189-205.
