For my master's thesis I am spending five months in Botswana to study male African savannah elephants, but what exactly am I looking for? and why did I choose elephant research? In this blog post, I will tell you all about it!
Studying the African savannah elephant in the wild has always been a big dream of mine. Now that I am actually here in Botswana, and living this dream, it still feels unreal. Shortly after starting my master's in 2020, we were expected to find our supervisor and project for our graduation research. Having only one professor focusing on research projects in Africa made him an easy choice for my supervisor; the project itself was more difficult. He was not leading any projects at that time, and I was not willing to settle for a project in other parts of the world.
Meaning that I had to find an organisation willing to work with me. Long story short, I did. Elephants for Africa allowed me to come to their research camp and help me realise my research project. I will be looking at the influence of age, body size, and physical condition on the foraging behaviour and woody species selection of male African savannah elephants in Makgadikgadi Pans National Park, Botswana.
Elephant research topic
My topic was chosen in combination with the information Elephants for Africa was looking for, and my personal preferences. I was looking for a study where I would use behavioural data. Elephants for Africa have a long-term plan to look into the nutritional content of the vegetation. This is realized in the hope to understand why the elephants are coming to this region. My research will give the team a great baseline for this research by giving them information on where to start their research. For example, the species heavily favoured by the elephants. A match made in heaven!
Now you are probably thinking, foraging behaviour and woody species selection of elephants. Hasn't that been studied many times by now? Yes, it has, but also no, it has not. There has been lots of research on this topic, but all these studies compare the different behaviour and selection between the male groups and female breeding herds. Where my research will be different from this is my comparison of different age groups of solely male elephants. I will make my research a bit broader by also looking at their physical condition. I am also going to try to look at differences between habitat types and possibly even seasonality.
Why is there a difference between males and females?
These differences in their feeding behaviours and species selection are related to their body size, following the Jarman-Bell principle. The Jarman-Bell principle states that body size influences feeding behaviour in three different ways: metabolic rate, gut size, and the time food remain in the digestive tract. Body size has a substantial influence on energy requirements due to the different growth rates of the metabolic rate. This means that larger individuals, in this case, the male elephants. Have a reduced energy requirement per kg of body mass. This enables the adult male elephant, in contrast to the smaller female elephant, to consume and digest larger quantities of low-quality forage and still obtain great nutritional benefits from it. Therefore, the benefit of abundance will outweigh the costs of searching for high-quality forage. Meaning that male elephants are often choosing quantity over quality while females choose quality.
Foraging behaviour
The first part of my elephant research focuses on foraging behaviour. I will be studying this with several different variables. I will be looking at what plant species they are eating, but also what part of the plant. Are they eating leaves, complete branches, or even bark or roots? I will be looking at the height of the plant they choose to feed on and at which height the actually feeding takes place. Lastly, I will use the duration of their feeding bout, the number of mouthfuls, and the amount of biomass removed from the tree to decide the intensity of the feeding behaviour. Are they feeding selectively? Or do they choose to use intense methods to collect as much food in a short period of time?
Woody species selection
The second part is on the woody species selection. After collecting the foraging behaviour data I will be doing vegetation plots along the path they have been feeding. I will use two different plots, the first one is called a feeding plot. This plot is placed around a recently browsed tree, inside this plot all woody species are identified, and the number of individuals counted. 50 meters from the feeding plot a control plot will be positioned and sampled the same way as the feeding plot.
This means I collect data of x individuals of y different species in their diet, in their feeding plot and in the control plot. Where the diet data represents use, and the feeding plot represents availability. Allowing the calculation of a selectivity index for each tree species. This way you learn which plant species are being favoured by the elephants and which tree species they avoid. Using this selectivity index together with the feeding plots and control plots I can test if the elephant target quality forage or target quantity. If you have questions about how exactly I am going to do this, let me know in a comment!
Predictions for the elephant research
As previously mentioned, there is a big size difference between males and females. This leads to differences in their feeding behaviour, but there is also a great size difference among male elephants. They experience two periods of significant growth and also continue growing their whole life. Meaning that the elephants that just left the herd, around 10 to 15 years, are significantly smaller than the elephants that are 36 years or older. So, what I predict is that younger elephants, as well as elephants in poorer conditions, will feed more selective to reduce fibre intake and target quality feeding areas. Whereas older elephants, as well as elephants in excellent condition, will show intense foraging behaviour and target feeding areas with a high quantity instead of quality.
How their age and physical condition will affect their species selection is not yet published in academia, for now, it is just a guess...