African elephants are the most studied big mammal species in Africa. But in spite of all we know about them, there is still a lot that we don’t know.
A project being conducted by the Wildlife Environmental Physiology team at the University of the Witwatersrand’s school of physiology is exploring how the elephant’s body functions in the heat of the savannah.
The team is studying thermoregulation in these magnificent animals — how they manage and cope with heat.
“Elephants are of particular interest to us as thermal biologists because of their large size,” says team member and MSc student Philippa Hidden. “Because elephants are so large, they produce a lot of body heat. Everyone will agree that an elephant produces far more body heat than a mouse. But a mouse loses heat more easily because the surface area of its body, relative to its body mass, is greater than that of an elephant.”
Hidden explains that an elephant produces a lot of heat and has the disadvantage of a relatively smaller surface from which to lose this heat — so in a very hot environment such as an African savannah, the big question is how do elephants not overheat?
“Previous studies of body temperature and of how elephants attempt to keep their temperature stable have been conducted,” says Hidden. “However, the researchers were limited by the technology available, and they did not have access to animals that were free living and unsedated. Due to advances in technology, we now have much-improved techniques for conducting such investigations. We also have a unique opportunity to study elephants that are living in their natural habitat, but which are also tame enough for us to obtain information that we could never get by studying free-living, wild elephants.”
The elephants Hidden is referring to are those belonging to the Pilanesberg Elephant-Back Safaris (Pebs) — a well-respected elephant tourism operation based at the Letsatsing Game Reserve adjacent to the Pilanesberg National Park.
Hidden says the advantage of working with the elephants at Pebs is that they are tame, enabling her team to observe them closely, and are not stressed by human presence. This is important because stress affects body temperature and behaviour.
All of the elephants at Pebs were orphaned in the Zimbabwean culls of the 1980s and have been hand-reared. Hidden says that while the Pebs elephants are captive, they are living in their natural habitat and given time during the day when they can employ “normal” elephant behaviour in their natural habitat, by being turned out to browse freely for hours at a time.
“Previous studies have either worked with wild elephants that have been anaesthetised, or with individuals living in zoos,” says Hidden. “Although these studies have provided researchers with much valuable insight, the conditions under which they were conducted may have influenced the animals’ responses. Also, most of the studies looked at only one aspect of the elephant’s thermal biology at a time. Using these studies as a guide, the aim of my MSc project is to build up as complete a picture as possible of how elephants would go about regulating their body temperature under natural conditions.”
Why is it so important for an animal to maintain a stable body temperature? Hidden explains that temperature affects metabolism — the chemical processes occurring in the body to keep an animal alive.
“Keeping body temperature constant can be challenging when the temperature of the animal’s environment is constantly changing, and particularly if the environment becomes far hotter or colder than the animal. An animal can regulate its body temperature by choosing to take a particular course of action, but the mammalian body is also designed to respond automatically to many situations.”
To illustrate her point more practically, Hidden uses the example of it being mid-afternoon on a cloudless African summer’s day. “A herd of ellies has been browsing and ambling along since dawn, exposed to gradually increasing solar radiation as well as the heat of the still air surrounding them. The environment is at its hottest now, having slowly collected the heat of the day. The elephants are producing their own body heat as they move and eat and they certainly don’t want to pick up more heat from their environment [when the environment is hot there is a temperature gradient between the elephant’s skin and the environment, and heat energy will move down this gradient — that is, from the environment into the elephant’s body]”, she explains.
‘To prevent heat gain, one of the elephants’ first responses is to seek shade. A tree, or clump of trees, provides a ‘micro-climate’ — a localised, slightly different set of environmental conditions. Another option is to spray water and mud over their bodies and ears to make use of evaporative cooling. The elephants may flap their ears too, fanning air over their bodies to try to cool down even further. The large vessels in their ears widen, bringing hot blood to the surface of the skin where heat can be ‘dumped’.
“But to really understand how an elephant is keeping cool when it is hot, we need to thoroughly investigate how the animal responds under different environmental conditions and how effective these responses are in regulating their body temperature.”
To do this Hidden is recording behaviour, climatic information, body temperatures and body responses using technology such as infrared thermography (a special camera designed to detect the heat energy emitted by an animal/object and which interprets this heat energy for us so that we can get a measure of the animal/object’s surface temperature).
“By comparing surface temperature [or skin temperature, in animals lacking a fur coat] with the measurements of internal body temperature, we are able to assess the amount of blood flow through the skin. The amount of blood passing through vessels close to the skin surface plays a role in determining how much heat an animal will lose to its immediate environment. This blood flow is regulated automatically by the elephant’s body, depending on whether the animal needs to reduce or increase heat loss.”
Hidden will look at all these factors — climatic conditions, behavioural and physiological reponses — together to determine how an elephant goes about keeping its body temperature stable under different circumstances.
She has been assisted by Professor James Mercer, with the department of medical physiology at the University of Tromsø in Norway.
“Professor Mercer came out to help us with the filming of the infrared pictures [he is involved in using the technology to diagnose illness in human patients — they can detect infection, monitor post surgery recovery, detect some cancers amongst other things]. He has also worked as a comparative physiologist, investigating the physiology of arctic mammals. We also got help from Tjaart Broodryk, a camera expert who assisted us with the filming — he works for Rohloff, the distributors of the infrared cameras made by FLIR [an American/Swedish company] in South Africa. Rohloff provided all the cameras for the filming at no cost to us.”
Hidden winds up by saying that if we understand how elephants respond to different environmental conditions (behaviourally and physiologically), we can ensure that they are not placed in a situation where they cannot cope with the environmental conditions with which they are presented (either because they are unable to employ the appropriate behavioural response or because the environmental conditions are too extreme).
“In short: we can look after them better,” she says.