Getting to know Africa's 'little elephants'

Posted on March 18, 2015

Despite the great advancements made by humankind through research, which is an exclusively human ability, nature still holds many unexplored secrets. Researchers at the University of Pretoria’s Department of Zoology and Entomology are seizing the opportunity to enrich the pool of knowledge and answer some of the questions that have long remained unanswered.

In this particular case the questions relate to the elephant shrew, also known as the sengi. Dr Heike Lutermann of the Department has been studying this small mammal, which is endemic to Africa, for several years. Large populations of a number of sengi species are found across most of the country.

Over the past few years, several new species have been identified, and Dr Lutermann suspects that more will be discovered as her research progresses. The elephant shrew is a fascinating small mammal, despite its confusing name. Its closest relatives are dassies (hyrax), elephants, dugongs and golden moles. This strange classification is based on the genetic relationship among these animals, which are among Africa’s most ancient surviving mammals. Elephant shrews are thought to be monogamous, which is rather strange since less than 3% of mammals subscribe to this way of life. Their monogamy is even stranger as they rarely seem to interact or touch. A male and female may share a home range, but they seldom move around together. 

Their morphology is also very interesting: they have very long hind legs and a tongue that is almost the same length. Studies have shown that proportionate to size, sengis are in fact faster than cheetahs! Babies are born fully furred with eyes that are wide open and they are fully mobile almost immediately after birth. They grow very quickly and are weaned in less than a month. Dr Lutermann believes that the young are born fully furred because elephant shrews live among taller grasses and do not have nests in which to shelter their young. Depending on the species, their weight can range from 45 grams to two kilograms.

Sengis living in the wild appear to have very specific trail systems and are very particular about the environment within that system. If there is an intruder, for instance another sengi, or even a twig or rock that causes an obstruction, they will do everything in their power to remove it. Maintaining the trail system is a duty they take very seriously. If one knows what to look for, these trail systems are clear to see, especially in the case of grassland species. 

Their physiology is fascinating and they can lower their body temperature substantially to conserve energy. When they need to increase their body temperature, they lie in the sun so as not to expend energy unnecessarily. Although they are considered to be insectivores, Dr Lutermann’s dietary evaluation has proved that they are happy to try just about anything – at least once. Some of her colleagues have even discovered that sengis have a sweet tooth and enjoy the nectar of certain plants, which means that they also play an important role as pollinators.

Dr Lutermann and her research team have successfully established a thorough baseline for this ancient small mammal and are now ready for more detailed and exciting research. Throughout her research career, Dr Lutermann has had a specific interest in parasites, and apart from the fact that they are ridiculously cute, what originally attracted her to sengis was the fact that they were covered in ticks. A small rock elephant shrew that weighs about 45 grams can easily have more than 300 ticks hiding in its fur!

Ticks go through three stages in their life cycle, namely the larval, nymph and adult stages. Adult ticks are found on livestock, and if one considers the economic value of livestock it seems only natural that a great deal of research has been done on adult ticks, while very little has been done on the hosts of immature ticks. Many small mammals harbour ticks that, in their adult stage, have a negative impact on the livestock economy. Furthermore, ticks are vectors of a large number of diseases that affect both livestock and humans.

This, according to Dr Lutermann, explains why it is so important to understand the full life cycle of ticks. She is not only interested in the relationship between parasite and host, but also in the factors that drive the dynamics between them. She is currently looking at seasonal dynamics and environmental factors, as well as the differences between animals and why some animals, and individuals of the same species, attract more parasites than others.

Results obtained by this research team suggest that by targeting one specific parasite, unexpected and even unwanted effects may result. After treating wild sengis with Frontline™, the topical product that targets ticks and fleas, researchers found that although it effectively got rid of the ticks, the number of mites increased dramatically. Further tests will have to be conducted in this very complex area, but the preliminary evidence suggests that a holistic approach is essential in combating parasites.

While sengis may be small and relatively unknown, they are certainly not insignificant contributors to a healthy ecosystem. Dr Lutermann’s research promises not only to offer greater insight into a species that has not been thoroughly studied, but also to improve recommendations regarding parasite control. It has the potential to provide more cost effective alternatives to the livestock farmer and to reduce zoonoses and other tick-borne diseases. 

- Author Louise de Bruin

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