Elephant shrews in Goegap
By Annette Wiedon and Carsten Schradin

The small animal is sniffing excited with its trunk like extended nose – by observing this you see easily what gave the elephant shrew its name. The elephant shrew entered the trap and is now waiting for the things to come. All this excitement is in vain. It is simply taken out of the trap, weight and sexed. To identify it during later trapping sessions it gets an ear tag with a number on it. That’s it and the elephant shrew can be released back into the vastness of Namaqualand
The species occurring at our field site in the Goegap Nature Reserve is the round-eared elephant shrew (Macroscelides proboscideus). Despite the length of the name and nose it is measuring just 23 cm from nose to tail. Adults can weigh up to 45 g. We trap mainly for striped mice, but sometimes elephant shrews go into the traps as well. As we plan studies about this species in the near future, data of the trapped individuals are already collected. If you continue reading, you will find some interesting details about this species!
Elephant shrews occur only in Africa and here mainly South of the Sahara desert. They belong to the order Macroscelidea although for a long time they were wrongly classified as insectivore. However, besides of ants, spiders, termites and other small invertebrates they also feed on green parts of plants, young roots and fruits. Now they are regarded as omnivores. The herbal part of the diet is about 50%. In winter months, when insects are hardly found, the herbal part can even rise up to 60%. Each food item is first collected in the cheek pouches and eaten later in a safe hiding place. Elephant shrews do not need to drink. They cover their water requirements with the food. The specialized caecum helps to minimize water loss over excretion.
For refuge elephant shrews prefer holes in the ground which either already exist or are burrowed by themselves, especially if the ground consists of sandy and loose material. But also dense shrubs or crevices can offer refuge to them. They usually live alone in their shelter, which is why they could be wrongly specified as a solitary species. However, in fact they are monogamous. One pair shares a territory and defends it against other pairs. But there is no pair bond and the pair spends only very little time together. Social contacts appear just for short periods, e.g. for mating or while a mother is rearing her pubs.
Elephant shrews frequently change their dwellings. By doing this the animals are moving very fast with a ricochetal locomotion and they can reach speeds up to 20 km/h. In contrast, foraging is rather slow.
Elephant shrews are active both at night and during the day, but their activity is highest during dawn and dusk. The reasons for this could be a better protection of predators as well as the possibility to minimize water loss by avoiding the high temperatures during hot summer days. The high flexibiliy in their activity and as well their special foraging behaviour reflect the tolerance to the occupied habitats which are usually arid or semi-arid.
One special feature of Macroscelides proboscideus is the ability to fall into torpor. That means, the elephant shrews are able to reduce significantly their metabolic rate and body temperature, in some extreme cases even down to 10°C! The torpor is initiated during cold winter nights and in the case of acute food deficiency to keep energy demands as low as possible. The animal can stay in this low energy-level for a maximum of 18 hours and the reactivation seems to be synchronized with the sunset. The exploitation of radiant heat plays an important role for passive rewarming.
The reproduction is not restricted to a few months, like it is the case for most of the mammals, but can occur around the whole year. Most of the juveniles (77%) trapped by Bernard et al. (1995) are nevertheless trapped in the months september til february. So the reproduction at least seems to have a seasonal trend. The researchers provide for this an indirect coherence to the intake of calcium over fresh plant material in sping. Calcium plays an important role for pregnancy and especially for nursing the pubs.

 

In 2009, Melanie Schubert finished her PhD thesis about elephant shrews at the University of Bayreuth, Germany. Two publications arose from this work:

  1. Schubert, M., Pillay, N., Ribble, D. O. & Schradin, C. 2009. The Round-Eared Sengi and the Evolution of Social Monogamy: Factors that Constrain Males to Live with a Single Female. Ethology, 115, 972-985.
  2. Schubert, M., Schradin, C., Rödel, H. G., Pillay, N. & Ribble, D. O. 2009. Male mate guarding in a socially monogamous mammal, the round-eared sengi: on costs and trade-offs. Behav Ecol Sociobiol, 64, 257-264.