Desert-dwelling elephants: New insights on ‘desert’ elephants

By Dr Keith Leggett, Namibian Elephant and Giraffe Trust

Elephant conservation is a challenge and for many a calling. In both cases, the need for facts is vital.

It is rare in any conservation debate that elephants are not mentioned. Why? For a start they are probably one of the most recognised animals on the planet, being the largest land mammal and still occupying large parts of Africa and Asia. Modern conservationists use several terms to describe them, such as charismatic megafauna, keystone and flagship species, the latter meaning a species that should represent a multitude of other species that need conserving.

More myths about desert-dwelling elephants have permeated the debate than about any other group. Two of the most common are that desert-dwelling elephants have longer legs and are taller. This is not true. The desert-dwelling variety is physiologically and genetically identical to the Etosha elephant, Loxodonta africana. However, due to the lack of vegetation in their habitats, they don’t carry the same body mass as Etosha or other savannah elephants; consequently they appear longer in the leg and taller. However, they do have larger feet; this comes from walking on soft sand all their lives and is not a morphological difference.

Desert elephants

What exactly is a desert-dwelling elephant? The definition is a little difficult, as there is no easy way to define this group. Early observers based the description on the fact that the elephants crossed the dunes to get to their seasonal or annual home ranges. This is not a particularly good definition, as later movement studies have showed that some of these same elephants also move to the east and stay for a period in the area around the Hobatere Game Reserve. Then they were thought to be a sub-species or at least geneti-cally different. However, neither of these notions is true. The most practical definition is that desert-dwelling elephants occupy an arid habitat for at least part of the year. They are, in fact, an eco-type, with special behavioural characteristics – large annual and seasonal ranges and a social structure and daily activities that cope with the environment.

Movement and ranges

In order to establish the home ranges of elephants in north-western Namibia, an initial GPS collaring exercise was undertaken in September 2002. This has been repeated three times since and there are currently eight GPS-collared elephants in north-western Namibia. Some of these ele-phants have been continuously monitored for six years, with the current collars set to expire in 2009. The GPS collars collected data every 24 hours and transmitted the information to a server in South Africa, from where it was forwarded it to scientists in Namibia. The home-range GPS-collared elephants in north-western Namibia are presented schematically in Figure 1.

Desert Elephants by Paul van Schalkwyk

In terms of range, the standout elephant is WKM-10, having one of the largest recorded home ranges of any elephant. During 2002–2006, his home range was 14 210 square kilometres. Moving 625 kilometres from the Hoarusib to the Hoanib River, into the Etendeka Mountains south of Sesfontein, then east into the eastern Hoanib River, ending approximately 12 kilometres at his closest point from Hobatere Game Reserve, he then returned the way he came. This round trip takes up to five months and he has repeated it in four of the past six years.

Social structure

The social structure of African elephants is normally based on female groups or herds composed of related adults, usually dominated by the eldest female, called the matriarch. A family unit is defined as the basic unit of elephant society and consists of one or several related females and their offspring. Related families may form defensive units and kin-based allegiances, which in turn may have a positive affect on calf-survival rate. These bond or kin groups are comprised of up to five closely related family groups. When bond groups meet, elaborate greeting ceremonies are often exhibited along with synchronous behaviour. Families and bond groups that have the same seasonal ranges are classed as clans. Clans are used to define a level of association around habitat use. It is unclear whether this is a functioning elephant social unit.

In most areas of Africa, adult male ele-phants are frequently solitary or found in small groups (bachelor herds), except during breeding periods, which are generally associated with musth. Musth is an unusual period of elevated testosterone, accompanied by increased movement, interest in females and aggressiveness. Musth periods occur throughout the year. However, individuals only experience musth once a year. Outside of musth, males do not generally associate with the family units.

Desert Elephants by Paul van Schalkwyk

The more I studied desert-dwelling elephants, the less likely these definitions appeared to apply to them. After many years, several things became obvious, namely that herd structure was very loose, with bond groups meeting up all the time, then splitting again without elaborate greeting behaviour and interaction. This fluid nature also existed between bond groups with family units coming and going, with only the family units remaining stable. In addition, there appeared to be a lack of leadership within the bond groups, without a dominant female acting as matriarch. Rule appears to be ‘determined by committee’ rather than by one individual female dominating the others. It was obvious that some other explanation was needed to describe the social structure of desert-dwelling elephants.

One of the possible reasons for this diverse nature of the bond groups could be ascribed to the history of desert-dwelling elephants. The western elephants had been severely depleted by poaching and disturbance during the late 70s and early 80s. The Hoarusib elephants, which had numbered approximately 80 individuals in the late 60s, were all shot except for three individuals during this poaching event. These three individuals moved south to the Hoanib River and joined up with other remnant herds that had been similarly decimated. This being the case, there was no direct or very few family links between any of the other family units in the area. The group associations were more for social interaction and offspring nurturing than any direct family relationships.

Desert elephants. Photo ©Paul van Schalkwyk. http://www.tala.com.na/

Adult males were mostly seen as single ani-mals, although a significant number were also observed in pairs. What is surprising is that adult males were found with the bond groups in a large number of observations. Most of these associations were of non-musthing males with bond groups. It appears as though the adult males come into the bond groups for social reasons and after a short period of time (ranging from a few hours to two days) they move off again by themselves. The adult females appear to be remarkably tolerant of the adult males and make no attempt to chase them from the bond groups as has been reported from other areas of Africa. Longer-term (two days to a week) associations between adult males and the bond groups occurred when the males were in musth and searching for females in oestrus. The lack of bachelor herds could be due simply to a lack of numbers.

Behaviour

What do desert-dwelling elephants do during the day? By undertaking a series of diurnal studies to assess the behaviour of elephants over a five-year period, researchers have a reasonable idea of what elephants get up to.

Feeding, resting, social, drinking and walking activities were recorded, and, as would be expected from animals living in the desert, their drinking behaviour was most interesting. Desert-dwelling elephant males can go without water for five days, females and calves up to three days. This is unusual as elephants in other parts of Africa drink either daily or every second day, although desert-dwelling elephants are opportunistic drinkers and drink more readily when water is available.

Walking activity was also high throughout the seasons. This was due to the distances that elephants needed to cover between food and water. Walking was at its maximum during the cold dry season when temperatures were at their coolest and adult males were in musth and in constant motion to find receptive females. During both the wet and hot dry seasons, walking dropped off, as it is generally too hot to walk in the middle of the day.

Debate about elephants continues to swirl in conservation circles. It raises emotions, awareness and more questions. As long as these questions are met with action, elephants and other animals that occupy the same range will be protected.

This article appeared in the 2008/9 edition of Conservation and the Environment in Namibia.