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Monthly activity centres of african elephants in a small game reserve

Xiaohua Dai^1,2 And Kevin Duffy¹

1 Centre for Systems Research, Durban University of Technology, Durban 4000, South Africa. E-mail: kevind@dut.ac.za

2 School of Chemistry and Life Science, GanNan Normal University, Ganzhou 341000, Jiangxi Province, China. E-mail: ecoinformatics(at)gmail.com

Keywords: African elephants, centre of activity, home range, harmonic mean, marula

Introduction Due to habitat heterogeneity and environmental variation, the home range and habitat utilization of African elephants varies in different years and different seasons, not only in large protected areas but also in small reserves (Shannon et al., 2006). Although there are many studies on seasonal changes of elephant home ranges, no articles on finer temporal shifts within elephant home ranges are published. Monthly movement rhythms should provide more detail on elephant foraging and its impacts and help the conservation and management of both elephants and their habitats, especially in small reserves.

Materials and Methods Radio and satellite collars on the elephants were fitted by a veterinary surgeon in a humane manner, and in accordance with laws governing animal anticruelty in South Africa. All elephant locations were projected into UTM 1983 (Zone 36) datum. Since the datasets are sampled differently, the analyses include only the first daily location and separated by sex. Using these data monthly harmonic mean centres of elephants were determined using ArcView Animal Movement Analyst Extension (the number of divisions of the X axis: 100).

Results For both bulls and cows the elephants are more active in the northern PGR, with oscillations to other regions in other months. These monthly regional preferences are generally consistent across years and a generalised cadence pattern is given in Fig. 1. For bulls the monthly cadence in activity is primarily between the northern PGR and the high marula densities area. The cow herd activity oscillates between the northern region and the southern PGR. These patterns of activity are partly disrupted in the dry months i.e. activity centres are more widely distributed. In February both bulls and cows are found in the central part of the PGR which appear to relate to the marula distribution area (Fig. 1). For the months adjoining months January and March they are in the north. From late April or May, elephant activity centres shifted from the north. From September or October when the first spring rains fell elephant activity centres shifted back to the north (Fig. 1). Bull and cow activity centres were only close together in the wet season from November to February (Fig. 1).

Conclusions Our results show that elephant activity over that period had similar month-by-month rhythms in different years, which appeared to be related to rainfall, vegetation, distribution of cow herd, marula (Sclerocarya birrea) fruiting and hunting. Food appears to play an influencing role in the elephant movements. Monthly activity centres of both bulls and cows were more widely distributed in the dry months than in the wet months. Bulls keep relatively close to the herd only in very wet months. There is a close association between fruiting of marula and the distribution of elephants in February. Rainfall appears to have an indirect but influencing impact on elephant ranging behaviour. Knowledge of elephant monthly movements is not only helpful for the design of suitable management strategies but could be used for the estimation of minimum size for a small reserve.

References

Shannon, G., Page, B.R., Duffy, K., Slotow,R. 2006. African elephant home range and habitat selection in Pongola Game Reserve, South Africa. Afr. Zool. 41: 37–44.