Elephant Research

The elephant research that I have been involved with since 2001 has centred upon four distinct field projects, which have explored various aspects of elephant ecology and behaviour. A wide range of methods have been employed from remote sensing and direct observation to playback experiments. These research interests are summarised below, while relevant publications can be found here.

Elephant cognition - exploring age and experience as determinants of acquired knowledge


In September 2006 we began an 18 month study that set out to compare the social knowledge of elephants with distinctly different developmental histories. The natural family groups of Amboseli National Park, Kenya were compared with the artificially constructed families found in Pilanesberg National Park, South Africa. The Pilanesberg population was founded in the early 1980‘s with orphan elephants from the Kruger National Park following management culls of adult and older juvenile animals.


Elephants are long-lived, large brained mammals that exhibit complex social behaviour. They naturally occur in fluid fission-fusion populations and due to their extensive ranges come into contact with a large number of individuals during the course of a year. In such a situation acquiring detailed information with regard to the familiarity and association of other elephants can be advantageous and has a direct influence on survival and reproductive success. Karen’s earlier research demonstrated that the social knowledge of the matriarch can determine the social knowledge of the group as a whole. Furthermore, older matriarchs were much more successful at discriminating the contact calls of strangers versus those of familiar elephants McComb et al. 2001.


We employed innovative playback paradigms to allow us to directly explore the knowledge that wild African elephants have of their social companions. The playbacks involved broadcasting elephant contact calls through custom built speakers that were able to accurately reproduce the very low frequencies associated with elephant vocalisation. In March 2009 we started the second phase of our research, which focused specifically on how age and experience of the matriarch influences the social and ecological knowledge of the family group as a whole. Abilities to discriminate between different levels of predatory threat (ecological knowledge) were tested by giving elephant family units playbacks of three lions versus a single lion roaring and, within these categories, roaring from male versus female lions.


Our work on matriarch age and knowledge of lion predators provided the first empirical evidence that individuals within a social group may derive significant benefits from the influence of an older leader because of their enhanced ability to make crucial decisions about predatory threat. We have also recently published work that explores the effects of profound social disruption on social function, and provided the first evidence that elephants are able to distinguish the threat presented by different groups of humans on the basis of voice and language.

 

The effects of sexual dimorphism on the movement behaviour and foraging ecology of the African elephant


I began my PhD in late 2002 at the University of KwaZulu-Natal, Durban with Rob Slotow, Bruce Page and Kevin Duffy. The fieldwork involved 2-years of studying elephants in northern Zululand. The research focussed on exploring the role of sexual dimorphism in foraging and movement behaviour.


Large herbivores are key components of terrestrial biomes because of their relative abundance and pronounced influence on ecosystem functioning and habitat structure. To manage and conserve these species effectively requires greater understanding of their distribution and use of resources at varying spatial and temporal scales. Sexual dimorphism is one aspect of large herbivore ecology likely to have a significant effect on resource use and community level interactions, particularly as body size plays a major role in determining both the energy demands of an individual and the methods by which nutrients are extracted from the environment.


Elephants present an ideal species to test the influence of sexual dimorphism due to their marked body size and pronounced behavioural differences. My PhD used location and behavioural data collected over an 8-year period in five different South African reserves, all of which had well documented elephant populations.

The data were collected through direct observation of the movement behaviour and foraging patterns of male and female elephant in conjunction with remote sensing (GPS collars were fitted to the elephants which downloaded regular location data).


Results indicated that male and female elephants resolve their available range at distinctly different scales. Both sexes were shown to expand their ranges with increasing forage quality, however males were the most flexible in their temporal and spatial response during periods of low resource availability. Females were more selective than males, targeting higher quality forage and being less destructive in their feeding approach. This may well be driven by female elephants having higher mass specific energy requirements associated with their smaller body size and substantial reproductive investment. They were also constrained by the costs of group living compared to male elephants that range independently.


Sexual segregation is a consequence of body size dimorphism and was investigated at both the habitat and plant scale to elucidate the mechanism driving the spatial and temporal separation of the sexes. Whilst individual habitat preferences exist, these did not seem sufficient to segregate the sexes. Instead, the marked sexual segregation appeared to be caused by social organisation, reproductive strategies and the divergent foraging behaviour of males and females at the plant scale. This research highlights the importance of considering male and female dimorphic herbivores as ecologically distinct species. For example, male elephants are likely to be driving the majority of destructive foraging bouts and this will often be in a heterogeneous manner, especially during periods of resource scarcity. Therefore, the effective management of elephants requires considering population structure, individual behaviour and population size.

Mapping elephant paths in Tembe Elephant Park


In 2001 I travelled to South Africa for the first time to conduct my Masters degree research. The project investigated elephant ranging patterns in Tembe Elephant Park (a densely forested protected area on the border of Mozambique) by mapping and analysing data on their movement and foraging paths. The results demonstrated a strong relationship between path size and distance to water. We also discovered a number of elephant ‘rest areas’ along these paths, which tended to be close to water and in the rare sand forest habitat.


Managers of protected areas in African savanna ecosystems often provide artificial water points to maintain populations of large herbivores and provide viewing opportunities for visitors. However, such interventions lead to increased ranging and foraging pressure, which can impact on sensitive habitats and species. Therefore, there is a need to understand the effects of artificial water provision when balancing the requirements of key herbivore populations, broader biodiversity and ecotourism. Our study provided further evidence that manipulating surface water availability can be a useful tool for managing large herbivore impacts on vegetation and acts as the basis for further research on the trade-offs between conservation and tourism objectives.

Savanna dynamics and the role of elephants in the utilisation of woody vegetation


In early 2006, David Druce and I designed and implemented a research project that aimed to develop methods and monitoring techniques to quantify the impacts of elephant, fire and disease on large trees (>5 m) in the Kruger National Park (KNP). Large trees provide foraging opportunities and refuges for a myriad of species, whilst also playing a key role in the cycling and distribution of nutrients, and as such are considered keystone structures in the savanna landscape. The study was initiated in response to concern over the increasing elephant population and a paucity of reliable data on the changes in vegetation over time, and ultimately the factors that might be driving this. Methods needed to be established which were readily repeatable and yet still provided sufficient data to answer questions on vegetation impacts, the relative effects of different ecological drivers and the rates of change. 


The fieldwork involved surveying 22 vegetation transects (average 3 km in length & 10 m wide) in the southern section of the Kruger National Park on foot. The total length of the transects was 67 km and data were collected for 3082 individual trees. In November 2008 the fieldwork was repeated to determine the rates of change in utilisation and impact that had occurred in the preceding 2.5-year period. We were able to locate each tree that had been surveyed in 2006 using the unique GPS location and the details of the individual tree (species, dimensions and utilisation).


The results demonstrated that large-tree structure in the Southern KNP was dominated by a comparatively small number of species that exhibited a type-two survival curve – where mortality is relatively constant with age. The majority of trees were < 10m in height with only 1% reaching 15m or more. These very large trees were generally found close to the main river courses, where soil moisture and nutrient levels are at their highest. We concluded that high densities of large trees are unlikely to be a common feature of dynamic savanna ecosystems. It is also improbable that the decline of large trees in KNP is linked solely to the foraging behaviour of elephant, despite their well-documented impacts and the augmentation of water.


Our methods enabled us to track the changes in savanna dynamics over time, and recently the third survey was completed by Abi Tamim Vanak, Maria Thaker & Alain Smith – providing us with five years of data. Analysis of this long-term dataset has enabled the research team to demonstrate that there is a very strong interaction between the effects of elephant utilisation and the impact of fire. Indeed, for trees that were pushed over in 2006, probability of mortality was 47 times higher if they suffered from subsequent fire and 25 times higher if they were further utilised by elephant. Our results highlighted the synergistic relationship between fire, elephant, and abiotic factors in driving the utilisation and mortality of large trees in this savanna system. These impacts, operating in conjunction with increasing elephant population densities, may be sufficient to cause this ecosystem to undergo a regime shift. It is therefore essential that monitoring be focused at measuring appropriate leading indicators of change over time. These findings highlight that keystone features such as large trees show differential vulnerability to mortality that is landscape-specific. For conservation managers, this implies that the dynamic drivers (elephant and fire) of tree mortality have to be managed at the landscape-level.