Spatial and social structure of the elephant population in Samburu, Kenya
A long-running and detailed genetic, behavioral and spatial study of the Samburu elephants reveal the most complex social structure seen in any (non-human) animal yet studied. George Wittemyer began research on the Samburu elephant population in1997, started the individual ID file that is used and updated by STE today, and set up the Samburu research camp. He has also helped train the STE team during his nine years with Save the Elephants. In 2000, he began fieldwork for his doctoral dissertation which he completed in 2005 through the University of California at Berkeley. His doctoral work explored the ecological factors influencing the reproductive biology, social behavior and spatial organization of the Samburu elephants.
In particular he is focusing on:
• the kinship basis for the association of elephants
• kin discrimination and all mother-calf interactions
• factors affecting social cohesion and separation.
The results of his work are available both in his doctoral thesis title and scientific publications. He is currently a National Science Foundation International Post Doctoral Fellow working on the population genetics of the Samburu elephant populations as well as the genetic basis for the social and spatial organization among focal individual elephants.
Results from genetic analyses, carried out in collaboration with researchers from the Wildlife Genetics Project at Makerere University in Uganda and the University of Copenhagen in Denmark, will elucidate the role of kinship in defining social structure. The genetic data was collected non-invasively from fecal samples from over 400 known individual elephants utilizing the Samburu and Buffalo Springs National Reserves.
His work includes use of the GPS data to explore the genetic basis for differences in individual ranges and spatial behavior. In addition to the genetic work, he has been using stable isotopes to explore foraging behavior among focal elephants and am involved in projects looking at endocrine functioning in relation to reproduction and chemical communication.
Quantitative analysis of elephant social structure for his doctoral work was carried out on association data of 382 elephants: the 111 most frequently observed breeding females and 271 of their constantly associated offspring. Results quantitatively demonstrate the existence of four social tiers (1. mother-calf dyads, 2. family units, 3. bond groups and 4. clans) in a free-ranging population of African elephants from a cluster analysis of individual association data, with the existence of the third tier dependent upon season.
Additionally the analysis suggests that neither families nor bond groups coalesce around an ideal size but that families led by matriarchs 35 years and older (those more likely than not to be grandmothers) are significantly larger than those of younger matriarchs. This is the first time that the existence of four organizational tiers has been statistically demonstrated in any non-human animal, as has been published in the Animal Behavior journal under the title “The socioecology of elephants: analysis of the processes creating multitiered social structures”.
The function of higher order structuring in elephant societies is thought to serve as a platform for intra-specific information exchange during times of drought and may also emerge during periods of human predation.
Building on the social organization work, analysis of GPS radio tracking data suggests that ranging behavior of family groups is influenced by social relationships. Specifically, dominant groups appear to control access to limited resources driving lower ranking groups to travel further for water and forage. Social influences on spatial behavior were only manifested during the dry season when resources are clustered and monopolizable. Seasonal variation in resource availability was also found to drive the reproductive timing among the Samburu elephants.
Demographic work shows the probability of successfully conceiving in Samburu is strongly correlated to the amount of vegetative productivity in the ecosystem. During droughts and excessively dry periods, the Samburu elephants appear to experience anoestrous and stop all reproductive activity until conditions improve.
In particular he is focusing on:
• the kinship basis for the association of elephants
• kin discrimination and all mother-calf interactions
• factors affecting social cohesion and separation.
The results of his work are available both in his doctoral thesis title and scientific publications. He is currently a National Science Foundation International Post Doctoral Fellow working on the population genetics of the Samburu elephant populations as well as the genetic basis for the social and spatial organization among focal individual elephants.
Results from genetic analyses, carried out in collaboration with researchers from the Wildlife Genetics Project at Makerere University in Uganda and the University of Copenhagen in Denmark, will elucidate the role of kinship in defining social structure. The genetic data was collected non-invasively from fecal samples from over 400 known individual elephants utilizing the Samburu and Buffalo Springs National Reserves.
His work includes use of the GPS data to explore the genetic basis for differences in individual ranges and spatial behavior. In addition to the genetic work, he has been using stable isotopes to explore foraging behavior among focal elephants and am involved in projects looking at endocrine functioning in relation to reproduction and chemical communication.
Quantitative analysis of elephant social structure for his doctoral work was carried out on association data of 382 elephants: the 111 most frequently observed breeding females and 271 of their constantly associated offspring. Results quantitatively demonstrate the existence of four social tiers (1. mother-calf dyads, 2. family units, 3. bond groups and 4. clans) in a free-ranging population of African elephants from a cluster analysis of individual association data, with the existence of the third tier dependent upon season.
Additionally the analysis suggests that neither families nor bond groups coalesce around an ideal size but that families led by matriarchs 35 years and older (those more likely than not to be grandmothers) are significantly larger than those of younger matriarchs. This is the first time that the existence of four organizational tiers has been statistically demonstrated in any non-human animal, as has been published in the Animal Behavior journal under the title “The socioecology of elephants: analysis of the processes creating multitiered social structures”.
The function of higher order structuring in elephant societies is thought to serve as a platform for intra-specific information exchange during times of drought and may also emerge during periods of human predation.
Building on the social organization work, analysis of GPS radio tracking data suggests that ranging behavior of family groups is influenced by social relationships. Specifically, dominant groups appear to control access to limited resources driving lower ranking groups to travel further for water and forage. Social influences on spatial behavior were only manifested during the dry season when resources are clustered and monopolizable. Seasonal variation in resource availability was also found to drive the reproductive timing among the Samburu elephants.
Demographic work shows the probability of successfully conceiving in Samburu is strongly correlated to the amount of vegetative productivity in the ecosystem. During droughts and excessively dry periods, the Samburu elephants appear to experience anoestrous and stop all reproductive activity until conditions improve.