Thursday, 20 February 2014

Female elephants stick with their relatives

A new study looking at genetic structure and relatedness of forest elephants in Lopé National Park has been published in PLOS One, by our colleagues at the University of Missouri and in collaboration with ANPN.
We know from observational studies that elephant group sizes are small at Lopé (average = 2.5), typically composed of adult females and their offspring, while males are solitary. Although groups containing more than one adult are often seen, associations are temporary and change composition, and groups larger than 6 individuals are rare. Telemetry studies on females have also suggested that they seem to stay in fairly limited home ranges, only occasionally venturing out to make longer journeys elsewhere. This new study adds to our knowledge by looking at how individuals are related at different spatial and temporal scales.
By analyzing DNA from dung samples collected in the north-east of the park, the relationship between genetic similarity and distance was examined at distances up to 15 km and at different temporal scales, and network models were created to look at associations between individuals.
Results from the different tests were inconsistent, showing overall weak genetic structure, with negative structure at 5-10 km and positive genetic structure at 0–5 km, with strongest signals from samples collected within a single day (this also happens to be the distance telemetry studies have shown that elephants never exceed when travelling in a single day). Individuals within groups were significantly more related to each other than to individuals between groups.
While dung sample analysis identified groups of up to 6 individuals together at any one time, network models showed that elephants have a more complex social repertoire, sometimes associating with many more individuals in the population than observations might suggest. Social networks were variable, but up to 22 individuals were found, mostly related females.
This study supports the hypothesis that elephant sociality is formed on a fission-fusion system, typically groups of kin based on matrilines, with some individuals associating with multiple related individuals.  

Reference (download pdf here)
Schuttler, S. G., Philbrick, J. a, Jeffery, K. J., & Eggert, L. S. (2014). Fine-scale genetic structure and cryptic associations reveal evidence of kin-based sociality in the african forest elephant. PloS One, 9(2), e88074.

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