The dynamics of social networks among female Asian elephants

<p>Abstract</p> <p>Background</p> <p>Patterns in the association of individuals can shed light on the underlying conditions and processes that shape societies. Here we characterize patterns of association in a population of wild Asian Elephants at Uda Walawe National Park in Sri Lanka. We observed 286 individually-identified adult female elephants over 20 months and examined their social dynamics at three levels of organization: pairs of individuals (dyads), small sets of direct companions (ego-networks), and the population level (complete networks).</p> <p>Results</p> <p>Corroborating previous studies of this and other Asian elephant populations, we find that the sizes of elephant groups observed in the field on any particular day are typically small and that rates of association are low. In contrast to earlier studies, our longitudinal observations reveal that individuals form larger social units that can be remarkably stable across years while associations among such units change across seasons. Association rates tend to peak in dry seasons as opposed to wet seasons, with some cyclicity at the level of dyads. In addition, we find that individuals vary substantially in their fidelity to companions. At the ego-network level, we find that despite these fluctuations, individuals associate with a pool of long-term companions. At the population level, social networks do not exhibit any clear seasonal structure or hierarchical stratification.</p> <p>Conclusions</p> <p>This detailed longitudinal study reveals different social dynamics at different levels of organization. Taken together, these results demonstrate that low association rates, seemingly small group sizes, and fission-fusion grouping behavior mask hidden stability in the extensive and fluid social affiliations in this population of Asian elephants.</p

Camera traps unveil enigmatic crop raiders in Udawalawe, Sri Lanka

We studied Asian elephants (Elephas maximus) entering three villages bordering the Udawalawe National Park, Sri Lanka, by placing camera traps on road openings of the boundary electric fence of the park. We identified 35 individuals that crossed the fence, all of which were males. Identified individuals were of differing age/size classes and the majority were solitary. Elephants left the park at dusk and retuned at dawn. Individual variation was observed in method and time of fence crossing. Elephants showed localized movement over the small area of the study. Our results suggest a high degree of crop raiding by males in the area and underscore the failure of current management activities in preventing human-elephant conflict

Demography of Asian elephants (Elephas maximus) at Uda Walawe National Park, Sri Lanka based on identified individuals

We provide estimates of population size and other demographic variables for individually-identified Asian elephants (Elephas maximus) in Uda Walawe National Park (UWNP), Sri Lanka based on systematic year-round observations. Two hundred and eighty-six adult females and 241 adult males were identified, of which four adults (2% of males) had tusks. Sightings-based demographic models showed seasonal immigration and emigration from the study area. The total population, including non-adults, was between 804 and 1160 individuals. Density ranged from 102 to 116 adult females per 100 km2 and remains at this level throughout the year. This large, un-fragmented population of Asian elephants should be of high conservation priority. We find that estimates of survivorship and migration rates should be based on long sampling intervals when possible, but estimates of density and population size can still be made when observations are constrained to shorter intervals, if spatial data are available. We offer suggestions to guide census design for other elephant populations or cryptic species. We urge that other locations be systematically surveyed as well using photographic identification

Collective movements during visits to water bodies in wild Asian elephants

Collective movements feature multiple consecutive processes involving diferent types of initiative behavior. It remains unclear whether, and to what extent, the same individual consecutively performs diferent initiative behaviors in a single collective-movement event. We conducted behavioral observations of wild Asian elephants (Elephas maximus) visiting a water body in Udawalawe National Park, Sri Lanka. We analyzed 32 collective-movement events involving 51 individually identifed adult females. We used randomization tests to compare the observed and expected frequencies of initiative behavior by a particular individual. We found that adults were more likely to exhibit such behavior than the expected frequencies. We also found that a single female, generally the oldest female, consecutively engaged in three types of initiative behavior more frequently than expected, although their occurrence did not constitute the majority of cases (6/23). This low consecutiveness among Asian elephants may be related to their fssion–fusion dynamics and lack of core groups. Our results highlight the importance of analyzing multiple initiative behaviors associated with collective movement