Group size and social organization of the endangered Eld's deer (Rucervus eldii thamin): Results from a long-term study in Myanmar

Abstract

The Eld's deer (Rucervus eldii thamin) is an endangered endemic species of Myanmar. The largest existing wild population of this species is localized in Shwesettaw Wildlife Sanctuary (SWS). Although SWS is believed to hold the largest population of wild Eld's deer, there has been no investigative research carried out on the field ecology of this species in this specific region. In this study, we examined the status of social organization with increasing population density of Eld's deer in SWS by analyzing long-term monitoring data (2001–2018). We also investigated the potential environmental factors that might affect their social organization and grouping patterns by analyzing five years data (2014–2018) in SWS. We found that the mean group size and crowding of Eld's deer for the hot dry season in Myanmar was 7.6 ± 0.9 and 11.1, respectively. The population of Eld's deer in SWS has increased steadily during these 18 years, and the fawn to adult female ratio (the proportion of fawns) has increased and is positively associated with increasing density of Eld's deer. Although the adult sex ratio was slightly skewed towards females, this ratio did not show any detectable relationship with increasing population density. Eld's deer strongly avoided areas close to human settlements and roads. Larger groups of Eld's deer showed preferences of scrub and grassland to the degraded forest habitat because this type of habitat in SWS is commonly associated with military areas where intrusion by people is strictly prohibited. We conclude that it is crucially important to manage or protect the remaining natural habitat of Eld's deer in SWS so that disturbance is reduced and the population can be conserved effictively.