Decline in body condition and high drought mortality limit the spread of wild chital deer in north-east Queensland, Australia

Abstract

Chital deer (Axis axis) were introduced to the Burdekin district of northern Queensland, Australia in 1886. Compared with most successful ungulate introductions they have been slow to expand their distribution and increase in abundance (Moriarty 2004). In this study we consider the possibility that forage shortages caused by periodic droughts have caused sufficient mortalities to limit the increase and spread of chital in the region. The Burdekin district experiences fluctuations in forage according to seasonal rainfall as well as multi-year droughts. This study recorded the decline in body condition, measured as kidney fat index (KFI) and bone marrow fat (BMF), over the wet and dry seasons of two successive years in two chital deer populations during a period when annual rainfall was ~40% below average. We relate the falls in mean KFI from ~45–15%, and mean BMF from ~80–50% to the surveyed decline in chital populations of ~80%. The extent of the decline implies increased mortalities in all age classes as well as reduced reproductive output. We propose that it is likely that chital populations have experienced several such drought mortality events since the 1890s which have contributed to their limited spread.