Mortality of Amur tigers: The more things change, the more they stay the same

Abstract

Poaching as well as loss of habitat and prey are identified as causes of tiger population declines. Although some studies have examined habitat requirements and prey availability, few studies have quantified cause-specific mortality of tigers. We used cumulative incidence functions (CIFs) to quantify cause-specific mortality rates of tigers, expanding and refining earlier studies to assess the potential impact of a newly emerging disease. To quantify changes in tiger mortality over time, we re-examined data first collected by Goodrich et al. (; study period 1: 1992-2004) as well as new telemetry data collected since January 2005 (study period 2: 2005-2012) using a total of 57 tigers (27 males and 30 females) monitored for an average of 747 days (range 26-4718 days). Across the entire study period (1992 to 2012) we found an estimated average annual survival rate of 0.75 for all tigers combined. Poaching was the primary cause of mortality during both study periods, followed by suspected poaching, distemper and natural/unknown causes. Since 2005, poaching mortality has remained relatively constant and, if combined with suspected poaching, may account for a loss of 17-19% of the population each year. Canine distemper virus (CDV) may be an additive form of mortality to the population, currently accounting for an additional 5%. Despite this relatively new source of mortality, poaching remains the main threat to Amur tiger survival and, therefore, population growth.

Keywords: Panthera tigris altaica; canine distemper virus; cause-specific mortality; cumulative incidence function; poaching.