Characteristics of natural and anthropogenic mortality of an endangered brown bear population

Abstract

Large carnivores’ far ranging habits and their requirements for wide areas often led them to move into unprotected lands, making them especially vulnerable to various human threats. Therefore, it is crucial to better understand their mortality characteristics and potential threats so to help guide conservation efforts. Brown bear is a protected species in Iran, however, knowledge on its population structure and causes of mortality are sparse. The main objective of this study was to understand the causes and spatio-temporal patterns of brown bear mortality in Iran. We carried out a systematic survey of internet media sources to answer (1) the mortality of which age and sex group is reported in the media; (2) what are the most common causes of mortality; (3) what are the temporal and spatial patterns of brown bear mortality?. Overall, we found 135 mortalities of brown bears in Iran from 2004 to 2019. Our findings showed that 84% of mortalities were related to anthropogenic causes and being shot (59%) was the most common cause followed by vehicle collisions (18.7%). Only 2% of reported mortalities were due to natural causes, and no information on the causes of mortality was available for 14%. We further found no differences in the sex distribution of bears killed, but adults (68%) were more commonly killed than subadults (22%); and age was unknown in 9% of mortalities. Most mortalities (75%) were reported in summer and autumn. We found that the number of bear mortality increased with increasing elevation, road density, proportion of forest cover, and that it was higher in areas with a higher proportion of protected areas (PA). However, most reported mortality cases were found outside of PAs. The main takeaway messages from our study are that the conservation of large carnivores in Iran must occur in co-existence with humans in a human-dominated landscape. It is also essential to obtain reliable data on population structure as well as more data on mortality rates and causes. We propose, among other conservation actions, the establishment of a central database for the systematic collection of data on human-carnivore conflicts as well as a compensation scheme for reimbursement of damages by large carnivores.