Species behavioral characteristics lead to unique fragmentation threats: The Nubian ibex as a case study

Abstract

The behavioral characteristics of species may result in certain populations being inherently more susceptible to fragmentation. For example, species exhibiting spatial sexual segregation or those constrained to elongated and narrow habitats. We studied the fragmentation threats, spatial dynamics, resource utilization, and movement ecology of a particularly vulnerable species that is both sexually segregated and constrained to elongated and narrow habitat—the north Judean Desert population of Nubian ibex (Capra nubiana). From 2016‒2020 we tracked 48 marked ibex (27 male, 21 female), of which 38 (20 male, 18 female) also had global position system (GPS) collars. Using GPS-collar and camera-trap data in zones delineated around perennial water sources (PWSs), we calculated ibex drinking frequencies and individual utilization distributions by season and sex, focusing on their overall (95% isopleth) and core (50% isopleth) home ranges. We quantified joint space use between sexes using a utilization distribution overlap index (UDOI) and ibex daily movements and space use via movement indices. Female groups formed philopatric activity centers that were anchored around PWSs year-round and arranged in a metapopulation-like structure, with no female movement detected between them. Conversely, movement of adult males changed seasonally, with the cores of male groups anchored around PWSs only during the dry season, and long-range movement between female activity centers during the rut. Female groups also spent more time at steeper terrain and higher elevations compared with male groups. Outside the rut, groups of males and groups of females exhibited minimal joint space use (i.e., average dry season UDOI was 0.06). These patterns indicate high sensitivity of this population to intersexual fragmentation by obstacles (physical or virtual). Management strategies to mitigate fragmentation threats for such populations should be sex-specific and landscape-oriented.