Population viability of red deer as a free-ranging population in the Obedska bara region of Vojvodina, Serbia

Abstract

Red deer populations in Vojvodina are continuously present in the forested areas of the province, mainly within fenced enclosures with stock sizes fluctuating around 4,000 individuals, while established free-ranging populations throughout the province being up to five times less abundant (total estimated stock being up to 5,000 individuals). South of the Danube and Sava rivers, their populations frequently go locally extinct due to illegal hunting and habitat degradation. According to established state priorities for artiodactyls as followed up by the dominant management authority in the region (JP “Vojvodinašume”), we assessed red deer viability in the Obedska bara region (cc. 360 km2). Presently, around 190 red deer are present in fenced enclosures, up to 30 are free ranging. First we assessed a habitat suitability profile for the area. We used five readily available forest management factors – urbanised and agricultural areas were separately assessed. Additionally, two factors related to anthropogenic pressure and disturbance were scored based on data obtained through fieldwork. Optimally suitable habitat patches were identified. Second, we used a spatially explicit demographic model with quantitative parameters following recently proposed and consensually accepted modelling guidelines, for viable and persistent free-ranging red deer populations. The full model for the area was iterated with a complex protocol of initial conditions over a time span of 15 full generations under a proposed regime of demographic and environmental stochasticity (20%). Four suitable demes, widely differing in size with sporadically present inter-deme dispersion were identified. Average HS values for the four demes were 8.11/10. Roughly 66% of the area was unsuitable for red deer, while 22% was at least moderately suitable (> 7.5/10). The predicted best-case capacities for HS values greater than 7.5/10, were around 155 individuals (≈0.5 individuals per km2 for the whole area, 1.13 ind. per km2 for suitable demes area). The overall meta-population was viable for initial conditions for at least K/8 with ER < 10%. Two of the four demes had average occupancy < 20 time steps and ER >> 10%). The estimated MVP of the overall population is between 14 and 20 individuals with initial sex-ratios of 3:1 (pre-reproductive females to pre-reproductive males) for ER < 10%. The area has moderately high habitat suitability for free-ranging red deer. Factors related to anthropogenic pressure were the most important HS determinants. Synchronization of adaptive management practices is considered the most effective strategy for maintaining a continuous red deer presence with sufficient abundances.