Brown Bear Ursus Arctos Marsicanus Research Articles

Estimating survival in the Apennine brown bear accounting for uncertainty in age classification

AbstractFor most rare and elusive species, estimating age‐specific survival is a challenging task, although it is an important requirement to understand the drivers of population dynamics, and to inform conservation actions. Apennine brown bears Ursus arctos marsicanus are a small, isolated population under a severe risk of extinction, for which the main demographic mechanisms underlying population dynamics are still unknown, and population trends have not been formally assessed. We present a 12‐year analysis of their survival rates using non‐invasive genetic sampling data collected through four different sampling techniques. By using multi‐event capture–recapture models, we estimated survival probabilities for two broadly defined age classes (cubs and older individuals), even though the age of the majority of sampled bears was unknown. We also applied the Pradel model to provide a preliminary assessment of population trend during the study period. Survival was different between cubs [ϕ = 0.51, 95% CI (0.22, 0.79)], adult males [ϕ = 0.85, 95% CI (0.76, 0.91)] and adult females [ϕ = 0.92, 95% CI (0.87, 0.95)], no temporal variation in survival emerged, suggesting that bear survival remained substantially stable throughout the study period. The Pradel analysis of population trend yielded an estimate of λ = 1.009 [SE = 0.018; 95% CI (0.974, 1.046)]. Our results indicate that, despite the status of full legal protection, the basically stable demography of this relict population is compatible with the observed lack of range expansion, and that a relatively high cub mortality could be among the main factors depressing recruitment and hence population growth.

Assessing habitat quality for conservation using an integrated occurrence‐mortality model

Summary Habitat suitability models are usually produced using species presence or habitat selection, without taking into account the demographic performance of the population considered. These models cannot distinguish between sink and source habitats, causing problems especially for species with low reproductive rates and high susceptibility to low levels of mortality as in the case of the critically endangered Apennine brown bear Ursus arctos marsicanus. We developed a spatial model based on bear presence (2544 locations) and mortality data (37 locations) used as proxies for demographic performance. We integrated an occurrence and a mortality‐risk Ecological Niche Factor Analysis model into a final two‐dimensional model that can be used to distinguish between attractive sink‐like and source‐like habitat. Our integrated model indicates that a traditional habitat suitability model can provide misleading management and conservation indications, as 43% of the area suitable for the occurrence model is associated with high mortality risk. Areas of source‐like habitat for the Apennine bears (highly elevated areas rich in beech forests, far from roads, and with low human density and cultivated fields) are still present, including outside the currently occupied range. However, attractive sink‐like habitat (associated with high levels of pasture, low extent of mountain meadows, low steepness, low elevation, and closeness to secondary and urban roads) are present even inside protected areas. Synthesis and applications. Identifying attractive sink‐like habitat is crucial to prevent inappropriate management and to effectively address conservation issues: whereas existing source‐like habitats should be preserved to halt habitat loss and degradation, attractive sink‐like habitat should be managed to mitigate mortality risks or to decrease their attractiveness. In particular, area‐specific management interventions and proactive actions (increased patrolling, road closure, human activity management, threat monitoring, etc.) aimed at reducing human‐caused mortality are critical for the Apennine brown bear.