Identifying seasonal hotspots for cetacean calves in the Gulf of Taranto: a presence-only Bayesian approach using INLA

The Gulf of Taranto (northern Ionian Sea) is recognized as a critical habitat for several cetacean species, with the striped dolphin (Stenella coeruleoalba), common bottlenose dolphin (Tursiops truncatus), and Risso’s dolphin (Grampus griseus) representing some of the most frequently observed species in the study area. However, this basin is also characterized by intense and diverse anthropogenic pressures, including military activities, aquaculture, fishing, and maritime tourism. Understanding how these pressures intersect with critical life-history stages, such as calving, is essential for effective conservation. This study aims to identify, for each of the three target species, the hotspot areas of calf presence in different seasons. Data collected between 2013 and 2023 were analyzed. We implemented a presence-only marked point process model within a spatio-temporal Bayesian framework using the R package inlabru, accounting for barrier effects and spatial thinning. The model integrated presence data with a mark representing the calves’ proportion within each dolphin pod. A set of physico-chemical covariates characterizing the Gulf of Taranto was used to model habitat suitability and calf distribution. Our results provide an initial quantitative perspective on season-specific patterns of calf occurrence, potentially informing future conservation and management discussions in a basin subject to intense human pressures.