Habitat Selection

of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in The Northern Red Sea, Egypt.

Spatial assessments of species distributions are essential for data-driven conservation and management. This study applies ensemble species distribution modeling (SDM) to evaluate the spatial distribution and habitat utilisation of a resident Indo-Pacific bottlenose dolphin (Tursiops aduncus, IPBD) population (~418 identified individuals) within the northern coral reefs of the Red Sea, Hurghada, Egypt—an Important Marine Mammal Area (IMMA). This region comprises a complex archipelago where IPBD forage in open waters and utilise diverse benthic habitats, including coral reefs, shallow bays, seagrass meadows, and gorgonian assemblages, for key life-history behaviors such as resting, mating, socializing, and nursing. Notably, IPBD exhibit substrate-rubbing behavior on biogenic surfaces (sand, seagrass, corals, sponges), potentially linked to hygiene, social interaction, or sensory stimulation. These habitats face escalating anthropogenic pressures, including fisheries, habitat degradation, maritime traffic, and intensive tourism-related disturbances.

To assess these impacts on habitat suitability and population distribution, this study integrated long-term sighting data (2013–2024) from boat-based photo-identification surveys (mark-recapture techniques) and underwater focal follows (videography). Environmental variables and dolphin presence data were incorporated into R and QGIS 3.40.2 to construct SDMs. Four climatic predictors (depth, sea surface temperature, chlorophyll-a, and salinity) and one abiotic factor (bathymetry) were selected based on existing literature. Kernel density analysis assessed reef preferences among groups with and without calves, with a chi-square test confirming that sightings were non-uniform across reefs, suggesting additional drivers of habitat selection. Seasonal variation (winter: October–April; summer: May–September) and calf presence significantly influenced group size, with groups containing calves being larger. Future analyses will examine relationships between habitat and substrate types, alongside the effects of harassment and avoidance as a proxy of boat presence with group size, calf-presence, and season. Findings will be critical for Marine Protected Area (MPA) assessments and ecosystem-based management strategies to mitigate threats to this Near Threatened species.

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