Habitat Selection

of Indo-Pacific Bottlenose Dolphins (Truncatus aduncus) in The Northern Red Sea, Egypt.

An understanding of cetacean distribution and habitat preferences is essential for addressing knowledge gaps concerning the spatial ecology of vital ecological processes for species conservation-management. This study used spatio-temporal Maxent models to predict which environmental variables influenced habitat suitability for approximately 420 identified Indo-Pacific bottlenose dolphins (Truncatus aduncus) inhabiting the coral reefs of The Northern Red Sea, Egypt. This Important Marine Mammal Area (IMMA) is a complex network of islands where the study population forages in open waters, amid a variety of microhabitats (coral reefs, shallow bays, seagrasses, and gorgonians).

Our study population utilises the region for various behavioural activities such as resting, sleeping, mating, socialising, nursing, and selective self-rubbing on substrates containing bioactive metabolites for potential self-medication. Dolphin Watch Alliance collected photographic data (2013-2025) via boat-based surveys and underwater videography, alongside spatial, behavioural, and environmental data. Environmental variables and dolphin presence were incorporated into R Statistical Software 4.42 and QGIS 3.40.2 to build Maxent models.

Based on the literature, we selected three climatic predictors (sea surface temperature, chlorophyll-a, and salinity) and two abiotic factors (depth and slope). Kernel density analysis was used to assess whether groups with or without calves exhibited reef preferences. A chi-square test revealed that sightings were significantly non-uniform across reefs, suggesting other factors influenced reef popularity. Season (winter: October-April, and summer: May-September) and calf presence significantly impacted group size, whereby groups containing calves were significantly larger. Further analysis will aim to statistically investigate relationships between habitat and substrate types, coupled with harassment and avoidance behaviours (as proxies of boat presence) with group size, calf-presence, and season. The areas of highest habitat suitability often overlap with anthropogenic stressors comprising of illegal fishing, maritime traffic, and high-disturbance from the dolphin-swimming industry. These results could potentially inform conservationmanagement policies and adaptive ecosystem-based efforts to protect this study population.

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