Not only wide range shifts: Marine warming and heat waves influence spatial traits of a mediterranean common bottlenose dolphin population

Abstract

Understanding to what extent the living world will be affected by climate change is still to be achieved, especially in the sea. Thus, exploring in marine species the direction and timing of shifts in space use and movements related to climate changes should be considered a priority. In the present study, through a correlative approach, we investigated the influence of temperature and marine heat waves (MHWs) on the spatial traits (local occurrence and home range) of a small common bottlenose dolphin population in the Mediterranean Sea by analyzing 560 sightings from 2013 to 2020. The increase in sea surface temperature (SST) negatively influenced both dolphin occurrence and group size in the study area. Furthermore, regardless of the sex and social unit to which the animals belong, in July–September 2017–2020 individual home range size increased threefold (on average from 5 to 15 km2) compared to 2013–2016, when SST was on average 1.34 °C lower and MHWs shorter of 29 days/year. These results can help forecasting the range of consequences of warming effects and to assist local management efforts, in terms of marine protected areas design and management, suggesting that an integrated multi-level approach that examines the influence of warming on dolphin spatial traits together with the abundance and distribution of prey populations and ecological status of foraging habitats (such as the seagrass beds) could be useful in mitigating the effects of climate change on coastal dolphins.