820 I. C. Avila et al.


FIG. 2 Records of sperm whales Physeter macrocephalus in the Colombian Caribbean during 1988–2020.


human activities in this area (e.g. around the Lesser Antilles) are probably affecting the species (Whitehead & Gero, 2015; Gero &Whitehead, 2016). Although the sperm whale does not appear to conduct long migrations in equatorial waters, when feeding and survival conditions are poor sperm whales tend to roam widely (Whitehead, 2018). Therefore, considering the Caribbean is a relatively small basin, if Colombianwaters offer suitable conditions, it is not surpris- ing to find sperm whales from the eastern Caribbean there. This is the first study to describe the potential distribu-


tion of sperm whales in the Colombian Caribbean, using high resolution spatio-temporal variables that are likely to influence sperm whale distribution. Some studies of cetacean distribution in Colombian waters have used line transect surveys (e.g. Palacios et al., 2012), which is the most widely used method to estimate cetacean occurrence. However, this method has high costs and logistical chal- lenges, and low detectability for many cetacean species (Kaschner et al., 2012). Species distribution models, as used here, are useful to estimate the potential distribution of species, particularly in areas where there have not been any line transect surveys, such as in the offshore Colom- bian Caribbean. In our study, the model built with condi- tions at 1,000m depth had the best performance; the surface model had a relatively poor performance, failing to predict probability of occurrence in areas where the species


was recorded over the shelf break. This suggests that the analysis of sea surface conditions alone is insufficient to describe the distribution of sperm whales. This is not unexpected, as the sperm whale dives deeply to feed (Whitehead, 2003; Evans & Hindell, 2004). Our results in- dicate that of the environmental variables tested, the most important were distance to shore and ocean mixed layer thickness. The model for 1,000m depth identified that the area with a high probability of sperm whale occurrence is close to the shore (median = 106.9 km), with an average range in ocean mixed layer thickness of 29.7 m. These vari- ables may be related to the presence of sperm whale prey. Areas close to the continental shoreline are influenced by rivers and their nutrients, which favour the presence of prey. The ocean mixed layer, which has homogeneous dens- ity, temperature and salinity, varies greatly in time and space (e.g. in subpolar latitudes it can be ,20m in summer but .200m in winter; de Boyer Montégut et al., 2004), and plays an important role in phytoplankton and food chain dynamics (Carvalho et al., 2017). Our modelling indicates that the potential distribution


area of sperm whales includes the south and north-east Colombian Caribbean over the shelf break to waters up to c. 3,000m deep, and near the Archipelago of San Andrés, Old Providence and Saint Catherine in the north-west (Fig. 3). The south and north-east Colombian Caribbean


Oryx, 2022, 56(6), 814–824 © The Author(s), 2022. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605321001113


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