Habitat suitability, occurrence, and behavior of dwarf sperm whales (Kogia sima) off St. Vincent and the Grenadines, Eastern Caribbean.

Abstract

The genus Kogia includes two species that are some of the least known cetacean species around the globe. Here, we investigated the occurrence, behavior, and habitat suitability of dwarf sperm whales (K. sima) off St. Vincent and the Grenadines (Eastern Caribbean). Small boat dedicated surveys were conducted during May and June of both 2022 and 2023 along the south and west coast of the island of St. Vincent. A total of 2260 km was surveyed and 33 sightings of dwarf sperm whale were recorded, which was also the most frequently sighted cetacean species (37.5% of all cetacean sightings). Group size varied from 1 to 20 individuals (mean = 2.08, SD = 3.23). Traveling and breaching were the most commonly recorded behavioral categories and occurred at an equal proportion (28.6%). The distribution of dwarf sperm whales was restricted to the south and southwest portion of St. Vincent in depths ranging from 95 to 1104 m (mean = 650 m). Habitat suitability (in relation to depth and slope) was investigated using an ensemble model using three algorithms (GLM, GAM, and MaxEnt). The model revealed that slope, and to a lesser extent depth, were important in explaining the habitat suitability of dwarf sperm whales. This preliminary research highlights the existence of a globally important area for dwarf sperm whales off St. Vincent, where encounter rates are significantly higher than in any other known island-associated habitat.