Bogomolni, A.

Accurate species identification of marine mammals is key to improving our knowledge about them, including their distribution, natural history and the causes of their deaths. Marine mammals face many human-related challenges. Entanglement in active and discarded fishing gear poses a serious threat. Where their ranges overlap with human activities, marine mammals may also suffer from disturbance, vessel collision and exposure to contaminants, as well as loss of feeding, mating and nursery habitats. An impediment to marine mammal conservation is the scarcity of knowledge about their normal habitat, diet, behavior and demographics, and how human impacts affect these critical factors. Our principal hope is that this field guide will assist in correctly identifying stranded marine mammals, and that associated research will lead to an increased understanding of their lives, both for the sake of ‘filling the gaps’ of our knowledge and to design better conservation measures to protect them in the Wider Caribbean Region (WCR).

A stranded marine mammal is defined as a marine mammal found dead on the beach or one that is alive but in a helpless position; for example, one that comes ashore ill, weak or simply lost. Every year thousands of whales and dolphins are found stranded alive or dead on beaches all over the world. They may be alone or in groups. Some animals are old or unwell, but many of them are young and otherwise in good health. This is a natural phenomenon that has been recorded for centuries. The mechanisms behind such events, however, remain one of the great mysteries of the animal kingdom.

Single strandings are generally considered the result of normal mortality, disease processes or associated with human actions. Regardless of whether they strand alive or dead, single-stranded animals soon die. The expression mass-stranded generally refers to a simultaneous stranding of two or more cetaceans of the same species, other than a female and her calf. Mass strandings are harder to understand. They occur when a group of toothed whales come ashore alive. Such animals rapidly encounter serious problems with sunburn, dehydration and other aspects of exposure. Some mass strandings (i.e., beaked whales) exhibit a broader distribution in time and space than typical mass strandings, which are generally confined to a specific area.

This guide is produced by ECCN:

The Eastern Caribbean Cetacean Network (ECCN) is a regional volunteer organization that tracks sightings and strandings of whales and dolphins in the Eastern Caribbean (the Lesser Antilles). Through research and education, ECCN’s mission is to gain community support for the protection of resident and migratory whales and dolphins and their critical marine habitats. ECCN has been a primary contributor in the inception and development of the Action Plan for the Conservation of Marine Mammals (MMAP) of the Wider Caribbean Region (WCR) under the auspices of the United Nations Environment Programme’s (UNEP) Protocol for Specially Protected Areas and Wildlife (SPAW). Since 2005, ECCN has provided Marine Mammal Stranding Response Training Workshops in the Eastern Caribbean as well as the French and Dutch Antilles.

Abstract:

1. Killer whales Orcinus orca are found in all oceans of the world, but most of our knowledge on the species comes from studies conducted at higher latitudes. Studies on killer whales in the Caribbean have been scarce.

2. We compiled 176 records of killer whales from the Caribbean, including 95 previously unreported records and 81 records recovered from the literature, consisting of 27 capture or kill records, 4 stranding records and 145 sighting records.

3. Our results indicate that killer whales are widespread in the Caribbean Sea and can be found year-round in the region. Mean group size was 3.7 animals. A diversity of prey items was recorded, including sea turtles and marine mammals and possibly fish. We cannot exclude ecotype or morphotype-specific dietary specialization in the Caribbean population. A preliminary morphological analysis of 10 characters in 52 individuals from 21 different groups suggests that Caribbean killer whales do not represent any of the four Antarctic and subantarctic types, type 1 from the northwest Atlantic, or ‘resident’ and ‘transient’ killer whales from the northwest Pacific. Some Caribbean killer whales share a combination of characters typical of type 2 in the North Atlantic, whereas others share those typical of ‘offshore’ killer whales in the northwest Pacific. The significance of this is unclear. Comparison of Caribbean killer whales to previously described morphotypes and ecotypes is hampered by the lack of detailed, quantitative data on variation within other types, as well as by the lack of comparisons of genetic diversity.

4. Our study adds to the growing knowledge of the diversity of killer whales worldwide but underscores that additional research is warranted in the tropics.