Stranding Events of Kogia Whales along the Brazilian Coast

PLoS One. 2016 Jan 5;11(1):e0146108. doi: 10.1371/journal.pone.0146108. eCollection 2016.

Abstract

The genus Kogia, which comprises only two extant species, Kogia sima and Kogia breviceps, represents one of the least known groups of cetaceans in the global ocean. In some coastal regions, however, stranding events of these species have been relatively common over the last decades. Stranding provides the opportunity to investigate the biology of these cetaceans and to explore the epidemiological aspects associated with the mortality of the organisms found on the beach. A number of disturbances (including pelagic fisheries, chemical pollution, boat strikes, and noise pollution) have been confirmed to pose a particular threat to the Kogia species. However, no study has yet investigated potential relationships between environmental conditions and stranding events. Here we analyse how a collection of environmental, physical, and biological variables, such as wind, sea surface temperature (SST), water depth, and chlorophyll-a, correlate to Kogia stranding events along the Brazilian coast. The results of our statistical analyses suggest that K. sima is more likely found in warm tropical waters, which provide an explanation for the high frequency of stranding in northeastern Brazilian coast. In contrast, K. breviceps appears to have a preference for temperate and productive waters. Wind speed results to be also an important factor for predicting Kogia strandings in Brazilian coast. Additionally, literature information in combination with our own data and analyses of stomach contents confirms that oceanic cephalopods constitute the primary nutritional source of both Kogia species. By using the available information as a qualitative proxy for habitat preference and feeding ecology, our study provides a novel and comprehensive assessment of Kogia stranding data in relation to environmental conditions along the Brazilian coast.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brazil
  • Conservation of Natural Resources / methods*
  • Conservation of Natural Resources / statistics & numerical data
  • Ecosystem*
  • Geography
  • Movement / physiology*
  • Principal Component Analysis
  • Risk Assessment / methods
  • Risk Assessment / statistics & numerical data
  • Risk Factors
  • Seasons
  • Temperature
  • Whales / classification
  • Whales / physiology*
  • Wind

Grants and funding

JFM and AM were supported by the Alexander von Humboldt Foundation and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, project number BEX 0128/14-7). LRO was supported by the “Conselho Nacional de Desenvolvimento Científico e Tecnológico” (CNPq) and “Fundação Grupo Boticário de Proteção à Natureza”. ACOM and CPNS were sponsored by the “Programa Petrobras Ambiental”. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.