Scientific collaboration networks in research on human threats to cetaceans in Brazil

To better understand the threats posed by human activities on cetaceans, we compiled published studies and determined where, how, and by whom the research on this subject has been conducted in Brazil. We also determined which cetacean species were mostly investigated in these studies. We gathered the available scientific literature published from 1986 to 2016 that contained search terms in English that depicted major cetacean threats. Then, we developed a collaboration network among the authors' institutions and generated a distribution map of the investigated threats and study areas. From the 1047 compiled publications, we selected 103 studies that precisely addressed cetacean threats. The selected studies were carried out by 82 institutions from 12 countries. Most of these institutions were universities (n = 55), followed by non-governmental organizations (n = 15) and research institutes (n = 12). Among the two cetacean suborders, odontocetes were the most representative, with Sotalia guianensis and Pontoporia blainvillei present in 50 and 38 publications, respectively. For mysticetes, publications on Megaptera novaeangliae (n = 6) and Eubalaena australis (n = 5) were the most common. Among the addressed threats, more than half (54.4%) of the publications focused on pollution, followed by bycatch (19.4%) and vessel traffic (10.7%). Most of the study areas took place in the states of Rio de Janeiro (22.4%), São Paulo (19.7%), and Rio Grande do Sul (12.9%). Six institutions were the most prevalent in the collaboration networks, and their location corresponded to hotspots of cetacean diversity. Our findings may contribute to identifying research priorities and guide the conservation of cetacean species in Brazil.