70 The Open Marine Biology Journal, 2009, 3, 70-76 1874-4508/09 2009 Bentham Open Open Access Feeding Strategies of the Guiana Dolphin Sotalia guianensis Marcos R. Rossi-Santos *,1,§ and Paulo A.C. Flores 2 1 Centro de Ciências Biológicas, Universidade Federal de Santa Catarina and International Wildlife Coalition, Brasil 2 Centro Nacional de Pesquisa, Conservação e Manejo de Mamíferos Aquáticos – CMA, ICMBio CMA SC – Rod. Maurício Sirotsky Sobrinho, s/n, km02, Jurerê, Florianópolis, SC, 88053-700, Brasil Abstract: The aim of this study was to characterize the feeding behavior of the Guiana dolphin, S. guianensis, through description and quantification of the strategies used by the dolphins, and possibly to apply this patterns to other areas in its distribution. Data were collected during systematic boat surveys, between November/1996 and May/1997, with 120 hours and 13 minutes of total observations. Scheffé Test was utilized to determine whether some strategies were used more than others. Six basic strategies of dolphin feeding behavior were identified: Individual Random Feeding (IRF), Group Random Feeding (GRF), Circular Cooperative Feeding (CCF), Front Cooperative feeding (FCF), Crossing Cooperative Feeding (CRF) and Zig-zag Cooperative Feeding (ZCF). The strategy GRF was statistically different from the others (Scheffé 5%). Previous studies suggested that S. guianensis exhibit two basic feeding strategies, while here we show greater diversity on the feeding behavior, with more complex and varied foraging strategies than previously reported for this species. Observed variation in the coordination of individuals, group cohesion, movement patterns, prey availability and environmental features, demonstrates the complexity of the S. guianensis feeding behavior. Keywords: Feeding behavior, Strategies, Guiana dolphin, Sotalia guianensis. INTRODUCTION Animal species posses a diversified array of strategies to overcome the defenses of prey species that are difficult to locate or capture, likewise social living may, in some cases, aid in food location or capture. Group foraging, which is at times cooperative can late increase capture rates and a higher feeding and resulting in more success for all the participants [1, 2]. Cetaceans present a great complexity and variety in their feeding behavior, but, like other animals, they also obtain their food with some standardized procedures, with the finality of maximize the success of each attack (e.g., [3-6]). Cooperative feeding strategies have been reported for various cetacean species. Examples include the killer whale Orcinus orca [7-10], the bottlenose dolphin, Tursiops truncatus (e.g. [3, 11-15]), the spinner dolphins, Stenella longirostris [16, 17], the franciscana, Pontoporia blainvillei [18], Humpback whales Megaptera novaengliae [19-21] and some multi-species groups (e.g. [6, 22]). The Guiana dolphin, Sotalia guianensis (for adopted name see [23-25]) occurs continuously along the Atlantic coast of Central and South America [26] from Nicarágua [27] to Santa Catarina state, Southern Brazil [28]. Despite *Address correspondence to this author at the Instituto Baleia Jubarte. Avenida do Farol, s/n, C.P. 92, Praia do Forte, Mata de São João, Bahia, 48280-000, Brasil; Tel: 55 71 3676 1463; Fax: 55 71 3676 1463; E-mails: marcos.rossi@baleiajubarte.org.br, mrosantos@pop.com.br § Present Address: Instituto Baleia Jubarte. Avenida do Farol, s/n, C.P. 92, Praia do Forte, Mata de São João, Bahia, 48280-000, Brasil many studies of this species (e.g. [29-33]), there is little detailed information on feeding behavior. Two basic types of feeding strategies for the Guiana dolphin were initially described: random fishing and cooperative fishing [29, 34]. These feeding descriptions have been commonly used and accepted in previous reports [35, 36]. The aim of this study was to characterize the feeding behavior of the Guiana dolphin, S. guianensis in southern Brazil, through description and quantification of the strategies used by the dolphins. MATERIALS AND METHODS In the southern limit of S. guianensis distribution, the North Bay of Santa Catarina waters, southern Brazil, there is a resident population that has been studied since 1991. There, estuarine dolphins show a high site fidelity to specific zones within their range, especially a small cove called Enseada or Praia dos Currais [37], where they feed, mate, nurse calves and rest. The North Bay of Santa Catarina (Fig. 1) is located between Santa Catarina Island and the mainland, with mean depth less than 12 m, sandy substrate and some flagstones. There are eight islands and shores cut out by sandy beaches, rocky coasts, mangroves, Atlantic Forest and urban areas. The Environmental Protection Area of Anhatomirim, was created by the Federal law n° 528/ 1992/May/ 20, with the main goal to protect the resident dolphins’ population, the remaining Atlantic Forest and the rivers and streams in the area. Located in the EPA’s heart, the Enseada dos Currais (Fig. 1) is an approximately 1 Km cove, with maximum depths of about 5 m, sandy-siltic bottom, two sandy beaches, three rock coasts and a small island at the north point of the bay.