Abstract
Surface activities of humpback whale groups were studied during the reproductive seasons of 2008, 2009 and 2010 on the northern coast of Bahia State, Brazil, near the district of Praia do Forte. The level of surface activity exhibited by 342 groups of whales was evaluated according to the sea state (measured on the Beaufort scale) and cloud coverage. Five behaviours were recorded: breaching, head slapping, tail slapping, pectoral flipper slapping and tail breaching. Most of the sightings occurred with a sea state classified on the Beaufort scale as 2, and with a cloud coverage of 26 to 50%. The most recorded level of surface activity was pectoral flipper slapping. The results showed that humpback whale behaviours do not seem to be influenced by the sea state or by cloud coverage.
Highlights
Humpback whales (Megaptera navaeanglia Borowski, 1781) are characterized by their long pectoral fins (1/3 of the total body length), small dorsal fin, and head and lower jaw covered by tubercles (Palazzo Jr. & Both, 1988; Perrin et al, 2008; Deméré, 2014)
Most of the sightings occurred with a cloud coverage less than 50% (n = 230, 67.25%); observations with the sky covered by 26-50% of clouds were more common (n = 123, 35.96%) than observations with the sky covered by 51-75% of clouds (n = 46, 13.45%) (Table 3)
Sea state and cloud coverage did not influence the surface activities of humpback whales, not corroborating the results found by Herman & Antinoja (1977) and Scott &Winn (1979)
Summary
Humpback whales (Megaptera navaeanglia Borowski, 1781) are characterized by their long pectoral fins (1/3 of the total body length), small dorsal fin, and head and lower jaw covered by tubercles (Palazzo Jr. & Both, 1988; Perrin et al, 2008; Deméré, 2014). Along the Antarctic coast, humpback whales form different populations during the foraging season in the summer (Baker et al, 1995; Rizzo & Schulte, 2009; Andrews-Goff et al, 2018), but they migrate to the tropical areas during the winter to breed in shallow and warm waters near the coast of the continents (Lunardi et al, 2008, 2010; Zerbini et al, 2011; Gonçalves et al, 2018) One of these populations migrates to the Brazilian coast, concentrating in the Abrolhos Bank (southern Bahia State), which is considered the principal breeding area of the species (Rossi-Santos et al, 2008; Wedekin et al, 2010; Ristau et al, 2020). Aggressiveness, sexual stimulation, wound or irritation responses, play, intra- or interspecific communication are some of the suggested functions for surface activities (Herman & Tavolga, 1980; Frankel et al, 1995; Dunlop et al, 2008; Felix & Botero-Acosta, 2012; Dunlop et al, 2017; Kavanagh et al, 2017; Schuler et al, 2019)
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