Behavioural strategies in humpback whales,Megaptera novaeangliae, in a coastal region of Brazil

Abstract

The behavioural patterns of humpback whales are known to vary according to the social function of individuals in a group. To identify behavioural patterns related to specific group compositions, we observed events and behavioural states of humpback whales during research cruises in the Abrolhos Bank, Brazil, in the reproductive seasons from 1992 to 2003. We monitored 3022 groups and found a predominance of competitive groups without calves, when compared to competitive groups with calves. A Bayesian network analysis supplied occurrence probabilities for the behaviours analysed, indicating higher probabilities of occurrence for the behavioural patterns designated travelling and socializing. The model, generated from a binomial logistic regression, was able to predict competitive groups in association with the occurrence of the following aggressive behaviours: head-lunging, trumpet and bubblestreams. This study suggests the existence of behavioural patterns associated with specific group compositions and reinforces the concept that there is a clear-cut relation between competitive groups and the occurrence of aggressive behaviours. The preferential association of males to females with high reproductive potential for the following year (i.e. females without a calf) was also identified.

Humpback whale (

“…The decision as to which behaviour types would be designated into the behavioural categories was based on semantics and current available knowledge (Table 1). It is recognised that some behaviours, such as breaching and flippering, can represent communication between individuals or pods of humpback whales (Frankel et al 1995;Lunardi et al 2010). Surface behaviours that were observed during diverse social interactions between humpbacks were grouped into social communication.…”

“…Comparing observed behaviours between aggregation sites of humpback whales has not frequently been used as a technique of identifying the function of habitats. However, recent studies have shown that social organisation can dictate the habitat types used by particular groups of whales, and which behavioural patterns occur (Ersts and Rosenbaum 2003;Lunardi et al 2010). Previous research has used humpback whale behavioural data to determine whether whale watching and vessel presence have effects on whale behaviour (Fiori et al 2019;Schuler et al 2019;Amrein et al 2020) and to assess how humpback whales change their communication in response to increasing noise levels (Dunlop et al 2010).…”

Surface activity of Humpback whales Megaptera novaeangliae (Cetacea, Mysticeti) on the northern coast of Bahia, Brazil

“…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(Lunardi et al, , 2010Zerbini 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).…”

Climate change and marine mammals

“…Results from a study of behavioural strategies on humpback whales in a coastal region of Brazil by Lunardi et al (2010) indicate a clear-cut relationship between competitive groups and the occurrence of aggressive behaviours, and identified a preferential association of males with females of high reproductive potential for the following year (i.e. females without a calf).…”

“…In bottlenose dolphins, Tursiops truncatus , from Panama City, male associations are stronger than inter-sexual associations or those between females only (Bouveroux & Mallefet, 2010). Results from a study of behavioural strategies on humpback whales in a coastal region of Brazil by Lunardi et al (2010) indicate a clear-cut relationship between competitive groups and the occurrence of aggressive behaviours, and identified a preferential association of males with females of high reproductive potential for the following year (i.e. females without a calf).…”