The Social Structure and Strategies of Delphinids: Predictions Based on an Ecological Framework

Gowans, Shannon; Würsig, Bernd; Karczmarski, Leszek

doi:10.1016/s0065-2881(07)53003-8

Cited by 213 publications

(250 citation statements)

References 205 publications

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“…In fact, Breder (1954) suggested that the characteristics of such groups reflect an equilibrium between environmental attraction and repulsion that is primarily associated with feeding and predatory strategies. The balance between these factors results in an optimal group size, and individuals must decide to whether to join a specific group to maximize the benefits resulting from their particular abilities (GYGAX, 2002;GOWANS et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Group size and composition of Tursiops truncatus (Cetacea: Delphinidae), in a coastal insular habitat off southeastern Brazil

Lodi

2012

Biotemas

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ResumoTamanho e composição de grupo de Tursiops truncatus (Cetacea: Delphinidae), em um habitat insular costeiro no sudeste do Brasil. O objetivo do presente estudo foi descrever o tamanho e a composição de grupo do golfinho-nariz-de-garrafa-comum (Tursiops truncatus) no Arquipélago das Cagarras (23°01'S, 43°12'W), Rio de Janeiro, Brasil, baseado em um período de estudo de seis anos (2004 e 2006 a 2010). O tamanho dos grupos (n = 51) variou entre três e 30 indivíduos (média 13,7 ± 7,1) e sua frequência de distribuição apresentou duas modas: Palavras-chave: Arquipélago das Cagarras; Golfinho-nariz-de-garrafa-comum; Residentes sazonais AbstractThe aim of the present study was to describe the size and composition of groups of common bottlenose dolphins (Tursiops truncatus) in the Cagarras Archipelago (23°01'S, 43°12'W), Rio de Janeiro, Brazil based on six years of observation (2004 and 2006 to 2010). The group size (n = 51) ranged between three and 30 individuals (mean = 13.7 ± 7.1), and the frequency distribution of group size showed modes at six individuals and 19 individuals. The largest average group size occurred in 2004 (mean 21.4 ± 3.3) and the smallest in 2008 (mean 4.4 ± 0.8). The number of individuals/group decreased over the years and this decrease could be correlated with habitat quality. The average number of immature individuals (neonates, calves and juveniles), expressed as a proportion of the total group size, varied between 0.31 (2006) and 0.4 (2010). This proportion did not vary significantly among years. These results suggest that the Cagarras Archipelago should be considered critical habitat for the survival and /or population growth of T. truncatus in southeastern Brazil.

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Section: Introductionmentioning

confidence: 99%

Group size and composition of Tursiops truncatus (Cetacea: Delphinidae), in a coastal insular habitat off southeastern Brazil

Lodi

2012

Biotemas

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“…Herring can also undergo substantial changes in density and spatial distribution, particularly groups to more effectively find and exploit large prey schools (Gowans et al 2007 Analyses reported in this article can be reproduced using the data provided by Tavares et al…”

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confidence: 98%

A multilevel society of herring-eating killer whales indicates adaptation to prey characteristics

2016

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“…Average group size is similar to previous studies in the Sado area (dos Santos & Lacerda, 1987;Harzen, 1995) and similar to the one recorded in previous studies elsewhere (Scott & Chivers, 1990;Wells & Scott, 1994), but the typical group size (as experience by the individuals) is much larger, just over half of the current community size. Large groups with all age-classes are quite common, possibly representing a calf and subadult protection strategy, as suggested by Kerr et al (2005) and Gowans et al (2008). Younger classes have had a high mortality rate in the last decade, and contamination, fishing nets and other forms of habitat degradation are all possible causes (Gaspar, 2003).…”

Section: Discussionmentioning

confidence: 95%

Social structure of the declining resident community of common bottlenose dolphins in the Sado Estuary, Portugal

2011

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The resident population of common bottlenose dolphins (Tursiops truncatus) in the Sado Estuary, Portugal, has been declining at least during the past three decades. A complete photographic census produced a current count of 24 animals—19 adults, three subadults and two calves. It appears to be phylopatric and essentially closed, but given the likely importance that exchanges with neighbouring coastal groups may play, even if rare, the most adequate term to define this dolphin should be community and not population. Large groups with all age-classes are common in the community, possibly as a calf and subadult protection strategy, and this may be related to the fact that these age-classes have had high mortality rates in the last decade. Maternity of two calves was determined, and we found that the two mothers adopted different parenting strategies. While one mother spent more time alone with her calf, the other mother spent more time with her calf in larger groups. The average coefficient of association for this community is 0.45, quite high for this species. Associations and typical group size are similar between all individuals, with no patterning according to age-class or sex, which constitutes an atypical trait for dolphin societies. There are also no clear divisions in this community according to cluster analysis. Associations are preferred and long term, lasting approximately 34 days and fitting a pattern of casual acquaintances, where individuals associate for a period of time, disassociate and may reassociate after that. This reflects the fission–fusion character of the community, but in a more stable manner. We think this is caused by a combination of demographic characteristics and a stable and productive environment, which led to a decrease in competition between individuals.

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The Social Structure and Strategies of Delphinids: Predictions Based on an Ecological Framework

Cited by 213 publications

References 205 publications

Group size and composition of Tursiops truncatus (Cetacea: Delphinidae), in a coastal insular habitat off southeastern Brazil

Group size and composition of Tursiops truncatus (Cetacea: Delphinidae), in a coastal insular habitat off southeastern Brazil

A multilevel society of herring-eating killer whales indicates adaptation to prey characteristics

Social structure of the declining resident community of common bottlenose dolphins in the Sado Estuary, Portugal

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