The transition to independence: sex differences in social and behavioural development of wild bottlenose dolphins

Krzyszczyk, Ewa; Patterson, Eric; Stanton, Margaret A.; Mann, Janet

doi:10.1016/j.anbehav.2017.04.011

Cited by 41 publications

(32 citation statements)

References 97 publications

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“…The juvenile period is clearly one of vulnerability, as males must establish partners to protect themselves from attacks by older males (Stanton and Mann 2012). High tooth rake prevalence among juvenile females may be the result of frequent interactions with juvenile male dolphins (Krzyszczyk et al 2017). Additionally, it is important to note that tooth rakes are superficial wounds and do not represent serious aggressive behaviors such as ramming, body slams, and tail hits, which might be more lethal (e.g., Parsons et al 2003;Lusseau 2006).…”

Section: Discussionmentioning

confidence: 99%

“…Shark Bay Indo-Pacific bottlenose dolphins are often alone in the juvenile period (Krzyszczyk et al 2017) and no longer under maternal protection; this is especially the case for males who associate less with their mothers post-weaning than females (Tsai and Mann 2013). As such, juvenile males might be particularly vulnerable to aggression from older males.…”

Section: Introductionmentioning

confidence: 99%

“…We also hypothesized that there would be a sex effect on conflict rate. In addition to receiving aggression via sexual coercion, juveniles commonly participate in mixed-sex social groups (Krzyszczyk et al 2017) and may consequently acquire more tooth rakes. However, since females are rarely aggressive and avoid males (Scott et al 2005;Galezo et al 2018), we predict females would receive fewer attacks than their more aggressive male counterparts.…”

Section: Introductionmentioning

confidence: 99%

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Every scar has a story: age and sex-specific conflict rates in wild bottlenose dolphins

Lee

Wallen

Krzyszczyk

et al. 2019

Behav Ecol Sociobiol

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Social living brings competition over mates, relationships, and resources, which can translate to direct conflict. In dolphins, tooth rakes received from conspecifics are highly visible and reliable indicators of conflict. New rakes indicate recent conflicts while healed rakes suggest older instances of conflict. Here, we investigate the healing time of conspecific tooth rakes in wild bottlenose dolphins, create a demographic profile of injury risk in the population, and consider the implications for age-and sex-specific aggression. Using photographic and scarring data from the Shark Bay Dolphin Research Project spanning 31 years (N = 269 tooth rakes), healing time was analyzed using a subset of sequential photographs of the same body part over 1-12 years (N = 70 tooth rakes). Ninety percent of tooth rakes in males and 95% of tooth rakes in females were no longer visible within 400 days, with males taking longer to heal than females. Using the full sample, we examined age and sex-effects on the prevalence of new tooth rakes. A negative quadratic model best fitted tooth rake prevalence patterns from ages 0 to 13 and a positive linear regression best fitted tooth rake prevalence patterns from ages 13 to 30. Both analyses revealed significant age and sex effects, where males had more tooth rakes than females. Age differences in tooth rake prevalence may be attributed to life history events such as sexual maturity onset, male-male competition and alliance formation, and sexual coercion. These results contribute to our understanding of the relationship between social conflict and life history strategies in long-lived mammals. Significance statement In wild dolphins, tooth rake scars indicate conspecific conflict, and the timing of such conflict clarifies the challenges faced during each life history stage. Based on > 30 years of longitudinal data, we created a demographic profile of new tooth rakes to identify patterns of age-and sex-specific received aggression. Males had more tooth rakes than females, but females healed faster than males. Juveniles had the greatest tooth rake prevalence compared to calves and adults, suggesting greater exposure to some level of conflict. Differences in patterns of tooth rake prevalence and aggression have implications regarding the costs of sexual maturity and reproduction in dolphins. To our knowledge, no study has examined the rate of received aggression across the lifespan. Our methods can be applied to other studies of wild marine mammals, where agonistic encounters are difficult to observe, but wounds are apparent.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Every scar has a story: age and sex-specific conflict rates in wild bottlenose dolphins

Lee

Wallen

Krzyszczyk

et al. 2019

Behav Ecol Sociobiol

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“…This requires significant investment in social relationships and is, therefore, largely incompatible with a time-consuming, solitary and difficult-to-master activity like sponging [31,39]. Meanwhile, female offspring are expected to invest more into developing foraging skills to maximize food intake compared to male offspring [40,41]. Alternatively, Zefferman [42] proposed that the female sex-bias could be the result of a maternal teaching strategy, arguing that teaching a daughter would result in higher long-term fitness for a female: a potential advantage of sponging for a son would last only one generation, while a daughter can pass on the behaviour to subsequent generations which all gain potential benefits associated with sponging.…”

Section: Discussionmentioning

confidence: 99%

Multi-network-based diffusion analysis reveals vertical cultural transmission of sponge tool use within dolphin matrilines

et al. 2019

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Behavioural differences among social groups can arise from differing ecological conditions, genetic predispositions and/or social learning. In the past, social learning has typically been inferred as responsible for the spread of behaviour by the exclusion of ecological and genetic factors. This ‘method of exclusion’ was used to infer that ‘sponging’, a foraging behaviour involving tool use in the bottlenose dolphin ( Tursiops aduncus ) population in Shark Bay, Western Australia, was socially transmitted. However, previous studies were limited in that they never fully accounted for alternative factors, and that social learning, ecology and genetics are not mutually exclusive in causing behavioural variation. Here, we quantified the importance of social learning on the diffusion of sponging, for the first time explicitly accounting for ecological and genetic factors, using a multi-network version of ‘network-based diffusion analysis'. Our results provide compelling support for previous findings that sponging is vertically socially transmitted from mother to (primarily female) offspring. This research illustrates the utility of social network analysis in elucidating the explanatory mechanisms behind the transmission of behaviour in wild animal populations.

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“…Common reproductive trends have been identified among different bottlenose dolphin populations (Henderson et al 2014, Brough et al 2016, but some reproductive parameters, such as seasonality of births (Urian et al 1996, Thayer et al 2003, Karniski et al 2018, weaning period (Tavolga 1966, Cockcroft & Ross 1990, Mann & Smuts 1998, and age of first reproduction (which may vary between 7 and 12 yr for bottlenose dolphins, depending on region), may vary greatly among populations (Wells et al 1987, Schroeder 1990, Kasuya et al 1997 as a result of ecological and social factors, e.g. group size, protection from predators/conspecifics, and mate choice (Mann et al 2000, Krzyszczyk et al 2017.…”

Section: Introductionmentioning

confidence: 99%

Female reproductive output in a Mediterranean bottlenose dolphin Tursiops truncatus population

Blasi¹,

Bruno²,

Boitani

2020

Aquat. Biol.

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The reproductive output of wild bottlenose dolphins Tursiops truncatus has extensively been investigated; nevertheless, it remains widely unexplored in the Mediterranean Sea. We investigated the reproductive history of female bottlenose dolphins in the Aeolian Archipelago (Italy). Thirteen years of photo-identification data were used to track the reproductive pattern of 7 females and their 16 calves. The birth period was accurately estimated within 1 mo for 6 calves (37.5%), peaking in June/July. The mean number of calves for females was 2.3 ± 1.1 (SD), ranging from 1 to 4. The mean interbirth interval was 3.5 ± 1.6 yr, ranging from 2 to 7 yr. The mean weaning age was 3.2 ± 0.6 yr, although 1 calf may have been weaned as late as its fifth birthday. Mother-calf postweaning associations were tracked for 9 calves and ranged from 4 to 10 yr of residence in the maternal group of the calf. The age of first pregnancy was 7.5 yr. The number of calves was influenced by the mean maternal group size, with females that were sighted in larger groups having more calves. However, the number of calves was not influenced by the strength of the associations of mothers with other females. Calf mortality by age 1 was high (12.5%). Two juveniles also died postweaning within 6 yr of their birth. Finally, 2 females may have died during the study, as they were not re-sighted at the end of the study. Our results highlight the need to implement urgent conservation actions to protect this bottlenose dolphin population.

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The transition to independence: sex differences in social and behavioural development of wild bottlenose dolphins

Cited by 41 publications

References 97 publications

Every scar has a story: age and sex-specific conflict rates in wild bottlenose dolphins

Every scar has a story: age and sex-specific conflict rates in wild bottlenose dolphins

Multi-network-based diffusion analysis reveals vertical cultural transmission of sponge tool use within dolphin matrilines

Female reproductive output in a Mediterranean bottlenose dolphin Tursiops truncatus population

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