Why become speckled? Ontogeny and function of speckling in Shark Bay bottlenose dolphins (Tursiops sp.)1

To date, color patterns have been used to assess cetacean age and taxonomic status, but few studies have determined precise correlates of coloration with known age or investigated its function. Here, we examine the ontogeny of speckling in 88 bottlenose dolphins (Tursiops sp.) in Shark Bay, Australia, of known age, tracked from birth to age 34. Ventral speckles first appear in the genital area at a mean age of 10.2 ± 0.35 yr (range = 7.6–12.7 yr). Throughout their life span, speckles increase in number and density, particularly along the ventral and lateral sides. The timing of speckle onset does not significantly differ by sex but is related to sexual maturity in females. The age of speckle onset in the genital area correlates with the age of first known parturition. In terms of speckle function, we discuss two hypotheses commonly proffered to explain color variation, concealment, and communication. Concealment from predators or prey is unlikely to explain speckle development in Shark Bay Tursiops because the onset occurs long after peak predation risk and initial hunting success (at 3 mo of age). We suggest that speckle patterns offer reliable cues on reproductive status and/or condition and could, thus, serve a communicative or some other function.     

‘O sibling,where art thou?’‐ a review of avian sibling recognition with respect to the mammalian literature

Avian literature on sibling recognition is rare compared to that developed by mammalian researchers. We compare avian and mammalian research on sibling recognition to identify why avian work is rare, how approaches differ and what avian and mammalian researchers can learn from each other. Three factors: (1) biological differences between birds and mammals, (2) conceptual biases and (3) practical constraints, appear to influence our current understanding. Avian research focuses on colonial species because sibling recognition is considered adaptive where 'mixing potential' of dependent young is high; research on a wider range of species, breeding systems and ecological conditions is now needed. Studies of acoustic recognition cues dominate avian literature; other types of cues (e.g. visual, olfactory) deserve further attention. The effect of gender on avian sibling recognition has yet to be investigated; mammalian work shows that gender can have important influences. Most importantly, many researchers assume that birds recognise siblings through 'direct familiarisation' (commonly known as associative learning or familiarity); future experiments should also incorporate tests for 'indirect familiarisation' (commonly known as phenotype matching). If direct familiarisation proves crucial, avian research should investigate how periods of separation influence sibling discrimination. Mammalian researchers typically interpret sibling recognition in broad functional terms (nepotism, optimal outbreeding); some avian researchers more successfully identify specific and testable adaptive explanations, with greater relevance to natural contexts. We end by reporting exciting discoveries from recent studies of avian sibling recognition that inspire further interest in this topic.     

‘Who do you want to kill?’ Affectual and relational understandings at a sorcery rock art site in the southwest Gulf of Carpentaria,northern Australia

This article explores the affectual and relational contexts in which rock art is embedded through an exploration of the encounters, reactions, and responses to a well‐known sorcery rock art site known as Kurrmurnnyini in northern Australia's southwest Gulf country. These encounters with a culturally powerful place, and the emotions derived from people's personal memories and experiences of Kurrmurnnyini and its sorcery‐infused rock art, are vital to establishing an understanding of contemporary perceptions of what is clearly more than an ‘archaeological site’. We contend that by turning our attention to the often‐overlooked affectual and relational dimensions of rock art and the contexts in which it is found, researchers place themselves in a better position to access and become aware of the agency and affect of graphic imagery as well as the significance these powerful images and places hold for people today.