For the majority of social species, group composition is dynamic, and individuals are interconnected in a heterogeneous social network. In this study I investigate the mechanisms underpinning social structure in the endangered southern resident killer whale (Orcinus Orca) population using a long term dataset, and explore the consequences of these. My results demonstrate that resource availability may be an important determinant of social network structure. A significant relationship between the connectivity of the social network and salmon abundance occurred, with a more interconnected network in years of high salmon abundance. As networks are non-random, highly connected individuals may play a key role in population processes such as information and disease transmission. While associations occurred both within and between matrilines, females had a significantly higher number of associates than males, as did older individuals of both sexes. Older males played a more important role in interconnecting the network. The attributes of group leadership were then investigated in matrilines and in individuals. Leadership was not a factor of size or mean age of matriline. However, there was a significant relationship between leadership score and the matriline sex ratio. Individually, females had higher leadership scores than males, and there was a positive correlation between leadership score and age in both sexes. I suggest that the oldest females have the highest 4 leadership scores due to increased ecological knowledge that comes with a prolonged lifespan. Using multi-generational records for two populations of killer whales, I show that both reproductive and post-reproductive mothers increase the survival of offspring, particularly in older male offspring. This is consistent with theoretical predictions, and may explain why female killer-whales have evolved the longest post-reproductive lifespan of all non-human animals. Given the role that individuals of high network centrality can play in population processes, understanding the driving forces behind social network structure is vital when designing effective conservation and management plans.

Group living is a social strategy adopted by many species, where individuals can exhibit long-term social affiliation with others, strengthened through cooperative behaviour and often kinship. For highly social mammals, changes in group membership may have significant consequences for the long-term viability and functioning of a population. Detecting significant social events is essential for monitoring the social dynamics of such populations and is crucial to determining the factors underlying these events. Detecting when changes in social organization occur, especially with incomplete data, poses significant analytical challenges. To resolve this issue, I developed and assessed a straightforward, multi-stage and generalizable method with broad utility for ecologists interested in detecting and subsequently investigating causes of changes in social organization. My approach illustrates the frequency and ecological relevance of group fission and fusion events in a population of fish-eating ‘Resident’ killer whales (Orcinus orca). Group fission is a process commonly found in social mammals, yet is poorly described in many taxa, and has never been formally described in killer whales. To address this gap, I provided the first description of matrilineal fission in killer whales, from a threatened but growing Northern Resident killer whale population in which matrilineal fission has been observed for the past three decades. I also undertook the first comprehensive assessment of how killer whale intragroup cohesion is influenced by group structure, demography and resource abundance. Fission in Northern Resident killer whales occurred both along and across maternal lines, where animals dispersed in parallel with their closest maternal kin. I show that fission in this population is driven primarily by population growth and the demographic conditions of groups, particularly those dictating the nutritional requirements of the group. I posit that intragroup food competition is the most likely explanation for group fission in this population, where prey abundance also has ancillary effects. As group fission can have a direct impact on the fitness of group members and the long-term viability of a population, my findings underscore the importance of incorporating studies of sociality into the management of threatened populations of social mammals. / Graduate / 0329 / 0472

No description available.

Menopause, the cessation of female reproduction well before death, is a puzzling phenomenon, because evolutionary theory suggests there should be no selection for survival when reproduction has ended. Nevertheless, menopause does exist in a limited number of species, and besides humans it has predominately evolved among toothed whales (Odontoceti). The aim of this thesis is to review both adaptive and non-adaptive theories. Of the latter, the most prominent proposes that menopause is a product of a physiological trade-offs between reproductive benefits early in life and negative late-life reproduction. Among the adaptive theories the grandmother hypothesis is the most acknowledged. This theory is based on inclusive fitness benefits gained from increasing the reproductive success of kin at an advanced age, when prospects of successfully raising additional offspring is reduced. Alternatively, the mother hypothesis suggests that increased investment in already produced offspring at late life explains menopause. There are support for both the care of mothers and grandmothers, but whether this is enough to compensate for repressed reproduction is debated. The reproductive conflict hypothesis provides a complementary explanation, and suggests that inter-generational conflict between either in-laws or kin selects the older female to shift investment into the younger female’s offspring due to asymmetries in how older and younger females are related to one another’s offspring. The evolution of menopause is a complex issue, containing many factors, kinship dynamics among the most important. Theories apply unequally to various species and populations, meaning an integrated approach is necessary for decrypting the evolution of menopause.

Submitted by (edna.saturno@ufrpe.br) on 2017-02-23T12:25:14Z No. of bitstreams: 1 Williams Dantas Charles.pdf: 2829415 bytes, checksum: bf5d0ed2319bb047d509bf6837ebad7e (MD5) / Made available in DSpace on 2017-02-23T12:25:14Z (GMT). No. of bitstreams: 1 Williams Dantas Charles.pdf: 2829415 bytes, checksum: bf5d0ed2319bb047d509bf6837ebad7e (MD5) Previous issue date: 2007-02-15 / Since 50`s, industrial fisheries have been damaged by cetaceans in all oceans, with different intensity levels. According to specialists, this behavior is named depredation, which occurs when the animals eat the fishes caught by a fishing gear. Killer whale has been cited as an animal that shows this kind of behavior often, otherwise other species as a false killer whale or sperm whale have been recorded doing fishing gear interactions. After the creation of the On Board Observers Program (PROBORDO) it was possible to cover all tuna fleet working in northeast of Brazil, based on Natal-RN, Cabedelo-PB and Recife-PE ports. The covering was made by board observers that get important information to the fisheries dynamic knowledge made by pelagic long line. Interactions between false killer whales and killer whales are cited as an important scientific subject, in relation to these fisheries type, that the present study pretends to show up. Factors like interactions type, groups’ size, qualitative and quantitative descriptions of depredated fishes and spatial location of the interactions were analyzed. The false killer whale showed greater occurrence on the study area than other species, generally within groups of few individuals, however, there were situations that the group was composed by hundreds of individuals. This species showed food preference about the target species of this fisheries kind, in other words, tuna and swordfishes instead of others catched, but in case of low productivity, they feed with squid used as a bait on the hooks. Killer whales were observed in the Tropical Western Atlantic, interacting with the fisheries. Also, there were accidental catches of the cited cetaceans by the fishing gear, what can bring serious damage to the individuals caughted. / Desde a década de 50, a indústria pesqueira vem sofrendo perdas provocadas por cetáceos, em todos os oceanos, com diferentes níveis de intensidade, num comportamento denominado pelos especialistas como depredação, que ocorre quando esses animais se alimentam do peixe capturado pela arte de pesca. Orcas verdadeiras têm sido citadas como as que exibem esse comportamento com maior freqüência, porém outras espécies como as falsas orcas e cachalotes, são registradas interagindo com a pesca. Com a criação do Programa de Observadores de Bordo (PROBORDO) foi possível a cobertura de toda a frota atuneira arrendada que opera no nordeste, sediada nos portos de Natal-RN, Cabedelo-PB e Recife-PE por observadores de bordo, que coletam informações relevantes para o conhecimento da dinâmica da pesca realizada com espinhel pelágico monofilamento. Dentre os assuntos de grande valor científico cita-se a ocorrência de interações entre as falsas orcas e as orcas verdadeiras, com esse tipo de pescaria, que o presente trabalho pretende apresentar. Fatores como o tipo de interação, tamanho de grupo, descrição quali-quantitativa dos peixes depredados e localização espacial das interações, foram analisados. A falsa orca apresentou maior ocorrência na área de estudo, geralmente em grupos de poucos indivíduos, porém houve situações em que o grupo era composto por centenas de espécimens. Elas demonstraram preferência alimentar pelas espécies-alvo deste tipo de pescaria, ou seja, atuns e espadartes em detrimento da fauna acompanhante, mas no caso de produtividade baixa, também se alimentavam das lulas, utilizadas nos anzóis como isca. Orcas verdadeiras também foram observadas na região do Atlântico oeste tropical, interagindo com a pesca. Também houveram capturas dos referidos cetáceos pelo espinhel, o que pode causar danos sérios aos espécimens capturados.

An animal’s foraging ecology can vary over a range of temporal scales, mirroring seasonal and longer term changes in prey availability, as well as ontogenetic shifts in diet and distribution. Obtaining individual-based, longitudinal diet information through direct observation, however, is logistically challenging for marine mammals that pursue and consume prey underwater, and are often widely distributed. Isotopic profiling along continuously growing tissues like teeth and baleen, which archive dietary inputs at the time of growth in their stable isotope composition, allows for chronological dietary reconstructions over multi-year timespans. This thesis reports longitudinal diet studies of three Arctic whale species, killer whales (Orcinus orca), bowhead whales (Balaena mysticetus) and beluga whales (Delphinapterus leucas), derived from serial isotopic measurements along teeth and baleen. Study objectives varied by species, but general goals were to characterize seasonal, ontogenetic, and/or individual diet variation. Results revealed similar trophic-level diet, but regional spatial separation, among eastern Canadian Arctic/Northwest Atlantic killer whales. However, isotope and tooth wear differences between two individuals and the rest of the sampled whales suggested potential specialisation on sharks, while the other whales likely had diets comprising marine mammals. Cyclic isotopic variation along Eastern Canada-West Greenland bowhead whale baleen was consistent with year-round foraging, although at a reduced rate during winter. Resting zooplankton could be an important food resource outside of periods of peak productivity, and accessibility likely drives winter habitat selection. Isotopic cycling did not differ between female and male bowheads, or among age classes, indicating similar seasonal foraging patterns despite reported spatial segregation throughout their summer range. Individual beluga whales from three eastern Canadian Arctic populations varied in timing of ontogenetic diet shifts (i.e. weaning age), as well as overall trophic position, which could reflect size-specific energetic requirements and foraging capabilities. Population-specific beluga whale diet trends over a period of several decades likely reflected climate-related expansions of southern forage fish. Collectively, findings of seasonal, ontogenetic, and/or individual diet variation contribute a greater understanding of intrapopulation variation in foraging ecology of these species, and of large-scale structuring of Arctic marine ecosystems.

Killer whales are the oceans’ apex predator and are known to have important effects on ecosystems. At Subantarctic Marion Island, southern Indian Ocean, they have only been studied opportunistically, resulting in limited knowledge of their ecosystem impact here. This dissertation describes the prey and seasonal abundance, estimates the population size and assesses the predatory impact of killer whales on seals and penguins at Marion Island, using dedicated and opportunistic shore-based observations and photographic identification, from 2006 to 2009. During 823 sightings of killer whales at Marion Island (2006 to 2009) 48 predation events were recorded; in only 10 cases could prey be identified. Killer whales fed on fur seals, elephant seals and penguins. Constant effort (dedicated) observations (259 hours, 2008 to 2009) showed that killer whale abundance, which peaked in September to December with a secondary peak in April to May, is linked to the abundance of seals and penguins. Mark-recapture analyses were performed using nearly 10 000 photographs taken from 2006 to 2009. Following careful quality control criteria 37 individuals were identified and a population size of 42 (95% CI = 35-50) individuals estimated using the open population POPAN parameterization in the software program MARK. The analytical approach is more rigorous than that used in any previous population size assessment at Marion Island. Finally, the above data were integrated to assess whether top-down control of seal and penguin populations at Marion Island is generally plausible using a simple process of elimination. Based on published data I predicted the energetic ingestion requirements of adult male and female killer whales as 1 394 MJ.day-1 and 1 028 MJ.day-1, respectively. Expanding these requirements to the 37 killer whales photographically identified at Marion Island, the population requires 40 600MJ.day-1. Based on available energy density and mass data, I predicted the energy content of available seal and penguin prey and calculated the rates at which killer whales would consume these prey in various scenarios. Penguins and Subantarctic fur seals are relatively insensitive to killer whale predation owing to their large population sizes (10 000s to 100 000s), conversely, the smaller populations (100s to 1 000s) of Antarctic fur seals and southern elephant seals are sensitive to predation, particularly the latter as they have a high energy content (approximately 2 000 to 9 000 MJ). Populations of these seals are currently increasing or stable and I conclude that presently killer whale predation is not driving population declines, although they clearly have the potential for regulation of these smaller populations. Thus, if population sizes were reduced by bottom-up processes, if killer whale diet shifted, or if prey availability changed, top-down control by killer whales could become significant. This study provides baseline information for the informed management and conservation of killer whales at Marion Island, identifies avenues for further research, and provides a foundation for the continuation of structured and dedicated killer whale research at Marion Island. / Dissertation (MSc)--University of Pretoria, 2011. / Zoology and Entomology / unrestricted