Thesis (Ph.D.)-- University of Adelaide, Dept. of Geographical and Environmental Studies, 2000. / Bibliography: leaves 378-402.

No description available.

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.

No description available.

In this study, I characterize the maternal care patterns of humpback whales in southeast Alaska. Through a study of proximity behaviour, I show that humpbacks behave similarly to terrestrial ungulate 'followers': the cow and calf are rarely more than several body lengths apart; proximity between the cow and calf is greatest during periods of travel relative to other behaviours; and, proximity is greatest when the dive behaviour of the pair is synchronized. Unlike that observed in typical follower species, however, proximity is not found to decrease significantly as the pair's association lengthens. To account for this, I argue that the length of the observation period was insufficient to detect such a trend since maternal pairs remain together for several months after the last observations. In addition, I analyze the diving behaviour of the maternal pair to examine the potential negative consequences for the female associated with the follower tactic in humpbacks. The results suggest that several behavioural modifications are made by the cow and calf in an effort to minimize the duration of separation between the two. Ultimately, I argue that behaviour observed in humpback whales is commensurate in function with following behaviour in terrestrial ungulate followers. Humpbacks are migratory, and as in many migratory species, following behaviour provides a mechanism whereby the maternal dyad can maintain close proximity during periods of travel. Moreover, as with many follower species, humpbacks can rely upon their large size as a means of defence against offspring predation. Finally, although obvious differences exist between the habitats in which humpbacks and ungulate followers reside, arguably both are open habitats that lack the cover necessary to allow for offspring concealment.

The humpback whale is very maneuverable despite its enormous size and rigid body. This agility has been attributed to the use of its pectoral flippers, along the leading edge of which protuberances are present. The leading edge protuberances are considered by some biologists to be a form of passive flow control and/or drag reduction. Force and moment measurements along with qualitative and quantitative flow visualizations were carried out in water tunnel experiments on full-span and finite-span hydrofoil models with several different planforms and protuberance geometries. A NACA 634-021 cross-sectional airfoil profile was used for the baseline foil in all tests. Four planform geometries chosen included: a full-span set of foils which spanned the breadth of the water tunnel, a finite-span rectangular planform, a finite-span swept hydrofoil, and a scale flipper model that resembled the morphology of the humpback whale flipper. A variety of sinusoidal protuberance geometries which included three amplitudes equal to 2.5%, 5%, and 12% and wavelengths of 25% and 50% of the local chord were examined in combination with the different planform geometries. Testing included force and moment measurements and Particle Image Velocimetry (PIV) to examine the load characteristics and flow field surrounding the modified foils. Load measurements show that modified foils are capable of generating higher lift than the baseline at high angles of attack while at low angle of attack the baseline generally produces a lift coefficient equal to or greater than the modified cases. With the exception of the modified flipper model, the drag coefficients of the modified hydrofoils are either equal to or greater than their baseline counterparts. The increased drag reduces the lift-to-drag ratio. Flow visualizations show that vortical structures emanating from the shoulders of the protuberances are responsible for increased lift and drag at high angles. Cavitation tests show that modified foils cavitate in pockets behind the troughs of protuberances whereas the baseline foils produce cavitation along the entire foil span. Also, the cavitation numbers on modified hydrofoils were consistently higher than their baseline counterparts. This work shows the effect of leading edge protuberances on the aforementioned performance characteristics.

Stomach contents of 19 mature sperm whales, 18 males and one female, that stranded on New Zealand beaches between the mid 1990s and 2004 were examined, identified and measured. Three of the stomachs were empty. All other samples consisted almost entirely of cephalopod beaks. A total of 23,223 cephalopod beaks (10,647 upper and 12,576 lower), representing at least 36 species in 17 families were found in the remaining 16 stomachs. Non-cephalopod remains in the stomachs of sperm whales stranded in New Zealand included limited quantities of fish, salps, crustacean exoskeletons, a copepod, some wood and sand.The present investigation represents the most comprehensive study of the diet of sperm whales in New Zealand since the early 1960s. The results show that oceanic squid of the families Histioteuthidae, Cranchiidae, Onychoteuthidae and Octopoteuthidae are the most common remains found in the stomachs of sperm whales stranded on New Zealand beaches, with the families Onychoteuthidae, Histioteuthidae, Octopoteuthidae and Architeuthidae being the most important by estimated weight in whale diet, and the families Cranchiidae, Pholidoteuthidae and Ancistrocheiridae secondarily so.The beaks of three cephalopod species thought to be restricted to Antarctic waters (Kondakovia longimana, Mesonychoteuthis hamiltoni and Psychroteuthis glacialis) were found in 12 of the stomachs, suggesting these whales had recently migrated into New Zealand from more southern feeding grounds. The amount of local cephalopod beaks in the stomachs suggests some of the stranded sperm whales did not feed much within New Zealand waters in the days prior to stranding.The beaks of Taningia danae, Octopoteuthis megaptera, Octopoteuthis sp. 'Giant' and Lepidoteuthis grimaldii are illustrated and described. Oblique and lateral illustrations of the lower beaks are given, as well as sections of the rostrum, jaw angle, shoulder and lateral wall, to show the major identifying features for each of the species.Squid are an important component of food chains in the Southern Ocean and they act as both high-level predators and prey for apex predators. Therefore, seasonal fluctuations in their abundance must have cascading effects on the diets of apex predators. With increasing global fishing effort, and with cephalopods representing over 4% of the global annual catch, there are competing interests between the ocean's top teuthophagous predators and the fishing industry.Uncertainty of the effects fisheries have on the marine ecosystem has stimulated numerous research studies in recent years. However, despite the economic and ecological importance of cephalopods, there are few ecological studies on them or their significance in the trophic systems of the deep-sea and their life cycles and distribution patterns are only now beginning to be understood. Additional dietary studies that investigate the cephalopod composition and size-class structure in the diet of predators are needed to assess their importance in deepsea food webs, and the potential impact that deep-sea fisheries might have on associated and dependant species, namely apex oceanic predators.The results of this study provide the first significant insight into the diet of the sperm whale, one of the most important apex predators in New Zealand waters.

Graduation date: 1998

Although Icelandic and Norwegian killer whales are thought to have been in contact prior to the collapse of the herring stock in the 1960s, the Northeast Atlantic killer whales currently seem to show high site fidelity. So far, photoidentification data have suggested movement of a few individuals between East Iceland and North Scotland, and two calls have been shown to be shared by the Icelandic and Norwegian populations. Based on previous and newly analysed call samples, the aim of this study was to describe the geographic variation in the vocal repertoire of the Northeast Atlantic killer whales. Recordings have been conducted off Southwest Iceland in the summers 2004, 2008 and 2009 using sound recording tags attached using suction cups (Dtags), a 4-element vertical hydrophone array and a 2-element towed hydrophone array. From the 57 hours of recording analysed, 1742 calls were classified. In total, 56 distinct call categories composed of 35 call types and 31 subtypes were identified. This discrete call repertoire contained less biphonic calls but more calls composed of buzzes and/or clicks than the Norwegian repertoire. The reasons for these differences remain unknown. One Icelandic call subtype was defined as a compound call, a type of call that is common in the Norwegian population. The comparison of the different vocal repertoires of Northeast Atlantic showed four good or likely call matches in herring-eating killer whales (one between Southwest Iceland and Shetland, one between East Iceland and Norway, and two between Shetland and Norway). No matches were found between Southwest Iceland and East Iceland. I suggest that the four shared calls are most likely to have come from a common ancestral pod and have been transmitted through vocal learning. Over time, geographic isolation of the groups induced by changes in the migratory patterns of the herring might have been accompanied by divergence in their call repertoires.

It dives the deepest seas of the world. In total darkness it hunts its pray. On its head the circular scars tell a story of the many encounters with an almost unknown creature - the giant squid. It lives most of its life far away from shore at the open oceans. There it is seen resting in the light of the surface clearing its lungs and gathering oxygen for yet another dive into the blue abyss underneath. In its head the sperm whale carries the largest brain ever to have existed on earth. But what are its thoughts?