Information on the ecology of sympatric species provides important insights into how different animals interact with their environment, with each other, and how they differ in their susceptibility to threats to their survival. In this study habitat use and population ecology of Chilean dolphins (Cephalorhynchus eutropia) and sympatric Peale's dolphins (Lagenorhynchus australis) were investigated in the Chiloe Archipelago in southern Chile from 2001 to 2004. Distribution data collected during systematic boat-based sighting surveys revealed a distinct pattern of small-scale habitat partitioning, probably reflecting differences in foraging strategies and habitat preference. Chilean dolphins were sighted consistently in the same selected bays and channels in southern Chiloe. Peale's dolphins were distributed over wider areas, and were more frequently encountered in central Chiloe. Spatial overlap between both dolphin species and mariculture farms (for mussels and salmon) was extensive. Predictive habitat modelling using logistic regression in a model selection framework proved a useful tool to determine critical habitat from absence-presence data and enviromental parameters. Chilean dolphins preferred shallow waters (< 20 m) close to shore (< 500 m) with estuarine influence. Peale's dolphins also occurred predominantly in shallow nearshore waters, but preferred more exposed shores with sandy shoals and were found further from rivers and mussel farms than Chilean dolphins. Analysis of ranging and movement patterns revealed small-scale site fidelity and small ranging patterns of individually identifiable Chilean dolphins. Individuals differed in their site preference and range overlap suggesting spatial partitioning along environmental and social parameters within the population. Individual Peale's dolphins were resighted less regularly, showed only limited or low site fidelity and seemed to range beyond the boundaries of the chosen study areas. Mark-recapture methods applied to photo-identification data produced estimates of local population sizes of 59 Chilean dolphins (95% CI= 54 - 64) and 78 Peale's dolphins (95% CI= 65 - 95) in southern Chiloe, and 123 Peale's dolphins (95% CI= 97 - 156) in central Chiloe. An integrated precautionary approach to management is proposed based on scientific monitoring, environmental education in local schools, and public outreach to promote appropriate conservation strategies and ensure the dolphins' continued occupancy of important coastal habitat.

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198 leaves : ill., photos ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Pathology, 1978

The superior neocortex ratios in primates and their distinctive relationship with sociality among terrestrial mammals are well documented. However, there has been an absence of research into relative neocortex size, its evolution and correlates in marine mammals, such as cetaceans (dolphins, porpoises and whales). This study uses the advanced radiological techniques of computed tomography and magnetic resonance imaging to establish neocortex ratios in dolphins and to re-assess these values for humans. It was found that freezing and defrosting did not significantly alter the neocortex ratios of dolphins and thus extra material as included in the analysis. Furthermore, equations for the estimation of neocortex ratios from eT and MRI have been applied to the cranial volumes calculated for 19 toothed whale species, in order to extend the range of analysis. Using these techniques, it appears that dolphin neocortex ratios are higher than those of other mammals, except for primates. A notable finding is that dolphin values lie between human and other primates and are closer to human ratios at 4.1, than to non-human ratios reaching 3.2~ (Dunbar, 1992). The highest delphinid neocortex ratio from MRI was 3.94 for common dolphins, while the highest estimated neocortex ratio was at 3.95 for killer whales. To establish the correlates of such high neocortex ratios in dolphins, their scores were related to variables representing foraging ecology, sound and sociality. Although delphinid neocortex ratios do not appear to be related to foraging variables, they are significantly related with sound and sociality variables. Of these relationships, the most substantial finding exists with respect to the relationship of delphinid neocortex ratios and their mean group size. The capacity to predict group size from relative neocortex size has not been noted in non-primate species, and has formed the basis for current theories of social intelligence and mental evolution. The findings of this study are therefore of considerable interest and may have substantial implications. These may impact on current theories of primate-human mental evolution and therefore it is strongly recommended that the mental capacities of other mammals, such as dolphins, be examined in greater detail to support or refute these claims. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1998.

My dissertation research focused on the behavior, movement patterns, and foraging ecology of dusky dolphins (Lagenorhynchus obscurus) off the east coast of New Zealand's South Island. Information on growth, morphometrics, parasites and life history was also collected. Movement patterns and foraging behavior of New Zealand dusky dolphins were much different from those of dusky dolphins observed off the Argentine coast by Bernd Wursig, the only other study of dusky dolphin behavior. Unlike the Argentine dolphins, which cooperatively herd anchovy to the surface and contain them there for feeding, New Zealand dusky dolphins behave and forage more like Hawaiian spinner dolphins (Stenella longirostris). In summer and fall, New Zealand dusky dolphins remain near shore in morning and early afternoon hours, then move into deeper water with greatly increased activity levels in late afternoon. In winter and spring they remain farther from shore at all times of day, are found in somewhat larger groups, and appear to travel along shore more often than in other seasons. In summer, dive times of radio-tagged dolphins also varied on a daily cycle, most long dives occurring during crepuscular and night periods. Stomach contents of incidentally-netted and beachcast dolphins contained primarily a demersal fish and a few types of mesopelagic fishes and squid. Acoustic surveys along the east coast of South Island show a dense layer of mesopelagic fishes and squid that move to within 50-100 m of the surface at night. Like Hawaiian spinners, New Zealand dusky dolphins feed primarily on prey in and associated with the vertically migrating layer, probably as a means of increasing foraging efficiency. External measurements of L. obscurus specimens were analyzed using canonical variate analysis, which revealed measurements useful in discrimination of age/sex classes, including dorsal fin dimensions, and positioning of dorsal fin and flipper insertions. Tooth-section age analysis of specimens allowed construction of growth curves; life span maximum was about 35 years. The very large size of active testes (over 1 kg each) during summer breeding represents a large proportion of total body weight. Along with observations of group composition variability, this suggests a promiscuous mating system and a fluid, extended-group social system.

This study investigated a resident community of Atlantic spotted dolphins (Stenella frontalis) on Little Bahama Bank (LBB) in the Bahamas utilizing a noninvasive molecular approach. Genetic template material was collected and extracted from fecal material of S. frontalis. Fine-scale population structure was found within LBB according to mitochondrial DNA (mtDNA) and microsatellites (Fst = 0.25317, P < 0.0001 and Fst = 0.04491, P < 0.0001, respectively). Three main social clusters (North, Central, South/Roam) exist on LBB and all clusters were found to be genetically distinct according to microsatellite analyses. Mitochondrial haplotypes revealed North and South/Roam were not differentiated, but Central was different from both. When separated by sex, males were less genetically structured than females. Males showed no evidence of structure according to Ost or Rst. / Females of all clusters were differentiated according to microsatellites whereas mtDNA revealed the same pattern in females as was seen for the total population. The structuring patterns of the sexes clearly indicate a pattern of male dispersal and female philopatry for the LBB population. Genetic investigation of mating revealed patterns in the mating system of S. frontalis on LBB. Genotypes of females and offspring were analyzed and revealed that more than two males were required to explain the progeny arrays, indicating promiscuous mating among females. In addition, paternity assessment assigned seven males as fathers to ten of 29 mother-calf pairs. A pattern of reproductive skew according to age was revealed because reproductively successful males were in the oldest age class at the estimated time of conception of the calves. / Patterns in social cluster mating revealed that males from the Central cluster sired offspring with females from both the Central and North clusters, while Roaming males sired offspring with South and Central females indicating that males mate within their social cluster or with females from the next closest cluster. The study has important implications for cetacean research, specifically delphinids. Fine-scale population structure and mating patterns of male and female S. frontalis were revealed through noninvasive methodology presenting a valuable genetic framework with which to support ongoing investigations of life history, behavior, communication and social structure. / by Michelle Lynn Green. / Vita. / Thesis (Ph.D.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, FL : 2008 Mode of access: World Wide Web.

Photoidentification surveys of bottlenose dolphins (Tursiops truncatus) were conducted from December of 2002 through December of 2003 in Chocolate Bay, Texas, and the adjacent Gulf of Mexico area. The research represented the continuation of an ongoing study of the dolphins of this area. Behavioral sampling was carried out on a small resident community of dolphins that seasonally reside in Chocolate Bay, as well as on dolphins found along the gulf coastline. Resident dolphins had a daily behavioral pattern, with peaks of foraging activity in the morning, traveling at midday, and socializing in late afternoon. Gulf dolphins had small mean group sizes of 3.4 and were primarily observed foraging and traveling, with little socializing. When resident and gulf dolphins interacted, the mean group size increased to 12 and the proportion of social behavior increased. Association indices demonstrated no long-lasting associations among adult male dolphins, while strong associations existed between several females. Females revealed two patterns of association; they were either members of a female band with other mother-calf pairs, or were solitary with no strong affiliations with any dolphins other than their calf. Males seemed to disperse upon maturation, which maintained the community size of approximately 35 animals. Behavioral evidence indicates the resident community is matrilinealy related and composed largely of adult females and their offspring. A few adult males remain resident, while most young males disperse from the community and may rove among the gulf population. Although mating probably occurs between resident and gulf dolphins, sources of both maternity and paternity for residents need to be determined, and further behavioral work needs to be carried out to support this hypothesis.

Photoidentification surveys of bottlenose dolphins (Tursiops truncatus) were conducted from December of 2002 through December of 2003 in Chocolate Bay, Texas, and the adjacent Gulf of Mexico area. The research represented the continuation of an ongoing study of the dolphins of this area. Behavioral sampling was carried out on a small resident community of dolphins that seasonally reside in Chocolate Bay, as well as on dolphins found along the gulf coastline. Resident dolphins had a daily behavioral pattern, with peaks of foraging activity in the morning, traveling at midday, and socializing in late afternoon. Gulf dolphins had small mean group sizes of 3.4 and were primarily observed foraging and traveling, with little socializing. When resident and gulf dolphins interacted, the mean group size increased to 12 and the proportion of social behavior increased. Association indices demonstrated no long-lasting associations among adult male dolphins, while strong associations existed between several females. Females revealed two patterns of association; they were either members of a female band with other mother-calf pairs, or were solitary with no strong affiliations with any dolphins other than their calf. Males seemed to disperse upon maturation, which maintained the community size of approximately 35 animals. Behavioral evidence indicates the resident community is matrilinealy related and composed largely of adult females and their offspring. A few adult males remain resident, while most young males disperse from the community and may rove among the gulf population. Although mating probably occurs between resident and gulf dolphins, sources of both maternity and paternity for residents need to be determined, and further behavioral work needs to be carried out to support this hypothesis.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 95-103). Also available on the World Wide Web.