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    Studies of the life history of school sharks (Galeorhinus galeus) : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Ecology at Massey University, Albany, New Zealand
    (Massey University, 2025-09-26) Burton, Alex J. C.
    The school shark (Galeorhinus galeus) is a globally distributed, migratory species that was recently reclassified, globally, as Critically Endangered due to all but the New Zealand population having collapsed due to overfishing. Effective management and recovery of these populations is currently limited by a lack of accurate biological information, which is increasingly difficult to obtain due to the scarcity of school sharks throughout their range. By studying the last stable school shark population, located in New Zealand, the aim of this thesis is to provide accurate information on the biology of school sharks to better inform their management worldwide. Specifically, this thesis examines allometric relationships, inter-population variation in life-history stage transitions, intra-population variation in juvenile growth rates, extent of the transfer of elements from mother to pups, and the spatio-temporal connectivity of habitats important to life-history. To enable better standardisation of length data when combining datasets, the optimal model for converting between different length measurements of school sharks was first identified. After standardising length and life-history stage data, a novel Bayesian generative classifier model suggested that length at life-history stage transitions varied among several, globally distributed, school shark populations. A study of juvenile school shark growth across several regions in New Zealand (i.e., Kaipara Harbour, Tasman and Golden Bays, and the Canterbury Bight) revealed that somatic (increase in body length with age) and hepatosomatic (increase of energy stores in the liver with age) growth was consistent among regions, but body condition was generally greater in the Canterbury Bight compared to other two regions. Tracking the year-long, three-dimensional movements of large female school sharks tagged in the Kaipara Harbour with satellite tags showed these sharks dispersed to several potentially important reproductive and feeding habitats around New Zealand. Finally, nutrients and essential and non-essential elements maternally provided to developing young were likely sourced from those assimilated from the mother’s diet during vitellogenesis. This thesis has national and international implications for school sharks and other elasmobranch species, as it provides information and techniques crucial to better understanding the biology of species that is needed to inform more effective management and recovery efforts.
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    Population dynamics and anthropogenic threats to New Zealand fur seal (Arctocephalus forsteri) in New Zealand : a thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Veterinary Science at Massey University, Palmerston North, Aotearoa New Zealand
    (Massey University, 2025) Hall, Alasdair
    New Zealand fur seals (Arctocephalus forsteri; ‘NZFS’) are New Zealand’s most encountered pinniped. However, substantial gaps exist in the knowledge of their abundance and distribution. This study provides NZFS abundance and distribution data for Kaikōura and Banks Peninsula and investigates anthropogenic risks in both locations. Additionally, the thesis undertakes the first nationwide NZFS abundance estimate in ca. 50 years. The Kaikōura population study was the first since the 2016 earthquake. Kaikōura’s NZFS population has grown and spread post-earthquake, with an upper population estimate of 21,560 – 28,327 NZFS in the 2022/23 breeding season. However, pup production at Ōhau Point, the most impacted colony, has not grown, and breeding distribution has changed significantly. Following earthquake damage, State Highway 1 (SH1), which runs close to NZFS colonies, was reconstructed. This study detected an almost fivefold increase in the annual number of NZFS recorded on SH1 from 2012 – 2022, compared to 1996 – 2005. Ten statistically significant NZFS incident clusters were located, representing 89% of the incidents. Cluster location shifted following post-earthquake road reconstruction. Monthly NZFS incident numbers were significantly positively associated with traffic and windspeed, and significantly negatively associated with temperature and rainfall. Road-abutting NZFS breeding explained most of the spatial variation in NZFS incidents. An abundance estimate of 13,147 – 17,675 NZFS was calculated for Banks Peninsula in 2023/24, and 25 previously unrecorded colonies were assessed. This study considered response strategies for an oil spill impacting Banks Peninsula’s NZFS, as the region is classified as ‘high risk’ for such incidents. Priority response strategies include preventing oil from reaching colonies, and hazing individuals away from waterborne slicks. From the most recently available count data, a minimum nationwide population estimate of 131,338 – 168,269 NZFS was calculated. Using recent counts and stage-structured population modelling, a more reliable estimate of 181,646 – 239,473 NZFS was calculated, a substantial increase on the most cited nationwide abundance figure, 100,000 NZFS. This thesis’ population findings provide useful baselines and highlight the need for improved NZFS population monitoring. This is particularly important due to the changing human-NZFS relationship, evidenced by the Kaikōura road reconstruction and the risk of oil spills in Banks Peninsula.
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    Wild bovid habitat and infectious disease risk in Thailand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science, School of Veterinary Sciences, Massey University
    (Massey University, 2024-11-07) Horpiencharoen, Wantida
    Wild bovids are a diverse group of typically large, hoofed ruminant mammals that play crucial functions in ecosystems as seed transporters and prey for predators to maintain biodiversity. However, their conservation status varies from least concern to critically endangered with extinction, depending on the regions and remaining population. The expansion of agricultural areas and livestock farming has led to habitat loss and natural resource sharing, likely increasing the risk of disease transmission and pathogen circulation between humans, wildlife, and domestic animals at the shared habitats or the interface areas. This thesis aims to identify the habitat suitability of five wild bovids remaining in Thailand, understand the consequences of introducing infectious disease into the population, and identify where there is a risk of disease transmission. Therefore, three main studies were conducted: 1) identifying suitable areas for five wild bovid species, including gaur, banteng, wild water buffalo, mainland serow and Chinese goral in Thailand; 2) simulating the impact of infectious diseases of cattle on wild bovid populations, and; 3) mapping potential risk areas between wild bovids and cattle. Initially, I used ecological niche modelling to identify the habitat suitability of five wild bovids remaining in Thailand. Due to poor model predictions for two species (mainland serow and Chinese goral), I excluded these two models from further analyses. The results indicated that over 50% of the potentially suitable areas for the three modelled species (gaur, banteng, wild water buffalo) were located outside protected areas close to human populations and agricultural areas. Then, I simulated the number of animals in a model gaur population with and without infections over 100 years with 100 repetitions using stochastic mathematical models. I selected six bovine infectious diseases with different traits, such as incubation and infectious periods or fatality probabilities, including anthrax, bovine tuberculosis, haemorrhagic septicaemia, lumpy skin disease, foot and mouth disease and brucellosis. I introduced an individual infected animal into a closed population for each infectious disease. The disease-free gaur population grew over time, with infections with different traits having different impacts. The populations infected with chronic diseases (e.g. bovine tuberculosis and bovine brucellosis) showed the greatest decline, while diseases with high mortality but acute disease or high transmission rates with low mortality had less impact on the populations. Finally, I mapped the potential risk areas for disease transmission, assuming that high cattle density and habitat suitability increased transmission risk between wild bovids and livestock. The results also indicated that the potential high-risk areas were at the interface areas at the forest edges where interactions between wildlife and cattle occur. All my studies and findings will require further investigation and validation to gain a deeper and better understanding of the complexity of infectious diseases within wildlife populations and the dynamics of their distributions, but they contribute to supporting wildlife conservation and implementing disease mitigation measures to prevent disease transmission among the populations by highlighting where wild bovids might have suitable habitat, what types of infections may be problems and where mitigation may be better targeted.
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    Historical biogeography of marine ray-finned fishes (Actinopterygii) of the Southwest Pacific : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Marine Evolutionary Ecology at Massey University, Auckland, New Zealand
    (Massey University, 2023) Samayoa, André Philippe
    Current environmental and anthropogenic pressures are driving significant biodiversity loss and range shifts in marine environments. Understanding how biodiversity is generated and how it responded to past environmental changes is fundamental to inform future management strategies for marine resources. As the largest ubiquitous taxonomic group among marine vertebrates, ray-finned fishes (Actinopterygii) represent the best model to understand the generation of biodiversity and the processes that shaped contemporary geographic patterns in the sea. In this sense, centers of marine endemism are of evolutionary value as they translate evolutionary and ecological mechanisms that drive biodiversity dynamics. In the Pacific Ocean, endemism centers for marine fishes are mainly located in remote oceanic islands at the periphery of the tropical West Pacific which harbors the highest levels of biodiversity. Biogeographic research suggests that marine fish endemism in the oceanic islands of the Central Pacific originated via multiple independent jump-dispersal colonization events, and that the islands have acted as sources of new unique biodiversity. However, as the evolutionary setting starts to be revealed for marine fish endemism in the Pacific, processes that generate and maintain biodiversity in other peripheral islands remain unknown. My thesis aims to fill this gap by studying the origin, evolution, and processes that have shaped endemism and biodiversity of marine fishes in the Southwest Pacific. I examined the historical biogeography of the region´s marine fish fauna using open-access molecular data to infer evolutionary histories, and geographic distribution information to assess spatial patterns of endemism and biodiversity. Data were analyzed across three research projects based on time-calibrated phylogenies, probabilistic biogeographic modeling, and statistical analysis of phylogenetic measures of endemism and biodiversity. My results confirm the role of the subtropical islands of the Southwest Pacific as sources of new unique biodiversity, identify mainland Australia as the major source of endemic lineages, highlight the significance of jump-dispersal and vicariance in shaping endemism patterns, and reveal that the processes shaping patterns of endemism and biodiversity differ at local scales. My thesis contributes to the understanding of unique contemporary biogeographic patterns in the marine fish fauna of the Southwest Pacific.
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    Range shifts and the population dynamics of tropical, subtropical, and rare fishes in New Zealand : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Auckland, New Zealand
    (Massey University, 2022) Middleton, Irene
    The rate of species re-distribution during the Anthropocene is unprecedented. The expectation is that as global temperatures continue to rise, tropical regions will become increasingly inhospitable, and temperate regions will become more tropicalised and biodiverse as species track favourable conditions poleward. Climate change mediated range shifts are causing the distinctness of species assemblages and biogeographic regions to erode, and the most significant biodiversity changes are currently occurring in the coastal marine environment. Identifying the species currently undergoing range shifts and predicting where and when future climate-mediated range shifts will occur is critical to proactively manage changes in resource-based human livelihoods and meet conservation goals. However, identifying range shifts is often hampered by a lack of baseline distributional data. In the marine environment, large areas remain under-surveyed, and given that marine species are often cryptic, wide-ranging, and highly mobile, our knowledge of geographic distributions is far from complete. This thesis aimed to fill this knowledge gap by using a combination of novel data sources and methods to set an accurate baseline for the spatio-temporal distribution of tropical, subtropical and rare teleost fishes in a temperate marine setting and develop methods to allow us to monitor future biodiversity change. Teleost fishes are valuable indicators of current and future change; they are early responders to climate-mediated ocean warming and are charismatic and highly visible, increasing the ease of monitoring, particularly by citizen scientists. First, data sourced from published accounts, scientific surveys, commercial catches, and citizen science sources were examined to determine the spatio-temporal distribution of tropical, subtropical, and rare fish in NZ waters. I characterise their contribution to New Zealand’s marine biodiversity and set a baseline for future monitoring of climate-driven biodiversity changes. I found that the contribution of tropical, subtropical, and rare fishes to New Zealand biodiversity is significant, and their occurrences and diversity have increased over the past 50 years. Second, I present and test a novel method that combines citizen science with expert knowledge to classify out-of-range occurrences for marine fishes as potential range extensions or human-mediated dispersal events. The stepwise approach uses qualitative decision making and scoring tools to classify citizen science observations of tropical, subtropical and rare fishes and combines these classifications with expert validation to increase confidence. By applying the method to a range of focal species, I successfully identified species that had undergone range shift into or within New Zealand waters and one species whose range shift was facilitated by human-mediated dispersal. The ease of our approach and the intuitive outputs should appeal to managers and science practitioners concerned with climate-induced biodiversity changes and alien species detection. Third, I apply the classification methods and distributional baselines from Chapters 2 and 3 to citizen science occurrence data for tropical, subtropical and rare fishes in New Zealand waters to identify those species that are tohu (indicators) of change and identify the areas where biogeographic change is occurring. Labrids and Pomacentrids disproportionately contributed to out-of-range occurrences, and 87% of all out-of-range occurrences represented potential and actual range extensions. Locations with a high occurrence of potentially range shifting fishes were centred in north-eastern New Zealand, with occurrences of potentially range shifting fishes decreasing with increasing latitude. I surmise that climate-mediated biodiversity change in New Zealand fishes is occurring and present a list of species contributing to range shifts by region to facilitate effective monitoring and impact mitigation. Overall, this thesis contributes new knowledge regarding the rate of poleward climate-mediated range shifts of marine teleost fishes to New Zealand and a suite of novel tools to facilitate future monitoring and impact mitigation of climate-mediated range shifts. I successfully demonstrate the capacity of ocean-going citizen scientists to identify range shifts in the marine environment and overcome some of the common biases and sampling errors associated with citizen science data by incorporating expert validation and knowledge. My results suggest that New Zealand is currently not a hotspot for climate-mediated biodiversity shifts but biodiversity shifts are occurring and the contribution of tropical, subtropical and rare fishes to New Zealand diversity is increasing. These contributions of this thesis will provide a baseline and framework for resource managers, science practitioners and citizens, to monitor range shifts and manage the impacts of climate change on New Zealand’s marine ecosystem.
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    Systematics and phylogeography of the large land snail Powelliphanta : a thesis presented in fulfilment of the requirements for the degree of Doctor of Philosophy in Zoology, Massey University, New Zealand
    (Massey University, 2018) Walker, Kathleen Joy
    Without a generally accepted name, a species is less likely to receive conservation effort. For the large, colourful and carnivorous land snails in the New Zealand genus Powelliphanta, doubts about the validity of the existing morphologically-based nomenclature, and the absence of taxonomic assessment for many late-discovered taxa, have been hindering conservation efforts. Powelliphanta have been in decline due to continuing loss of habitat and a suite of predators recently introduced to New Zealand, but scarce conservation resources are targeted to formally described taxa. The aim of this study was to review and if appropriate revise the taxonomy of the genus to remove any taxonomic impediment to conservation action. Like other Pacific Ocean archipelagos, the fauna and flora of New Zealand is characterised by a small number of families with extensive radiations. Understanding of relationships is often hindered by the recency of lineage separations and requires multiple lines of evidence. Allozymes and mitochondrial sequences were used to identify genotypic clusters in Powelliphanta and to assess the relationship with presumed sister taxa Victaphanta. A matrix of morphological characters was assembled for multivariate analysis. These characters included for the first time in Powelliphanta, features of the soft body and Fourier coefficients describing subtle shape differences. Intraspecific variation within one of the species, P. lignaria, received detailed distributional, morphological and genetic evaluation to investigate the use of subspecies in the genus. Powelliphanta fiordlandica was found to be a sister taxon to all other Powelliphanta, with a deep genetic divergence and differences in morphology indicating it should be placed within its own monotypic genus. Allozymes, mtDNA and morphology all identified similar clusters, many of which equated to the already described taxa and to taxa which had been tag-named but remained undescribed. Shell colour, pattern and size, which show environmental plasticity in some molluscs, were found in Powelliphanta to be genetically-based and shape also proved informative. The described subspecies of Powelliphanta lignaria were found to be morphologically diagnosable, largely allopatric, and with gene flow limited to the extent that the integrity of each subspecies has been maintained. A recently discovered and critically threatened species was described as Powelliphanta augusta, and a new classification for the genus comprising 20 species and 59 subspecies (including the existing P. lignaria subspecies) was proposed.
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    Impact of human colonisation history on New Zealand avian diversity : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Auckland, New Zealand
    (Massey University, 2016) Amiot, Christophe Michel Gérard
    Human activity has transformed earth's ecology and exerts new selection forces on entire species communities. This thesis examines the influence of evolutionary and human history on the composition of local biodiversity in New Zealand terrestrial habitats. The Auckland region of New Zealand provides an excellent model system because these areas have only recently been colonised by humans, and there is a gradient of habitats ranging from urban to protected native bush. The history of humans in New Zealand is used to inform the response of naïve biodiversity to anthropogenic transformation. First, a general concept of the effect of human societies on biodiversity responses to anthropogenic impacts is explained in chapter one. I focus on three major historical phases - hunter-gather, Agrarian and Industrial- to outline the contrasting influences of each society on native species extinction and extirpation legacies. I then examine the impact of two waves of colonization by humans in New Zealand on avifauna, to establish an understanding of the influence of different human societies on species communities. My results how that New Zealand’s extinction rates are the highest recorded, and are associated with the post-colonisation period by European society and a more advanced human niche construction. This caused more advanced cultural, ecological transformations at various spatial scales. In addition, for exotic bird species in New Zealand, I examined whether the extent of previous coexistence with humans was a potential determinant of establishment success. My findings suggest that previously co-existing with humans is a potential key factor driving the establishment success of exotic species, particularly in habitats transformed by humans. To verify the idea that species functional diversity responds in different ways to human civilisation, I characterise differences in species biological traits among a gradient of habitats with variable degrees of anthropogenic disturbance. I show that no clear assemblages of traits are currently found along extant New Zealand native avifauna. I argue that this can be explained by the different experiences that NZ native avifauna has had with humans in comparison to exotic species. To investigate the possibility of a time-lag response of birds to human habitat transformations, the response of an avifauna assemblage in a remnant forest in the urban habitat is investigated over a period of 26 years of human habitat changes. My results suggest that the community assemblage changed over that time, driven by the arrival of new exotic species. This resulted in a change of community composition to one dominated by exotic species. Finally, nestsite selection of exotic and native avifauna is examined across an anthropogenic gradient to understand the role of evolutionary history in shaping their behavioural response to habitat change. I found further support for the effect of species past-experience with humans. Indeed only native species more naive to anthropogenic habitats and its disturbance tend to alter their nest site strategy in relation to the degree of terrestrial predation. By using the history of a recently colonised location like New Zealand, this research has been able to show the potential importance of human society characteristics during colonisation and how previous levels of human coexistence of biodiversity has implications for current and future ecological consequences in an Anthropogenic world. This thesis highlights the importance of considering species’ past-experiences with humans to inform ecological and evolutionary research and conservation strategies.
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    Context-specific signal plasticity of two common bottlenose dolphin ecotypes (Tursiops truncatus) in Far North waters, New Zealand : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Conservation Biology at Massey University, Albany, New Zealand
    (Massey University, 2018) Peters, Catherine H.
    Common bottlenose dolphin (Tursiops truncatus, referred to hereafter as bottlenose dolphin) fission-fusion groupings are temporary in nature, lasting from minutes to hours, necessitating efficient signal exchange. The selective pressures and contexts acting on signal exchange, such as ecotype variation, are not well understood. The objectives of the current study are three-fold to: 1) quantify the density, distribution and abundance of bottlenose dolphin ecotypes and identify the nature and areas of spatial overlap between the two in Far North waters; 2) examine aspects of mechanical signal exchange based on biotic and abiotic factors; and 3) estimate the effect of key ecotype specific contexts on group multimodal signal exchange. This thesis applies a holistic approach to the assessment of signal exchange in ecotypes using the highly social bottlenose dolphin as a model genus. Additionally, this body of work provides the first comprehensive assessment of oceanic bottlenose dolphin distribution, abundance, and behaviour ecology and the first ecotype spatial and behavioural overlap within New Zealand waters. Knowledge of population size, social behaviour, threats, and ability to integrate new individuals is required to define management units. Although it has long been recognised that the nationally endangered coastal bottlenose dolphin is not resident in the Bay of Islands but genetically part of a North East coast population, no studies have quantified bottlenose dolphin distribution in Far North waters outside of the Bay of Islands. This study provides the first systematic analysis of detectability, distribution, and spatial overlap of both the coastal bottlenose dolphin and the previously unquantified oceanic bottlenose dolphin in Far North waters. Results suggest Far North waters are important for the coastal bottlenose dolphin, supported by a higher average density (0.620 individuals/kilometre) than that reported for the coastal bottlenose dolphin in other areas of the North East coast population. The importance of assessment outside areas of commercial interest is further reinforced in this study. The Bay of Islands local abundance is not reflective of the coastal bottlenose dolphin in the wider area, as indicated by the higher Far North waters estimates of 212.8% (Austral Summer) and 196.1% (Austral Winter). With no previous density or abundance estimates for oceanic bottlenose dolphin in New Zealand, no comparisons can be drawn with other studies or historic research. However, the distance sampling-based population estimate of 3,634 (SE = 152) indicates oceanic bottlenose dolphin abundance is much higher than the 389 (SE = 108) coastal bottlenose dolphin abundance estimate in Far North waters, even though their distribution is seasonal with detection only in austral Summer and Autumn. Kernel density also indicates the representative ranges (95 % kernel range) of the coastal bottlenose dolphin are smaller than the oceanic bottlenose dolphin, extending over a total area of ~794 km2 and ~1,003 km2, respectively. This study further suggests these ecotypes should be described as largely parapatric and non-resident in nature, with a minimal spatial overlap of only 7.4 % of Far North waters surveyed (~196 km2). This is further supported by no sightings of the two ecotypes within the same survey zone on the same day (n = 372 bottlenose dolphin sightings) during the present study. Behaviour can further add insight into the partitioning and variation of parapatric units within a species. In Far North waters, whilst research on surface behaviour has been previously conducted in the Bay of Islands, behavioural assessment in wider areas and based on a holistic assessment of multiple signal forms is lacking in the literature. This study, however, applies a systematic sampling technique and integrated analysis to identify trends in signal exchange use. This is done by examining multiple behavioural modes (states and events, surface and subsurface) concurrently. This ultimately provides an additional method for quantifying group behavioural plasticity as a result of covariates acting on parapatrically occurring bottlenose dolphin groups. In one assessment, cues were taken from avian acoustic research to accurately quantify and analyse ecotype variation in call repertoire. In support of the parapatric definition, call repertoire was correctly assigned to ecotype, with an 89.4% success rate (n = 31,432 calls). Of all parameters examined, 71.4% exhibited significant variation, with harmonics and contour inflections used significantly more in oceanic bottlenose dolphin. Both Dynamic Time Warping in Luscinia and Hidden Markov Models add reliable insight into the categorisation of key signal parameters and important tools for the primary assessment of differences in bottlenose dolphin behaviour within Far North waters. Including the full behavioural repertoire of oceanic bottlenose dolphin and coastal bottlenose dolphin through Hidden Markov Models adds additional insight to the possible drivers behind the divergence in the call parameters noted. It is notable that signal parameters are not influenced by the same key drivers for both ecotypes. This is an important finding in a species in which most communication exchanges involve acoustic signals in some form. The formation of interspecific groupings has the largest effect on social signal exchange in oceanic bottlenose dolphin of all covariates considered. The response magnitude is associated with group parameters, for example, the ratio of individuals (e.g. pilot whales (Globicephala sp.) to oceanic bottlenose dolphins) and the behaviour and/or overall size of the focal group. These aspects in turn determine the effect of participation in interspecific groups on oceanic bottlenose dolphin behaviour. Oceanic bottlenose dolphins in interspecific groups with pilot whales display higher call plasticity, both in the time and frequency domain, utilising significantly higher measures for 66.7% of parameters, including longer and more complex calls (increased number of harmonics and inflects), than in intraspecific oceanic bottlenose dolphin groups. Signal adaptation is more evident when oceanic bottlenose dolphins and pilot whales are directly interacting with each other during social events. During socialising states, the predominant subsurface event type observed is aggression (59.4%, n = 233). As the ratio of pilot whales to oceanic bottlenose dolphins increases, the use of long-distance signal exchange decreases. This suggests that the observed decreases in interspecific similarity of whistle parameters during social interactions may act to increase the ability to differentiate species-specific rather than whole group signal exchange cues. Although species-specific call differentiation is likely heightened by variation in gross morphology, phylogeny and geographical constraints, frequency domain characteristic overlap between oceanic bottlenose dolphins and pilot whales. The detected adjustments in signal structure away from intermediate values may suggest a decrease in the increment in this overlap. Support is given to the theory that signal exchange might be modified not only as a result of group behaviour state but also due to the signaller’s motivational state (i.e. stress). While the full biological effects of changes in whistle rates and parameters remain uncertain, these changes add initial insights to the dynamics of interspecific groupings. Number of vessels had largest effects on coastal bottlenose dolphin social signal exchange, with response magnitude significantly related to group composition (ex. with or without calves) and use of other signal exchange behaviours (ex. tactile type and rate). The response is also influenced by acoustic parameters considered (frequency or call rate). The highest coastal bottlenose dolphin density area, the Bay of Islands, contains the highest proportion of groups with calves and the highest level of vessel traffic in Far North waters. Groups with calves favour sounds typically used for short-distance signal exchange, appearing to increase the use of mechano-reception in the presence of vessels. Overall, coastal bottlenose dolphins are more likely to: (1) leave the low-call-rate state in the presence of one to two vessels (within 300m); (2) leave the high-call-rate state when three or more vessels (adults only), or two or more vessels in the case of groups with calves, are within 300m; and (3) stay in a relatively silent state when more than three vessels are present. Furthermore, coastal bottlenose dolphins are more likely to (1) leave the low-call-rate state when contact rate is low; (2) leave the high-callrate state when contact rate is high; and (3) stay in a relatively silent state when contact rate is high. This suggests an inverse relationship exists between call rate and contact rate, i.e. as possible vessel effect increases, vocalisation-mediated coordination decreases, and mechanomediated coordination increases with a lower threshold for groups with calves than groups without. Several drivers of elevated signal exchange rates have been suggested in the presence of vessels. These include an increased motivation for individuals to stay close together, a changed group cohesion and amplified arousal. However, this study adds new insights with the quantification of multi-modal signal exchange in the presence of vessel. This has not been the focus of previous research in any of the bottlenose dolphin populations in New Zealand. Distribution, density, and abundance is now available for both bottlenose dolphin ecotypes, with multimodal group behaviour in ecotype specific contexts additionally quantified. As such, supplementary monitoring and reviews of the coastal bottlenose dolphin and oceanic bottlenose dolphin parapatric populations in New Zealand are essential. Pre-emptive rather than reactive conservation is recommended to effectively manage both bottlenose dolphin ecotypes separately and efficiently in New Zealand waters.
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    Spatial ecology of delphinids in Queen Charlotte Sound, New Zealand : Implications for conservation management : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Marine Ecology Massey University, Albany, New Zealand
    (Massey University, 2019) Cross, Cheryl Lynne
    Understanding species’ ecological interactions and area usage depends on clear insight into their temporal and spatial patterns. Such information combined with recognition of regional human-invested interests, is crucial for developing conservation management efforts. Queen Charlotte Sound (QCS), South Island, New Zealand is a unique environment inhabited by diverse marine life, including several cetacean species. The area is subject to rising levels of anthropogenic activity inclusive of marine farming, tourism and vessel traffic. With conservation management in mind, this thesis focused on three key delphinid species: Hector’s (Cephalorhynchus hectori), bottlenose (Tursiops truncatus) and dusky dolphins (Lagenorhynchus obscurus). Specifically, this study sought to: 1) explore long-term historical temporal and spatial trends in delphinid occurrence 2) identify recent patterns in delphinid distribution, density and range 3) investigate delphinid species’ habitat use 4) initiate research of regional swim-with-dolphin tourism. Dolphin sighting data were: 1) collated from tour vessel logbooks spanning 1995–2011 and 2) collected during dedicated surveys aboard opportunistic platforms from 2011–2014. Dynamic and static environmental variables were sourced from local government agency databases to use in analyses with both datasets. Historical delphinid presence (from logbook data) was correlated with dynamic environmental variables during two separate time frames (1995–2002; 2003–2011), using Generalized Additive Models (GAMs) and Generalized Linear Models (GLMs). Spatial patterns of these sightings were explored across temporal periods (i.e., seasons; blocks of year). Dedicated survey data were used to generate kernel density estimates and to determine species’ range and central range. These dolphin density estimates were correlated with static and dynamic habitat parameters using (GAMs). Spatial predictions were then generated from the resultant significant variables. Bottlenose dolphin engagement in swim-with-dolphin encounters was assessed according to several proxies using Linear Models (LMs) and GLMs. A total of 5,295 historical records consisting of 6,055 delphinid sightings were compiled, demonstrating a long-term presence of the focal species. Of these, Hector’s dolphins consistently had the highest trip encounter rate. Seasonal patterns indicated peaks in occurrence for Hector’s during summer/autumn, bottlenose during autumn/winter and dusky dolphins during winter/spring. Further investigation with GAMs suggested that each species’ presence was associated with a unique set or range of dynamic variables. Annual variation occurred amongst all species. During both historical time frames (1995–2002 and 2003–2011), Hector’s dolphin occurrence was associated with higher SST values. Bottlenose dolphins displayed an association with mid-low SST (during 1995–2002) and with high turbidity (during 2003–2011). Dusky dolphins were influenced by low SST (during both time frames) and from 2003–2011 were also influenced by low turbidity and mid-value tidal range. Spatial patterns illustrated that Hector’s and dusky dolphins have become more restricted in their use of QCS over time. Finally, logbook data indicated an increased prevalence of swim-with-dolphin encounters, suggesting an expansion of local tourism from 2004–2011. A total of 677 dedicated opportunistic surveys were completed. These equalled 1,613 hrs of search effort spanning 263 km2. Sighting rate calculations indicated that Hector’s and bottlenose dolphins occurred more frequently than dusky dolphins. Seasonality was particularly notable amongst Hector’s dolphins, whereas the sighting and encounter rates were higher during summer and autumn. The collective range of all species suggests that delphinids utilized most of QCS. However, both the range and central range of Hector’s dolphins were more limited. Notable spatial patterns included peaks in Hector’s dolphin density mid-Sound, during summer/autumn and peaks in bottlenose dolphin density toward the outer Sound during summer/autumn. Temporal overlap was relatively high for bottlenose and Hector’s dolphins (0.67) and low for Hector’s and dusky dolphins (0.22), while spatial overlap was quite low for all species combinations. The patterns explored here offer evidence of temporal and spatial multi-species habitat partitioning within QCS. This may be due to the broader ecological trends within New Zealand and is likely attributed to the availability and movement of prey. Habitat models (GAMs) indicated a unique set of significant drivers associated with dolphin density for each species. Hector’s dolphins displayed an association with dynamic and static variables (SST, fluorescence, depth, slope and distance to the closest marine farm). Dusky dolphins were influenced by the same variables, as well as year. Consistency with the earlier models in the association with SST for Hector’s (higher values) and dusky dolphins (lower values) was detected. Bottlenose dolphins were only influenced by static variables (depth, slope and distance to the closest marine farm) and year. The habitat differences suggested by these models offer further insight to the ecological meaning of dolphin spatial patterns in QCS. In particular, these findings offer additional evidence of delphinid resource partitioning, specifically on a trophic scale. This likely occurred because all three species exhibit both dietary and foraging plasticity. While similarities were observed between comparable studies in other areas, the presence of some variation is likely due to unique physical and hydrographic regional characteristics. Spatial predictions that were generated from significant model variables were valuable in estimating potential locations of dolphin density beyond sighting locations, including areas that they previously occupied. Data representing animal area usage, like those presented here, are integral to conservation management, especially amidst growing anthropogenic influences, like tourism. This first ever tourism-based study in QCS indicated bottlenose dolphins as the main target species for swim-with-dolphin activity. A total of 190 bottlenose dolphin swim encounters were assessed according to several proxies. Interactions were very short (𝑥̅=4.2 min), with most dolphin reactions neutral (82.9 %), suggesting animal disinterest. Swim encounters occurred regularly, irrespective of group composition or behavioural state. Furthermore, tour operators travelled great distances (𝑥̅=11.7 km) amongst dolphin groups to complete swim encounters, demonstrating pursuit of interaction. Collectively, these proxies suggest a lack of dolphin engagement in swim activity. This thesis encompassed the first multi-species comprehensive assessment of delphinid density, range, habitat use and swim-with-dolphin tourism in QCS. It established a baseline of data, contributing to regional ecological knowledge. Detailed evidence of when and where three sympatric dolphin species utilized QCS was provided. Moreover, this work established an understanding of delphinid inter-specific interactions and associations with habitat variables. Applications of the findings presented here include contributions to developing comprehensive conservation management and further research. Periods and regions of high density and predicted density may be considered in regional management decisions regarding anthropogenic use of the Sound and during the design of future surveys.