Ph.D. Students

Sperm whale distribution, movement patterns and social structure throughout the Indian Ocean

Supervisors: Christine Erbe, Robert McCauley

Sperm whales (Physeter macrocephalus) remain one of the least studied, large cetaceans in the world, primarily due to their offshore distribution. Although populations have been studied worldwide, very little data exist across the Indian Ocean and Australian national waters on their distribution, social structure, movement and habitat use.
Sperm whales are highly acoustic animals that use echolocation to navigate and find prey, feeding in submarine canyons on average of at least 1000 m in depth. They have strong social structures and produce short patterns of clicks called codas. Codas are strongly linked to social activity and have been recorded in breeding areas.
Sperm whale presence and abundance can be identified by passive acoustic monitoring, a tool that is used for both scientific research and management. Sperm whale positions derived from satellites allow scientists to better visualise their movements, resulting in data increasingly being used to address conservation and management related questions.
Increasingly, online portals host a number of presence-only datasets such as visual sightings of animals with date, time, and geolocation and sometimes passive acoustic detections. Species distribution modelling tools, such as Maximum entropy modelling (Maxent), can utilize these data for sperm whales to map and better understand habitat preferences.
Critical habitats for cetaceans are defined as areas essential for survival and population growth. The International Union for the Conservation of Nature (IUCN) lists sperm whales as vulnerable under their Red List of threatened species. Using bioacoustics data in conjunction with satellite telemetry technology and data sourced from online portals, critical habitats of sperm whales will be identified.
As a result of human activities, our global oceans are changing profoundly, impacting the distribution of marine species (Avila et al., 2018; Hussey et al., 2015; Nelms et al., 2021). Improved “knowledge of animal movements, interactions, and how the physiological and environmental processes influence distributions” will be required for global management (Dunn et al., 2019; Hussey et al., 2015; Sequeira et al., 2019).
Using passive acoustics we can model sperm whale presence to assist policymakers in managing critical habitats for cetaceans including sperm whales (Johnson et al., 2016). Movement data obtained by satellite telemetry can help us map, manage and protect migration corridors. As sperm whales our oceanic predators, we have little to no data on how migration occurs, if at all, throughout the Indian Ocean.

The acoustic ecology of the Omura’s whale (Balaenoptera omurai) in Australia

Supervisors: Christine Erbe, Rob McCauley

The Omura’s whale (Balaenoptera omurai) was described as a new species of baleen whale in 2003, and was only identified alive in the wild in 2013. It was previously misclassified as ‘pygmy’ or ‘small-form’ Bryde’s whale due to similarities in appearance, but a distinctly smaller size. It is known from a few stranding and whaling specimens, opportunistic sightings, and a single in-depth field study conducted off the coast of Madagascar. Globally there remains a large absence of knowledge on the Omura’s whale’s behaviour and ecology. The Madagascan field study attributed vocalisations to the Omura’s whale which can be used to identify the species. Similar vocalisations have been detected off the northwest coast of Australia from Exmouth to the Timor Sea, but there has been no dedicated studies on the species’ ecology in Australian waters.

The aim of this research project is to improve our understanding of the bioacoustics, ecology and distribution of the Omura’s whale in Australia. I aim to 1) describe the structure of the Omura’s whale song detected in Australia; 2) determine the spatial distribution and seasonality of the Omura’s whale in Australian waters using acoustic presence; 3) model the environmental drivers of Omura’s whale presence; and 4) investigate any variations in Omura’s whale song or calling patterns in response to ambient noise.

The study will utilise long-term underwater acoustic recordings collected by Curtin University or as part of the Australian Integrated Marine Observing System over the past 20 years. Positive detections of Omura’s whale vocalisations can be used to identify presence of the species in a given area, at a given time, and can be used to determine their distribution and seasonality. Additionally, when acoustic presence of the species is correlated with oceanographic variables (e.g., sea surface temperature, chlorophyll-a concentration), prey biomass, and acoustic variables (e.g., presence of other species, anthropogenic noise, wind noise) we can determine drivers of the Omura’s whale’s distribution and any variation in calling behaviour in relation to ambient noise. These findings will provide important information on the Omura’s whale’s acoustic ecology and critical habitats, contributing towards conservation and management policies of the species in Australia and globally.

The acoustic ecology of dwarf minke whales in Australian waters

Supervisors: Christine Erbe, Rob McCauley

The dwarf minke whale (Balaenoptera acutorostrata, unnamed sub-species) is an under-described sub-species of the common minke whale and is widely distributed throughout the southern hemisphere only. Dwarf minkes whales have been acoustically recorded and visually observed at various locations around Australia, including the Great Barrier Reef Marine Park (GBRMP) off Queensland and North-west Marine Region (NWMR) off Western Australia (WA), particularly during the austral winter months. It is presumed that these areas provide important habitat for the sub-species during its suspected calving and breeding seasons, however further investigation is required to confirm this and to drive effective conservation management effort for the sub-species and its habitat. This research aims to improve our understanding of the acoustic behaviour and ecological requirements of dwarf minke whales in Australian waters. This will be the first dedicated study on dwarf minke whales off WA, based on passive acoustic monitoring (PAM).

PAM is a non-invasive and remote method commonly used for investigating underwater soundscapes and it can provide crucial information on vocal species’ behaviour and ecology. Dwarf minke whales produce stereotypical song by which they can be identified and monitored. PAM tools can be used to determine dwarf minke whale vocal presence in an area, at a given time, allowing us to study their large-scale migratory movements, distribution and seasonality, as well as their specific ecological and habitat requirements. Knowledge of the environmental drivers of dwarf minke whale habitat utilisation can help us to identify areas that may be of biological significance to the sub-species. Furthermore, PAM allows us to investigate dwarf minke whales’ acoustic behaviour and their responses to anthropogenic threats (including the ever-increasing anthropogenic noise in the marine environment) and the effects of other sounds in the marine environment (e.g., other marine animals and ambient noise) on their behaviour.

Long-term assessments of dwarf minke whale seasonal movements, habitat preferences and acoustic and ecological interactions will provide crucial information for assessing the vulnerability and response of the sub-species to potential pressures (and their ecological risk) in the NWMR off WA. This risk assessment approach will facilitate science transfer to regulatory bodies to assist with the implementation of a more comprehensive risk management framework, within which management priorities and long-term monitoring and conservation plans may be identified for dwarf minke whales off WA.

The socioeconomic value and acoustic ecology of the pygmy blue whale (Balaenoptera musculus brevicauda) in Australian waters

Supervisors: Rob McCauley, Christine Erbe

Accelerating climate change is expected to cause profound changes to our marine ecosystems, especially in Antarctic waters, associated with far-reaching impacts from declining ice cover to reduced primary and secondary productivity, particularly affecting great whales throughout their expansive migratory habitats. Human-based activities too, are exponentially rising. As a response, historical spatial and temporal ranges of whales are shifting.

The pygmy blue whale (PBW) (Balaenoptera musculus brevicauda), a subspecies of the blue whale, is one of the world’s most iconic marine animals, listed as endangered in Australia, yet classified as “Data Deficient” globally, on the IUCN species Red List. Little is known of their recovery since the cessation of whaling. With the demand for marine-based industry on the rise (e.g., shipping, oil and gas, mining), particularly in the North-west Shelf (NWS) marine region and off the North-west Cape (Exmouth, WA), PBWs may be increasingly vulnerable to anthropogenic threats.

While there is a high-level understanding of this species’ ecology, range, and behaviour in Australian waters, a more granular understanding of spatial and temporal distribution, and drivers of variability in distribution, is crucial to better inform environmental management and monitor EIOPBW recovery in Australian waters. The aim of this research is to facilitate more informed decision-making processes, by defining new areas of biological importance, quantifying the exposure to acoustic threats, and investigating seasonal variability of EIOPBW whale distribution in Australian waters, particularly in areas with increasing exposure to threats such as oil and gas exploration and production, and shipping.

Conventional, visual observation methods are logistically difficult and expensive for monitoring PBWs due to their low population densities, cryptic underwater nature, and often remote, offshore distribution. However, PBWs emit highly stereotypical song for hours to days at a time, by which they can be identified and tracked. Therefore, this project will utilise Passive Acoustic Monitoring (PAM), which enables more affordable, non-invasive (remote), long-term, and comprehensive datasets to be acquired. Starting with an existing archival dataset of 20 years of underwater recordings off WA, which will be augmented by 12-month recordings at key (missing) locations, a combination of computer-assisted and manual detection methods will yield a database of PBW acoustic presence in space and time. Ambient noise in PBW habitat will be quantified based on the same recordings, and non-acoustic features of the habitat will be derived from other (including satellite remote sensing) databases, allowing the development of a PBW acoustic habitat model (AHM).

The outputs of this project will include an estimate of the socioeconomic value of the species and improved understanding of drivers of blue whale habitat selection and anthropogenic threats. The application of these findings is to identify critical habitats and biologically important areas (BIAs) of the pygmy blue whale, to inform marine spatial planning and impact assessments for offshore developments. This information will be directly relevant to the 2025 revision for the Conservation Management Plan for the Blue Whale. Overall, this broadened understanding will directly contribute to the targeted implementation of increased conservation measures of this endangered and iconic species.

Characterising the vocal repertoire of the endangered Burrunan dolphin (Tursiops australis) and marine soundscape of Victoria, Australia

Supervisors: Christine Erbe, Kate Robb and Robert McCauley

The Burrunan dolphin (Tursiops australis) is a novel species of delphinid described in 2011, currently listed as Critically Endangered under Victoria’s Flora and Fauna Guarantee Act 1988. Given the species has only recently been described, there is still much to be understood about the biology and population ecology of T. australis. Two populations of the species are currently known to exist in Victoria, Australia, both inhabiting highly urbanised and agricultural areas. To date, we have very little understanding of the acoustic repertoire of T. australis, the marine soundscape, or the threatening processes to which it is exposed.

The aim of this research project is to understand and classify the acoustic repertoire and associated behaviours of T. australis through studying two resident and genetically distinct populations within two previously uncharacterised marine soundscapes in Victoria. The project will also explore the potential of anthropogenic noise as a threatening process.

This study will utilise passively recorded acoustic data, opportunistically recorded hand-held hydrophone data, and focal-follow behavioural data collected in collaboration with the Marine Mammal Foundation. The project will allow for better understanding of the novel, threatened species T. australis, improved comprehension of anthropogenic noise as a threatening process for Tursiops species, and more informed conservation management.

Decoding coral reef soundscapes at Ningaloo, a Natural World Heritage site

Supervisors: Christine Erbe, Miles Parsons, and Robert McCauley

Coral reefs are among the most biodiverse places on Earth and support vital ecosystem services for more than one billion people around the world. These important coastal habitats are critically declining worldwide due to a combination of anthropogenic stressors, including climate change. Their rapid and widespread collapse is calling for assessment and resilience-building tools that cope with these changes and contribute to effective management and restoration of coral reefs. The coral reef soundscape is an emerging tool that offers a potential solution to tackle these challenges, but a better understanding of its spatial and temporal variation as well as its relationship with the biological ensembles and ecological process are necessary. Passive acoustic monitoring offers a non-destructive, non-invasive, remote, fast, accurate, long-term, and cost-effective solution to study the coral reef soundscape to aid in closing the gaps between the acoustics and its ecological significance in coral reefs.

This research project aims to understand the main attributes and patterns of the coral reef soundscape. These aims will be pursued by 1) determining environmental drivers of spatial and temporal variation; 2) identifying the main soundscape’s biological components; 3) analysing its ecological implications; and 4) providing evidence of ecosystem restoration associated to coral reef restoration initiatives. This research will be conducted with the contribution of the Centre of Marine Science and Technology (CMST) and the Australian Institute of Marine Science (AIMS). The acoustic and ecological data has been obtained from a series of underwater acoustic recordings in natural reefs and artificial patch reefs in the Coral Bay lagoon, Ningaloo coast, as part of the project “Reef Song: Building Reef Resilience through Enhancement of Fish and Corals” of the AIMS and BHP Group Operations Pty Ltd.

This study will determine the soundscape baseline in Ningaloo, its main biological contributors, and its ecological relevance for this reefs’ ecological dynamics. The results will also aid to assess the efficacy of different methods used in a coral reef restoration project conducted in this region. This research will contribute to our growing understanding of the importance of sound in coral reef ecosystems and its application in restoration initiatives in other coral reefs. The information gathered can help to advise the development of management and restoration strategies in Ningaloo.

Understanding the link between environmental drivers, primary productivity, and baleen whale presence to assist vessel traffic management in the Perth Canyon

Supervisors: Robert McCauley, Christine Erbe

The Perth Canyon is a productivity hotspot along the otherwise oligotrophic coastline of Western Australia and supports a variety of marine species. In 2018, the Perth Canyon became a marine park where human activities are regulated through zoning. However, large merchant vessels are allowed to transit the marine park, putting marine animals at risk of noise exposure and collision with vessels. Particularly vulnerable are baleen whales whose hearing range and call frequency overlap with low-frequency vessel noise, while their relatively slow manoeuvrability and surface behaviours make them more prone to collisions. Seventeen years of acoustic data collected in the Perth Canyon have confirmed the seasonal presence of six migrating baleen whale species. Three of these species (i.e., pygmy blue whales, Balaenoptera musculus brevicauda, Antarctic blue whales, Balaenoptera musculus intermedia, and fin whales, Balaenoptera physalus) are either known or presumed to use the canyon as a foraging waystation and thus, may spend several days to weeks in the marine park. Assessing the risk of vessel presence to these species is paramount for developing effective conservation measures and necessitates knowledge of the driving factors behind their temporal presence. While whale presence is presumably related to canyon productivity, our understanding of the link between environmental drivers, productivity, and whale presence in the Perth Canyon is currently limited. This project aims to gain a deeper understanding of the link between environmental drivers of productivity and baleen whale presence and, subsequently, to assess the risk of vessel presence for different years of productivity. The outcome of this study will provide crucial information for long-term vessel traffic management in the Perth Canyon marine park.

Foraging, migration, and communication in eastern Indian Ocean pygmy blue whales Balaenoptera musculus brevicauda

Supervisors: Robert McCauley, Christine Erbe, Michele Thums, Curt Jenner, Micheline Jenner

Blue whale Balaenoptera musculus populations are structured throughout every ocean basin forming numerous sub-populations across 4 confirmed subspecies. In the eastern Indian Ocean, a discrete population of the pygmy subspecies B. m. brevicauda exists, migrating between their tropical terminus in southern Southeast Asia and temperate waters south of Australia. It is not yet clear if this migration is a result of their reproductive habits or foraging ecology. Rather than the feast and famine life history, these pygmy blue whales forage year-round upon ephemeral and seasonal food resources in the form of various planktonic Euphausiid krill species. Understanding the environmental drivers behind their selection of foraging locations is key to investigating the motivations of their migratory behaviour. Pygmy blue whales communicate with conspecifics using a variety of vocalisations that can be monitored passively to identify their presence, and potentially be deciphered to reveal behaviour. This research aims to understand the driving factors behind migration, foraging, and communication in the eastern Indian Ocean pygmy blue whale, which will enable the identification of areas important to the ecology of this population.

Pre-existing biotelemetry tag datasets will be employed to explore movement and foraging behaviours across multiple data resolutions. To improve our understanding of pygmy blue whale foraging ecology in this region, we will attempt to explain the derived behaviours with environmental processes in two locations: Perth Canyon and Ningaloo. The context of eastern Indian Ocean pygmy blue whale vocalisations will be investigated by deploying tags capable of acoustic logging and orientation estimation at an individual level, ideally identifying acoustic signals of foraging behaviours. Finally, habitat suitability modelling for pygmy blue whale vocalisations on the Northwest Shelf of Australia will be conducted to identify areas of importance of this population in this region, accounting for knowledge accumulated during this project. This research is crucial for the effective management of this pygmy blue whale population and will improve our ability to understand how the population will react to a changing climate.

Acoustic ecology of Western Indian Ocean pygmy and Antarctic blue whales

Supervisors: Christine Erbe, Salvatore Cerchio, Emmanuelle Leroy, Evgeny Sidenko

My PhD aims to understand the distribution, habitat use, and acoustic behaviour of two blue whale subspecies in the Western Indian Ocean. Using an extensive dataset of passive acoustic recordings across three main locations, I am looking into song detection, song variations, and recent changes in the distribution and seasonality of Antarctic and pygmy blue whales. These elusive animals can be found in the same location at different times of the year, which leads to think that their habitat use, foraging niches, and acoustic ecologies are partitioned to decrease competition and optimise the use of shared resources. My thesis is supported by the Quieter Western Indian Ocean (QWIO) project.

Ecological and acoustic investigation of anthropogenic noise effects on humpback whales in the Western Indian Ocean

Supervisors: Christine Erbe, Violaine Dulau, Salvatore Cerchio, Cristina Tollefsen

Humpback whales (Megaptera novaeangliae) utilise breeding grounds in the Western Indian Ocean, where they are exposed to increasing anthropogenic noise, primarily from shipping. This noise exposure can disrupt their behaviour, including communication, movement, and habitat use. This research project aims to improve our understanding of the humpback whale population in this region and the acoustic environment. The project will explore the behaviour of mother-calf pairs in coastal regions and investigate differences according to ambient noise levels. This will include deploying biologging tags in the context of whale tourism in La Réunion waters (whale watching and swim-with-whale activity). At a different scale, the research project will evaluate noise risk areas by mapping out the ship traffic and the noise produced in the Western Indian Ocean, including the weather conditions that influence the background noise. Ultimately, the research project will provide insights into mitigation through simulations to reduce the vessels’ impact on humpback whales. Research supported by the Quieter Western Indian Ocean (QWIO) project.

The acoustic ecology of Antarctic minke whales (Balaenoptera bonaerensis)

Supervisors: Christine Erbe, Paul Nguyen Hong Duc, Cristina Tollefsen, Robert McCauley, and Brian Miller

The Antarctic minke whale is one of the most abundant baleen whale species found in the southern latitude waters of Antarctica. Despite this, the acoustic behaviour of this species is poorly understood. In 2014, the mysterious “bio-duck” sound was attributed to this species. Retrospectively, multiple variants of bio-duck have been documented, with vocal repertoires reported in West Antarctica. In contrast, there is a lack of broad-scale understanding of bio-duck presence in East Antarctica and Western Australia.

The overall aim of this research is to fill the gaps of knowledge on Antarctic minke whale acoustic presence and behaviour in East Antartica and Western Australia. This will be achieved through 1) The development of machine learning tools to identify bio-ducks in acoustic datasets; 2) Characterising the acoustic repertoire of Antarctic minke whales in East Antarctica and Western Australia; 3) Investigating spatiotemporal patterns of bio-duck presence and drivers for habitat usage; 4) Estimate the source level of bio-duck calls using recordings obtained from acoustic tracking grids.

This study will utilise long-term acoustic underwater recordings spanning over twenty years; collected by the Australian Antarctic Division, Curtin University or the Australian Integrated Marine Observing System. Detections of bio-duck vocalisations can be used to identify the presence of this species, their distributions and seasonality. An estimated source level of bio-duck calls will inform the proximity of detected Antarctic minke whale vocalisations. Vocal repertoires inform the variance of calls and when overlapped with spatiotemporal modelling; can suggest functionality such as reproductive display, general communication or foraging. These findings will provide important information on the acoustic ecology of Antarctic minke whales, contributing towards the management of this species in rapidly changing environments.