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Current Research Topics

© Carmen Or

Indo-Pacific humpback dolphins in the coastal systems of Pearl River delta: Ecology of a threatened regional biodiversity icon

Humpback dolphins (Sousa chinensis) inhabiting the Pearl River Delta (PRD), locally known as Chinese white dolphins, are believed to be the largest population of this species in the world. However, all current Marine Protected Areas (MPAs) within PRD fail to secure the minimum habitat requirement of these animals to accommodate sufficiently viable population size.  Our recent findings indicate a rapid decline in population numbers which, in conjunction with the degraded state of the environment, may place these animals under a serious threat within a life-span of just three generations. Our demographic models suggest that over 70% of the population may vanish within 60-70 years.  In a time-scale of ~40 generations, the PRD population is doomed to become extinct unless effective conservation measures can rapidly reverse the current population trend. One of these measures is the need to better understand population processes that determine population vulnerability and its biological viability.  This includes population models that factor in effects of environmental stochasticity.  Population range and structure and socio-behavioural dynamics have to be investigated, and the displacement of individuals over time needs to be quantified to evaluate the type and intensity of natural and human-induced pressures on individuals, groups, and the overall population.  Continuous information from mark-recapture sighting histories of individually recognizable animals is needed to construct demographic models and perform quantitative analyses that can facilitate population viability assessment.  We have recently generated such data for the dolphins in Hong Kong waters and PRD-wide estimates are soon forthcoming. 


This work is conducted in partnership with colleagues from Sun Yat-sen University in Zhuhai and represents a multifaceted approach to conservation research that integrates a diverse range of expertise and research tools; and expands across political borders.  Jointly, we are generating an important scientific contribution to the conservation of Chinese white dolphins in the PRD, and to broader biodiversity research in southeast Asia and beyond. 

This project received initial seed-funding support from the University of Hong Kong and Ocean Park Conservation Foundation and, subsequently, four substantial grants from the General Research Fund of the Research Grants Council (RGC) of Hong Kong (RGC-GRF: HKU 768110M, 768913M, 17100015M and 17163316M) and corporate funding support provided by a consortium of sponsors.

This project received initial seed-funding support from Ocean Park Conservation Foundation and RGC/GRF proposal is currently under consideration.

Acoustic niche and essential marine soundscape of sympatric coastal cetaceans in Hong Kong waters 


Soundscape, a collection of environmental sound, biological sound, and anthropogenic noise, represents an important sensory signal for the habitat selection of marine animals.  Anthropogenic noise is known to affect the physiology and behaviour of marine organisms, especially marine mammals that rely greatly on their acoustic sensory systems.  Long-term noise can alter the soundscape and disrupt the acoustic communication of soniferous organisms.  Therefore, soundscape is among the most important indicators of the marine environment quality.  As the Pearl River Estuary is among the world's most developed coastal regions, with massive construction projects spanning the entire estuary, which generate intense underwater noise, the resulting impacts on marine mammals inhabiting this shallow-water coastal habitat are likely vast and unceasing, yet very little of it has been adequately investigated. 


Indo-Pacific humpback dolphins (Sousa chinensis) and finless porpoises (Neophocaena phocaenoides) are two cetacean species inhabiting Hong Kong waters year-round.  In this study, we investigate the relationship between the pattern of dolphin/porpoise habitat use and marine soundscape.  We explore the temporal variability of soundscape, including varying biological and non-biological sound by the means of long-term acoustic field recordings, and we compare acoustic complexity and diversity - the quantitative indicator of local biodiversity - between the core and non-core habitats of these two sympatric coastal odontocetes.  We map the soundscape of Hong Kong waters by the means of onboard acoustic surveys, while long-term underwater recordings are collected at five designated stations.  With a large volume of long-term data, we will gain considerable insights into the habitat use and acoustic behaviour of dolphins and porpoises in Hong Kong waters as well as soniferous fishes and invertebrates, generating important data on prey availability, local biodiversity, and overall habitat quality.  This study will significantly advance our understanding of the interactions between humpback dolphins, finless porpoises and human activities in one of the world's most industrialised and urbanised costal environment.




© Leszek Karczmarski

Sympatric ecology of island-associated cetaceans 

Very little is known of the socio-behavioural dynamics of island-associated cetaceans, and even less about multi-species assemblages such as those seen in the Philippines.  In this study, we investigate intra- and inter-species behavioural dynamics, quantify population parameters, and map spatial patterns of habitat preferences of several cetacean species (spinner dolphins Stenella longirostris, Indo-Pacific bottlenose dolphins Tursiops aduncus, pantropical spotted dolphins Stenella attenuata, melon-headed whales Peponocephala electra, and Risso’s dolphins Grampus griseus) in waters of Tañon Strait Protected Seascape, central Philippines.  Our research area, the central and southern Tañon Strait, offers an excellent location to study the socio-spatial dynamics within and among species.  Because of the its semi-enclosed and semi-pelagic habitat of the Strait and easy access, it can facilitate empirical testing of various hypotheses pertaining to the functional dynamics and processes that shape complex odontocete societies and multi-species assemblages.  By using photo-identification mark-recapture and quantitative geo-spatial techniques, this study investigates intra-specific socio-behavioural dynamics, inter-specific interactions, and the relationships between the species and their habitat.  With multi-state population models we estimate population parameters while with the application of socio-ecological modeling techniques we quantify population structure and model socio-behavioural dynamics, and undertake the task of unraveling the intricacies of sympatric coexistence.  This study advances our understanding of the ecology of group-living of large marine vertebrates, the ecology of sympatricity and the socio-ecological processes that shape the functional structure of delphinid communities.  It also advances our fundamental understanding of the conservation ecology of vulnerable island-associated cetacean communities, and generates information directly applicable to the ongoing management plan development project for the Tañon Strait Protected Seascape – a regional initiative of high conservation significance.

This study received initial funding support from the Research Grants Council (RGC) of Hong Kong (grant RGC-GRF: HKU 768511M) and the Faculty of Science of the University of Hong Kong; and is currently supported with funding from the Research Department of Ocean Park Corporation, Hong Kong.  

© Carmen Or

Population ecology, genetics and socio-dynamics of Heaviside's (Benguela) dolphins. 

Heaviside’s dolphins (Cephalorhynchus heavisidii), known also as Benguela dolphins, are endemic to the west coast of southern Africa and among the least known cetaceans.  Our current knowledge lacks in virtually all aspects of their ecology and behavioural biology.  This research project applies genetic and mark-recapture techniques to quantify population parameters and generate reliable population estimates at the southern portion of the species range.  Models of population structure are being currently generated using both mark-recapture and molecular techniques, including patterns of geographic fidelity, dispersal, and population connectivity on a broader regional scale.  Socio-behavioural and demographic dynamics will soon be analysed with modern modelling techniques using photographic sighting histories of individually identifiable animals, while GIS analyses will unravel the spatiotemporal patterns of movement, range and habitat use.  Chemical analyses of tissue samples (currently underway) will provide further assessment of regional geographic structure and baseline data on heavy metal concentrations.  Given the current severe deficiency of data regarding Benguela dolphins, our work will generate a novel, valuable and much needed scientific contribution. 


This project received funding support from the South African National Research Foundation (NRF), International Union for the Conservation of Nature (IUCN) Species Survival Commission,  Andrew W. Mellon Foundation and the Faculty of Science of the University of Hong Kong.

© Leszek Karczmarski

Delphinid social systems: The spinner dolphin model


Spinner dolphins (Stenella longirostris) pose an interesting challenge to the study of delphinid social ecology as they display intraspecific variation in dispersal, genetic structure and social structure across a worldwide distribution in tropical and subtropical waters.  In contrast to pelagic forms of spinner dolphins in the Eastern Tropical Pacific, the majority of other spinner dolphin populations associate with nearshore habitats of islands and atolls, which appear to be related to the predictability of prey along the slopes of the islands and the availability of protective inshore resting habitat in the shallow waters near islands and within atoll lagoons.


Social and population structure of spinner dolphins associated with islands and atolls have been studied in the Society Islands and Hawaiian Archipelago.  Off the main Hawaiian Islands, spinner dolphins have generally a fission-fusion social structure and moderate group sizes comparable to those in the Society Archipelago.  In the far-western Hawaiian Islands, however, at Midway and Kure atolls, spinner dolphins form much larger groups with long-term social affiliates; with group stability greater than other spinner dolphin population studied to date, with philopatry of both sexes and several indicators of socio-ecological dissimilarity across the Hawaiian Island chain.  Our ongoing research utilises our long-term datasets on spinner dolphins from remote atolls of far-western Hawaii and our more recent work in the Red Sea and archipelago systems of western Pacific (e.g. Philippines).  We explore behavioural complexities in spinner dolphin societies and test conceptual socio-ecological framework that relates behavioural plasticity to environmental variation and geographic barriers.

This project received funding support from the National Geographic Society, Pacific Marine Life Foundation and Marisla Foundation; and facility support from the Division of Forestry and Wildlife of the State of Hawaii, Midway Atoll National Wildlife Refuge of the U.S. Fish & Wildlife Service, Oceanic Society and Hurghada Environmental Protection and Conservation Association (HEPCA).

© Leszek Karczmarski

© Leszek Karczmarski

© Cynthia Vanderlip

© Nana Takanawa

This research topic received funding support from the Japan Society for the Promotion of Science (JSPS) and Texas Institute of Oceanography (TIO) of Texas A&M University; and facility support from the Lab of Human Evolution Studies of Kyoto University, Mammal Research Institute and Centre for Wildlife Management of University of Pretoria, Centre for African Ecology of University of the Witwatersrand and The University of Hong Kong.

Comparative mammalian behavioural ecology


Long-term field studies of terrestrial mammals have provided empirical data on the relationship between various tradeoffs of group living and environmental variability.  Several studies suggest that social systems are not fixed features of species and frequently display considerable intraspecific variation.  Studies of carnivore ecology and predator-prey interactions have shown that predators affect the population of prey not only through direct predation but also indirectly through affecting prey behaviour and space use (the 'landscape of fear' theory) and consequently their fitness.  This socio-behavioural and spatio-behavioural variability is generally associated with an equivalent diversity of ecological conditions and appears to be a result of individual attempts to maximize fitness under local environmental constraints.  As information on delphinid ecology accumulates, it is increasingly evident that patterns of behavioural complexity and fundamental ecological dynamics are comparable, sometimes even parallel to terrestrial mammals.  Through collaborative studies that involve terrestrial mammalogists, behavioural and spatial ecologists, we investigate the realm of comparative behavioural ecology and socio-dynamics of group living mammals, both marine and terrestrial.

© Scott Chui

Socio-spatial ecology of African elephants


African elephants (Loxodonta africana) live in one of the most complex mammalian social systems.  This advanced social complexity makes them susceptible to drastic changes in their societal structures due to anthropogenic factors.  With this new research project, conducted in South Africa, we investigate socio-spatial dynamics of elephants in two substantially different type of habitats, the transition zone between Kalahari and Lowveld (Pilanesberg National Park, PNP) and in Associated Private Nature Reserves (APNR) which is part of the largest interconnected bushveld ecosystem in southern Africa. 


With the application of individual photographic identification, we study the behavioural dynamics of social networks of the PNP’s elephants, which is greatly facilitated by the relative accessibility of open areas across most of the park.  Methodologically, this study takes advantage of the photo-identification mark-recapture techniques that have been mastered in similar studies of marine mammals.  Given a sufficiently thorough photo-coverage of each encountered group, the photo-ID technique provides the means for describing the social structure with a bottom-up approach, i.e. from basic dyadic relationships to general social structure, and gaining valuable insights into the structural foundations of the social organisation of Pilanesberg's elephants.  In APNR, which is located west of Kruger National Park, we use long-term satellite-linked tracking data (thanks to our collaboration with ‘Elephants Alive’, a local NGO engaged in research and conservation) to analyse elephant movement and quantify factors affecting their habitat selection.  The knowledge of socio-spatial and key environmental determinants of elephant movements will provide valuable information for parks and reserves, helping with their efforts to minimise potential human-elephant conflicts.  Rooted in both fundamental and applied science, this large-scale study contributes to the rapidly developing field of comparative behavioural ecology and to the advancement of on-the-ground management practices relevant to complex mammalian societies.   




This study received facility support from the Pilanesberg National Park and Copenhagen Zoo (Denmark), while its operational expenses are born exclusively through our individual/private and our Lab’s internal funding.  

DISCOVERY: A photo-identification data management system for  individually recognizable animals.


Individual photographic identification (photo-ID) represents a powerful technique to study behavioural and population ecology of free-ranging animals.  All photo-ID studies require many hours of intensive field surveys and even longer hours of subsequent, labour-intensive processing of photographic material.  Recent advances in digital technology have greatly enhanced the quality and quantity of collected photographic material.  However, fast accumulation of data poses obvious and often considerable obstacles to data management.  DISCOVERY was designed to facilitate this process by providing a user-friendly platform and a comprehensive data-management system to process, store, manage, visualize and analyse all photo-ID information and associated data for single or multi-study site and/or species application.  DISCOVERY assists at all processing/data entry levels from filtering of raw photographic data, file-naming routines, incoming/group matching, individual-ID catalog matching, GPS data extraction, sighting information with environmental, geographic, and numerous user-defined parameters as well as any other user-defined datasheets.  DISCOVERY also provides GIS displays of sighting/individual/effort data and basic analyses of the data with export options to other tools, such as MARK, SOCPROG, etc.  DISCOVERY is adaptable to any species, marine or terrestrial, and particularly useful for maintaining a single database for research projects collecting data at large geographical scales and between multiple research teams working on different databases.  There are a number of dynamic capabilities in DISCOVERY to meet a multitude of project-specific requirements and user-specific needs.  With the increasing concern of human-related impact on populations, quick, efficient and accurate processing of photo-ID data may allow for rapid assessment of potential impacts, and timely responses to possible management issues.




This project received initial funding support from the South African National Research Foundation (NRF) and was subsequently facilitated by operational expenses of Research Grants Council (RGC) GRF grant HKU 768110M and HKU 768511M, the Faculty of Science of the University of Hong Kong and L. Karczmarski's personal funding.

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