Population Of Bottlenose Dolphins Research Articles

Assessing Residency and Site Fidelity in Bottlenose Dolphins: A Literature Review and Bibliometric Analysis

Residency and site fidelity are important parameters in population ecology for many species as they indicate the temporal and spatial use for individuals. Although both terms are clearly different, they are used interchangeably due to lack of clarity in their definitions and the ways to assess them, especially in bottlenose dolphins (Tursiops spp.). Individuals with well-defined patterns of residency and site fidelity may be more vulnerable to anthropogenic disturbances; thus, the study of these parameters may help to better assess such impacts. However, interspecific differences and logistical restrictions for the study of dolphins have prevented consensus. We set out to investigate the factors that have influenced measurements of residency and site fidelity in bottlenose and a set of other dolphin species through a retrospective (~30 y: 1990 to 2019) literature review. We found 117 scientific papers with a two-fold increasing trend approximately every 15 years, with 50% published in only four journals. Most of the studies were developed in the United States, followed by Australia and Europe, likely due to strict policies for marine mammal conservation. Author collaboration network analysis showed highly atomized national groups in which North American organizations formed the biggest cluster, followed by Australia, Africa, and Europe. However, large worldwide gaps still exist, possibly because of the heterogeneity in marine mammal sampling efforts and limited information availability in the North Pacific, Central and South America, Africa, Asia, and the Indian Ocean. We found 30 different classification methods in which 12 were based on defined categories. We provide conceptual aid to distinguish between the use of both terms, as well as guidance to tackle the challenge of defining patterns of temporal use due to the variability of thresholds for classifying individuals. A paradigm shift is needed to create comprehensive, standardized, and generalized assessments of residency and site fidelity, which can be compared based on their performance across different populations of bottlenose dolphins around the world.

An update on the development of a bottlenose dolphin, Tursiops truncatus, immune reagent toolkit

There are extensive immunological reagents available for laboratory rodents and humans. However, for veterinary species there is a need for expansion of immunological toolkits, with this especially evident for marine mammals, such as cetaceans. In addition to their use in a research setting, immune assays could be employed to monitor the health status of cetaceans and serve as an adjunct to available diagnostic tests. Such development of specific and sensitive immune assays will enhance the proper care and stewardship of wild and managed cetacean populations. Our goal is to provide immune reagents and immune assays for the research community, clinicians, and others involved in care of bottlenose dolphins. This review will provide an update on our development of a bottlenose dolphin immunological toolkit. The future availability and continued development of these reagents is critical for improving wild and managed bottlenose dolphin population health through enhanced assessment of their responses to alterations in the marine environment, including pathogens, and improve our ability to monitor their status following vaccination.

Population distribution and drivers of habitat use for the Burrunan dolphins, Port Phillip Bay, Australia.

Bottlenose dolphin (Tursiops) populations, also described as the Burrunan dolphins, consist of a resident population of approximately 150 individuals in Port Phillip Bay (PPB), Victoria. Previous reports indicate distribution across a small southern region of PPB; however, little is known about their full distribution patterns across the entire PPB region. Here, we investigate the spatiotemporal distribution of the Burrunan dolphins across four zones representative of PPB benthic habitats and bathymetry to gain a better understanding of the potential drivers of the population's habitat use. Port Phillip Bay, Victoria, Australia. One hundred and twenty-nine boat-based surveys were undertaken between March 2015 and August 2021, encompassing 181 sightings. Generalised linear models (GLMs) were used to investigate annual, seasonal and zonal variation. We found no variation in sighting frequencies between years. Austral summer and winter had a significantly higher sighting frequency than autumn. We found that Burrunan dolphins utilise the entire bay, further extending the species range, and show a significantly higher number of sightings in the southern zone than in any other zones. Overlaying dolphin sightings with known oceanographic characteristics within PPB, we found bathymetry and benthic habitats were potential drivers for the Burrunan dolphins distribution and habitat use within the bay, with the dolphins significantly favouring the 5-10 and 10-15 m contour depths. These results show a more widespread distribution across the bay than previously documented. We recommend expansion of the current marine protected areas in the north and south of the bay. This study has increased our understanding of the vital habitat for the Burrunan dolphin populations. By providing evidence-based conservation recommendations, we hope to improve and contribute to future research, conservation management plans and effective marine protected areas across PPB for the resident Burrunan dolphin population.

Photo-Identification and Skin Lesion Prevalence of Bottlenose Dolphins (Tursiops erebennus) in the Waters of New York and New Jersey

Cetaceans can serve as sentinel species in marine environments as long-lived, apex predators that can concentrate environmental contaminants with potential health consequences. Thus, monitoring the well-being of these species may provide an additional indicator of ecosystem health. In cetaceans, one method for assessing individual and population health is by examining skin conditions. For decades, skin lesions have been increasingly documented in coastal populations of bottlenose dolphins (Tursiops spp.) worldwide. Lesion presence can indicate diminished health and may reflect environmental stressors. Herein, we document the prevalence of epidermal lesions/marks in bottlenose dolphins from the waters off New York and New Jersey during their seasonal presence from spring to fall. Photographs of distinct individuals sighted from May to October 2017 to 2021 were compiled into a catalog, and skin lesions were categorized and counted. Annually, the lowest skin lesion prevalence was in 2021 (p = 0.31), and the highest was in 2017 (p = 0.81). By month, prevalence generally decreased from spring to fall. Overall lesion prevalence in this population was higher than reported estimates for other populations in the coastal waters of the United States. The five most common categories were cloudy white spots, dark spots, white amorphous lesions, tattoo lesions, and dark fringe lesions; and the three most common groups were potentially pathogenic lesions, hypopigmentation, and rake mark-associated potentially pathogenic lesions. Some of the observed lesions have been associated with viral infections that may be exacerbated by environmental stressors. This research establishes an important baseline for further studies into bottlenose dolphin population health in and around the New York–New Jersey Harbor Estuary, particularly given the continued expansion of anthropogenic activities, including those related to forthcoming offshore wind development.

Potential Residence and Coexistence Strategy of Tursiops truncatus in a Coastal Lagoon in the Southern Gulf of Mexico: Ecological Inferences Using Stable Isotopes

AbstractThe Terminos Lagoon Flora and Fauna Protection Area is the largest coastal lagoon in the southern Gulf of Mexico and has the largest population of bottlenose dolphins, Tursiops truncatus, reported in the region. Photo identification studies have reported permanent and seasonal residence of dolphins; however, how dolphins coexist ecologically is unknown. In the present study, from 17 dead specimens stranded on the coast of Isla del Carmen (barrier island) between 2014 and 2016, stable isotopes in the liver, heart, and muscle, which represent different time scales, were analyzed to determine residence through δ13C values and niche width and trophic coexistence through δ15N values. Differences between sexes (δ13C liver: p = 0.009; heart: p = 0.01) and age classes (δ15N muscle: p = 0.02) were found, which indicated trophic sexual segregation and changes in resource use during growth, respectively. The lack of significant differences in δ13C values indicated isotopic equilibrium between the tissues, indicating the possible permanent residence of 12 dolphins in Terminos Lagoon as a coastal ecotype (− 16‰) and a second group (five dolphins) as an oceanic ecotype (− 18‰). In conclusion, most dolphins stranded in the Terminos Lagoon are potential permanent residents of this habitat, with evidence of resource partitioning as a coexistence strategy.

Evidence of geographic variation in the non-signature whistle repertoires of two isolated populations of New Zealand common bottlenose dolphin

ABSTRACT Dolphins are social animals that depend on sound to communicate, navigate, and find food. The aim of our research was to describe dolphin whistle characteristics and compare whistles between two isolated populations of bottlenose dolphins in New Zealand. We focused on three aspects of dolphin bioacoustics (1) classification of whistles; (2) comparison of the whistles of two discrete bottlenose dolphin populations; and (3) comparison of whistles of dolphin populations from around the world. At Great Barrier Island, the most common type of whistle was upsweep followed by sine, while at Doubtful Sound, convex and sine whistles were the most common whistle types. Random Forest models discriminated between whistles from the two populations with an estimated accuracy of 90%. The key differences were whistle-type contour, duration, and end frequency. Linear Mixed models show that whistle acoustic parameters were influenced by location but not by group size or the presence of immatures. Whistle parameters of both populations fell within the range of multiple populations from around the world. This studyprovides a benchmark for future research into drivers of geographic variation in dolphin vocal communication.

Evidence of a small, island-associated population of common bottlenose dolphins in the Mariana Islands

Small, island-associated populations of cetaceans have evolved around numerous oceanic islands, likely due to habitat discontinuities between nearshore and offshore waters. However, little is known about the ecology and structure of cetacean populations around the Mariana Islands, a remote archipelago in the western Pacific Ocean. We present sighting, photo-identification, and genetic data collected during twelve years of surveys around these islands that reveal the existence of a small, island-associated population of bottlenose dolphins. Nearly half of the photo-identified individuals were encountered in more than one year. Both haplotypic and nuclear genetic diversity among sampled individuals was low (haplotypic diversity = 0.701, nuclear heterozygosity = 0.658), suggesting low abundance. We used mark-recapture analysis of photo-identification data to estimate yearly abundance in the southern portion of the population’s range from 2011 to 2018. Each abundance estimate was less than 54 individuals, with each upper 95% confidence interval below 100. Additional survey effort is necessary to generate a full population abundance estimate. We found extensive introgression of Fraser’s dolphin DNA into both the mitochondrial and nuclear genomes of the population, suggesting at least two hybridization events more than two generations in the past. The Mariana Islands are used extensively by the U.S. military for land and sea training operations. Thus, this unique bottlenose dolphin population likely faces high exposure to multiple threats.

Finite mixtures in capture-recapture surveys for modeling residency patterns in marine wildlife populations.

This work aims to show how prior knowledge about the structure of a heterogeneous animal population can be leveraged to improve the abundance estimation from capture-recapture survey data. We combine the Open Jolly-Seber model with finite mixtures and propose a parsimonious specification tailored to the residency patterns of the common bottlenose dolphin. We employ a Bayesian framework for our inference, discussing the appropriate choice of priors to mitigate label-switching and nonidentifiability issues, commonly associated with finite mixture models. We conduct a series of simulation experiments to illustrate the competitive advantage of our proposal over less specific alternatives. The proposed approach is applied to data collected on the common bottlenose dolphin population inhabiting the Tiber River estuary (Mediterranean Sea). Our results provide novel insights into this population's size and structure, shedding light on some of the ecological processes governing itsdynamics.

The social behaviour of the common bottlenose dolphin Tursiops truncatus (Montagu, 1821) in the coastal waters of Lampedusa Island (Strait of Sicily, Italy)

Abstract Research on social structure and residency provides important information on the dynamics of a population, improving knowledge of the species' behaviour and ecology. This study investigated the social network, site fidelity, and residency patterns of common bottlenose dolphins (Tursiops truncatus) off Lampedusa Island. Direct visual detection and photo‐identification methods were used to collect data during 124 boat‐based surveys conducted from 2013 to 2020. A total of 117 groups (mean size 4.5 ± 3.3) were sighted; 73 well‐marked animals were identified, of which 59% were resighted over the years. The estimate of social differentiation was 0.72 (SE = 0.07), suggesting differentiated social groups within the community. Data were somewhat representative of the true social system, as the correlation coefficient was close to 0.4. However, the half‐weight index averaged 0.07 (±0.03), indicating individuals' low tendency to associate. Five social clusters were identified with strong relationships between individuals within each cluster, in which 94% of maximum association indices were ≥0.4. The data also highlighted preferred and avoided associations and stable relationships. The removal of individuals with the highest values of strength and eigenvector centrality from the network did not affect its connectivity, suggesting inherent robustness. Despite the different levels of site fidelity among individuals, the results indicated rather high levels of yearly sighting rate. Temporary migration into and out of the area shown by this study indicates that Lampedusa coastal waters are an important, regularly used bottlenose dolphin habitat. These results suggest extensive ranging behaviour, which implies the need for networking between institutions and organizations from the various states bordering the Strait of Sicily to address conservation efforts and inform regional management of the Mediterranean bottlenose dolphin population.

Using citizen science data to assess the vulnerability of bottlenose dolphins to human impacts along England's South Coast

AbstractCoastal bottlenose dolphin populations are highly vulnerable due to their small population sizes and proximity to human activities. Long‐term studies in the UK have monitored populations protected within Special Areas of Conservation (SACs) since the 1990s, but a small community of bottlenose dolphins inhabiting the coastal waters of southern England has received much less attention. The English Channel is one of the most heavily impacted marine ecosystems worldwide and increasing anthropogenic pressures pose a severe threat to the long‐term viability of this population. Conservation measures to protect these animals have been hindered by a lack of knowledge of population size, distribution and ranging behaviour. This study aimed to fill these knowledge gaps. A citizen science sighting network yielded 7458 sighting reports of bottlenose dolphins between 2000 and 2020. Resightings of identified individuals were used to estimate abundance, distribution, and ranging behaviour. Social structure analysis revealed a discrete interconnected group of animals in shallow coastal waters, which did not appear to mix with conspecifics identified further offshore. A Bayesian multi‐site mark–recapture analysis estimated that this population comprises around 48 animals (CV = 0.18, 95% HPDI = 38–66). These dolphins ranged between North Cornwall and Sussex, with an average individual range of 530 km (68–760 km). Areas of high‐modelled habitat suitability were found to overlap with high levels of anthropogenic pressure, with pollution and boat traffic identified as the most pervasive threats. Although adult survival rates indicated that the population was relatively stable from 2008 to 2019 (0.945 (0.017 ± SE)), the small population size implies a significant risk to their long‐term viability and resilience to environmental change. By highlighting the most deleterious anthropogenic activities and regions of conservation significance, our results will be useful for developing management policies for threat mitigation and population conservation, to protect this vulnerable group of dolphins.

Dolphins from a prehistoric midden imply long-term philopatry of delphinids around Tokyo Bay

Abstract Cetaceans of the family Delphinidae are widely distributed throughout the global ocean, and it has been suggested that females exhibit philopatry. However, the duration of time that a maternal group of these highly mobile creatures spends inhabiting a particular region remains unknown. The objective of this study is to examine the genetic diversity of delphinids in the past and to shed light on the above question. In this study, we amplified and sequenced the mitochondrial DNA D-loop region from the skeletal remains of delphinids that were excavated from the Shomyoji Midden, a site situated on the western coast of Tokyo Bay and dating to 5000–3000 years before the present. We acquired prehistoric D-loop sequences of seven bottlenose dolphins, six Pacific white-sided dolphins, and a false killer whale. Notably, one or more haplotypes from the prehistoric individuals were detected in the geographically proximate modern conspecific populations across all three species. Whilst the genetic diversity of prehistoric and modern Pacific white-sided dolphin populations appears to be comparable, the modern bottlenose dolphin population demonstrates significantly lower genetic diversity when compared to its prehistoric counterpart in the vicinity of Tokyo Bay. The maternal groups of these species are speculated to have persisted in the same habitat for at least 4000 years.

Areas of spatial overlap between common bottlenose dolphin, recreational boating, and small-scale fishery: management insights from modelling exercises.

Sustainable management requires spatial mapping of both species distribution and human activities to identify potential risk of conflict. The common bottlenose dolphin (Tursiops truncatus) is a priority species of the European Union Habitat Directive, thus, to promote its conservation, the understanding of habitat use and distribution, as well as the identification and spatial trend of the human activities which may directly affect populations traits, is pivotal. A MaxEnt modeling approach was applied to predict the seasonal (from April to September) habitat use of a small population of bottlenose dolphins in the north-western Sardinia (Mediterranean Sea) in relation to environmental variables and the likelihoods of boat and fishing net presence. Then, the overlapping areas between dolphin, fishing net and boat presence were identified to provide insights for the marine spatial management of this area. Three of the main factors influencing the seasonal distribution of bottlenose dolphins in the area are directly (boating and fishing) or indirectly (ocean warming) related to human activities. Furthermore, almost half of the most suitable area for dolphins overlapped with areas used by fishing and boating. Finally, relying on fishing distribution models, we also shed light on the potential impact of fishing on the Posidonia oceanica beds, a protected habitat, which received higher fishing efforts than other habitat types. Modelling the spatial patterns of anthropogenic activities was fundamental to understand the ecological impacts both on cetacean habitat use and protected habitats. A greater research effort is suggested to detect potential changes in dolphin habitat suitability, also in relation to ocean warming, to assess dolphin bycatch and the status of target fish species, and to evaluate sensitive habitats conditions, such as the Posidonia oceanica meadow.

Assessing spatial patterns and density of a dolphin population through signature whistles

AbstractSome dolphin species produce signature whistles, which may allow the identification of individual dolphins using passive acoustic monitoring (PAM). Identifying individuals by their sounds may enhance the opportunities for monitoring and addressing biological and ecological questions about these species. Here, we explored the potential of signature whistles to investigate ecological aspects of a resident bottlenose dolphin population. Using a limited data set, with few individuals recognized by signature whistles, combined with spatial capture‐recapture (SCR) methods, we investigated how effective such approach is describing spatial use patterns and estimating density for this population. The data were collected using 4–6 stationary bottom‐moored recorders. Since only eight signature whistles were identified, our density estimate may represent a subset of the entire population. However, even with only a few signature whistles identified, our results confirmed the center of the core area used by these dolphins as the area with the highest encounter probability. In addition, our results provided evidence that these dolphins have the same spatial use pattern at night as during the day. This study shows that SCR analysis of signature whistle data can improve our ecological knowledge and understanding of dolphin populations.

Using ecotourism boats for estimating the abundance of a bottlenose dolphin population in south-eastern Australia.

It is challenging to collect robust, long-term datasets to properly monitor the viability and social structure of large, long-lived animals, especially marine mammals. The present study used a unique long-term dataset to investigate the population parameters and social structure of a poorly studied population of bottlenose dolphins (Tursiops sp.) in southern Port Phillip Bay, south-eastern Australia. Photo-identification images have been collected between 2012-2022 both opportunistically and following a protocol by patrons, staff, and volunteers of ecotourism companies using their vessels as platforms. The resulting large dataset was available to be processed through the online platform Flukebook and used in capture recapture models to estimate abundance and demographic parameters. In addition, the social structure of the population and the reproductive parameters were investigated. The marked adult population abundance (45.2 ± 2.7 individuals) was found to be stable over the last decade and the calving rate ranged between 0.06-0.19 new calves per identified individuals per year, while the inter-birth interval was 3.7 ± 0.8 years. Social analysis suggested the population has a fission-fusion structure with no apparent clusters. The stability of the population over the study period suggests no deleterious effect of anthropogenic or environmental factors during the last decade. This study is the outcome of the effort of the ecotourism organisations and the results obtained, along with their similarity to those of other dolphin populations worldwide, highlight the importance of such data sources for long-term information that would otherwise be too expensive or logistically difficult to obtain.

Distribution of small cetaceans within a candidate Special Area of Conservation; implications for management

Information on cetacean distribution plays an important role in the identification of suitable boundaries for marine protected areas, but is also crucial for developing management and monitoring programmes. In response to the European ‘Habitats Directive’, a candidate Special Area of Conservation (cSAC) has been established in the Moray Firth, northeast Scotland to protect a small and isolated population of common bottlenose dolphins (Tursiops truncatus). Limited data on the distribution of bottlenose dolphins and on temporal changes in distribution have recently constrained attempts to mitigate against the impacts of new developments upon this population. In response to the need for current information on the distribution of dolphins throughout the cSAC, this study aims to provide data on the distribution of dolphins and other small cetaceans throughout the Moray Firth. Changes in the distribution patterns of dolphins in the inner Moray Firth were examined using data collected between 1990 and 2000. In addition, combined passive acoustic and visual survey techniques were used to determine the distribution of dolphins and harbour porpoises (Phocoena phocoena) on a broader scale across the whole Moray Firth. Dolphin schools were distributed throughout the inner Moray Firth, but there were concentrations of sightings around three deep, narrow channels that were consistent over the ten year study period. Results from surveys across the whole of the Moray Firth showed that all sightings and acoustic detections of dolphins were made within the area of the cSAC. In contrast, porpoise sightings were widely distributed throughout the Moray Firth. The median encounter rate of porpoises across the whole Moray Firth was 1.69 per 100km. Encounter rates of porpoises were similar in the outer Moray Firth and the cSAC. This combination of distribution studies at differing spatial scales provides a valuable tool for monitoring the distribution of animals and identifying important habitats, and the results of this study have directly supported efforts to manage the cSAC.

An expert-based system to predict population survival rate from health data.

Timely detection and understanding of causes for population decline are essential for effective wildlife management and conservation. Assessing trends in population size has been the standard approach, but we propose that monitoring population health could prove more effective. We collated data from 7 bottlenose dolphin (Tursiops truncatus) populations in the southeastern United States to develop a method for estimating survival probability based on a suite of health measures identified by experts as indices for inflammatory, metabolic, pulmonary, and neuroendocrine systems. We used logistic regression to implement the veterinary expert system for outcome prediction (VESOP) within a Bayesian analysis framework. We fitted parameters with records from 5 of the sites that had a robust network of responders to marine mammal strandings and frequent photographic identification surveys that documented definitive survival outcomes. We also conducted capture-mark-recapture (CMR) analyses of photographic identification data to obtain separate estimates of population survival rates for comparison with VESOP survival estimates. The VESOP analyses showed that multiple measures of health, particularly markers of inflammation, were predictive of 1- and 2-year individual survival. The highest mortality risk 1year following health assessment related to low alkaline phosphatase (odds ratio [OR]=10.2 [95% CI: 3.41-26.8]), whereas 2-year mortality was most influenced by elevated globulin (OR=9.60 [95% CI: 3.88-22.4]); both are markers of inflammation. The VESOP model predicted population-level survival rates that correlated with estimated survival rates from CMR analyses for the same populations (1-year Pearson's r=0.99, p=1.52×10-5 ; 2-year r=0.94, p=0.001). Although our proposed approach will not detect acute mortality threats that are largely independent of animal health, such as harmful algal blooms, it can be used to detect chronic health conditions that increase mortality risk. Random sampling of the population is important and advancement in remote sampling methods could facilitate more random selection of subjects, obtainment of larger sample sizes, and extension of the approach to other wildlife species.

Not only wide range shifts: Marine warming and heat waves influence spatial traits of a mediterranean common bottlenose dolphin population

Understanding to what extent the living world will be affected by climate change is still to be achieved, especially in the sea. Thus, exploring in marine species the direction and timing of shifts in space use and movements related to climate changes should be considered a priority. In the present study, through a correlative approach, we investigated the influence of temperature and marine heat waves (MHWs) on the spatial traits (local occurrence and home range) of a small common bottlenose dolphin population in the Mediterranean Sea by analyzing 560 sightings from 2013 to 2020. The increase in sea surface temperature (SST) negatively influenced both dolphin occurrence and group size in the study area. Furthermore, regardless of the sex and social unit to which the animals belong, in July–September 2017–2020 individual home range size increased threefold (on average from 5 to 15 km2) compared to 2013–2016, when SST was on average 1.34 °C lower and MHWs shorter of 29 days/year. These results can help forecasting the range of consequences of warming effects and to assist local management efforts, in terms of marine protected areas design and management, suggesting that an integrated multi-level approach that examines the influence of warming on dolphin spatial traits together with the abundance and distribution of prey populations and ecological status of foraging habitats (such as the seagrass beds) could be useful in mitigating the effects of climate change on coastal dolphins.

A note on divergent mtDNA lineages of bottlenose dolphins from coastal waters of southern Australia

Bottlenose dolphins have a global distribution throughout tropical and temperate waters, both inshore and offshore. Many studies demonstrate the existence of at least two Tursiops species: Tursiops truncatus, consisting of inshore and offshore eco-types and T. aduncus, a coastal Indo-Pacific type known to extend south into temperate waters down the east coast of Australia. To clarify the taxonomic status of two populations (Port Phillip Bay and Gippsland Lakes) of coastal bottlenose dolphins along Australia’s south coast (Victoria), a 346bp region of the mitochondrial-DNA (mtDNA) control region was sequenced from ten individuals and they were incorporated into phylogenetic analyses involving published sequences of other Tursiops spp., Stenella spp. and Delphinus spp., found worldwide. Both neighbour-joining and maximum parsimony trees place Victorian coastal haplotypes in a highly-supported group separate to those from the other dolphins, including those from the southern part of the Australian eastern coast. Victorian haplotypes are least divergent from T. truncatus (average 5.5%) and most divergent from T. aduncus (9.1%), with intermediate levels of divergence from Stenella and Delphinus spp. These data suggest that the Victorian coastal dolphins, similar to other world-wide coastal populations, are genetically unique, long isolated and therefore likely to be locally adapted. This has important implications for management and conservation.

Effects of dolphin-swim activities on the behaviour of an Indo-Pacific bottlenose dolphin population off the south coast of Mozambique

Swim-with-dolphin (SWD) activities are popular but can negatively impact target populations. It is important to consider the behavioural responses of dolphins, and quantify the impact on individuals and populations, as well as maximise opportunities for sustainable tourism that benefits socio-economic growth while encouraging pro-environmental behaviour. This is of relevance in `developing countries, where ecological studies are scarce and tourism industries may have developed before science-based management measures were implemented.This study aimed to determine the effects of SWD tourism on the behaviour of resident Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the Ponta do Ouro Partial Marine Reserve (PPMR), Mozambique. Markov-chain models were used to describe dolphin behaviour transition probabilities in different tourism contexts between 2007 and 2009 (low tourism) and 2017–2019 (high tourism). Results detected significant short-term changes in the behaviours of dolphins. In the early years (2007–2009), dolphins were likely to remain in their preceding behaviour if they were resting, travelling, and foraging. However, for later years (2017–2019) this only occurred if they were travelling. Overall, after tourist swims, and under both tourism contexts, dolphins were more likely to travel and less likely to socialise, rest, or forage. The findings raise concerns that, despite current management measures, SWD activities still affect dolphin behaviour and impose short-term negative effects to their activity budget. Our study recommends time- and area-closures, speed restrictions, and mandatory training programmes to all SWD staff. Given that SWD and whale-watching activities take place along the coast of Mozambique, national regulations are urgently needed to minimise potential long-term negative effects on cetacean populations.

Delphinids of southern Africa: A review of their distribution, status and life history

Eighteen species of delphinids have been recorded from Africa, south of l 7°S. This review includes analyses of the distribution and status, life history and feeding habits for each species, primarily using published data from strandings, incidentally caught animals and sightings. Although there is little known for most of the species distributed over the continental shelf, it appears that there is presently little human-induced threat to these. However, more research emphasis should in future be placed on possible detrimental interactions due to overfishing of delphinid prey stocks. Increased commercial fishing pressure will inevitably also increase interactions between the fishery and the affected delphinids. Only three inshore species are presently considered to be vulnerable: Heaviside's dolphins (Cephalorhynchus heavisidil), bottlenose dolphins (Tursiops truncatus) in KwaZulu-Natal and Namibia, and Inda-Pacific hump-backed dolphins (Sousa chinensis) in KwaZulu-Natal. Heaviside's dolphins are endemic and, although presently probably able to sustain mortalities following interactions with commercial fishing gear, may become negatively impacted should fishing activities increase. The bottlenose dolphin population in Namibia appears localised in its distribution and may therefore also be vulnerable to any future coastal development or commercial fishery expansions, while in KwaZulu-Natal they are subjected to ongoing incidental catches in shark nets, heavy pollution levels, habitat destruction and increased competition with fishermen for limited food resources. In KwaZulu-Natal, Inda-Pacific hump-backed dolphins are subjected to the same pressures as experienced by bottlenose dolphins, albeit more severely, while in Mozambique it is occasionally caught incidentally in gillnets or in a targeted fishery. Although generally considered an offshore species, southern right whale dolphins (Lissodelphis peronii) also appears to be extremely localised in distribution within southern Africa, and any future planned expansion of commercial driftnet fisheries off Namibia should be carefully monitored for incidental catches which may impact this population.