Hector's Dolphins Research Articles

New Insights Into the Population Structure of Hector's Dolphin (Cephalorhynchus hectori) Revealed Using Environmental DNA

ABSTRACTEnvironmental DNA (eDNA) is frequently used for detecting species and describing biodiversity through metabarcoding techniques. More recently, there has been emerging evidence that eDNA can be used to investigate intraspecific variability, providing novel pathways to explore population genetics questions. However, it can be difficult to distinguish between true intraspecific variation and PCR/sequence error, and the presence of DNA from multiple individuals makes using traditional frequency‐based approaches challenging. Here, we explore how eDNA can be used to investigate population structure of Hector's dolphin (Cephalorhynchus hectori), an endemic, endangered, and culturally important (taonga) species. In doing so, we present a simple and effective method to filter out noise due to PCR/sequence error and show how treating haplotype detections equally can provide similar results to frequency‐based approaches from traditional sampling methods. Over the 2022/23 Austral summer, we collected 85 water samples close to Hector's dolphins, and three negative controls, across three areas on the east coast of Aotearoa New Zealand's South Island: Banks Peninsula (n = 41), Timaru (n = 33), and Dunedin (n = 14). We targeted a 348 bp region of the cetacean D‐loop in the mitochondrial DNA (mtDNA) and obtained positive detections in 68 (77%) water samples, confidently identifying seven haplotypes across the study area. The occurrence of specific haplotypes and the overall frequencies in Banks Peninsula and Timaru matched well with previous tissue‐based studies and were similar to other East Coast South Island (ECSI) subpopulations. In Dunedin, however, our results indicate a closer relationship to South Coast populations, suggesting that the membership within the ECSI population be reconsidered, which has implications for how this subpopulation is managed. We show that eDNA sampling can be used to elucidate matrilineal population structure for Hector's dolphin and provide a simple method that could be applied to other eDNA‐based studies of any taxa.

Testing spatial transferability of species distribution models reveals differing habitat preferences for an endangered delphinid (Cephalorhynchus hectori) in Aotearoa, New Zealand.

Species distribution models (SDMs) can be used to predict distributions in novel times or space (termed transferability) and fill knowledge gaps for areas that are data poor. In conservation, this can be used to determine the extent of spatial protection required. To understand how well a model transfers spatially, it needs to be independently tested, using data from novel habitats. Here, we test the transferability of SDMs for Hector's dolphin (Cephalorhynchus hectori), a culturally important (taonga) and endangered, coastal delphinid, endemic to Aotearoa New Zealand. We collected summer distribution data from three populations from 2021 to 2023. Using Generalised Additive Models, we built presence/absence SDMs for each population and validated the predictive ability of the top models (with TSS and AUC). Then, we tested the transferability of each top model by predicting the distribution of the remaining two populations. SDMs for two populations showed useful performance within their respective areas (Banks Peninsula and Otago), but when used to predict the two areas outside the models' source data, performance declined markedly. SDMs from the third area (Timaru) performed poorly, both for prediction within the source area and when transferred spatially. When data for model building were combined from two areas, results were mixed. Model interpolation was better when presence/absence data from Otago, an area of low density, were combined with data from areas of higher density, but was otherwise poor. The overall poor transferability of SDMs suggests that habitat preferences of Hector's dolphins vary between areas. For these dolphins, population-specific distribution data should be used for conservation planning. More generally, we demonstrate that a one model fits all approach is not always suitable. When SDMs are used to predict distribution in data-poor areas an assessment of performance in the new habitat is required, and results should be interpreted with caution.

Using passive acoustic monitoring to assess the overlap between endemic endangered Hector's dolphin (Cephalorhynchus hectori hectori) and mussel farms in the Banks Peninsula Marine Mammal Sanctuary, New Zealand

Abstract Aquaculture has maintained a sustained growth trend over the last 50 years, worldwide and in Aotearoa New Zealand. This industry is known to have environmental consequences, such as impacts on benthos, water column and higher trophic levels. Some of these impacts have been thoroughly studied, while others, such as the effects on cetaceans, are not well understood. This study used passive acoustic monitoring (PAM) to assess, for the first time, the overlap between kūtai—New Zealand greenlipped mussel (Perna canaliculus)—farms and habitat use by endemic endangered Hector's dolphins (Cephalorhynchus hectori hectori) within the Banks Peninsula Marine Mammal Sanctuary. T‐PODs were deployed in six bays, three with mussel farms and three without, between 2018 and 2019. Occurrence of dolphins, expressed as ‘dolphin positive minutes per day’ (DPM/day), was modelled using generalized linear mixed models. Results showed a strong interaction between farm (presence/absence) and season (summer/winter), with fewer acoustic detections of dolphins in winter if farms were present. Furthermore, in bays with mussel farms, there were significantly more click train detections on the opposite side of the bay, compared to the side by the mussel farm. Considering that results from this study suggest potential displacement of the dolphins due to the mussel farms, the recommendation is a precautionary approach. Further expansion of aquaculture in Hector's dolphin habitat should be done carefully, taking into account their habitat use, and conducting intensive monitoring including a robust ‘before and after’ design prior to the establishment of new farms.

Multi‐disciplinary surveys reveal a small subpopulation of Hector's dolphins is frequently exposed to the risk of bycatch

Abstract Hector's dolphin (Cephalorhynchus hectori) is an endangered species endemic to the coastal waters of Aotearoa New Zealand. To address the unsustainable bycatch of Hector's dolphins, restrictions on commercial gillnetting within 4 nautical miles of the coast were implemented in 2008, covering most of the South Island's east and south coasts. A small subpopulation of Hector's dolphins, estimated at 42 (95% CI: 19–92) in 2012, is located off Dunedin, on the south‐east coast of the South Island. It is known from other locations that Hector's dolphins are distributed well beyond 4 nautical miles from the coast and hence are vulnerable to ongoing gillnetting. In this study, a combination of boat‐based surveys, passive acoustic monitoring (PAM) and analysis of fishing effort were used to generate an up‐to‐date abundance estimate for Hector's dolphins off Dunedin and assess their vulnerability to commercial fishing. In the summer of 2021, abundance was estimated at 41 individuals (95% CI = 31–54), providing no evidence for population change since 2012. Analysis of visual sighting data indicated ongoing overlap between Hector's dolphins and commercial fishing effort. Using PAM, Hector's dolphins were detected on 94% of days at a location approximately 0.3 nautical miles from the coast, suggesting that shallow waters provide critical habitat for these dolphins year‐round. At an offshore mooring, approximately 4.5 nautical miles from the coast and therefore outside the area in which gillnetting is prohibited, detections were made on 35% of days, indicating potential for direct overlap with commercial fisheries. The inherent vulnerability of small populations to extinction highlights the need to take a precautionary approach to the management of Dunedin's Hector's dolphins if population recovery is to be facilitated.

Hector's dolphins (Cephalorhynchus hectori) produce both narrowband high-frequency and broadband acoustic signals.

Odontocetes produce clicks for echolocation and communication. Most odontocetes are thought to produce either broadband (BB) or narrowband high-frequency (NBHF) clicks. Here, we show that the click repertoire of Hector's dolphin (Cephalorhynchus hectori) comprises highly stereotypical NBHF clicks and far more variable broadband clicks, with some that are intermediate between these two categories. Both NBHF and broadband clicks were made in trains, buzzes, and burst-pulses. Most clicks within click trains were typical NBHF clicks, which had a median centroid frequency of 130.3 kHz (median -10 dB bandwidth = 29.8 kHz). Some, however, while having only marginally lower centroid frequency (median = 123.8 kHz), had significant energy below 100 kHz and approximately double the bandwidth (median -10 dB bandwidth = 69.8 kHz); we refer to these as broadband. Broadband clicks in buzzes and burst-pulses had lower median centroid frequencies (120.7 and 121.8 kHz, respectively) compared to NBHF buzzes and burst-pulses (129.5 and 130.3 kHz, respectively). Source levels of NBHF clicks, estimated by using a drone to measure ranges from a single hydrophone and by computing time-of-arrival differences at a vertical hydrophone array, ranged from 116 to 171 dB re 1 μPa at 1 m, whereas source levels of broadband clicks, obtained from array data only, ranged from 138 to 184 dB re 1 μPa at 1 m. Our findings challenge the grouping of toothed whales as either NBHF or broadband species.

Peale's dolphins (Lagenorhynchus australis) are acoustic mergers between dolphins and porpoises

Most dolphin species produce broadband clicks for echolocation (i.e., biosonar pulses), and whistles and burst-pulsed calls for communication purposes. A few dolphin species in the southern hemisphere are reported to only produce clicks of a more narrowband high-frequency (NBHF) type, very similar to the clicks produced by porpoises. Here, we use underwater acoustic recordings of Peale's dolphins (Lagenorhynchus australis) in the Falkland Islands to show that they also can produce broadband clicks and tonal whistle sounds similar to other whistling odontocete species in addition to NBHF clicks. Whistles and broadband clicks co-occurred in seven out of twelve acoustic encounters with Peale's dolphins. The co-occurrence of whistles and broadband signals, which were predominately burst-pulses, produced by Peale's dolphins in this study points to a probable function as communication signals. Furthermore, the measured frequency and time parameters of Peale's dolphin whistles were comparable with whistles recorded from four additional species in the Lagenorhynchus genus in various parts of their ranges. This is the only species of Lagenorhynchus recorded to date that can relax acoustic crypsis in a similar manner as Heaviside's (Cephalorhynchus heavisidii), Commerson's (C. commersonii), and Hector's (C. hectori) dolphins. Our findings make it likely that additional NBHF species have the ability to generate both pulsed signal types and whistles, and further challenges the acoustic classification of NBHF species.

Using epigenetic clocks to investigate changes in the age structure of critically endangered Māui dolphins.

The age of an individual is an essential demographic parameter but is difficult to estimate without long-term monitoring or invasive sampling. Epigenetic approaches are increasingly used to age organisms, including nonmodel organisms such as cetaceans. Māui dolphins (Cephalorhynchus hectori maui) are a critically endangered subspecies endemic to Aotearoa New Zealand, and the age structure of this population is important for informing conservation. Here we present an epigenetic clock for aging Māui and Hector's dolphins (C. h. hectori) developed from methylation data using DNA from tooth aged individuals (n = 48). Based on this training data set, the optimal model required only eight methylation sites, provided an age correlation of .95, and had a median absolute age error of 1.54 years. A leave-one-out cross-validation analysis with the same parameters resulted in an age correlation of .87 and median absolute age error of 2.09 years. To improve age estimation, we included previously published beluga whale (Delphinapterus leucas) data to develop a joint beluga/dolphin clock, resulting in a clock with comparable performance and improved estimation of older individuals. Application of the models to DNA from skin biopsy samples of living Māui dolphins revealed a shift from a median age of 8-9 years to a younger population aged 7-8 years 10 years later. These models could be applied to other dolphin species and demonstrate the ability to construct a clock even when the number of known age samples is limited, removing this impediment to estimating demographic parameters vital to the conservation of critically endangered species.

Vessel traffic influences distribution of Aotearoa New Zealand's endemic dolphin (Cephalorhynchus hectori)

AbstractCetacean tourism and vessel traffic have grown considerably around the world in recent decades. At Akaroa Harbor, Aotearoa New Zealand, recreational vessel traffic, dolphin tourism, and cruise ship presence increased substantially between 2008 and 2020. We examined the relationship between vessel traffic parameters and the presence of Hector's dolphins (Cephalorhynchus hectori) during the austral summer 2019–2020, using automated vessel tracking and autonomous passive acoustic monitoring. Data were collected between December 2019 and May 2020, including the entirety of the first COVID‐19 nationwide lockdown. Generalized additive models revealed that increasing levels of motor vessel traffic, the presence of cruise ships, and high levels of dolphin tour vessel traffic resulted in decreases in acoustic detections of dolphins. Our findings suggest that Hector's dolphins at Akaroa Harbor were displaced from core habitat in response to each of these vessel traffic parameters. We recommend that managers use immediately actionable tools to reduce the impacts of vessels on these dolphins.

An observed decline in the mark rate of Hector's dolphins at Banks Peninsula, New Zealand

An observed decline in the mark rate of Hector's dolphins at Banks Peninsula, New Zealand

Cats among the Conservationists

Cats among the Conservationists

Modelling the spatial distribution of cetaceans in New Zealand waters

AbstractAimCetaceans are inherently difficult to study due to their elusive, pelagic and often highly migratory nature. New Zealand waters are home to 50% of the world's cetacean species, but their spatial distributions are poorly known. Here, we model distributions of 30 cetacean taxa using an extensive at‐sea sightings dataset (n > 14,000) and high‐resolution (1 km2) environmental data layers.LocationNew Zealand's Exclusive Economic Zone (EEZ).MethodsTwo models were used to predict probability of species occurrence based on available sightings records. For taxa with <50 sightings (n = 15), Relative Environmental Suitability (RES), and for taxa with ≥50 sightings (n = 15), Boosted Regression Tree (BRT) models were used. Independently collected presence/absence data were used for further model evaluation for a subset of taxa.ResultsRES models for rarely sighted species showed reasonable fits to available sightings and stranding data based on literature and expert knowledge on the species' autecology. BRT models showed high predictive power for commonly sighted species (AUC: 0.79–0.99). Important variables for predicting the occurrence of cetacean taxa were temperature residuals, bathymetry, distance to the 500 m isobath, mixed layer depth and water turbidity. Cetacean distribution patterns varied from highly localised, nearshore (e.g., Hector's dolphin), to more ubiquitous (e.g., common dolphin) to primarily offshore species (e.g., blue whale). Cetacean richness based on stacked species occurrence layers illustrated patterns of fewer inshore taxa with localised richness hotspots, and higher offshore richness especially in locales of the Macquarie Ridge, Bounty Trough and Chatham Rise.Main conclusionsPredicted spatial distributions fill a major knowledge gap towards informing future assessments and conservation planning for cetaceans in New Zealand's extensive EEZ. While sightings datasets were not spatially comprehensive for any taxa, these two best available approaches allow for predictive modelling of both more common, and of rarely sighted, cetacean species with limited available information.

Avoiding post-truth environmental conflict in New Zealand: communicating uncertainties in endangered species science

Keyes [2004, p. 15] says: “In the post-truth era we don't just have truth or lies but a third category of ambiguous statements that are not exactly the truth but fall short of a lie”. In this paper about Hector's and Maui dolphin management in New Zealand, we argue that some scientific knowledge about these species presented and disseminated in ways that equate to this third category and as such may be classed as ‘post-truth type communication’. This generates citizen mistrust in science, scientists and government agencies and inflames conflict among informed stakeholders. We argue trust may be rebuilt by a combination of deliberative approaches to environmental governance, transparency about uncertainties, information gaps and divergent scientific opinions, and reformulation of normal scientific approaches and assumptions to those advocated by post-normal science.

Using a recreational grade echosounder to quantify the potential prey field of coastal predators.

Quantifying the distribution of prey greatly improves models of habitat use by marine predators and can assist in determining threats to both predators and prey. Small epipelagic fishes are important prey for many predators yet their distribution is difficult to quantify due to extreme patchiness. This study explores the use of recreational grade echosounders (RGE) to quantify school characteristics of epipelagic fish and link their distribution to that of their predators at Banks Peninsula, New Zealand. The hydro-acoustic system was ground-truthed with 259 schools of epipelagic fish. During 2015 and 2016, 136 hydro-acoustic surveys were conducted with concurrent observations of Hector’s dolphin (Cephalorhynchus hectori) and little penguins (Eudyptula minor). The relative abundance of the two predator species during surveys was modelled according to the relative abundance of potential prey using generalised additive mixed models. Schools of epipelagic fish were readily detected by the RGE system and were more abundant in summer compared to winter. The models performed well, explaining 43% and 37% of the deviance in relative abundances of dolphins and penguins respectively. This is the first study to link the distribution of Hector’s dolphin to that of their epipelagic prey and confirms the utility of RGE in studies of habitat use in marine predators. Limitations associated with a lack of formal acoustic calibration and data formatting can be overcome and would make RGE valuable, inexpensive tools for investigating variability in populations of small pelagic fishes.

Impact of pile-driving on Hector's dolphin in Lyttelton Harbour, New Zealand

Several dolphin species occur close inshore and in harbours, where underwater noise generated by pile-driving used in wharf construction may constitute an important impact. Such impacts are likely to be greatest on species such as the endangered Hector's dolphin (Cephalorhynchus hectori), which has small home ranges and uses this habitat type routinely. Using automated echolocation detectors in Lyttelton Harbour (New Zealand), we studied the distribution of Hector's dolphins using a gradient sampling design over 92 days within which pile-driving occurred on 46 days. During piling operations, dolphin positive minutes per day decreased at the detector closest to the piling but increased at the mid-harbour detector. Finer-grained analyses showed that close to the piling operation, detections decreased with increasing sound exposure level, that longer piling events were associated with longer reductions in detections, and that effects were long-lasting - detection rates took up to 83 h to return to pre-piling levels.

The Influence of Selection on MHC DQA and DQB Haplotypes in the Endemic New Zealand Hector's and Māui Dolphins.

Strong balancing selection on the major histocompatibility complex (MHC) can lead to different patterns in gene frequencies and neutral genomic variation within species. We investigated diversity and geographic structure of MHC genes DQA and DQB, as well as their inferred functional haplotypes, from 2 regional populations (East and West Coast) of the endangered Hector's dolphin (Cephalorhynchus hectori hectori) and the critically endangered Māui dolphin (Cephalorhynchus hectori maui) (West Coast, North Island), and contrasted these results with patterns from neutral microsatellites. The Māui had the lowest number of alleles for DQA (2) and DQB (3), consistent with strong genetic drift acting on this remnant population. However, the 2 retained DQA alleles are among the most divergent combinations of all 4 alleles found across the Hector's metapopulation, potentially reflecting the retention of divergent alleles due to balancing selection. The high frequency of the divergent DQB*04 allele also gave this population the highest nucleotide diversity for DQB. Strong differentiation was evident for DQA, DQB, and DQA-DQB haplotypes between the regional populations of Hector's dolphins (FST > 0.213) and both subspecies (FST > 0.311). Differentiation was generally greater than observed at neutral microsatellite loci, suggesting the influence of selection between geographically proximate East and West Coast populations. This might be the result of spatial differences in directional selection on those opposite coastlines. In addition, measures of the ratio of nonsynonymous to synonymous substitutions (dN/dS) were consistent with balancing selection over evolutionary time. Together, these results suggest a complex interplay of balancing selection, directional selection, local fidelity, and genetic drift.

Fine scale distribution for a population of New Zealand's only endemic dolphin (Cephalorhynchus hectori) shows long‐term stability of coastal hotspots

AbstractMarine mammal populations often have “hotspots” of distribution. Understanding what drives these is important for understanding relationships with habitat and evaluating exposure to threats. Few studies investigate the stability of hotspots, yet this information is vital in assessing their importance. In this study, over 9,000 sightings made during systematic surveys over 29 yr are used to establish the existence, locations, and temporal dynamics of hotspots for Hector's dolphins at Banks Peninsula, New Zealand. Sightings were divided into four seasons and three time periods to assess temporal trends in habitat use. Kernel density analysis was performed on sightings, weighted by survey effort. Density values at hotspots and reference areas were modeled according to season and time period using linear mixed models. Fifty percent of weighted sightings (n = 4,513) occurred within 21% of the study area. Hotspots had significantly higher densities during summer and these high‐density areas have remained consistent over time. Such consistency implies importance of these areas to the dolphins' ecology. This information adds to our knowledge of how this endangered species uses its habitat, suggests candidate areas for protection from threats, and provides a baseline for assessing habitat related impacts on Hector's dolphins at Banks Peninsula.© 2018 Society for Marine Mammalogy

Underwater noise levels of pile-driving in a New Zealand harbour, and the potential impacts on endangered Hector's dolphins

Impact pile-driving generates loud underwater anthropogenic sounds, and is routinely conducted in harbours around the world. Surprisingly few studies of these sounds and their propagation are published in the primary literature. To partially redress this we studied pile-driving sounds in Lyttelton Harbour, New Zealand, during wharf reconstruction after earthquake damage. That Lyttelton harbour is routinely used by Hector's dolphins (Cephalorhynchus hectori), an endangered species found only in New Zealand, provided further context for this study. Steel piles of 0.61 or 0.71 m diameter were driven using three different pile-drivers. Maximum calculated source SEL was 192 dB re 1 μPa2s @ 1 m (SPL0−p of 213 dB re 1 μPa @ 1 m). Propagation of piling noise was strongly influenced by harbour bathymetry and a rock breakwater near the piling operation. We calculated range estimates at which Hector's dolphins may suffer temporary hearing threshold shift and behavioural change.

An Online Survey of Public Knowledge, Attitudes, and Perceptions Toward Whales and Dolphins, and Their Conservation

In 2015, an online survey was conducted to investigate public attitudes and perceptions toward key cetacean (whale, dolphin, and porpoise) conservation and 'hot topic' issues such as legislative protection and whaling (n=858). The vast majority of the participants in this study indicated their permanent residence was the United States (n=577) or India (n=251). Perceptions of participants on the conservation priority of cetacean species did not match with the factual IUCN status, where most participants assumed that the larger and more charismatic whales (blue whale, 24.01%; humpback whale, 22.14%; and killer whale, 23.43%) were more endangered or more to conserve than the small cetacean species such as the Vaquita or Hector's dolphin. Additionally, 39.74% of participants indicated the bottlenose dolphin was the most to conserve. More members of the public highlighted non-existent (fake) species (e.g. pygmy short-fined whale, lump-headed dolphin, and majestic spotted dolphin) as being of conservation concern than certain species of actual genuine concern. The majority of participants considered dolphins and whales to be under protected or only slightly protected (29.95%; 41.96%, respectively) and expressed that marine mammal conservation laws and policies were very or important (47.43%; and 37.88%, respectively). In addition, 86.83% of participants expressed opposition to the hunting of dolphins and whales (57.93% strongly opposed and 28.90% opposed); however, only 47.44% of participants were aware that several countries are still involved in whaling. A lack of awareness of the conservation status of whales and dolphins and continued whaling activities suggests that greater outreach to the public about the conservation status of whale and dolphin species is needed.

Genotype-based estimates of local abundance and effective population size for Hector's dolphins

Conservation and management decisions for wild populations are often based on demographic estimates of abundance (N̂), and less frequently, on genetic estimates of effective population size (N̂e). We used genotype-based methods to estimate both parameters from the same set of biopsy samples, while also providing information on the geographic closure of a local population of Hector's dolphins in Cloudy Bay, New Zealand. The assumption of closure in Cloudy Bay was supported by the lack of genetic differentiation between the two survey years and the absence of any genetically detectable migrants. Using recapture analysis based on genotype identifications, we estimated the abundance of individuals age 1+ (N̂1+) to be 269 (95% CL=233−319, CV=0.12). This was similar to, but more precise than, N̂=230 (95% CL=130−407, CV=0.30) from the more traditional analysis using contemporaneously collected photo-identifications. The N̂e of the parental generation was 191 (95% CL=23−362), and the resulting N̂e/N̂1+ of 0.71 was in reasonable agreement with species of similar life history characteristics. Although N̂e was below the recommended threshold (500, recently increased to ≥1000) thought to be necessary to preserve long-term evolutionary potential in perpetuity, genetic connectivity with neighboring populations on a generational time scale is likely to mitigate the negative effects of low local Ne. Our work demonstrates the breadth of management-relevant information (e.g., N, Ne, sex ratio, genetic diversity, and connectivity to neighboring populations) that can be obtained from a genotype-based analysis, and how conservation implications can change when demographic and genetic population size are considered along with connectivity.

Brucellosis in Endangered Hector's Dolphins (Cephalorhynchus hectori).

Brucella spp infections of marine mammals are often asymptomatic but have been associated with reproductive losses and deaths. Zoonotic infections originating from marine isolates have also been described. Hector's dolphins (Cephalorhynchus hectori) are an endangered species with a declining population, and the role of infectious disease in population dynamics is not fully understood. In this study, 27 Hector's dolphins found dead around the New Zealand coastline between November 2006 and October 2010 were evaluated for lesions previously associated with cetacean brucellosis. Tissues were examined using histological, immunohistochemical, and molecular (polymerase chain reaction [PCR]) techniques. Seven of 27 dolphins (26%) had at least 1 tissue that was positive on PCR for Brucella spp. Lesions consistent with brucellosis were present in 10 of 27 (37%) dolphins, but in 8 of these dolphins Brucella infection could not be demonstrated in lesional tissues. Two dolphins (7%) were diagnosed with active brucellosis: 1 female with placentitis and metritis, and 1 stillborn male fetus. Brucella identified in these 2 dolphins had genetic similarity (99%) to Brucella pinnipedialis. The omp2a gene amplicon from the uterus of the female had 100% homology with ST27 genotype isolates from a human in New Zealand and a bottlenose dolphin of Pacific origin. The remaining 5 PCR-positive dolphins were assessed as having asymptomatic or latent infection. While most Brucella infections identified in this study appeared to be subclinical, the finding of 2 dolphins with reproductive disease due to Brucella infection suggests that this disease has the potential to affect reproductive success in this species.