The study of animal movement is critical in biological and ecological sciences. However, such studies are often challenging due to the difficulty of continuously observing wild animals. This is especially true for large baleen whales which can travel across vast distances in the open ocean. The use of animal‐borne telemetry tags, which allow for real‐time data collection of geographical positions of an individual, has therefore significantly advanced our knowledge on baleen whale movement patterns and currently forms an essential component of cetacean research. However, as satellite tags are invasive, there is concern about their potential effects on an individual’s health and wellbeing, and possible implications at the population level. Southern right whales (n = 21) were instrumented with Telonics ST‐15 consolidated satellite tags in 2001 in coastal South Africa. Fourteen of these individuals (13 females and one male) were photo‐identified either at the time of tagging or subsequently. Given the long‐term photo‐identification‐based monitoring of this population, 13 of these individuals could be resighted up to 21 years post‐tagging. This study builds on previous assessments of tag effects by providing an extra decade of information on sighting history and calving rates of the tagged individuals. Results showed no decadal tag effects when tagged whales were compared with untagged individuals. Visual assessment showed full healing of the tag site, with only small divots present in the last 10 years. Given the impact of environmental variability on the maternal body condition and reproductive success of this population, this study suggests no increased vulnerability to such stressors due to tagging. With 21 years of post‐tagging data, this is the longest follow‐up study on southern right whales to date. Considering the overall concern of the effect of tagging on the health and wellbeing of individuals, studies like these are critically important to ensure quality data collection with the least possible impact on tagged individuals.

The use of satellite tags has yielded important information to better understand cetacean ecology and to improve cetacean conservation. However, tag deployment duration has been highly variable and typically shorter than their battery life on most large whale species. Between 2011 and 2018, 80 consolidated satellite tags were deployed in North Atlantic humpback whales (Megaptera novaeangliae) in the Gulf of Maine (GoM) to study whale movements, to assess tag impacts, and to understand causes of tag rejection and tag failure. The strong site fidelity of individual whales to the GoM, long feeding ground residency, and high observer effort allowed repeated sightings of animals instrumented with satellite tags. In early deployments multiple structural deficiencies were documented on the tags, revealing the need to improve the mechanical design and manufacturing of the instruments. These tag deficiencies not only resulted in short tag transmission durations, but also in negative health impacts on individual animals. Incremental modifications to the mechanical design and the manufacturing processes to resolve the observed deficiencies included: (1) changes in the anchor tip, retention devices, and anchor articulation, (2) the removal of the interface between the transmitter housing and the anchor and (3) the redesign of the posterior end of the tag. More robust instruments were produced by welding deficient tag parts or by using 3‐dimension (3‐D) metal printing processes to manufacture integrated instruments. Deployments of redesigned satellite tags resulted in 65–85% significantly longer average transmission durations when compared to earlier designs that showed structural deficiencies. This study highlights the importance of developing satellite tagging technology in association with follow‐up monitoring of tagged individuals and provides new tag designs that are structurally more robust and less impactful for use with large cetaceans.

We applied passive acoustic monitoring and Hierarchical Density-Based Spatial Clustering of Applications with Noise clustering to define spatiotemporally cohesive groupings of franciscana dolphin (Pontoporia blainvillei) echolocation click trains. This unsupervised, objective method identified biologically relevant click train clusters, offering rare insights into the species' social organization. The observed structure revealed consistent intra-cluster cohesion and inter-cluster separation, supporting the effectiveness of the approach. Our findings demonstrate that clustering acoustic detections can serve as a robust framework for delineating social groups and can be integrated into future density estimation protocols, enhancing the ecological understanding and conservation potential for this cryptic and vulnerable species.

Understanding how marine predators explore dynamic ocean environments is key for assessing the ecological significance of different habitats and for informing conservation efforts. This is particularly critical in remote and poorly surveyed regions, where marine predators can serve as ecosystem sentinels and provide valuable biological and oceanographic data. Here, we examined the foraging strategies of southern right whales (Eubalaena australis, SRW) using a large-scale satellite tagging dataset from two neighbouring populations: Aotearoa New Zealand and Western Australia. We linked foraging behaviour, inferred from bio-logging data, with remotely sensed environmental data to assess habitat use in relation to Southern Ocean oceanographic features. At broad spatial scales, foraging areas were identified near major frontal systems, but while the New Zealand population primarily targeted the Subtropical Front, the Australian population visited a wider range of oceanic features, including the Antarctic ice edge. At finer scales, both populations co-located with mesoscale eddies, preferentially foraging in cyclonic (cold-core) eddies. Satellite tracking data also suggested that foraging SRWs may exhibit quasi-planktonic behaviour by drifting around eddies. Differences in foraging strategies between the New Zealand and Western Australian populations may have important implications for their continued recovery under climate change. Furthermore, this work showcases SRWs as a sentinel species that highlights key foraging habitats that remain overlooked by high seas conservation efforts.

Hundreds of large whales have been tracked using consolidated (Type‐C) satellite tags, yet there have been few studies on their impacts on whale health. In 2011, we initiated the first study designed to evaluate the effects of these tags on a baleen whale. Between 2011 and 2018, we tagged 79 North Atlantic humpback whales (Megaptera novaeangliae) in the Gulf of Maine. We initially deployed commonly‐used tags with an articulation between the anchor and transmitter (n = 35, 2011–12), before evidence of breakage prompted the development and use of more robust, integrated tags (n = 45). Tagged individuals were photographed immediately before, during and up to 11 years after tagging. They were re‐encountered on an average of 41.3 days (SD = 44.3), yielding 2,971 photographed sightings through 2022. An objective scoring system was developed to characterise tag‐site tissue responses based on photographs and to identify risk factors for prolonged healing. The initial tissue response to tagging was minimal, followed by skin loss around the tag, sometimes a degree of subcutaneous swelling, occasional extrusion of blubber, changes in skin colour, local depression formation around the implant site, tag loss and skin healing over the tag site, sometimes with a depression remaining. At last sighting, most non‐integrated and integrated tag sites exhibited small, shallow skin depressions (58.8% and 66.7%, respectively). Some exhibited deeper depressions with differing adjacent skin coloration (26.5% and 15.6%, respectively) or barely detectable marks (11.8% and 15.6%, respectively). Mild subcutaneous swellings occasionally persisted at the tag site, but this was uncommon for both tag designs (2.9% and 2.2%, respectively). More severe tissue responses were associated with non‐integrated tags and placements lower on the body. This study highlights the importance of using robust tag designs to minimise negative effects from Type‐C tags. Furthermore, because tag placement was shown to affect outcome, precision equipment, experienced taggers and vessel operators are critical for optimal deployment.

South American river dolphins face significant threats from intense human activities, resulting in habitat loss, fragmentation of their natural connectivity, overfishing, pollution, and incidental and intentional catches for use as bait for fisheries. From 1998 to 2022, 12 surveys were conducted in a river system in the Mamore River (Ibare-Tijamuchi-Mamore) basin, one of the primary distribution areas of the Bolivian river dolphin (BRD - Inia geoffrensis boliviensis). Generalized linear models (GLMs) were used to assess population trends. The most supported model does not definitively indicate a decline in population. The estimated mean annual rate of population change for BRDs over the 24-year monitoring period was -0.0115 per year. The average count of BRDs in the Ibare River is lower (mean = 20, n = 4) compared to the mean of Tijamuchi (mean = 260, n = 4), and the same pattern is observed with the Mamore River (mean = 76, n = 4). There is tentative visual evidence of negative trend for the count of BRD based on the GLM curves, but the statistics are still inconclusive to the sub-basin of the Mamore River. This study highlights the importance of continue with monitoring efforts on river dolphin populations. Similar population dynamics are observed in other river dolphin species in the Amazon region, requiring immediate actions to reduce mortality and reverse the concerning decreasing trend exhibited by these populations.

Isolation by distance and biogeographical boundaries define patterns of population genetic structure for harbour porpoise along the Pacific coast from California to British Columbia. Until recently, inadequate sample sizes in many regions constrained efforts to characterise population genetic structure throughout the coastal waters of Alaska. Here, tissue samples from beachcast strandings and fisheries bycatch were supplemented with targeted environmental DNA (eDNA) samples in key regions of Alaska coastal and inland waters. Using a geographically explicit, hierarchical approach, we examined the genetic structure of Alaska harbour porpoises, using both mitochondrial DNA (mtDNA) sequence data and multilocus SNP genotypes. Despite a lack of evidence of genetic differentiation from nuclear SNP loci, patterns of relatedness and genetic differentiation from mtDNA suggest natal philopatry at multiple geographic scales, with limited gene flow among sites possibly mediated by male dispersal. A priori clustering of sampled areas at an intermediate scale (eastern and western Bering Sea, Gulf of Alaska and Southeast Alaska) best explained the genetic variance (12.37%) among regions. In addition, mtDNA differentiation between the Gulf of Alaska and eastern Bering Sea, and among regions within the Gulf of Alaska, indicated significant genetic structuring of harbour porpoise populations in Southeast Alaska. The targeted collection of eDNA samples from strata within Southeast Alaska was key for elevating the statistical power of our mtDNA dataset, and findings indicate limited dispersal between neighbouring strata within coastal and inland waters. These results provide evidence supporting a population boundary within the currently recognised Southeast Alaska Stock. Together, these findings will prove useful for ongoing management efforts to reduce fisheries conflict and conserve genetic diversity in this iconic coastal species.

Southern right whales (SRWs, Eubalaena australis) typically migrate between summer, high-latitude offshore foraging grounds and winter calving grounds located in coastal, temperate waters.Premodern and modern whaling operations nearly extirpated SRWs; the species declined from about 100,000 individuals in the early 1800s to a few hundred

How animals navigate during long-distance migration remains a mystery. Many theories have been proposed1 (Keeton, 1979), with the Earth’s magnetic field emerging as a clear potential source of orientational information for navigational decision-making across diverse taxa2 (Putman, 2022). Yet, the mechanics involved in magnetic navigation remain unknown3 (Schneider et al., 2023). Globally distributed records available from historic whaling4-5 (AOWLD, 2023; Yablokov et al., 1998) in combination with modern satellite-tracking datasets6 (Horton et al., 2022) for baleen whales create a unique opportunity to illuminate the mechanics of cetacean navigation. Here, we show that baleen whale migratory destinations over the last >200 years are systematically distributed in horizontal plane magnetic coordinates. Specifically, blue (Balaenoptera musculus), bowhead (Balaena mysticetus), fin (Balaenoptera physalus), gray (Eschrichtius robustus), humpback (Megaptera novaeangliae), and right (Eubalaena spp.) whales non-randomly inhabit areas where magnetic declination (MD) closely approximates integer and half-integer multiples of the Earth’s 23.44° axial tilt. Our findings, which are highly reproducible through both space and time, demonstrate that baleen whale navigation between seasonal habitats occurs via the integration of magnetic and astronomic orientation cues3. By referencing MD values to the rise and set azimuths of the Sun, baleen whale movements define mechanistic horizontal plane heliomagnetic coordinate trajectories across all ocean basins.

Understanding animals' movements is essential to assess habitat use, life-history strategies, and population dynamics. Here, we investigate the movement and behavior patterns of 153 humpback whales in the Southwest Atlantic Ocean (SWA) using data obtained by satellite telemetry between 2003 and 2019 during the species' breeding season (August-December) off the Brazilian coast. Switching state space models were applied to estimate behavior states (bmode) classified as Area Restricted Search (ARS), Transiting (TRANS), or uncertain. Whales were distributed from 4 degrees S to 24 degrees S, and five clusters of ARS behavior were identified along the Brazilian coast. Generalized linear mixed modeling revealed three main results: (1) a transition towards more sinuous behavioral states with increasing latitude; (2) more sinuous movement behavior around new moons; (3) movement behavior was temporally dynamic throughout the breeding season over the years, particularly in 2019. The results then revealed important regions where humpback whales cluster to engage in mating and nursing behaviors, highlighting the influence of spatial location and environmental cycles on their behavior. Estimated movement behavior presented here improves the knowledge about the habitat use and movement patterns of SWA humpback whales in their breeding ground and can be used to mitigate potential human-related impacts.

Most baleen whale populations are increasing after the end of industrial whaling, but their recovery patterns challenge long-standing assumptions about density dependence. It has long been assumed that population growth rates will decline with recovery, until reaching equilibrium ('carrying capacity', K). Indeed, the International Whaling Commission assumes that growth rates will slow long before K is reached, with maximum productivity at 0.6K. This 0.6K population level is used as an international benchmark that forms the basis of whaling regulations and decisions about whether baleen whale populations are declared depleted. We fit models to four long-term data sets for baleen whales with multiple abundance estimates that span the range from low to high abundance, finding strong evidence that increase rates remain at near-maximal levels across a wide range of abundance levels, and only decline as the population nears K. As a result, maximum productivity occurs at 0.69-0.87 of K across these populations, which predicts more rapid recovery for baleen whale populations than currently assumed. The overall mean of these values (0.8K) would be a more sensible default choice than the 0.6K currently assumed. Synthesis and applications. Estimated recovery rates imply that management thresholds currently used are lower than actual maximum productivity and that populations can increase rapidly even at high abundance. However, if population models continue to assume that maximum productivity is at 0.6K, they will estimate abundance relative to K to be lower than it is, providing conservative assessment results. Our results should stimulate further discussion about the role of maximum sustainable yield as a fundamental concept in fisheries and wildlife management.

We consider how the ongoing recovery of baleen whale populations requires improved understanding when managing the largest commercial fishery in the Southern Ocean, the fishery for Antarctic krill. Baleen whales already represent one of the major consumers of krill, and as such compete with the fishery. However, they are not explicitly included either in the monitoring programme or the krill fisheries management approach of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Individual baleen whales are at direct mortality risk from ship strike, entanglement, or by-catch. In addition, sub-lethal impacts on individuals, albeit with population-level consequences, via decreased body condition and reproductive rates, may arise from local depletion of prey and prey-field disturbance that increases whale energetic costs. Mitigating these risks requires that baleen whales, including those species not yet recovered, are fully integrated into management procedures. A vital issue will be to facilitate the ongoing recovery of blue, fin and sei whales, populations of which are still heavily depleted relative to their pre-whaling abundance. Part of the answer to this will be how CCAMLR resolves outstanding issues related to its newly emerging revised krill fishery management framework. Management of the krill fishery is data-poor, with much of the scientific support reliant upon data that are now decades old. The decision rules for determining sustainable yields need careful re-evaluation, given they were negotiated at a time when baleen whales were rarely observed, and krill fishery catches were low in relation to the estimated available krill biomass. The Antarctic marine ecosystem is spatially and temporally dynamic, and is changing, yet CCAMLR still assumes a static system. An explicit commitment to collect up-to-date monitoring data about krill and baleen whales is vital to help inform the revised management framework. Precaution argues that catch levels should not increase until adequate data are available for effective management. Knowledge about the status of baleen whales will inevitably require close collaboration with the International Whaling Commission.

Marine protected areas (MPAs) are a commonly used management tool to safeguard marine life from anthropogenic impacts, yet their efficacy often remains untested. Evaluating how highly dynamic marine species use static MPAs is challenging but becoming more feasible with the advancement of telemetry data. Here, we focus on southern right whales ( Eubalaena australis, , SRWs) in the waters off Aotearoa/New Zealand, which declined from 30,000 whales to fewer than 40 mature females due to whaling. Now numbering in the low thousands, the key socializing and nursery areas for this population in the remote subantarctic islands are under the protection of different types of MPAs. However, the effectiveness of these MPAs in encompassing important whale habitat and protecting the whales from vessel traffic has not been investigated. To address this, we analyzed telemetry data from 29 SRWs tagged at the Auckland Islands between 2009 and 2022. We identified two previously unknown and currently unprotected areas that were used by the whales for important behaviors such as foraging, socializing, or resting. Additionally, by combining whale locations and vessel tracking data (2020-2022) during peak breeding period (June to October), we found high spatiotemporal overlap between whales and vessels within several MPAs, suggesting the whales could still be vulnerable to multiple anthropogenic stressors even when within areas designated for protection. Our results identify areas to be prioritized for future monitoring and investigation to support the ongoing recovery of this SRW population, as well as highlight the overarching importance of assessing MPA effectiveness post-implementation, especially in a changing climate.

The sub-Antarctic waters of South Georgia Island (Islas Georgias del Sur, SG/IG) are a regularly visited feeding ground for southern right whales (Eubalaena australis, SRW) in the southwest Atlantic. Satellite telemetry and photo-identification records were compared to better understand the role of SG/IG in the SRW migratory network. We present the first insights from SRW satellite-tracked from the SG/IG feeding ground, habitat use patterns in the Scotia Arc, and movements to Antarctic habitats. Photo-identification comparisons to calving and feeding areas across the South Atlantic and a review of sightings of cetaceans reported from Bird Island (west of SG/IG) since 1979 illuminate long-term habitat use patterns in SG/IG. We present the first recorded migratory movement between SG/IG and multiple countries: Argentina, Uruguay, and Brazil. Photo-identification (1) linked SG/IG to a female SRW with a long-term sighting history in Brazil, and (2) provided the first match between SG/IG and the western Antarctic Peninsula, suggesting the latter could extend the feeding area for southwest Atlantic SRW. Satellite tracking and opportunistic sightings suggest that shelf and coastal waters west of SG/IG represent an important multi-season SRW feeding habitat and add to our overall understanding of habitats and ranges occupied by recovering southwest Atlantic SRW.

Harbor porpoises (Phocoena phocoena) are the only cetaceans routinely sighted in Hood Canal, a narrow fjord that comprises the western edge of Puget Sound, Washington, USA. Harbor porpoises are sensitive to anthropogenic sounds, including noise from recreational and commercial vessel traffic, and the United States Navy, which conducts military training and testing within Hood Canal that can include underwater sound sources. This study was funded as part of the Navy monitoring program to assess potential impacts of naval activities on cetaceans. We conducted vessel-based line-transect surveys for harbor porpoises in Hood Canal in 2022-2023 to derive seasonal estimates of abundance and density. We carried out surveys over 37 days and surveyed the entire canal twice per season totaling 2,176 km of on-effort track line. We recorded 809 on-effort harbor porpoise groups and 1,385 individuals. Seasonal abundance estimates were lowest in winter (308 animals, 95% CI = 189-503) and gradually increased through spring and summer to a peak of 1,336 animals (95% CI = 826-2,160) in fall. Overall porpoise density was highest in central Hood Canal, an area that includes a designated United States Navy training range, though porpoise sightings were notably absent in a 21-km(2) area adjacent to the naval submarine base within this otherwise high-density region. Though we collected only a single year of data, these results suggest that harbor porpoise abundance in Hood Canal increased significantly since it was last estimated (2013-2015). The notable seasonal fluctuation of harbor porpoise abundance suggests Hood Canal may host a larger percentage of the overall Washington Inland Waters stock during the fall season, raising important management considerations.

South American river dolphins face significant threats from intense human activities, resulting in habitat loss, fragmentation of their natural connectivity, overfishing, pollution, and incidental and intentional catches (e.g., for use as bait for fisheries). From 1998 to 2022, twelve surveys were conducted in a river system in the Mamore River (Ibare-Tijamuchi-Mamore) basin, one of the primary distribution areas of the Bolivian river dolphin (BRD - Inia geoffrensis boliviensis ). Generalized linear models (GLMs) were used to assess population trends. The most supported model does not definitively indicate a decline in population. The estimated mean annual rate of population change for BRDs over the 24-year monitoring period was − 0.0115 per year. The mean count of BRDs in the Ibare River is approximately 21.2% of the mean count in Tijamuchi, while in the Mamore River, it is 41.1%. However, there is still no evident decline in the populations in the sub-basin of the Mamore River. This study highlights the importance of still monitoring river dolphin populations. Similar population dynamics are observed in other river dolphin species in the Amazon region, necessitating immediate actions to mitigate or reduce mortality and reverse the concerning trend exhibited by these populations.

The first dedicated aerial surveys for beluga whales in the Norton Sound/Yukon Delta region of Alaska were flown during May, June and September 1992. During May 1992 surveys, all of the survey area was covered with pack ice and only a few belugas were seen. In June 1992, many whales were seen in the region of Pastol Bay and the Yukon River Delta, with a few animals seen in eastern Norton Sound. In September 1992, whales were more dispersed and occurred both off the Yukon Delta and in coastal waters of northern Norton Sound. Based on those results, subsequent surveys were flown in June 1993–95 and 1999–2000. In all years except 1999 when there was extensive sea ice in the area, belugas were common off the Yukon Delta and in southern Norton Sound. In most years they were also seen in central Norton Sound. Density and abundance were estimated from the 2000 survey as it represented the most recent data and had the most complete and systematic coverage of the area. In June 2000, belugas were rare in the northern portion of Norton Sound, so the study area was reduced to central and southern Norton Sound and the Yukon Delta, which was divided into four strata by latitude. The density that was estimated with the model that received most Akaike Information Criterion support was 0.121 belugas km–2 and the number of belugas at the surface in the study area was estimated to be 3,497 (CV = 0.37). A generally accepted correction factor for availability of 2.0 was applied, resulting in an abundance estimate for the eastern Bering Sea beluga stock in June 2000 of 6,994 (95% confidence interval 3,162–15,472). This estimate is likely to be conservative. There are no previous abundance estimates for this region, so a population trend cannot be determined. The available evidence suggests that the current Alaska Native subsistence harvest from this stock is sustainable. Beluga consumption of prey populations is likely significant in the regional ecosystem and may have a particular impact on some stocks of Pacific salmon.

Statistical modelling of animal distributions has been widely applied to explain how mobile species use their habitats. The distribution of and habitat use by humpback whales Megaptera novaeangliae off the eastern coast of Brazil have previously been investigated by modelling visual survey data. Here, we modelled distribution in their breeding range using individual tracking data to compare ecological inferences with those from previous models from line transect data. A generalised estimating equation framework was used to model the tracking data and pseudo-absences as functions of spatial covariates. Covariates considered were latitude and longitude, sea surface temperature (SST), current and wind speeds near the surface, distances to shelf-break and the coast, sea bottom depth and slope, and a factor variable representing ‘shelter’. Two modelling exercises were developed: a habitat use model (HUM) and a distribution model (DIM). Covariates retained in the selected HUM were SST, distance to coast and shelf-break, current and wind speeds and shelter. Covariates retained in the selected DIM were latitude/longitude, current speed and distances to shelf-break and coast. The modelled relationships between whale occurrence and environmental covariates using tracking data were similar to those using line transect data. Distribution maps were also similar, supporting higher densities around the Abrolhos Archipelago and to its south. We showed that habitat use and distribution of this population in the area could be similarly inferred by modelling either line transect or tracking data. Using these 2 approaches in conjunction can strengthen the understanding of important ecological aspects of animal populations.

Improving our understanding of the effects of satellite tags on large whales is a critical step in ongoing tag development to minimise potential health effects whilst addressing important research questions that enhance conservation management policy. In 2014, satellite tags were deployed on 9 female southern right whales Eubalaena australis accompanied by a calf off Australia. Photo-identification resights (n = 48) of 4 photo-identified individuals were recorded 1 to 2894 d (1-8 yr) post-tagging. Short-term (<22 d) effects observed included localised and regional swelling, depression at the tag site, blubber extrusion, skin loss and pigmentation colour change. Broad swelling observable from lateral but not aerial imagery (~1.2 m diameter or ~9% of body length) and depression at the tag site persisted up to 1446 d post-tagging for 1 individual, indicating a persistent foreign-body response or infection. Two tagged individuals returned 4 yr post-tagging in 2018 with a calf, and the medium-term effects were evaluated by comparing body condition of tagged whales with non-tagged whales. These females calved in a typical 4 yr interval, suggesting no apparent immediate impact of tagging on reproduction for these individuals, but longer-term monitoring is needed. There was no observable difference in the body condition between the 2 tagged and non-tagged females. Ongoing monitoring post-tagging is required to build on the sample size and statistical power. We demonstrate the value of long-term monitoring programmes and a collaborative approach for evaluating effects from satellite-tagging cetaceans to support species management.