Eubalaena Australis Research Articles

Population changes in a Southern Ocean krill predator point towards regional Antarctic sea ice declines

While foraging, marine predators integrate information about the environment often across wide-ranging oceanic foraging grounds and reflect these in population parameters. One such species, the southern right whale (Eubalaena australis; SRW) has shown alterations to foraging behaviour, declines in body condition, and reduced reproductive rates after 2009 in the South African population. As capital breeders, these changes suggest decreased availability of their main prey at high-latitudes, Antarctic krill (Euphausia superba). This study analysed environmental factors affecting prey availability for this population over the past 40 years, finding a notable southward contraction in sea ice, a 15–30% decline in sea ice concentration, and a more than two-fold increase in primary production metrics after 2008. These environmental conditions are less supportive of Antarctic krill recruitment in known SRW foraging grounds. Additionally, marginal ice zone, sea ice concentration and two primary production metrics were determined to be either regionally significant or marginally significant predictors of calving interval length when analysed using a linear model. Findings highlight the vulnerability of recovering baleen whale populations to climate change and show how capital breeders serve as sentinels of ecosystem changes in regions that are difficult or costly to study.

Seabird attacks contribute to calf mortality in a whale population

Reports of seabirds attacking marine mammals have become frequent in the 2000s. Southern right whales Eubalaena australis off Península Valdés (PV), Argentina, have suffered the effects of micropredation by kelp gulls Larus dominicanus since at least the 1970s. During 2003-2013, this population experienced 9 yr of unprecedented high calf mortality. Using a 25 yr dataset (1995-2019) of focal follows of gull-whale interactions, we studied long-term changes in gull attack intensity (attacks h-1) and frequency, and explored whether they influenced calf mortality. We also asked whether calf mortality was affected by prey density at maternal feeding grounds during gestation. Applying Bayesian models, we found that the intensity and frequency of attacks increased significantly from 1995 to the 2000s, and that in 2004-2019, calves received 2.85 times as many attacks as did mothers. Moreover, attacks significantly contributed to increase the probability of calves dying, such that a year with average overall harassment had 2.26 times the mortality of a hypothetical year with no attacks. In years of high intensity and frequency of attacks, many older calves died near the end of the season, probably reflecting the cumulative effect of gull harassment on calf health. However, calf mortality was not affected by prey density, and extremely high mortality was not related to extremely high frequency or intensity of attacks, indicating that deaths are also influenced by other unidentified factors. These findings imply that chronic micropredation contributed to the unprecedented high calf mortality observed in PV and that other marine mammal populations experiencing seabird attacks could be threatened.

Seasonal Occurrence of Southern Right Whales (Eubalaena australis) in Miramar, Buenos Aires Province, Argentina, Between 2016 and 2019

Seasonal Occurrence of Southern Right Whales (Eubalaena australis) in Miramar, Buenos Aires Province, Argentina, Between 2016 and 2019

The Northernmost Record of a Stranded Southern Right Whale (Eubalaena australis) Calf in Ecuador’s North Coast: Notes on Stranding Causes and Distribution Expansion in the Southeastern Tropical Pacific

The Northernmost Record of a Stranded Southern Right Whale (Eubalaena australis) Calf in Ecuador’s North Coast: Notes on Stranding Causes and Distribution Expansion in the Southeastern Tropical Pacific

Short Communication: Humpback whales demonstrate group protection response to killer whale harassment in Brazil

Mixed species groups are usually associated with group protection to avoid predation. Reports of killer whale (Orcinus orca) occurrence and attacks are scarce in Brazilian waters. Here we report the first case of an attack by killer whales on a mixed group of humpbacks (Megaptera novaeangliae) and a southern right whale (Eubalaena australis). This is also the first report of humpback whales possibly interfering with killer whales harassing right whales. The recent increase in humpback and southern right whale populations in Brazil may be influencing the presence of killer whales, which are known to attack humpback whales.

Global warming and coastal protected areas: A study on phytoplankton abundance and sea surface temperature in different regions of the Brazilian South Atlantic Coastal Ocean.

In this study, we examined the relationship between sea surface temperature (SST) and phytoplankton abundance in coastal regions of the Brazilian South Atlantic: São Paulo, Paraná, and Santa Catarina, and the Protection Area of Southern right whales (Eubalaena australis) in Santa Catarina (APA), a conservation zone established along 130 km of coastline. Using SST and chlorophyll-a (Chl-a) data from 2002 to 2023, we found significant differences in SST between the regions, with São Paulo having the highest SST, followed by Paraná and Santa Catarina. All locations showed a consistent increase in SST over the years, with North Santa Catarina, APA and São Paulo experiencing the lowest rate of increase. Correlation analyses between SST and Chl-a revealed a stronger inverse relationship in North Santa Catarina and APA, indicating an increased response of Chl-a to SST variations in this region. The presence of protected area appears to play an essential role in reducing the negative impacts of increasing SST. Specifically, while there is a wealth of research on the consequences of global warming on diverse coastal and oceanic areas, heterogeneity among different settings persists and the causes for this necessitating attention. Our findings have implications for both localized scientific approaches and broader climate policies, emphasizing the importance of considering coastal ecosystem resilience to climate change in future conservation and adaptation strategies.

Foraging dives of southern right whales (Eubalaena australis) in relation to larger zooplankton size prey availability in Golfo Nuevo, Península Valdés, Argentina

Southern right whales (SRWs, Eubalaena australis) have been observed feeding both at and below the surface (< 10 m) in Golfo Nuevo (42°42′ S, 64°30′ W), Península Valdés, Argentina, an area traditionally recognized as calving ground. In addition, we documented diving feeding behavior in SRWs during their stay in this gulf, which has not been previously described. We assessed this behavior using suction-cup-attached video-imaging tags (CRITTERCAMs) on individual whales. A total of eight CRITTERCAM deployments were successful, and feeding events were documented in all SRWs successfully equipped with CRITTERCAMs. The highest speeds occurred during the ascent phase, and the average diving time was 6 min 45 s ± 3 min 41 s for SRWs. Concurrently, zooplankton samples were collected from the subsurface and bottom of the water in areas where tagged whales dived to assess differences in composition, abundance, and biomass. Copepods dominated the upper layer, while euphausiids were more abundant in the deeper sample. Furthermore, zooplankton total biomass was five times higher at depth (2515.93 mg/m3) compared to the subsurface (500.35 mg/m3). Differences in zooplankton characteristics between depths, combined with CRITTERCAM videos, indicated that SRWs exploit high concentrations of organisms near the seafloor during daytime feeding dives. This study provides baseline insights into how SRWs utilize Península Valdés during their stay in the area.

A reconstruction of the marine mammal harvest by the Real Compañía Marítima through the analysis of historical sources (AD 1790–1804)

Humans have altered marine ecosystems over very long-time scales and historical data is often needed to understand the true magnitude of human impacts. The Southwest Atlantic Ocean has a long history of large-scale removal of marine vertebrates due to whaling, sealing, and fishing in the past three centuries. Historical catch records are crucial in assessing the conservation status of these historically over-exploited populations and setting suitable recovery goals. However, several gaps in the history of exploitation of many populations limit our ability to judge recoveries success. This study examines the history of the Spanish fishing company, the Real Compañía Marítima (Royal Maritime Company), and reconstructs its catches of marine mammals in Patagonia and on the north coast of the Río de la Plata. The analysis of a wide range of historical sources reveals that, between the years 1790 and 1804, the Company extracted less than 100 southern right whales Eubalaena australis, some 200,000 South American fur seals Arctocephalus australis and South American sea lions Otaria flavescens, and a few southern elephant seals Mirounga leonina. Although the Company’s whale catch is negligible compared to that of other nations in the same whaling grounds, the amount of fur seals and sea lions removed from the ecosystem deserves attention. This historical survey provides us with the first estimate of the catches made by the Real Compañía Marítima. However, these figures only represent a small part of the extractive activities that took place in the region and further research is encouraged to assess the true dimension of human impacts on Southwest Atlantic ecosystems. The incorporation of retrospective data into ecological studies can be laborious and may have inherent biases, but it also provides valuable information for comprehending modern ecosystems and formulating appropriate conservation plans.

Allosuckling in southern right whale calves

Allosuckling, the suckling of milk from a non-biological mother, occurs in some species of mammals. Allosuckling has not been quantified in baleen whale calves; therefore, we examine allosuckling in southern right whales (SRWs; Eubalaena australis) off Australia. SRWs are listed as Endangered under the Australian Environment Protection and Biodiversity Conservation Act as their numbers remain below the estimated historical abundance. On a small aggregation area, where there were three mother–calf pairs present, we aimed to quantify the proportion of time that calves allosuckled relative to the time spent filial suckling. To achieve this, we conducted unmanned aerial vehicle focal follows on mother–calf pairs and video recorded all interactions among pairs (n = 22 interactions, 3 h total observation time). During interactions, allosuckling occurred in seven interactions, and filial nursing occurred in 11 interactions. One of the calves performed allosuckling, and it was the largest calf with the largest mother. The calf allosuckled from both of the non-biological mothers present. The average proportion of time allosuckling per interaction was 4% (95% CI = ± 0.01, range = 0–0.25), whilst filial nursing for the same calf was 8% (95% CI = ± 0.02, range = 0–0.37). It is important to understand the frequency of allosuckling, and to quantify the energetic benefits for allosuckling calves and the energetic cost incurred by targeted non-biological mothers. This is particularly pertinent for capital breeders who do not replenish lost energy reserves until they migrate to their feeding grounds.

Photo‐identification and satellite telemetry connect southern right whales from South Georgia Island (Islas Georgias del Sur) with multiple feeding and calving grounds in the southwest Atlantic

AbstractThe 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.

First direct observation of a successful southern right whale (Eubalaena australis) birth in South African coastal waters

First direct observation of a successful southern right whale (<i>Eubalaena australis</i>) birth in South African coastal waters

Energy expenditure of southern right whales varies with body size, reproductive state and activity level.

Quantifying the energy expenditure of animals is critical to understand the cost of anthropogenic disturbance relative to their overall energy requirements. We used novel drone focal follows (776 follows, 185 individuals) and aerial photogrammetry (5,372 measurements, 791 individuals) to measure the respiration rate and body condition loss of southern right whales (Eubalaena australis) on a breeding ground in Australia. Respiration rates were converted to oxygen consumption and field metabolic rates (FMR) using published bioenergetic models. The intra-seasonal loss in body condition of different reproductive classes (calves, juveniles, adults, pregnant and lactating) was converted to blubber energy loss and total energy expenditure (TEE). Using these two metrics, we tested the effects of body size, reproductive state and activity level on right whale energy expenditure. Respiration rates and mass-specific FMR decreased exponentially with an increase in body size, as expected based on allometric scaling. FMR increased curvilinearly with an increase in swim speed, likely as a result of increased drag and increased locomotion costs. Respiration rates and FMR were 44% higher for pregnant and lactating females compared to adults, suggesting significant costs of foetal maintenance and milk production, respectively. The estimated FMR of adults based on their respiration rates, corresponded well with the estimated TEE based on body condition loss. The rate of decline in body condition of pregnant and lactating females was considerably higher than expected based on respiration rates, which likely reflects the milk energy transfer from mothers to calves, which is not reflected in their FMR.

Exploring and verifying the acoustic presence of southern right whales (Eubalaena australis) off Elephant Island, Antarctica.

Passive acoustic monitoring (PAM) can be used to monitor acoustic presence and behaviour of cetaceans, providing continuous, long-term, and seasonally unbiased data. The efficiency of PAM methods, however, depends on the ability to detect and correctly interpret acoustic signals. The upcall is the most prevalent vocalization of the southern right whale (Eubalaena australis) and is commonly used as a basis for PAM studies on this species. However, previous studies report difficulties to distinguish between southern right whale upcalls and similar humpback whale (Megaptera novaeangliae) vocalizations with certainty. Recently, vocalizations comparable to southern right whale upcalls were detected off Elephant Island, Antarctica. In this study, these vocalizations were structurally analyzed, and call characteristics were compared to (a) confirmed southern right whale vocalizations recorded off Argentina and (b) confirmed humpback whale vocalizations recorded in the Atlantic Sector of the Southern Ocean. Based on call features, detected upcalls off Elephant Island could be successfully attributed to southern right whales. Measurements describing slope and bandwidth were identified as the main differences in call characteristics between species. With the newly gained knowledge from this study, additional data can be analyzed providing further insight into temporal occurrence and migratory behaviour of southern right whales in Antarctic waters.

Effect of kelp gull harassment on southern right whale calf survival: a long-term capture-recapture analysis.

Kelp gulls (Larus dominicanus) commonly feed on the skin and blubber of surfacing southern right whales (SRW, Eubalaena australis) in the near shore waters of Península Valdés (PV), Argentina. Mothers and especially calves respond to gull attacks by changing their swimming speeds, resting postures and overall behaviour. Gull-inflicted wounds per calf have increased markedly since the mid-1990s. Unusually high mortality of young calves occurred locally after 2003, and increasing evidence points to gull harassment as a factor contributing to the excess deaths. After leaving PV, calves undertake a long migration with their mothers to summer feeding areas; their health during this strenuous exertion is likely to affect their probabilities of first-year survival. To explore the effects of gull-inflicted wounds on calf survival, we analysed 44 capture-recapture observations between 1974 and 2017, for 597 whales photo-identified in their years of birth between 1974 and 2011. We found a marked decrease in first-year survival associated with an increase in wound severity over time. Our analysis supports recent studies indicating that gull harassment at PV may impact SRW population dynamics.

Calls recorded from North Pacific right whales (Eubalaena japonica) in the eastern Bering Sea

Calls from North Pacific right whales (Eubalaena japonica) were recorded in the eastern Bering Sea during a visual and acoustic survey aboard the US Coast Guard buoy tender Sweetbrier, in July 1999. Calls were commonly detected to 20km, and in one case approximately 30km, via deployment of arrays of directional sonobuoys. Acoustic detections (clusters of right whale calls separated by time and location) numbered 26, but only five right whales were seen. Only one right whale produced calls while under visual observation. The types of calls recorded from North Pacific right whales were similar in duration and frequency to calls recorded from right whales in the South Atlantic. The predominant call type (85%; 436 of 511 calls) was the ‘up’ call, a signal sweeping from about 90Hz to 150Hz in 0.7s. Two call types are described as ‘down’ and ‘constant’ calls, based upon nomenclature established for southern right whales (Eubalaena australis). One call type, the ‘down-up’ was unique to the North Pacific repertoire. Right whales commonly produced calls in series lasting several minutes and then became silent for an hour or more, with some animals not calling for periods of at least four hours. Other cetaceans detected acoustically by ‘random’ sonobuoy deployments during the cruise included fin whales (19 times), killer whales (3 times) and sperm whales (once).

How many are they? Estimates of demographic patterns of reproductive females of southern right whale (Eubalaena australis) in the southern coast of Brazil

AbstractSouthern right whales use the Brazilian coast as a wintering area. This population was severely depleted by whaling up until 1973. Since the 1980s, studies have shown that this species is now restricted to the southern waters of Brazil. Using photo‐identification data obtained via standardized aerial surveys from Florianópolis, State of Santa Catarina (SC) (−27.797°/−48.533°) to Torres, State of Rio Grande do Sul (RS) (−29.396°/−49.763°), mark‐recapture methods were used to estimate survival capture and recruitment probability, population size using the POPAN model for reproductive females. Data were collected between 2004 and 2021. The final model was selected based on the lowest Akaike Information Criterion value. Of the 396 female whales identified, 41.41% were recaptured at least once. The final POPAN model showed time dependence in all parameters. The population size was estimated to be 397 reproductive females. This is the first update on the population trends for southern right whales in Brazilian breeding grounds since 2010.

Baleen whales in the Scotia Sea during January and February 2003

Different species of baleen whales display distinct spatial distribution patterns in the Scotia Sea during the austral summer. Passive acoustic and visual surveys for baleen whales were conducted aboard the RRS James Clark Ross in the Scotia Sea and around South Georgia in January and February 2003. Identified calls from four species were recorded during the acoustic survey including southern right (Eubalaena australis), blue (Balaenoptera musculus), fin (B. physalus) and humpback whales (Megaptera novaeangliae). These acoustic data included up calls made by southern right whales, downswept D and tonal calls by blue whales, two possible types of fin whale downswept calls and humpback whale moans and grunts. Visual detections included southern right, fin, humpback and Antarctic minke whales (B. bonaerensis sp.). Most acoustic and visual detections occurred either around South Georgia (southern right and humpback whales) or south of the southern boundary of the Antarctic Circumpolar Current (ACC) and along the outer edge of the ice pack (southern right, blue, humpback and Antarctic minke whales). Fin whales were the exception, being the only species acoustically and visually detected primarily in the central Scotia Sea, along the southern ACC front. In addition to identifiable calls from these species, two types of probable baleen whale calls were detected: 50Hz upswept and pulsing calls. It is proposed that minke whales may produce the pulsing calls, based on their similarities with minke whale calls recorded in the North Atlantic Ocean. There was an overlap between locations of fin whale sightings and recordings and locations of 50Hz upswept calls in the central Scotia Sea, but these calls were most similar to calls attributed to blue whales in other parts of Antarctica. More study is required to determine if baleen whales produce these two call types, and if so, which species. The efficiency of acoustics and visual surveys varied by species, with blue whales being easier to detect using acoustics, Antarctic minke whales being best detected during visual surveys and other species falling in between these two extremes.

Long-term stability in the circumpolar foraging range of a Southern Ocean predator between the eras of whaling and rapid climate change

Assessing environmental changes in Southern Ocean ecosystems is difficult due to its remoteness and data sparsity. Monitoring marine predators that respond rapidly to environmental variation may enable us to track anthropogenic effects on ecosystems. Yet, many long-term datasets of marine predators are incomplete because they are spatially constrained and/or track ecosystems already modified by industrial fishing and whaling in the latter half of the 20th century. Here, we assess the contemporary offshore distribution of a wide-ranging marine predator, the southern right whale (SRW, Eubalaena australis), that forages on copepods and krill from ~30°S to the Antarctic ice edge (>60°S). We analyzed carbon and nitrogen isotope values of 1,002 skin samples from six genetically distinct SRW populations using a customized assignment approach that accounts for temporal and spatial variation in the Southern Ocean phytoplankton isoscape. Over the past three decades, SRWs increased their use of mid-latitude foraging grounds in the south Atlantic and southwest (SW) Indian oceans in the late austral summer and autumn and slightly increased their use of high-latitude (>60°S) foraging grounds in the SW Pacific, coincident with observed changes in prey distribution and abundance on a circumpolar scale. Comparing foraging assignments with whaling records since the 18th century showed remarkable stability in use of mid-latitude foraging areas. We attribute this consistency across four centuries to the physical stability of ocean fronts and resulting productivity in mid-latitude ecosystems of the Southern Ocean compared with polar regions that may be more influenced by recent climate change.

Decadal decline in maternal body condition of a Southern Ocean capital breeder

The changing physical properties of the Southern Ocean are known to impact the recruitment and survival of Antarctic krill (Euphausia superba). For oceanic krill predators, the resulting reduced energy intake may lead to population-level effects likely preceded by an alteration in the animals’ body condition. This is especially true for capital breeders that rely on stored energy for successful reproduction. One such Southern Ocean capital breeder, the southern right whale (Eubalaena australis), has been monitored over the past 43 years in their South African wintering ground. Changes in the population have been documented in the past decade, including a decreased reproductive rate and a shift in foraging strategy. To evaluate if a reduced foraging success is an underlying factor, we assessed the temporal variation in morphological body condition through aerial photogrammetry. Results showed a 23% reduction in maternal body condition, potentially contributing to the decreased reproductive rate of the population. To the best of our knowledge, this is the first study to quantify a decadal reduction in the body condition of a capital breeder dependent on Southern Ocean productivity. Understanding the bioenergetic consequences of environmental change is vital to predicting species’ resilience to climate change.

Distribution and habitat use patterns of southern right whales, Eubalaena australis, off Uruguay

Aerial surveys and behavioural observations from land were conducted 2001-03, between July and November, to evaluate the status and habitat use patterns of the southern right whale (Eubalaena australis) along 220km of the Uruguayan Atlantic coast. Photo-identification was carried out only during the aerial surveys, and group composition as well as spatial and temporal distribution was studied. For the analysis of distribution, the area was divided into four zones. Behaviour was studied from nine fixed points along the coast, analysing the relative frequency of three states (interacting, travelling and resting) and five events (flipper, spy hopping, tail-up, belly-up and flipper slap). Most individuals (90%) were seen from August to October (H=16.446, p=0.003) and there was no significant difference in sightings between the four zones (H=5.11, p=0.163). In 80 sightings, 174 individuals were observed, of which 8% (n=14) were cow-calf pairs and 92% (n=160) were unaccompanied whales (whales without calf). Out of these, 76.9% (n=123) were found in groups that ranged 2-13 individuals (mean=3.4; SD=2.7) and the rest (23.1%; n=37) were solitary. Sixty individuals were identified, one of which was re-identified within a season. Focal sampling on unaccompanied whales took place on ninety-three occasions; 64 on groups and 29 on solitary individuals. For groups, the most frequent behavioural state was interaction (57.8%), and all events were observed, spy hopping being the most frequent. Given the high proportion of unaccompanied whales and interacting groups recorded, Uruguay is thought to be an important social area for the species, where behaviour similar to those previously described as courtship and mating were observed. The dynamics of the different categories of individuals off the Uruguayan coast is discussed and investigation priorities are suggested.