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Long-term fixed passive acoustic monitoring of cetacean populations is a logistical and technological challenge, often limited by the battery capacity of the autonomous recorders. Depending on the research scope and target species, temporal subsampling of the data may become necessary to extend the deployment period. This study explores the effects of different duty cycles on metrics that describe patterns of seasonal presence, call type richness, and daily call rate of three blue whale acoustics populations in the Southern Indian Ocean. Detections of blue whale calls from continuous acoustic data were subsampled with three different duty cycles of 50%, 33%, and 25% within listening periods ranging from 1 min to 6 h. Results show that reducing the percentage of recording time reduces the accuracy of the observed seasonal patterns as well as the estimation of daily call rate and call type richness. For a specific duty cycle, short listening periods (5–30 min) are preferred to longer listening periods (1–6 h). The effects of subsampling are greater the lower the species' vocal activity or the shorter their periods of presence. These results emphasize the importance of selecting a subsampling scheme adapted to the target species. [ABSTRACT FROM AUTHOR]

Extremes in organismal size have broad interest in ecology and evolution because organismal size dictates many traits of an organism's biology. There is particular fascination with identifying upper size extremes in the largest vertebrates, given the challenges and difficulties of measuring extant and extinct candidates for the largest animal of all time, such as whales, terrestrial non-avian dinosaurs, and extinct marine reptiles. The discovery of Perucetus colossus, a giant basilosaurid whale from the Eocene of Peru, challenged many assumptions about organismal extremes based on reconstructions of its body weight that exceeded reported values for blue whales (Balaenoptera musculus). Here we present an examination of a series of factors and methodological approaches to assess reconstructing body weight in Perucetus, including: data sources from large extant cetaceans; fitting published body mass estimates to body outlines; testing the assumption of isometry between skeletal and body masses, even with extrapolation; examining the role of pachyostosis in body mass reconstructions; addressing method-dependent error rates; and comparing Perucetus with known physiological and ecological limits for living whales, and Eocene oceanic productivity. We conclude that Perucetus did not exceed the body mass of today's blue whales. Depending on assumptions and methods, we estimate that Perucetus weighed 60-70 tons assuming a length 17 m. We calculated larger estimates potentially as much as 98-114 tons at 20 m in length, which is far less than the direct records of blue whale weights, or the 270 ton estimates that we calculated for body weights of the largest blue whales measured by length. [ABSTRACT FROM AUTHOR]

We have validated these data before integrating them into the baseline data of Bryde's whale from Kuwait. Among the nine species of Balaenopterid whales, only four species, viz., I Balaenoptera musculus i , I B. edeni i , I B. omurai i , and I Megaptera novaeangliae i are reported from the Arabian/Persian Gulf (Al-Robbae, 1967, 1971; Al-Sayegh, 2014; Dakhteh et al., 2017; Ranjbar et al., 2016). [Extracted from the article]

The exact number of cetacean species present in Mauritanian waters is unknown. A first overview was published only in 1980, the latest in 1998. Yet, published information remains modest compared to, e.g., neighboring Senegal (first review in 1947). The complex oceanography of Mauritanian waters permits a mixed assemblage of cetacean fauna, with the distribution of both cool temperate and (sub)tropical species. In this review, we use our own observations from strandings, bycatches and vessel-based surveys, as well as published and grey literature, to support an updated inventory of cetaceans of Mauritania. This checklist includes two new authenticated species records: Kogia sima (Owen) (Kogiidae) and Lagenodelphis hosei Fraser (Delphinidae). Stenella coeruleoalba (Meyen) (Delphinidae) is verifiably documented for the first time. Further, a first specimen record of Stenella longirostris (Gray) (Delphinidae) is described, as well as second specimen records of Mesoplodon europaeus (Gervais) (Ziphiidae), Steno bredanensis (G. Cuvier) (Delphinidae) and Megaptera novaeangliae (Borowski) (Balaenopteridae). Of 30 reported species, 27 (of six families) are fully supported, while three species lack (accessible) voucher material though probably (P) occur in Mauritania: Balaenopteridae: Megaptera novaeangliae, Balaenoptera musculus (Linnaeus), B. borealis Lesson, B. omurai Wada, Oishi and Yamada, B. acutorostrata Lacépède, B. physalus (Linnaeus) and B. brydei Olsen (P); Physeteridae: Physeter macrocephalus Linnaeus; Kogiidae: Kogia sima (Owen) and K. breviceps (de Blainville); Delphinidae: Sousa teuszii (Kükenthal), Tursiops truncatus (Montague), Delphinus delphis Linnaeus, Stenella frontalis (G. Cuvier), Stenella attenuata (Gray), Stenella coeruleoalba (Meyen), Stenella longirostris (Gray), Stenella clymene (Gray), Steno bredanensis (G. Cuvier), Peponocephala electra (Gray) (P), Lagenodelphis hosei (Fraser), Grampus griseus (G. Cuvier), Globicephala macrorhynchus Gray, Globicephala melas (Traill) (P), Orcinus orca (Linnaeus) and Pseudorca crassidens (Owen); Ziphiidae: Ziphius cavirostris G. Cuvier, Mesoplodon europaeus and Mesoplodon densirostris (de Blainville); Phocoenidae: Phocoena phocoena (Linnaeus). Finally, we report the first case for continental northwest Africa of tattoo skin disease in a stranded D. delphis. [ABSTRACT FROM AUTHOR]

Cetaceans are a group of aquatic mammals with the largest body sizes among living animals, including giant representatives such as blue and fin whales. To understand the genetic bases of gigantism in cetaceans, we performed molecular evolutionary analyses on five genes (GHSR, IGF2, IGFBP2, IGFBP7, and EGF) from the growth hormone/insulin-like growth factor axis, and four genes (ZFAT, EGF, LCORL, and PLAG1) previously described as related to the size of species evolutionarily close to cetaceans, such as pigs, cows, and sheep. Our dataset comprised 19 species of cetaceans, seven of which are classified as giants because they exceed 10 m in length. Our results revealed signs of positive selection in genes from the growth hormone/insulin-like growth factor axis and also in those related to body increase in cetacean-related species. In addition, pseudogenization of the EGF gene was detected in the lineage of toothless cetaceans, Mysticeti. Our results suggest the action of positive selection on gigantism in genes that act both in body augmentation and in mitigating its consequences, such as cancer suppression when involved in processes such as division, migration, and cell development control. [ABSTRACT FROM AUTHOR]

The article reports that ship traffic can negatively affect marine wildlife including cetaceans, especially in areas where these mammals carry out relevant ecological activities. Topics include examines ship strikes can be caused by several types of large vessels as well as by smaller recreational boats.

Blue whales Balaenoptera musculus are the most abundant and widely distributed cetacean species in Sri Lankan waters. A vessel-based opportunistic line transect survey focusing on marine mammals was conducted in Sri Lankan waters between 24 June to 12 July 2018, while an ecosystem survey was performed by the R/V Dr. Fridtjof Nansen. The entire transect length was 2090 km within an area of 3895 km2. Overall, 72% (n = 57) of blue whale observations were group assemblages ranging between 1 and 5 individuals out of a total of 79 sightings. The largest aggregations of blue whales were recorded at the intersection of the submarine canyon off the coastline of Mirissa and busy shipping lanes between Dondra Head and Galle, where previous ship strikes were recorded. Overall, the average observed group size was 2.64 (CV, 12.34%; 95% CI, 2.07–3.38), the average group density was 0.0029 km−2 (CV, 35.96%; 95% CI, 0.00145–0.00610), and the total blue whale abundance within the survey area was 513 individuals (CV, 38.02%; 95% CI, 243–1083). These survey results fill vital knowledge gaps regarding the abundance and distribution of blue whales in Sri Lanka, which is essential for the establishment of management and conservation strategies. [ABSTRACT FROM AUTHOR]

Multiplet pregnancies are rare in cetaceans, and live‐born multiple births even rarer. We used whaling data collected from pregnant females and held by the International Whaling Commission to examine multiplets in 16 cetacean species, finding that 0.87% (2,197 out of 252,651) of pregnancies included multiple fetuses, including 12 instances of five or more fetuses in five different species, all rorquals. For six species, we estimate the proportion of twins that are identical using Weinberg's differential rule. Identical twins are less common than fraternal twins in all species (4%–34%) except humpback whales (57%). To infer survival rates of twins to term, we fitted models to the proportion of twins by fetal length, finding that the probability of surviving twins declined exponentially to near zero with increasing fetal length for sei, fin, and blue whales; but not for sperm, humpback, and Antarctic minke whales. Because some fetuses may be missed at smaller lengths, we repeated this analysis excluding fetuses shorter than 2 ft (61 cm), finding that twin survival declined with increasing fetal length for sei, fin, blue, and Antarctic minke whales. We conclude that few multiple pregnancies (<1 in 500) end in live birth, and even these pregnancies experience high mortality after birth. [ABSTRACT FROM AUTHOR]

Emerging technologies are changing how scientists and the public see and interact with cetacean specimens. As staff at a small, rural, marine science center, we employed LIDAR (light detection and ranging), x‐ray, computational tomography, and structured light scanning along with three‐dimensional (3D) printing to study and exhibit the remains of a 7.9‐m transient male killer whale (Orcinus orca) and a 22.4‐m female blue whale (Balaenoptera musculus). In collaboration with larger institutions, we applied these technologies to bone replication, skeletal articulation, soft‐tissue anatomical studies, and digital modeling to create high‐quality specimen replicas. These techniques surpass traditional modeling and restoration methods, and advance specimen‐associated research and documentation. In addition, 3D technology supports education and public awareness through in‐person and online exhibits and demonstrations. The decreasing cost and increasing appeal of advanced imaging can be used to enhance community engagement and the accessibility of science. [ABSTRACT FROM AUTHOR]

The Humboldt Current Ecosystem (HCE) is one of the most productive marine ecosystems, sustaining one of the largest fishing industries in the world. Although several species of cetaceans are known to inhabit these productive waters, quantitative assessments of their abundance and distribution patterns are scarce and patchy. Here, we present the first abundance and distribution estimates for fin whale (Balaenoptera physalus), southeast Pacific blue whales (Balaenoptera musculus), sperm whale (Physeter macrocephalus), dusky dolphin (Lagenorhynchus obscurus), and common dolphin (Delphinus spp.) in the entire Chilean portion of the HCE. Line transect surveys were conducted during 2016–2021 between 18° S and 41° S and up to ~ 200 km offshore, and data were analyzed using distance sampling methods. Group counts were modelled as a function of environmental variables using single step Bayesian Binomial N-mixture model (BNMM), which allows full uncertainty propagation between model components. By using spatially explicit predictions of cetacean densities and observed vessel densities in the HCE, we provide quantitative assessments on the relative probability of cetaceans encountering vessels (RPCEV). Dusky dolphin and fin whale showed the largest distribution overlap with industrial and artisanal fishery fleets. Our results highlight areas where effort should be prioritized to address the extant but unquantified negative interactions between vessels and cetaceans in Chilean HCE. [ABSTRACT FROM AUTHOR]

The distribution of marine mammal species in many areas remains poorly understood, especially as observations for some taxa are rare and large-scale surveys are time consuming and extremely costly. Here, we present 36 records of 7 cetacean species (Balaenoptera brydei, B. musculus subspp., Delphinus delphis, Globicephala sp., Grampus griseus, Physeter macrocephalus, Pseudorca crassidens) in the New Caledonia Basin, Tasman Sea, along with their associated biological and environmental data. Data were derived from a platform of opportunity during a seismic survey that ran between December 2015 and March 2016, inclusively. The two most frequently encountered species were sperm whales (Physeter macrocephalus, 13 sightings, 5 acoustic detections) and blue whales (Balaenoptera musculus subspp., 8 visual detections). All encountered species are known to occur in New Zealand waters at least occasionally, based on historical sightings and stranding records. However, data presented here are the first cetacean records for this specific area and demonstrate that seismic vessels can act as a platform of opportunity for studying cetacean distribution in poorly accessible areas. Such data will aid future research efforts including species distribution models on cetaceans in the South Pacific. [ABSTRACT FROM AUTHOR]