Mark rate, or the proportion of the population with unique, identifiable marks, must be determined in order to estimate population size from photographic identification data. In this study we address field sampling protocols and estimation methods for robust estimation of mark rate and its uncertainty in cetacean populations. We present two alternatives for estimating the variance of mark rate: (1)

Environmental conditions in the Chukchi Sea are changing rapidly and may alter the abundance and distribution of marine species and their benthic prey. We used a metabarcoding approach to identify potentially important prey taxa from Pacific walrus (Odobenus rosmarus divergens ) fecal samples (n = 87). Bivalvia was the most dominant class of prey (66% of all normalized counts) and occurred in 98% of

An understanding of cetacean distribution is necessary to gain insights into crucial ecological processes for species conservation management. However, cetacean habitat preference and distribution in the northern Savu Sea, Indonesia, are still poorly understood. We use maximum entropy modeling with five environmental predictors to describe habitat preference and distribution of seven cetacean species

Reproductive parameters of 168 franciscana dolphins, Pontoporia blainvillei (73 females and 95 males) incidentally caught (n = 163) or stranded (n = 5) between 2005 and 2016 in southeastern Brazil are presented. Ovarian macroscopic analysis revealed 55 immature (75.3%) and 18 mature (24.7%) females. Annual pregnancy rate was estimated to be 0.36, with a calving interval of 2.8 years. Testicular histology

The Guadalupe fur seal (GFS) currently is recovering from near extinction and prey availability is an important factor. Scat and stable isotope analyses (SIA) were used to assess GFS foraging on Guadalupe Island during 2013–2016. This period was characterized by normal (2013) ocean temperatures followed by warm conditions (2014–2016). Scat samples (~40/year) were collected for prey identification.

In animal societies with fission‐fusion dynamics, demographic disturbances can influence the social and spatial structure of the population. Within the Indian River Lagoon (IRL), Florida, common bottlenose dolphins (Tursiops truncatus ) have experienced recurrent unusual mortality events (UMEs) providing an opportunity to examine postdisturbance population and social cluster restructuring. This study

Unmanned aerial vehicles (UAVs) are increasingly used for wildlife research and monitoring, but little information exists on their potential effect on marine mammals. We assessed the effects of a UAV on the behavior of southern right whales (Eubalaena australis ) in Australia. Focal follows of ten right whale mother‐calf pairs were conducted using a theodolite. Control data were recorded for 30 min

Two ecotypes of the common bottlenose dolphin (Tursiops truncatus ) occur in New Zealand waters: a widely studied Nationally Endangered coastal ecotype and a little‐known oceanic ecotype. Site fidelity and association patterns of the oceanic ecotype, and home range overlap with the coastal ecotype, are examined from photo‐identification records collected off northeastern New Zealand between 2005 and

The Irrawaddy dolphins (Orcaella brevirostris ) are an endangered species. Thus, up‐to‐date information on the distribution pattern of dolphins is critical for its proper management and conservation. Using a towed passive acoustic monitoring device, the distribution pattern of the Irrawaddy dolphins in the middle reaches of the Ayeyarwady River, Myanmar, was investigated during a vessel‐based survey

Killer whales (Orcinus orca ) are highly social and occasionally gather in large aggregations that reach 150 individuals. During 338 encounters with Southern Alaska resident killer whales, we collected 1,352 hr of behavioral data to assess the probability of various behaviors based on season, number of pods present, presence of rarely sighted pods, and number of mitochondrial DNA haplotypes present

The weaning period for gray whale (Eschrichtius robustus ) calves is important for maternal instruction and learning. We examined observational and acoustic data from a foraging site for evidence of calf development and mother‐young information transfer. Site survey data demonstrated an initial prioritization of calf protection by using shallow shoreline areas. Foraging in more open water was only

Dolphin interactions with coastal fisheries are of major concern, reportedly leading to gear damage, which increases the cost of coastal fishing globally and in the Mediterranean Sea. The aim of this study was to determine the effect that gear, target species, mesh size, depth, soaking duration, fishing area, and season have on net depredation frequency and to offer insights on possible mitigation

Little is known about the dynamics of baleen whale respiratory cycles, especially the mechanics and activity of the blowholes and their interaction with seawater. In this study, the duration of complete respiration cycles (expiration/inhalation events) were quantified for the first time in two species: North Atlantic right whale (NARW) and humpback whale (HW) using high resolution, detailed imagery

Shore‐based theodolite tracking of eastern gray whale (Eschrichtius robustus) movements was conducted to test for potential whale responses to a high‐frequency sonar system. Southbound migrating whales were observed from two California shore observation stations as the whales swam past the source vessel that was moored in their migration path. The sonar transducer was deployed from the vessel during

We used microsatellite loci to understand the current population genetics of Japanese harbor seals, and found that they were subdivided into two distinct populations, one in Erimo and the other in eastern Hokkaido, despite being only 150 km apart and having no obvious geographical boundaries between them. Strong population subdivision between the two areas may be due to the small number of haul‐out

Spatial analyses of marine mammal stranding data can be used to identify stranding patterns and improve surveillance and monitoring. Using ArcGIS and SaTScan, we analyzed 12 years (2002–2014) of dead beachcast marine mammals from San Juan County, Washington, to better understand patterns of carcass deposition. We plotted the locations for 631 dead marine mammals and aggregated strandings into 1,000 m

Few studies have explored the mating patterns of free‐ranging cetaceans, largely because of logistical challenges. We used an unmanned aerial vehicle (UAV) to follow and video‐record 25 groups of mating dusky dolphins (Lagenorhynchus obscurus) near the surface of the water and examine how behavior patterns varied with mating group type. We collected aerial footage of dolphins mating in traditional

The Florida manatee, Trichechus manatus latirostris , is a fully aquatic, threatened marine mammal for which increased understanding of their physiology, reproduction, and nutrition supports management decisions. Manatees may use taste to distinguish saltwater gradients, toxin detection, food assessment, and social interactions. This study sought to locate and characterize manatee taste buds comparing

This study represents the first comprehensive assessment of the population dynamics and residency of common bottlenose dolphin around Reunion Island (southwest Indian Ocean). Understanding dynamics and movement patterns of this local population is essential to guide effective conservation efforts, notably in a context of growing dolphin‐watching activities. Dedicated surveys based on photo‐identification

We analyzed patterns of aggregation and spatial distribution of the epizoic barnacle Xenobalanus globicipitis on the flukes of Mediterranean striped dolphins, Stenella coeruleoalba , assessing its potential use as an indicator of the host's hydrodynamics based on data from 55 dolphins. Barnacles occurred along the trailing edge with the cirri oriented towards the oncoming flow. Nearest neighbor analyses

Inhabiting temperate and subarctic regions of the North Atlantic (Wimmer & Whitehead, 2004), northern bottlenose whales (NBWs; Hyperoodon ampullatus [Forster, 1770]) are typically found in open‐ocean habitats greater than 500 m depth (Hooker, Whitehead, Gowans, & Baird, 2002; Wimmer & Whitehead, 2004). This offshore distribution is typical of all beaked whales (Cetacea: Ziphiidae) and, in addition

Killer whales are top predators in marine trophic chains, and therefore their feeding preferences can substantially affect the abundance of species on the lower trophic levels. Killer whales are known to feed on many different types of prey from small fish to large whales, but a given killer whale population usually focuses on a specific type of prey. Stable isotope analysis is widely used to study

Guadalupe fur seals (GFS), Arctocephalus philippii townsendi , an U.S. Endangered Species Act threatened pinniped, have recently reappeared in their historic range along the western seaboard of the continental United States. Starting 2005 through 2016, 169 GFSs stranded in Washington and Oregon, involving two designated unusual mortality events. The circumstances surrounding GFS strandings, mortality

A previously undescribed skin abnormality, referred to as “linear skin markings” (LSM), has been identified in free‐ranging common bottlenose dolphins (Tursiops truncatus ) in the Indian River Lagoon, Florida (IRL). The lesions were identified during photo‐identification surveys conducted from 2002 and 2015. LSM presented as distinct, parallel lines running dorso‐ventrally on the torso and varied in

This study describes the age structure and sex‐specific growth patterns of Lahille's bottlenose dolphins (Tursiops truncatus gephyreus ), a subspecies endemic to the Southwest Atlantic Ocean (SWAO). The ages of 120 animals collected in southern Brazil between 1976 and 2017 were determined. We found high frequencies of young animals, mostly males, with no sex bias among adults. A temporal change in

Fin whales (Balaenoptera physalus ), the second largest baleen whale and an endangered species, occur worldwide and are found in all major oceans (Reilly et al., 2013). Fin whales produce two main types of stereotypical, frequency downswept, high‐amplitude, short duration (<1 s) calls, that are known by their primary frequencies as “20‐Hz” and “40‐Hz” calls (Širović, Williams, Kerosky, Wiggins, & Hildebrand

Killer whales (Orcinus orca ) have strong social matrilineal bonds and form groups and long‐lasting associations, but little is known about their population or social structure in an equatorial setting such as the waters around the Galápagos Islands. Using 91 encounters and identification photographs from 1991 to 2017, we identified 64 killer whales of which 18 individuals were locals with high resighting

Studies of the whistles of Irrawaddy dolphins (Orcaella brevirostris ) have traditionally been restricted to analyses of the human audio range (below 20 kHz). In this study, broadband acoustic recordings of Irrawaddy dolphins in Brunei Bay were obtained using a sampling frequency of 512 kHz. Among the 984 whistles collected, eight (0.81%) high‐frequency whistles were detected with fundamentals above

Little research has been conducted on the somatosensory system of toothed whales and it remains uncertain how tactile sensitivity varies about their bodies. In this study, tactile sensitivity to high‐frequency (250‐Hz) displacement of the skin was quantified in three trained adult common bottlenose dolphins ( Tursiops truncatus ) using a vibratory device (tactor). The magnitude of skin displacement

The life history of Risso's dolphins (Grampus griseus ) remains poorly known and data from strandings can help provide important information. Data from 126 Risso's dolphins stranded or bycaught along the southeastern coastline of South Africa between 1958 and 2017 were analyzed in relation to their sex, age structure, and diet. Mean estimated length at birth was 146.9 cm, while maximum length was 325 cm

Sperm whales communicate using codas (stereotyped click sequences). Females and juveniles live in long‐term social units, and units with similar coda repertoires share vocal clan membership. Vocal clans exhibit culturally defined differences in their multilevel social structure. Here, we aimed to identify different social units among sperm whales in Mauritius in the southwestern Indian Ocean, and to

Photo analysis offers a simple, noninvasive approach to characterizing and quantifying skin lesions in cetaceans; however, this process involves methodological considerations that have often gone unaddressed or have varied in approach among investigators. Subjectivity associated with classifying skin lesion types of unknown etiology and quantifying measures of skin lesion prevalence and extent from

Seasonal occurrence, diel‐vocalizing patterns, and call‐types of Antarctic minke whales are described using bio‐acoustic recordings from the west coast of South Africa and the Maud Rise, Antarctica. In Antarctica, minke whale bioduck calls were detected in seven of nine months of hydrophone deployment (peaking in May and September) while downsweeps were only detected in June. Bioduck calls were sporadically

An animal's physiology limits the environmental conditions where it can persist; quantifying the physiology of the walrus is timely since they are being impacted by alterations in sea ice. We examined postnatal changes in hematology, an important attribute that supports diving, by analyzing a longitudinal data set from aquaria walruses (five males and nine females) sampled from 0.04 to 12.0 years of

Robust population size estimates are essential for informing population conservation status. Residency dynamics show population habitat use through time. Population size of Indo‐Pacific humpback dolphins (Sousa chinensis) has been extensively investigated in Chinese waters, but their residency dynamics are rarely known. Mark‐recapture analysis based on photo‐identification records was applied to humpback

Declines in Arctic sea ice cover are influencing the distribution of protected endemic marine mammals, many of which are important for local Indigenous Peoples, and increasing the presence of potentially disruptive industrial activities. Due to increasing conservation concerns, we conducted the first year‐round acoustic monitoring of waters off Gambell and Savoonga (St. Lawrence Island, Alaska), and

Long‐distance migration in whales has historically been described as an annual, round‐trip movement between high‐latitude, summer feeding grounds, and low‐latitude, winter breeding areas, but there is no consensus about why whales travel to the tropics to breed. Between January 2009 and February 2016, we satellite‐tagged 62 antarctic killer whales (Orcinus orca) of four different ecotypes, of which

We examined the trend in residence patterns and abundance of male sperm whales in Nemuro Strait, Japan, based on long‐term photo‐identification (1,513 survey days, total 2,969 photos) between 2006 and 2017. A total of 225 unique individuals were identified during this study, with an average of 36 (SE = 2.55) new individuals identified in each season. The model chosen by maximum likelihood suggests

Diet analysis allows exploring how coastal dolphins interact with the environment and their role in the marine food webs. We studied the diet and feeding ecology of the Guiana dolphin, Sotalia guianensis, through analysis of stomach content from 42 animals stranded on the eastern coast of Brazil. A total of 1,336 semidigested prey items (fish, otoliths, cephalopod beaks, and crustaceans) were identified

In dolphins, centrum shape is one of the features that allows determination of stable and flexible regions in the vertebral column. The Commerson's (Cephalorhynchus commersonii; n = 37), Peale's (Lagenorhynchus australis; n = 24), dusky (Lagenorhynchus obscurus; n = 29), and hourglass dolphins (Lagenorhynchus cruciger; n = 10) are closely related species inhabiting the Southern Hemisphere that have

Understanding the social organization of coastal dolphins, particularly those that reside adjacent to major cities and urbanized regions, is important for understanding the vulnerability of populations to human impacts. We investigated the sexual segregation and social dynamics in a population of Australian humpback dolphins (Sousa sahulensis) inhabiting the near‐urban embayment of Moreton Bay, Queensland

Marine mammals often exhibit significant sexual segregation in their diet and habitat use but these differences have not been studied systematically in historic or ancient populations due to the difficulties associated with determining the sex of skeletal elements based on gross morphology. Using a combined ancient DNA and stable isotope approach, we document a sexual difference in the foraging ecology

The acanthocephalan parasite, Corynosoma enhydri, uses sea otters (Enhydra lutris) as definitive host. Despite high prevalence and abundance in southern sea otters (E. l. nereis), sublethal impacts of infection on otter health are unknown. Parasites are an integral part of ecosystem structure and functioning. Many affect host behavior, reproduction, predation, or prey preference. Parasites can suppress

Many species of whales went through recent bottlenecks due to commercial whaling. These declines were rapid and recent relative to the life spans and generation times of these species, raising questions regarding to what degree commercial whaling influenced the genetic characteristics of these populations. We analyzed mitochondrial and nuclear DNA from pre‐ and postwhaling samples from two populations

Vessel impacts on marine mammals are of growing concern, and marine mammals in urbanized marine environments are at particular risk of exposure. Port Phillip Bay (Victoria, Australia) is one such environment, in which Australian fur seals (AUFS; Arctocephalus pusillus doriferus) haul‐out to rest, yet little is known about the impacts of vessels on resting seals. We used remote camera traps to investigate

The franciscana (Pontoporia blainvillei) is endemic to coastal waters from Brazil to Argentina. The species is regarded as one of the most threatened cetaceans in South America due to high bycatch levels. Four management units (FMAs) were defined throughout the species’ range. FMA II includes states along southeastern and southern Brazil, and represents one of the least known units. Recently, genetic

The Cape Solander Whale Migration Study is a citizen science project that annually counts northward migrating humpback whales (Megaptera novaeangliae) off Cape Solander, Sydney, Australia. Dedicated observers have compiled a 20‐year data set (1997–2017) of shore‐based observations from Cape Solander's high vantage point. Using this long‐term data set collected by citizen scientists, we sought to estimate