Several Species Of Marine Mammals Research Articles

Guidelines to merge stranding databases: the case of franciscana (Pontoporia blainvillei) in the extreme South of Brazil

Strandings of several species of marine mammals have been monitored over the years off the south coast of Rio Grande do Sul State, southern Brazil. A long time series of records implies extensive databases on strandings. In the region, these databases are maintained by two institutions: (i) Núcleo de Educação e Monitoramento Ambiental (NEMA) [Environmental Education and Monitoring Nucleus] and (ii) Laboratório de Ecologia e Conservação da Megafauna Marinha (ECOMEGA) [Ecology and Conservation of Marine Mefagauna Laboratory] at the Federal University of Rio Grande – FURG. In order to make the time series as complete as possible and to make it a reliable source for research related to a particular species and region, the present work proposes a methodology for unifying both databases for franciscana (Pontoporia blainvillei) for the period 2000 - 2020 (NEMA, n = 3,029; FURG, n = 4,629). To build the unified database, specific metrics were outlined for the species and region, in order to confirm a ‘match’ of a record. The ‘match’ variable is a subjective value that classifies the resighting of a stranded animal as excellent (1), good (2), or regular (3). With the implementation of guidelines to merge stranding databases 1,812 ‘excellent’ and 97 ‘good’ combinations were recorded. Sixty records classified as 30 ‘regular’ matches were kept in the database, as they are possibly not recounts due to large differences in our primary and secondary metrics. To characterize a reliable match between distinct databases, the general guidelines outlined here need to be adapted according to the species of interest and the specificities of each monitoring program. The methodology developed to unify the databases had as its main objective the identification of matches.

Evidence of Type A-Like Killer Whales (Orcinus orca) Predating on Marine Mammals Along the Atacama Desert Coast, Chile

Killer whales (Orcinus orca) are marine apex predators distributed across the world’s oceans. In the last 40 years, researchers have increasingly differentiated killer whales into ecotypes based on genetics, morphology, behaviour, acoustic repertoire, habitat, and trophic ecology. While killer whale ecotypes in the Northern Hemisphere are well studied, the recognition of distinct killer whale forms in the Southern Hemisphere is mainly limited to Antarctic waters. Although present in less studied regions, such as along the Atacama Desert coast in the Southeast Pacific Ocean, limited information is available regarding their biology or trophic ecology. Herein, multiple lines of evidence are presented for killer whale predation on marine mammals in northern Chile. Using information from systematic boat-based surveys, whale-watching tour surveys, and reports from fishermen/citizen scientists, 19 killer whale sightings are reported along the coast of northern Chile (from the Arica and Parinacota region in the north to the Atacama region in the south). Killer whales were photo-identified as corresponding to the Southern Hemisphere Type A-like ecotype according to their dorsal fin shape and white eye patch. One killer whale pod, which included two males, one female, one juvenile, and one calf, was resighted six times from 2016 to 2021 in northern Chile and was observed hunting South American sea lions (Otaria flavescens), dusky dolphins (Lagenorhynchus obscurus), and long-beaked common dolphins (Delphinus cf. capensis). Killer whales were observed taking advantage of large aggregations of sea lions associated with the offshore purse-seine fishery. Adult killer whales used the hulls of fishing vessels to prevent sea lions from escaping. Photo-identification analysis of a fin whale (Balaenoptera physalus) catalogue from Mejillones Peninsula showed that 2.6% of all identified whales had apparent rake marks from killer whale teeth on their dorsal fins. These data show that Type A-like killer whales in northern Chile prey on several species of marine mammals.

Marine mammals are natural hosts of Oceanivirga salmonicida, a bacterial pathogen of Atlantic salmon.

During 1992 and 1993, a bacterial disease occurred in a seawater Atlantic salmon Salmo salar farm, causing serious mortalities. The causative agent was subsequently named as Oceanivirga salmonicida, a member of the Leptotrichiaceae. Searches of 16S rRNA gene sequence databases have shown sequence similarities between O. salmonicida and uncultured bacterial clones from the digestive tracts of marine mammals. In the current study, oral samples were taken from stranded dolphins (common dolphin Delphinus delphis, striped dolphin Stenella coeruleoalba) and healthy harbour seals Phoca vitulina. A bacterium with growth characteristics consistent with O. salmonicida was isolated from a common dolphin. The isolate was confirmed as O. salmonicida, by comparisons to the type strain, using 16S rRNA gene, gyrB, groEL, and recA sequence analyses, average nucleotide identity analysis, and MALDI-TOF mass spectrometry. Metagenomic analysis indicated that the genus Oceanivirga represented a significant component of the oral bacterial microbiomes of the dolphins and seals. However, sequences consistent with O. salmonicida were only found in the dolphin samples. Analyses of marine mammal microbiome studies in the NCBI databases showed sequences consistent with O. salmonicida from the common dolphin, striped dolphin, bottlenose dolphin Tursiops truncatus, humpback whale Megaptera novaeangliae, and harbour seal. Sequences from marine environmental studies in the NCBI databases showed no sequences consistent with O. salmonicida. The findings suggest that several species of marine mammals are natural hosts of O. salmonicida.

An end-to-end approach for true detection of low frequency marine mammal vocalizations

Research into automated systems for detecting marine mammal vocalizations within acoustic recordings is expanding internationally due to the necessity to analyze large collections of data collected for passive acoustic monitoring. Recent work towards the development of such systems using Convolutional Neural Networks (CNNs) shows great promise and these systems are capable of generalizing to additional species without having to re-train the entire network [1]. However, to the best of our knowledge, the current deep learning implementations do not perform what we refer to as true detection. Instead these systems are simply capable of determining the presence or absence of a vocalization within a spectrogram. In this work we present a CNN trained on spectrograms containing labelled bounding boxes around low-frequency vocalizations produced by several species of marine mammals. In this way, the CNN can precisely detect vocalizations in terms of both time and frequency, while maintaining the advantage of being generalizable to additional species. [1] M. Thomas, B. Martin, K. Kowarski, B. Gaudet, and S. Stan, Marine mammal species classification using convolutional neural networks and a novel acoustic representation, in ECML PKDD 2019 (Springer, Cham, 2019).Research into automated systems for detecting marine mammal vocalizations within acoustic recordings is expanding internationally due to the necessity to analyze large collections of data collected for passive acoustic monitoring. Recent work towards the development of such systems using Convolutional Neural Networks (CNNs) shows great promise and these systems are capable of generalizing to additional species without having to re-train the entire network [1]. However, to the best of our knowledge, the current deep learning implementations do not perform what we refer to as true detection. Instead these systems are simply capable of determining the presence or absence of a vocalization within a spectrogram. In this work we present a CNN trained on spectrograms containing labelled bounding boxes around low-frequency vocalizations produced by several species of marine mammals. In this way, the CNN can precisely detect vocalizations in terms of both time and frequency, while maintaining the advantage of bein...

Ranking vessel noise emissions using measurements from an underwater listening station

Commercial shipping routes pass through important habitat areas for several species of marine mammals in the coastal waterways of southern British Columbia. The Vancouver Fraser Port Authority, through its Enhancing Cetacean Habitat and Observation (ECHO) program, has undertaken studies to develop mitigation measures that will lead to a quantifiable reduction in threats to whales resulting from shipping activities. This includes long-term measurements of vessel noise at a cabled underwater listening station in Georgia Strait (the ECHO ULS) where JASCO, in partnership with Ocean Networks Canada, has been measuring source levels of vessels calling at the Port using JASCO's PortListen® software. PortListen® receives and processes real-time acoustic and AIS data to calculate vessel source levels using ANSI standard methods (S12.64-2009 R2014). Since September 2015, PortListen® has collected a database of thousands of source level measurements, which has been used to implement ranking system for vessel noise emissions. The ranking system uses a data-driven model to adjust the ranking of each measurement according to the vessel characteristics (e.g., size, class) and measurement conditions (e.g., speed, wind, and draft). In addition to an unweighted noise ranking, the system also provides weighted rankings for five marine mammals hearing groups using NOAA (2016) auditory weighting curves.

Seasonal Patterns in Ocean Ambient Noise near Sachs Harbour, Northwest Territories + Supplementary Appendix 1 (See Article Tools)

Ocean ambient noise is a crucial habitat feature for marine animals because it represents the lower threshold of their acoustically active space. Ambient noise is affected by noise from both natural sources, like wind and ice, and anthropogenic sources, such as shipping and seismic surveys. During the ice-covered season, ambient conditions in the Arctic are quieter than those in other regions because sea ice has a dampening effect. Arctic warming induced by climate change can raise noise levels by reducing sea ice coverage and increasing human activity, and these changes may negatively affect several species of marine mammals and other acoustically sensitive marine fauna. We document ambient noise off the west coast of Banks Island near Sachs Harbour, Northwest Territories, to provide baseline noise levels for the eastern Beaufort Sea. Noise levels were comparable to those found in other studies of the Canadian Arctic and Alaska and were typically much lower than levels reported farther south. Stronger wind increased noise, whereas greater ice concentration decreased it, dampening the effect of wind speed. Future work should expand monitoring to other locations in the Arctic, model the impact of increased human activities on ambient noise levels, and predict the impact of these changing levels on marine animals.

Length of intervals between epidemics: evaluating the influence of maternal transfer of immunity.

The length of intervals between epidemic outbreaks of infectious diseases is critical in epidemiology. In several species of marine mammals and birds, it is pivotal to also consider the life history of the species of concern, as the contact rate between individuals can have a seasonal flux, for example, due to aggregations during the breeding season. Recently, particular interest has been given to the role of the dynamics of immunity in determining the intervals between epidemics in wild animal populations. One potentially powerful, but often neglected, process in this context is the maternal transfer of immunity. Here, we explore theoretically how the transfer of maternal antibodies can delay the recurrence of epidemics using Phocine Distemper in harbor seals as an example of a system in which epidemic outbreaks are followed by pathogen extinction. We show that the presence of temporarily protected newborns can significantly increase the predicted interval between epidemics, and this effect is strongly dependent on the degree of synchrony in the breeding season. Furthermore, we found that stochasticity in the onset of epidemics in combination with maternally acquired immunity increases the predicted intervals between epidemics even more. These effects arise because newborns with maternal antibodies temporarily boost population level immunity above the threshold of herd immunity, particularly when breeding is synchronous. Overall, our results show that maternal antibodies can have a profound influence on the dynamics of wildlife epidemics, notably in gregarious species such as many marine mammals and seabirds.

Lateralization, praxis, and communicative gestures: Developmental and comparative perspectives

This special issue is the result of a workshop held in the fall of 2012 at Paris Descartes Universite, Paris, France. The goal of the workshop was to explore the relationships between different aspects of hand-use lateralization, that is, hand preference for praxis and communication through their developments in human infants, and by comparing them with nonhuman primates who also lack language. The workshop brought together an interdisciplinary group of scholars: comparative and developmental psychologists, ethologists, and neuroscientists convened for 1 day of talks and discussions. This special issue gathers the contributions of some of those participants. The first article (MacNeilage) places hand-use lateralization within a larger context by synthesizing evidence of left brain/right side asymmetries in routine whole-body actions in several species of marine mammals. The reported data suggest a commonality of patterns between humans and marine mammals for leading the right side in turning asymmetries. MacNeilage postulates that such asymmetries may be the result of a left-hemisphere intentional control and more generally, a left-hemisphere specialization for movement dynamics (Sainburg, 2005). Three articles are concerned with the lateralization of motor behavior in human fetuses and human infants. Hepper notes the early emergence of lateralized behaviors during the prenatal period (from 10 weeks gestation). He proposes that mediation of these behaviors is most likely genetic and that the pattern of fetal lateralization is the precursor of the laterality observed postnatally. Although it can be tempting to relate the behavioral biases with structural and functional differences between the hemispheres, Hepper cautions against interpreting the former as a casual effect of the latter. In her article, Fagard questions the relationships between hand preference and hemispheric specialization for language. Even as early fetal signs of lateralization become better known, she notes that there is still too little evidence about: (1) how genetic and environmental factors interact to lead to mature handedness and language lateralization; and (2) what exactly is the nature of the relationship between both processes of lateralization. Are handedness and hemispheric specialization for language causally related (and in which direction) or independent in origin? To answer these questions, Fagard calls for considering their codevelopment during early ontogeny. In their article, Michel and colleagues tackle the issue of the relationships of the development of handedness and that of hemispheric specialization for speech processing. They borrow the developmental sequence proposed by Arbib’s (2006) mirror system hypothesis about the linkage of action and language. This view is based on the idea that hand preference must reflect a lateralized difference in neural control of manual actions and speech actions (gestures) that will ultimately lead to speech. Michel and colleagues employ embodiment theory to suggest that Manuscript Received: 21 June 2013 Manuscript Accepted: 21 June 2013 Correspondence to: Jacques Vauclair Article first published online in Wiley Online Library (wileyonlinelibrary.com): 19 July 2013 DOI 10.1002/dev.21152 2013 Wiley Periodicals, Inc. Developmental Psychobiology

The Significance of the North Water Polynya to Arctic Top Predators

The North Water polynya (~76°N to 79°N and 70°W to 80°W) is known to be an important habitat for several species of marine mammals and sea birds. For millennia, it has provided the basis for subsistence hunting and human presence in the northernmost part of Baffin Bay. The abundance of air-breathing top predators also represents a potential source of nutrient cycling that maintains primary production. In this study, aerial surveys conducted in 2009 and 2010 were used for the first time to map the distribution and estimate the abundance of top predators during spring in the North Water. Belugas (Delphinapterus leucas) were not detected north of 77°20'N but were found along the coast of West Greenland and offshore in the middle of the North Water with an abundance estimated at 2245 (95% CI 1811-2783). Narwhals (Monodon monoceros) were widely distributed on the eastern side of the North Water with an estimate of abundance of 7726 (3761-15870). Walruses (Odobenus rosmarus) were found across the North Water over both shallow and deep (>500m) water with an estimated abundance of 1499 (1077-2087). Bearded (Erignathus barbatus) and ringed seals (Phoca hispida) used the large floes of ice in the southeastern part of the North Water for hauling out. Most polar bears (Ursus maritimus) were detected in the southern part of the polynya. The abundances of bearded and ringed seals were 6016 (3322-10893) and 9529 (5460-16632), respectively, and that of polar bears was 60 (12-292). Three sea bird species were distributed along the Greenland coast (eiders, Somateria spp.), in leads and cracks close to the Greenland coast (little auks, Alle alle) or widely in open water (thick-billed guillemots, Uria lomvia).

Marine mammal bycatch in Spanish Mediterranean large pelagic longline fisheries, with a focus on Risso’s dolphin (Grampus griseus)

The western Mediterranean is an important fishing area in which the Spanish longline fleet operates. Longline fisheries affect several species of marine mammals, sea turtles, sharks and seabirds, all of which are espe- cially sensitive to fishing mortality. Given international efforts to identify and reduce the bycatch of sensitive species, an onboard observer program was implemented by the Spanish Oceanographic Institute (IEO, Instituto Espanol de Oceanografia). The aim of the present study was to report data on marine mammal bycatch in the western Mediter- ranean. The additional aim was to improve knowledge about the possible effects of the Spanish longline fisheries on cetacean populations, particularly Risso's dolphin, and to suggest improvements to fisheries management. Data on ma- rine mammal bycatch were collected during the period 2000−2009. Differences are reported for catch per unit effort (CPUE, defined as marine mammals per 1000 hooks) for each type of gear (n = 7), as well as their effect on specific marine mammal species. A total of 5 398 297 hooks were monitored, which yielded 56 marine mammals belonging to 4d ifferent species. Our results indicate that Risso's dolphin is the species most affected by the longline fishery in the western Mediterranean (n = 33). We built a predictive model for Risso's dolphin bycatch using variables associated with the technical characteristics of the fishery, geographic location and seasonality. We performed a binary logistic re- gression of the presence/absence of Risso's dolphin bycatch to test whether the probability of incidentally catching one or more dolphins may be predicted by some of the explanatory variables selected. Our results indicate that Risso's dol- phin was mainly caught using Japanese longline (LLJAP) or an experimental home-based longline (LLHBexp) over the continental shelf. Because LLHBexp is an experimental type of gear that was only used occasionally by the fleet, con- trolling the use of LLJAP over the continental shelf could strongly reduce the impact of these fisheries on populations of Risso's dolphin in the western Mediterranean.

The relationship between anthropogenic noise and frequency contours of southern resident killer whale (Orcinus orca) stereotyped vocalizations.

Marine mammals evolved alongside naturally occurring noise in underwater environments, but recent increases in ocean anthropogenic noise present challenges to effective acoustic communication. Several species of marine mammals have demonstrated compensation strategies to avoid masking, including modifying call duration, frequency, rate, or amplitude. This research explored the relationship between noise and the vocalization behavior of endangered southern resident killer whales threatened in part by vessel traffic. Using extracted frequency contours obtained from recordings made between 2001 and 2007 from bottom-mounted hydrophones, the null hypothesis of no difference in the frequency contours of stereotyped calls across noise classes was tested. The results will be discussed in the context of vocal compensation thresholds in species that communicate using stereotyped calls, and management implications will be suggested.

The Ilnik wolf Canis lupus pack: use of marine mammals and offshore sea ice

AbstractMost wolf Canis lupus studies have been conducted in inland regions and comparatively little data are available for wolves inhabiting coastal areas. We monitored four members of a coastal wolf pack on the Alaska Peninsula during 2006‐2008. Habitat selection ratios indicated a strong association with the coastline, and we documented pack members and other wolves feeding on several species of marine mammals in these areas. In addition, pack members were observed foraging on offshore sea ice on multiple occasions. Observed spatial use and utilization of marine mammals suggest that marine‐derived subsidies may provide an important food source to coastal wolf populations. If these subsidies constitute a significant food source for coastal wolves, they likely affect wolf demographics and predator‐prey relationships in these areas.

A spatial assessment of the risk to a mobile marine mammal from bycatch

Abstract Several species of marine mammals are at risk of extinction from being captured as bycatch in commercial fisheries. Various approaches have been developed and implemented to address this bycatch problem, including devices and gear changes, time and area closures and fisheries moratoria. Most of these solutions are difficult to implement effectively, especially for artisanal fisheries in developing countries and remote regions. Re‐zoning of the Great Barrier Reef World Heritage Area (GBRWHA) in 2004 closed 33% of the region to extractive activities, including commercial fishing. However, the impact of re‐zoning and the associated industry restructuring on a threatened marine mammal, the dugong (Dugong dugon), is difficult to quantify. Accurate information on dugong bycatch in commercial nets is unavailable because of the large geographic extent of the GBRWHA, the remoteness of the region adjacent to the Cape York Peninsula where most dugongs occur and the artisanal nature of the fishery. In the face of this uncertainty, a spatial risk‐assessment approach was used to evaluate the re‐zoning and associated industry restructuring for their ability to reduce the risk of dugong bycatch from commercial fisheries netting. The new zoning arrangements appreciably reduced the risk of dugong bycatch by reducing the total area where commercial netting is permitted. Netting is currently not permitted in 67% of dugong habitats of high conservation value, a 56% improvement over the former arrangements. Re‐zoning and industry restructuring also contributed to a 22% decline in the spatial extent of conducted netting. Spatial risk assessment approaches that evaluate the risk of mobile marine mammals from bycatch are applicable to other situations where there is limited information on the location and intensity of bycatch, including remote regions and developing countries where resources are limited. Copyright © 2008 John Wiley & Sons, Ltd.

Cetacean-reconstituted severe combined immunodeficient (SCID) mice respond to vaccination with canine distemper vaccine.

Morbillivirus infections have been responsible for mass mortalities in several species of marine mammals. Nevertheless, relatively little is known on the pathogenesis of the disease and the immune response to the agent, especially in cetaceans, hindering the treatment of individuals and the development of appropriate vaccines, given the difficulty of performing experimental work in marine mammals. The reconstitution of severe combined immunodeficient (SCID) mice, which do not have the ability to reject grafts, with lymphocytes from different species has been used with increasing success as a surrogate species model to study the immune system. We injected NOD/SCID mice with lymphocytes from different species of cetaceans and further vaccinated those mice with a commercial canine distemper virus (CDV) vaccine to develop a practical model to study cetacean immune response to a morbillivirus. Reconstitution was detected in 10/20 mice reconstituted with harbor porpoise spleen, 6/10 mice reconstituted with harbor porpoise lymph node cells, 8/10 mice reconstituted with fresh beluga PBMCs and none of the mice reconstituted with neonate bottlenose dolphin spleen or thymus cells when assessed 42-63 days after reconstitution. While a humoral immune response was detected in none of the reconstituted mice, a cell-mediated immune response to the CDV vaccine was detected in 6/15 (40%) and 2/18 (11%) of the SCID mice after reconstitution with cetacean immune cells after a single or booster vaccination, respectively, for a combined total of 8/33 (24%). This represents the first demonstration of successful reconstitution of SCID mice with marine mammal cells, and to the authors' knowledge, the first direct demonstration of a primary antigen-specific cell-mediated immune response in reconstituted SCID mice. This model will be useful for further research on the physiology of the marine mammal immune system and its response to infectious agents and vaccines, with possible important outcomes in conservation issues.

Toxoplasma gondii, Neospora caninum, Sarcocystis neurona, and Sarcocystis canis-like infections in marine mammals

Toxoplasma gondii, Neospora caninum, Sarcocystis neurona, and S. canis are related protozoans that can cause mortality in many species of domestic and wild animals. Recently, T. gondii and S. neurona were recognized to cause encephalitis in marine mammals. As yet, there is no report of natural exposure of N. caninum in marine mammals. In the present study, antibodies to T. gondii and N. caninum were assayed in sera of several species of marine mammals. For T. gondii, sera were diluted 1:25, 1:50, and 1:500 and assayed in the T. gondii modified agglutination test (MAT). Antibodies (MAT ≥1:25) to T. gondii were found in 89 of 115 (77%) dead, and 18 of 30 (60%) apparently healthy sea otters ( Enhydra lutris), 51 of 311 (16%) Pacific harbor seals ( Phoca vitulina), 19 of 45 (42%) sea lions ( Zalophus californianus), 5 of 32 (16%) ringed seals ( Phoca hispida), 4 of 8 (50%) bearded seals ( Erignathus barbatus), 1 of 9 (11.1%) spotted seals ( Phoca largha), 138 of 141 (98%) Atlantic bottlenose dolphins ( Tursiops truncatus), and 3 of 53 (6%) walruses ( Odobenus rosmarus). For N. caninum, sera were diluted 1:40, 1:80, 1:160, and 1:320 and examined with the Neospora agglutination test (NAT) using mouse-derived tachyzoites. NAT antibodies were found in 3 of 53 (6%) walruses, 28 of 145 (19%) sea otters, 11 of 311 (3.5%) harbor seals, 1 of 27 (3.7%) sea lions, 4 of 32 (12.5%) ringed seals, 1 of 8 (12.5%) bearded seals, and 43 of 47 (91%) bottlenose dolphins. To our knowledge, this is the first report of N. caninum antibodies in any marine mammal, and the first report of T. gondii antibodies in walruses and in ringed, bearded, spotted, and ribbon seals. Current information on T. gondii-like and Sarcocystis-like infections in marine mammals is reviewed. New cases of clinical S. canis and T. gondii infections are also reported in sea lions, and T. gondii infection in an Antillean manatee ( Trichechus manatus manatus).

Contamination and toxic effects of persistent endocrine disrupters in marine mammals and birds

In recent years, several species of marine mammals and birds have been affected by uncommon diseases and unusual mortalities. While several possible causative factors have been attributed for these events, a prominent suspect is exposure to man-made toxic contaminants. Particularly, some of these man-made chemicals can disrupt normal endocrine physiology in animals. At CMES, our studies focus on exposure and toxic effects of endocrine disrupting chemicals, particularly organochlorines, in higher trophic level wildlife. Endocrine disrupting chemicals, such as organochlorine insecticides, polychlorinated biphenyls, organotins etc. are found in tissues of a wide variety of wildlife. Extremely high concentrations have been found in animals afflicted with diseases and/or victims of mass mortalities. Elevated contamination by organochlorines has been found in open sea animals such as cetaceans and albatrosses, which seemed to be attributable to their low capacity to metabolize toxic persistent contaminants. Significant correlations between biochemical parameters (serum hormone concentrations and cytochrome P450 enzyme activities) and residues of endocrine disrupting chemicals were found in some species of marine animals, which indicates that these chemicals may impose toxic effects in animals even at the current levels of exposure. In general, water birds and marine mammals accumulated the dioxin-like compounds with much higher concentrations than humans, implying higher risk from exposure in wildlife. The future issues of endocrine disrupting chemicals in humans and wildlife will have to be focused in developing countries.

Gas transport and oxygen storage capacity in some pinnipeds and the sea otter

The present study summarizes the factors contributing to oxygen storage capacity in several species of marine mammals. Additional data are presented on respiratory properties of blood. Phocid seals showed the highest Hb concentration and hematocrit which correlate with longer and deeper dives in comparison with the otariid seals, the walrus and the sea otter which were also studied. A larger circulating blood volume in the phocid seals gave them a blood O 2 storage capacity more than twice the average for the other species studied. Muscle myoglobin concentration was also about twice as high in the phocid seals. The lung oxygen storage capacity calculated from maximum lung volume, was conversely smaller in the phocid seals than in the other species studied. The sea otter was exceptional with a very high lung O 2 storage capacity making up two thirds of the total capacity. The larger total O 2 storage capacity in the phocid seals is discussed in relation to the diving behavior of the animals. The respiratory properties of blood showed no significant adaptive features in O 2-Hb affinity or Bohr shift, but a distinctly higher buffering capacity distinguishes blood of marine mammals from terrestrial non-diving species.