Publisher's Synopsis
Mammals are a special group of animals with a combination of characteristics that separate them from all others: mammals are warm-blooded, have hair or fur, breathe air through lungs, bear live young, and nurse their young with milk produced by mammary glands. Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They do not represent a distinct taxon or systematic grouping, but rather have a paraphyletic relation. They are also unified by their reliance on the marine environment for feeding. Marine mammals have the same characteristics as all other mammals, but they have adapted to living all or part of their life in the ocean. To keep warm in the ocean, most of them depend on a thick layer of blubber (or fat). They have streamlined bodies to help them swim faster. Many species can stay under water for a long time, but must come to the surface to breathe. To be able to stay under water for long periods, they store extra oxygen in their muscles and blood. They also have more blood than land mammals in proportion to their body sizes, can direct their blood flow to only their vital organs (such as their heart and lungs), and can slow their heartbeat down so they are using less oxygen in a dive. Marine mammal adaptation to an aquatic lifestyle vary considerably between species. Both cetaceans and sirenians are fully aquatic and therefore are obligate water dwellers. Seals and sea-lions are semiaquatic; they spend the majority of their time in the water, but need to return to land for important activities such as mating, breeding and molting. In contrast, both otters and the polar bear are much less adapted to aquatic living. Their diet varies considerably as well; some may eat zooplankton, others may eat fish, squid, shellfish, sea-grass and a few may eat other mammals. While the number of marine mammals is small compared to those found on land, their roles in various ecosystems are large, especially concerning the maintenance of marine ecosystems, through processes including the regulation of prey populations. This role in maintaining ecosystems makes them of particular concern as 23% of marine mammal species are currently threatened. Current Approaches to Marine Mammals is compendium of articles by prominent contributors in field of marine mammals and their general biology. Marine mammals form a diverse group of 129 species that rely on the ocean for their existence. They do not represent a distinct taxon or systematic grouping, but instead have a paraphyletic relationship. They are also unified by their reliance on the marine environment for feeding. The level of dependence on the marine environment for existence varies considerably with species. For example, dolphins and whales are completely dependent on the marine environment for all stages of their life, seals feed in the ocean but breed on land, and polar bears must feed on land. Twenty three percent of marine mammal species are threatened. Marine mammals kept in the extremes of their temperature tolerance range are more susceptible to environmental and infectious disease. In general, cetaceans and pinnipeds are better adapted to cold than to heat, but species-specific tolerances differ. Inappropriately combining different species for display purposes can result in compromises that jeopardize the well-being of some species. Good air quality, especially in indoor facilities (10-20 air changes/hr) is as important as good water quality. Photoperiods, light spectral and intensity requirements, sound tolerances, and flight distance requirements are not well established for any cetacean. Extremes in any of these factors should be considered detrimental in the absence of specific data. Environmental requirements of pinnipeds are similar to those of cetaceans except that pinnipeds can "haul out" on land. Although captive pinnipeds can be kept in freshwater, saltwater pools that meet the specifications listed above for cetaceans are preferred. Most pinnipeds obtain their metabolic water requirements in food and do not require access to freshwater if provided fish with a high fat content. However, it is common practice to allow pinnipeds access to potable water. Mammals are a special group of animals with a combination of characteristics that separate them from all others: mammals are warm-blooded, have hair or fur, breathe air through lungs, bear live young, and nurse their young with milk produced by mammary glands. Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They do not represent a distinct taxon or systematic grouping, but rather have a paraphyletic relation. They are also unified by their reliance on the marine environment for feeding. Marine mammals have the same characteristics as all other mammals, but they have adapted to living all or part of their life in the ocean. To keep warm in the ocean, most of them depend on a thick layer of blubber (or fat). They have streamlined bodies to help them swim faster. Many species can stay under water for a long time, but must come to the surface to breathe. To be able to stay under water for long periods, they store extra oxygen in their muscles and blood. They also have more blood than land mammals in proportion to their body sizes, can direct their blood flow to only their vital organs (such as their heart and lungs), and can slow their heartbeat down so they are using less oxygen in a dive. Marine mammal adaptation to an aquatic lifestyle vary considerably between species. Both cetaceans and sirenians are fully aquatic and therefore are obligate water dwellers. Seals and sea-lions are semiaquatic; they spend the majority of their time in the water, but need to return to land for important activities such as mating, breeding and molting. In contrast, both otters and the polar bear are much less adapted to aquatic living. Their diet varies considerably as well; some may eat zooplankton, others may eat fish, squid, shellfish, sea-grass and a few may eat other mammals. While the number of marine mammals is small compared to those found on land, their roles in various ecosystems are large, especially concerning the maintenance of marine ecosystems, through processes including the regulation of prey populations. This role in maintaining ecosystems makes them of particular concern as 23% of marine mammal species are currently threatened. Current Approaches to Marine Mammals is compendium of articles by prominent contributors in field of marine mammals and their general biology. Marine mammals form a diverse group of 129 species that rely on the ocean for their existence. They do not represent a distinct taxon or systematic grouping, but instead have a paraphyletic relationship. They are also unified by their reliance on the marine environment for feeding. The level of dependence on the marine environment for existence varies considerably with species. For example, dolphins and whales are completely dependent on the marine environment for all stages of their life, seals feed in the ocean but breed on land, and polar bears must feed on land. Twenty three percent of marine mammal species are threatened. Marine mammals kept in the extremes of their temperature tolerance range are more susceptible to environmental and infectious disease. In general, cetaceans and pinnipeds are better adapted to cold than to heat, but species-specific tolerances differ. Inappropriately combining different species for display purposes can result in compromises that jeopardize the well-being of some species. Good air quality, especially in indoor facilities (10-20 air changes/hr) is as important as good water quality. Photoperiods, light spectral and intensity requirements, sound tolerances, and flight distance requirements are not well established for any cetacean. Extremes in any of these factors should be considered detrimental in the absence of specific data. Environmental requirements of pinnipeds are similar to those of cetaceans except that pinnipeds can "haul out" on land. Although captive pinnipeds can be kept in freshwater, saltwater pools that meet the specifications listed above for cetaceans are preferred. Most pinnipeds obtain their metabolic water requirements in food and do not require access to freshwater if provided fish with a high fat content. However, it is common practice to allow pinnipeds access to potable water. Mammals are a special group of animals with a combination of characteristics that separate them from all others: mammals are warm-blooded, have hair or fur, breathe air through lungs, bear live young, and nurse their young with milk produced by mammary glands. Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They do not represent a distinct taxon or systematic grouping, but rather have a paraphyletic relation. They are also unified by their reliance on the marine environment for feeding. Marine mammals have the same characteristics as all other mammals, but they have adapted to living all or part of their life in the ocean. To keep warm in the ocean, most of them depend on a thick layer of blubber (or fat). They have streamlined bodies to help them swim faster. Many species can stay under water for a long time, but must come to the surface to breathe. To be able to stay under water for long periods, they store extra oxygen in their muscles and blood. They also have more blood than land mammals in proportion to their body sizes, can direct their blood flow to only their vital organs (such as their heart and lungs), and can slow their heartbeat down so they are using less oxygen in a dive. Marine m
