By Emily Butsic, Kristy Porter, Adrienne Metz

A seals independence starts when it is only a month old. After suckling for a month the mother leaves her pup to fend for itself (Oceanic Research Group,1994). Most seal pups start out catching invertebrates near the beach where they were left. As they grow stronger, they swim deeper and farther away from their home islands. They also start using their sharp teeth to catch fish (Oceanic Research Group, 1994). The type of fish they catch depends on the part of the ocean they inhabit. Gray seals like to eat benthic fish such as sandeels and flounders, but don’t need to dive deep because they live near shore and do not travel out past the continental shelf edge (Sea Mammal Research, 1996). Elephant seals leave land for weeks at a time to travel into the deep waters off the shelf. Although they can often dive to the bottom they prefer to feed around 1,600-1,800 feet down where their is a rich zone containing hundreds of light producing fish, and squid (Le Boeuf, 1989). Some seals don’t need to dive at all for the favorite meals. Leopard seals often swim on the surface just off shore of a rookery waiting for an unsuspecting penguin to enter the water. Although they like to eat penguins they will eat anything they can find and are often seen diving deep to eat krill (Lipps, 1980). Crabeaters, another type of Arctic seal, also spends much of their time eating krill and have even developed special teeth to help them catch their prey (Allan,1984).

Gray seals live in the warm water off the coast of Britan and the U.S.. These seals never swim far from home. An average foraging trip lasts two to five days and only extends about 50 km from their haul out site (Sea Mammal Research, 1996). Gray seals do not need to be deep divers since they never leave the continental shelf. However a group of seals caught in deep waters were observed diving to depths of 300m to get food. Most Gray seals find their foods at much shallower depths with gravel or sand bottoms. These types of sediment are where the seals favorite food lives. Gray seals eat all sorts of fish including, flounder, herring and polack. Squid is also enjoyed when it can be found (Sea Mammal Research, 1996). It is thought that their foraging patterns may be influenced by their early feeding experiences when their mothers first leave them and they are left to fend for themselves.

Elephant seals also leave their young after only a month of nursing. During this time of nursing females loose 44 percent of their body mass so when they are done they return to sea to feed for seventy days (Le Boeuf, 1989). During these two months the seal spends almost its full time diving and foraging. Elephant seals make an average of 2 to 3 dives an hour or 64 dives a day. Dives normally last around a half hour and average 1,650 to 1,815 feet deep. Their surface time is rarely longer then 2 to 3 minuets (Le Boeuf, 1989). They do have resting periods at the surface that rarely extend past twenty minutes but do not seem to come after dives of great depth or time. Therefore these rest periods do not seem associated with the seals need to repellents oxygen; a need that many marine mammals have after long, deep dives. Elephant seals also exhibit an ability to dive to extreme depths. During a study conducted off the coast of California female elephant seals dived to over 3,300 feet. The exact depth is not known, because "The diamond stylus that traces the dives went off the paper" (Le Boeuf,1989). It was extrapolated that they were diving at least 4,000 feet. Elephant seals seem to dive to what ever depth necessary to find food. While on their swim out to the deep water they dive shallow over the shelf and get continuously deeper as the bottom depth deepens however, once they reach the edge of the shelf their dives level out. They no longer dive to the bottom but to the average depth mentioned above (Le Boeuf, 1989). It is believed that this layer is rich in light-producing organisms and squid which the seals like to eat. After diving for more them two months the Females return to the rookery to molt. It is for this reason that most of the information known about Elephant seals is about the females. The instruments used to track these animals are very expensive and the researchers like to recover them after a year of use. The females predictable habits make this relatively easy to do. The males seem to have no patterns to their locations and they also die more frequently (Le Boeuf, 1989).

Leopard seals are considered the most ferocious of all the seals. They live in the Antarctic and feed on what ever they can find. The most abundant food in the icy waters is krill. Like other marine mammals in the area krill is the main part of the seals diet. Leopard seals feed on krill by diving straight down. They dive for about two and a half minutes with a surface time of thirty seconds in between dives. Leopard seals also have special cheek teeth that fit together with their cusps to filter out the water and hold in the krill (Lipps, 1980). When Leopard seals are not diving for krill they may be found monitoring the rookeries of penguins. Penguins are hunted by Leopard seals waiting just under the waters surface. When the penguins enter the water or return from a swim, the seal strikes. He grabs the bird with his canine teeth and flips it with such a force that the body turns inside out. The seal can then eat the body with out having to choke down the feathers (Lipps, 1980). Although krill and penguins seem to be the leopards seals choice meals they have found every thing from clams, to sea lions, to a duck billed platypus in the stomach content of this species (Lipps, 1980).

The name sperm whale comes from the genus name, Physeter catodon. It comes from the cetacean family and is the largest toothed whale. It is also the most numerous of the great whales and is known for it's unmistakable blunt-nose. The largest on record weighed 38,000 kilograms (42 tons). Since they are toothed whales, they are carnivorous.

The diving technique of cetaceans, is very efficient and simple. Cetaceans have the advantage of a blow hole on top of their heads, which allow them to breathe while most of the body is underwater. This technique also allows them to eat and swallow without drowning. To get as much oxygen as possible, cetaceans hold their breath for 15 to 30 seconds, then rapidly exhale and take a new breath. 90% of the oxygen is exchanged during each breath. They are known to dive to 2,250 meters (7,380 feet) and can probably go much deeper. Sperm whales are also champion divers, they can stay under for at least an hour. After deep dives, Sperm whales may breach, fall on their backs, and make a splash that can be heard 4 kilometers (2.5 miles) and seen 28 kilometers (17.4 miles) away.

During feeding, Sperm whales catch their food without using their teeth, even if their teeth are actually of little help because they are present only in the lower jaw. They are fond of squid, including the giant deep-sea squid. They eat a variety of fish, including sharks, lobsters, and other marine animals. The giant squid are more than 10 meters (33 feet) long. The average speed of a Sperm whale is 2-4 knots, but catch squid that can swim at 30 knots. The hypothesis that many biologists agree on is that, when catching prey whole and it is still alive, that the whale stuns its prey with a blast of sound and then simply swallows it whole. After a while, the undigested squid beaks and other debris accumulate in the gut as large globs of a sticky material known as Ambergris, which is an ingredient in fine perfumes.

Most toothed whales do not migrate at all , though they do move about in search of food. The males do forage further north near the poles, while the females stay closer to the equator for nursing purposes. During a study in November of 1995, a group of biologists observed the closeness of a pod of Sperm whales. They noticed that during the afternoon, the pod broke off to go hunting and gathered for extended socializing. They also noticed the Morse-code like patterns, known as codas, appear to represent a system of communication unique to sperm whales. The jumble of clicks of a group of hunting Sperm whales, which together sound like radio static.

Thermoregulation in sea otters is highly dependent on their intense metabolism. Due to this high metabolic rate, otters must eat 23-33% of their body weight per day (Reidman, 1996). This means that sea otters spend a majority of the day foraging. Foraging patterns vary depending on the sex, age and reproductive status of individuals. In general, males spend less time foraging that females do and females with pups spend less time foraging than females without pups, since the pups need to be protected from predators (Cohn, 1998). Juvenile males tend to forage further off shore and dive deeper than adults do, while juvenile females tend to feed for longer periods (Ralls, et. al., 1995).

California and Alaskan sea otters consume similar and different prey types dependent upon what is available in their region. California sea otters have been found to be picky eaters, generally consuming 2-4 prey types of the approximately 33 prey types available to them (Cohn, 1998). Common prey types of the California sea otter include abalone, rock crabs, kelp crabs, purple and red sea urchins, octopus, innkeeper worms, rock oysters, brown turban snails, moonsnails, starfish and mussels (Reidman, 1996). Alaskan sea otters tend to forage for clams, mussels, barnacles, gastropods, green sea urchins, chiton, tunicates, cnidaria, nemertina, amphipods, shrimp, crabs, sand dollars, fish (lumpsuckers) and kelp (hold fasts with small invertebrates attached) (Doroff and DeGrange, 1994).

Foraging patterns for the California sea otter includes a typical foraging ground of subtidal areas (less than 25 meters deep) with dives of only a minute or so (VanBlaricom and Estes, 1988). Studies have shown that dive duration varies with prey type, not prey size, with dive success being highest for smaller prey. The length of the surface interval increased with prey size (Ralls, et. al., 1995). In general, 21-28% of daylight hours were spent foraging. The use of tools to obtain prey items is common with California sea otters and each otter seems to have its own distinctive diet (VanBlaricom and Estes, 1988). For example, in a study done by Marianne Reidman, one female, called Ab Queen, specializes in abalone, although she was also observed eating rock crab and purple sea urchins. Another female, # 508, favored octopus. Female # 5220 specialized in fat innkeeper worms, as well as rock oysters and crabs. One theory is that specialized diets result from differences in food gathering ability. Sea otters can exploit different food items without depleting any (Cohn, 1998). Another theory is that sea otters learn food preferences and foraging patterns from their mothers since they spend so much time together (Reidman, 1996).

Alaskan sea otters commonly forage at depths of 40+ meters. They use tools less frequently than California sea otters to dislodge prey items (VanBlaricom and Estes, 1988). 15-17% of daylight is spent foraging, however Alaskan sea otters also forage frequently at night. Females average a total of 43% of their time foraging, while males only average a total of 38% of their time foraging, as they tend to steal food from the females (Cohn, 1998).

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