Sea Otters Are a Special Marine Mammal in Danger of Extinction

The sea otter is a unique marine mammal in so many ways. Its habitat and interaction within its habitat is one that no other animal can relate to, from its feeding style to its troublesome bouts of near extinction due to human influences. The purpose of this paper is to explore the life of the sea otter, including it's habitat, reproductive behavior, feeding behavior and food choices, as well as how humans have effected this fragile marine mammal's population. To understand all the factors that form the sea otters way of life, one must first explore what a sea otter actually is.

The sea otter or enhydra lutis is a member of the Mustelid family and is considered to be the smallest marine mammal alive (Marine Mammal Center, 2007). The Marine Mammal Commission (2007) explain that at birth the sea otter weighs approximately two to two and a quarter kilograms or four to five pounds. By the time the mammal reaches the peak of its growth it can weigh approximately thirty-three to forty-five kilograms, the equivalent to seventy-five to one hundred pounds (Marine Mammal Commission, 2007).

Dissimilar to most marine mammals, the sea otter does not have a layer of insulating blubber to keep it warm (Castro & Huber, 2007, p. 189). Instead the sea otter's skin is protected from the water by two layers of incredibly thick fur (Marine Mammal Center, 2007). The bottom layer of the fur is called the undercoat and the top layer is called the guard hairs; together this fur forms an air trap next to the otters skin, allowing it to be in the water but never have the water touch the skin (Marine Mammal Center, 2007). The sea otter's fur is dark brown with lighter, cream colored guard hairs around the face and head (Marine Mammal Center, 2007).

Sea otters can be found relatively close to the shore in the waters of the North Pacific Ocean (Marine Mammal Commission, 2007). Though the mammals were also once prevalent in coastal areas of Mexico and Japan they now mainly live off the coast of California, Alaska, Russia, and Canada (Marine Mammal Commission, 2007). Sea otters reside either in or around kelp beds within these areas of water (Castro & Huber, 2007, p. 190). In addition, sea otters do not migrate during different seasons of the year, rather they typically remain within two to three miles of their established kelp beds, which the otters use secure themselves while resting or feeding (USGS, 2003a).

Within and around these precious kelp beds lies the sea otters key to survival, their food. Castro & Huber (2007) explain that a sea otters must consume approximately twenty-five to thirty percent of its total body mass each day in order to live (p. 190). As such, the significant part of their day is spent searching for food (Castro & Huber, 2007, p. 190). In general a sea otter's diet includes sea life such as sea urchins, crabs, mussels, worms, abalones, fish and fish eggs, and octopus (Pacific Wildlife Foundation, 2006). However, Cohn (1998) observes that although sea otters will eat a significant array of marine shellfish, mollusks, and fish, they tend to prefer to consume approximately two to four types of prey depending on one or more of the following factors: hunting and gathering ability, learned food preferences, or food accessibility. Cohn (1998) continues by explaining that by maintaining a finicky diet, which varies from otter to otter, they have managed to effectively use the food source without exhausting it. The sea otters diet also directly correlates to the control of sea urchin population in kelp beds (Castro & Huber, 2007, p. 190).

Sea otters gather their meals by a series of short dives of approximately thirty meters or less (Pacific Wildlife Foundation, 2006). While under water, the sea otter uses excess skin folds around the armpits to store the food it finds and bring it back to the surface (Marine Mammal Center, 2007). Castro & Huber (2007) explain that once above water the sea otter drifts on its back and uses a tool, such as a rock, to crack open prey protected by an outer shell (p. 190). The use of rocks has also been observed underwater, when the sea otter smashes the rock against the sea floor to free shellfish or sea urchins from their groundings (Pacific Wildlife Foundation, 2006). Feeding takes place at both day and night (USGS, 2003a); and is broken up between short periods of grooming and resting (Pacific Wildlife Foundation).

Since sea otters can be found in several different locations around the world, reproductive time periods can vary from place to place. The Pacific Wildlife Foundation (2006) explain that Sea otters who reside around Russia typically breed between the months of June and October; Sea otters indigenous to Alaska usually reproduce between September and October; and sea otters located around California mate between July and the month of October (Pacific Wildlife Foundation, 2006). A Female sea otter is able to give birth to her first otter pup when she reaches the age of four or five years old (Marine Mammal Center, 2007).

Sea otters begin breeding by initiating a mating courtship process, in which the male otter will nuzzle the female; if she is interested she allows the male to fondle; this courtship can take approximately one hour to complete (Pacific Wildlife Foundation, 2006). After courtship mating will ensue; while mating, the male engages in biting the female otters nose, a ritual that has been said to help discharge a females unfertilized egg (Pacific Wildlife Foundation, 2006). If mating is successful the female will give birth to her pup in about four or five months from the date of conception (Marine Mammal Center, 2007).

Like many other marine mammals, fish, and birds the sea otter is extremely susceptible to human activity within their habitat. Poachers and fur traders threatened the marine mammals existence until the adoption of the International Fur Seal Treaty, which aided in the mammals comeback from near extinction in 1911 (Cohn, 1998). Additionally, oil spills have proven to be particularly destructive to the sea otter and its habitat. The oil virtually strips the fur of its ability to insulate leaving the mammal unable to keep itself warm in the cold waters (NOAA, 2007). Another major problem is that the oil coating the fur after a spill is often ingested during daily grooming periods; the toxic substance causes serious illness and most likely death (NOAA, 2007). Sea otters also suffer the affects of other marine contaminants, such as sewage draining into the ocean, causing an increase in disease and infection raising the mortality rate of these precious marine mammals (USGS, 2005b). Oil spills also effect the shellfish and other marine life that sea otters feed on (Senkowsky, 2004). Senkowsky (2004) states that some researchers are taking considerable note in the decrease in life span by nearly ten to forty percent; additionally observing damaged and inflamed livers in a number of the deceased otters found.

Fortunately the sea otters appear to have a positive future. Cohn (1998) notes that even if the mammal is removed from the endangered species list as laid out in a plan by the US Fish and Wildlife Service; it will remain protected under the Marine Mammal Protection Act in hopes of ensuring this animal a successful future for years to come.

References:

Castro, P. & Huber, M.E. (2007). Marine biology (6th ed.). New York: McGraw-Hill Higher Education.

Cohn, J. P. (1998). Understanding Sea Otters. Bioscience, 48, 151-155. Retrieved Nov. 06, 2007, from First Search Database.

Marine Mammal Center. (2007). Sea Otter. Retrieved Nov. 06, 2007, from http://www.marinemammalcenter.org/learning/education/mammalinfo/seaotter.asp.

Marine Mammal Commission. (2007). Sea Otter. Retrieved Nov. 6, 2007, from http://www.mmc.gov/species/seaotter.html.

NOAA. (2007). What's The Story on Oil Spills? Retrieved Nov. 6, 2007, from http://response.restoration.noaa.gov/topic_subtopic_entry.php?RECORD_KEY%28entry_subtopic_topic%29=entry_id,subtopic_id,topic_id&entry_id(entry_subtopic_topic)=184&subtopic_id(entry_subtopic_topic)=8&topic_id(entry_subtopic_topic)=1.

Pacific Wildlife Foundation. (2006). Sea Otter Behavior. Retrieved Nov. 06, 2007, from http://www.pwlf.org/seaotter/behaviour.htm.

Senkowsky, S. (2004). The Oil and the Otter. Scientific American, 290 (5), 30-32. Retrieved Nov. 06, 2007, from Academic Search Premier Database.

USGS. (2003a). Sea Otter. Retrieved Nov. 06, 2007, from http://www.pwrc.usgs.gov/bioeco/seaotter.htm.

USGS. (2005b). Sea Otter Mortality. Retrieved Nov. 06, 2007, from http://www.nwhc.usgs.gov/publications/fact_sheets/pdfs/SeaOtter2005.pdf.