Population of Sea Otters - Assignment Example

 Sea Otters Describe the taxonomic place of the Sea Otter in the classification scheme of organisms on Earth and give its scientific name. The Integrated Taxonomic Information System contains six listings for the animal known commonly as the sea otter. Four of these entries are simply called sea otters while distinctions are also made for the northern sea otter and the southern sea otter. All descriptions place this animal in the Kingdom Animalia, Phylum Chordata, Subphylum Vertebrata, Class Mammalia, Subclass Theria, Infraclass Eutheria, Order Carnivora, Suborder Saniformia, Family Mustelidae and Subfamily Lutrinae. From the Fleming (1822) classification of the common sea otter as Genus Enhydra, the site classifies most other classifications as direct children, including the Species Enhydra lutris (Linnaeus, 1758) or the Nutria marina, sea otter, under which most of the remaining classifications are grouped. Of these, the Integrated Taxonomic Information System lists direct children of this species as the subspecies Enhydra lutris kenyoni (Wilson 1990) known by its common name of northern sea otter, the Enhydra lutris lutris (Linneaus, 1758) or common sea otter and the Enhydra lutris neries known as the southern sea otter. Among these classifications for sea otter listed with the system, the subspecies Enhydra lutris kenyoni (northern sea otter), the subspecies Enhydra lutris lutris (common sea otter) and the subspecies Enhydra lutris neries (southern sea otter) are also listed separately within the menu. Only one classification of sea otter did not fall within the same Genus category as the others. This was the smooth-coated otter. This type of otter is classified as being of the Genus Lutrogale (Gray 1865) and the Species Lutrogale perspicillata (I. Geoffroy Saint-Hilaire, 1826). The direct children listed as subspecies to the smooth-coated otter include the Lutrogale perspicillata perspicillata and the Lutrogale perspicillata sindica, although neither of these subspecies are included in the automatic search returns for the common name of sea otter. In addition to providing the entire taxonomic classification for the sea otter and its related subspecies, the site provides a great deal of additional information. Geographic location is listed on some, but not all of the classifications listed, illustrating that some form of otter is present in northern and southern Asia, North America, Europe and portions of Central America. Lists of references regarding the various subspecies are provided with links to the experts if available and comments are made when appropriate, such as when a particular subspecies is endangered or threatened. Where are Sea Otters found geographically and in what ecosystems do they reside? What role does the Sea Otter play in this ecosystem? Which direct interspecies interactions are most important...that is, how does it interact with other species? Sea otters are found generally on the coasts and on the islands of the Pacific, being present all the way from Japan in the west to the various islands found off the coast of California in the east, although they have been found in Mexico and in parts of Russia (“Education”, 2001). They reside in the kelp forest ecosystem. This ecosystem is fairly specific, existing only in shallow coastal waters that remain relatively clear in order to facilitate photosynthesis within the kelp. Water temperatures conducive to this ecosystem range between 4 and 20 degrees Celsius, or 39.2 and 68 degrees Farenheit. A mild, nutrient-rich current is also required, but kelp can grow in both soft and hard surfaces. Kelp forests are also the home of numerous kinds of sea urchins, providing sea otters with a plentiful supply of food (“Kelp Forest”, 2006). The role the sea otter plays in this ecosystem is significant. “Sea otters are a keystone species in the kelp forest ecosystem, eating sea urchins, clams, snails, sea stars, squid, octopuses and abalone” (Rodman, 2005). They are voracious eaters, eating as much as one quarter of its body weight every day, which amounts to approximately 10-15 pounds of food daily (Smith & Smith, 2006). This has a significant impact on the shellfish in the area. Therefore, the numbers of sea otters in the area determines the health of the area. When there are not enough sea otters, the numbers of shellfish, especially sea urchins, escalates. The rising number of sea urchins feed on the base of the kelp, weakening it to the point of death. When enough of the kelp stalks have been damaged, the kelp forest is decimated, causing much of it to simply float away leading eventually to the total destruction of the kelp forest. With the destruction of the kelp forest, other marine animals lose their habitat as well. The kelp is important to the otters in more than just providing a ready food supply. When eating or sleeping, otters will frequently wrap the kelp around them. This provides them with an anchor to prevent any kind of drifting as well as protection from larger predators (Rodman, 2005). By wrapping pups in kelp, mother otters are able to gain the time necessary to hunt for both themselves and the baby while remaining relatively certain of the location of their pup when they return. How do population numbers of Sea Otters fluctuate over time? What is the reproductive/life history of the Sea Otter? What are the primary factors/ selective pressures that influence population numbers? Describe ecological studies that have been done on Sea Otter populations. What factors contribute to the population cycles of these animals? How "important" is this population to the ecosystem? If Sea Otters were to vanish, what would be the likely outcome in the ecosystems they inhabit? The Sea Otter typically has its first pup at around the age of four or five years old and the gestation period is typically four to five months (“Education”, 2001). When born, baby Sea Otters can measure up to two feet in length and weigh more than five pounds (Smith & Smith, 2006). Although they can usually eat meat right away, they are usually nursed until they reach approximately 30 pounds. Pups usually remain with their mothers for the first eight months of their lives before separating naturally into male and female groups (“Education”, 2001). Females typically remain together in family groups but hunt alone. Male Sea Otters will often form their own, separate group. The population numbers of sea otters were drastically reduced, nearly extinguishing them, during the 18th and 19th centuries due to overtrapping by colonists and other explorers. For this reason, the Sea Otter was placed on the threatened list, providing some protection to the animals. “In 2003, it was estimated that this threatened marine mammal had a population size of 2,150 animals between Half Moon Bay and Point Conception” (Smith & Smith, 2006). Although efforts have been made to re-introduce the sea otter to previous habitats, these efforts have not been wholly successful. An attempt to re-establish a Sea Otter population on San Nicolas Island with a small initial group of 30 has shown little success (Smith & Smith, 2006). Research into the causes of otter deaths has indicated they are a highly susceptible mammal. Small populations located in relatively isolated areas increases their chances of being heavily impacted by a single oil spill, for instance, in which many otters die as a result of the natural insulation of their fur being impacted by the oil or by internal damages caused by ingesting oil while trying to groom. In addition, it has been discovered that otter deaths along the coasts are caused by Toxoplasma gondii, which is a protozoan parasite that commonly infects housecats (Smith & Smith, 2006). In otters, the effects of this particular parasite have been increased rates of meningitis and associated abnormal behavior. Because of experiments with mice, in which infection illustrated a lack of fear of cats, it is believed a similar reaction is taking place in otters as “otters killed by sharks have a higher than normal rate of infection” (Smith & Smith, 2006). However, with the disappearance of the sea otter, we must expect also the disappearance of the kelp forest ecosystem for reasons enumerated above. Describe the fluctuations in currents and water temperatures in the Pacific Ocean described as "El Nino" "La Nina" and "ENSO" (El Nino Southern Oscillation) events and describe the influences these changes in equatorial waters have on Northern Sea Otter populations. The El Nino/Southern Oscillation (ENSO) includes the climatic and current changes that occur with the two more familiar events known as El Nino and La Nina. The ENSO is a large oscillation pattern that affects the waters of the Pacific Ocean as well as those of the Indian Ocean. These changes impact the climatic conditions of just about every land form and have tremendous effects upon the marine life of these bodies of water. El Nino itself is a term confined to the Pacific Ocean as water temperatures in the equatorial regions change by as much as 4 degrees Celsius (Kamensky, 2006). This change in water temperature causes the surface of the water to swell. Because these changes occur in association with changing trade winds, scientists aren’t sure which is the cause and which the effect. However, the results of El Nino are significant. El Nino occurs when the eastern and central portions of the Pacific warm up and begin to move eastward rather than westward (Kamensky, 2006). This heats up the air, disrupting the usual wind patterns and adding moisture to the atmosphere. As a result, some areas experience drought while others, such as the northeast United States, experience warmer and wetter winters and warmer summers. La Nina, as the name might imply, has the opposite effect from El Nino. This weather pattern is characterized by cooler than normal water temperatures along the equator and weaker temperature differences between the equator and higher latitudes (Hagmeyer, 2003). Like El Nino, La Nina shifts the position of the jet stream, this time to the south. For the American continent, this means much drier conditions, increased chances of wildfires and cooler overall temperatures. The level of the water also drops with the cooling temperatures. In addition to having significant effects on human populations and habitats, these weather patterns have contributed significantly to the deaths of sea otters. This is for a variety of reasons. The first is due to severe winter storms that are increased in intensity with El Nino. “When big storms occur they produce high waves which can cause sea otters to lose sight of one another, and for the mothers and their young pups to become separated. The very intense winter storms during the El Nino of 1997-1998, and another in 1982-1983, caused an unusually high number of pups to become lost from their mothers, and many died” (“Natural Causes”, n.d.). Rising surface levels can also have an impact on the kelp forests, reducing the otter’s natural ecosystem and removing their source of protection. What are additional significant/interesting adaptations of Sea Otters that allow them to survive (...unique feeding mechanisms, camouflage, courtship rituals, escape/capture strategies, reproductive strategies, etc.)? There are several interesting things about the sea otter that are unique to this creature above all other marine mammals. To begin with, they have some of the densest fur of any mammal. This is because, unlike seals and other marine mammals, sea otters have no natural insulation of their own other than their fur. “The Southern Sea Otter have a fur density of 125,000-155,000 hairs per square centimeter … without a layer of blubber like other marine mammals, sea otters rely on a layer of air trapped within the undercoat next to the body” (Smith & Smith, 2006). More than simply keeping them warm, this fur plays a major role in the survival of otter pups as well as a significant role in their near extinction. Otter pups are kept safe by the extra air trapped within their fur. Their light weight prevents them from making prolonged dives or from diving too far below the water’s surface. As a result, they are typically wrapped with some kelp to keep them in place, bobbing like a cork on the water’s surface, while the mother hunts for food to feed them (“Education”, 2001). In addition, this incredibly dense fur proved to be both luxuriant and warm once they were discovered by trappers. This quality spurred large-scale hunting and trapping efforts, reducing the sea otter population to such an extent that they were nearly made extinct. Otters are also of a select group of mammals that employ the use of tools to achieve their ultimate ends. “Among the very few marine mammals known to use tools, they break open clams and abalone with stones to get at the meat inside” (Rodman, 2005). In addition, otters have been observed to dip their food into the water to wash off excess shell fragments and to use their stomachs as dinner plates while floating on their backs in the kelp beds. Rather than eating all their food as they catch it, sea otters tend to bring ‘plates’ of food up to the surface to eat at their leisure. However, they are also well adapted to their diet with extraordinarily strong jaws, teeth and jaw muscles. “The jaw muscles can exert a tremendous force and are so strong that the lower jaw could be dis-articulated if it were not for the special articulation that the jaw has with the skull” (Smith & Smith, 2006). In this special arrangement, the skull of the otter is wrapped around the jaw at the point of articulation, providing it with enough support to prevent dis-articulation from occurring. References Education Marine Mammal Information: Sea Otter. (January, 2001). The Marine Mammal Center. October 31, 2006 Hagemeyer, Bart. (2003). “El Nino and La Nina.” My Hazardous Weather. Melbourne National Weather Service. October 31, 2006 < http://www.floridadisaster.org/hwa03/el_nino.htm> Kamenski, Lauren. “El Nino.” (2006). Stonybrook University of New York, Department of Geosciences. October 31, 2006 < http://www.geo.sunysb.edu/classes/oldclasses/cei542/Workgroups/atmosphere/kamensky/index.html> “Kelp forest.” Wikipedia, The Free Encyclopedia. (October 13, 2006). Wikimedia Foundation, Inc. October 31, 2006 . “Natural Causes.” (n.d.). ThinkQuest. October 31, 2006 < http://library.thinkquest.org/J0111704/mainextcopy/naturalcause/naturalcause.html> Rodman, Andrew. “Sea Otters: A Beautiful Animal.” (June 1, 2005). Center for Biological Diversity. October 31, 2006 “Sea Otters.” Integrated Taxonomic Information System. (October 11, 2006). October 30, 2006 < http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt> Smith, Thomas & Smith, Robert. (2006). Elements of Ecology. (Sixth Edition). Pearson: Benjamin Cummings. Read More