Otter

Previous Animal - Enhydriodon Dikikae Future Animal - Enhydra Australis

** Modern Animal - Otter **

Introduction
The otter is the common name which refers to the semi-aquatic mammal of the subfamily //Lutrinae.// They are members of the weasel family, //Mustelidae// which includes other carnivores such as ferrets, martens, polecats, badgers, stoats and mink. There are thirteen species of otter //(see below)//, which belong to several genera; //Lutra, Aonyx, Enhydra, Lontra, Pteronura// and //Lutragale//.

Scientific Classification

 * **Level ** || **Classification ** ||
 * **Kingdom** || [|//Animalia//] ||
 * **Phylum** || [|//Chordata//] ||
 * **Subphylum** || [|//Vertebrata//] ||
 * **Class** || [|//Mammalia//] ||
 * **Order** || [|//Carnivora//] ||
 * **Suborder** || [|//Caniformia//] ||
 * **Family** || [|//Mustelidae//] ||
 * **Subfamily** || [|//Lutrinae//] ||

Species

 * **Family //Mustelidae//**
 * **Subfamily //Lutrinae//**
 * **Genus //Pteronura//**
 * Giant otter //(Pteronura brasiliensis)//
 * **Genus //Lontra//**
 * American river otter //(Lontra canadensis)//
 * Marine otter //(Lontra felina)//
 * Neotropical otter //(Lontra longicaudis)//
 * Southern river otter //(Lontra provocax)//
 * **Genus //Enhydra//**
 * Sea otter //(Enhydra lutris)//
 * **Genus //Lutra//**
 * Spotted necked otter //(Lutra maculicollis)// also, //(Hydrictis maculicollis)//
 * Eurasian otter //(Lutra lutra)//
 * Hairy nosed otter //(Lutra sumatrana)//
 * **Genus //Aonyx//**
 * Cape Clawless otter //(Aonyx capensis)//
 * Asian small clawed otter //(Aonyx cinerea)//
 * Congo otter //(Aonyx congicus)//
 * **Genus //Lutragale//**
 * Smooth coated otter //(Lutragale perspicillata)//

Description
Otters have a lithe, slender body with short legs, a flattened head with small ears, and a long neck, giving them the same general proportions as a weasel. On a global scale, they are the smallest of all marine mammals, although size varies according to species. Their weight ranges from the Oriental Small Clawed Otter (//Aonyx cinera)// at 2.7-5.4kg with the Sea Otter (//Enhydra lutris//) and the Giant Otter //(Pteronura brasiliensis)// weighing up to 45kg. The average length of otters is around 1.2 metres. A famous characteristic of otters is their very thick and durable fur, which are generally shades of brown which is also lighter on the underside and facial areas. Historically, they have been hunted for their pelt, which has led to a threatened conservation status for many species. They have webbed, mostly clawed feet and a strong, muscular tail, the base of which is almost as thick as the body, enabling it to easily navigate and move quickly through the water. An otter’s diet consists mainly of small aquatic animals; namely fish, as well as sea urchin but they are also able to eat birds. Their lung capacity, which is impressive for the size of the creature, allows it to travel underwater for approximately 400 metres without surfacing for air. However, otters are just as mobile on land, albeit their short limbs, being able to travel faster than humans can run. These creatures are positively viewed as fun, active and amiable, being willing to interact with humans. This is demonstrated where they slide down steep banks of mud or snow, and are seen plunging into water or a snowdrift. They are intelligent and inquisitive, and are easily able to be trained when young.

Sea Otters (//Enhydra Lutris//) – A Specific Example
This species of otter is highly unique, with a few special features, which make it different to the common otter (Eurasian otter, //Lutra lutra// and river otters of the genera //Lutra// and //Lontra//). The main difference is that they are fully aquatic, being able to live the entirety of their lives in the water. There are three recognised subspecies according to the World Register of Marine Species of the sea otter which are:
 * //Enhydra lutris lutris// – The Russian sea otter
 * //Enhydra lutris kenyoni// – The Alaskan sea otter
 * //Enhydra lutris nereis// – The Southern sea otter

Scientific Classification
Also commonly known as the Great Sea Otter, they were previously been hunted to near extinction in 1910 because of their coats. It is considered the most expensive otter fur, described as thick and lustrous, and is reddish to dark brown in colour. Fortunately, sea otters are now fully protected species, and are gradually increasing in numbers. The size of sea otters is around the average of all otters. Their length from head to body ranges from 76 – 120cm which excludes the 25 – 37cm tail. Their weight ranges from 16 – 41 kilograms. Sea otters have reduced forefeet and large hind feet which are broad and flipper like. An interesting characteristic of sea otters is that they are seen floating on their backs, with a stone on their chest. They use the stones as tools, for example, to smash molluscs, and in doing so, are one of the few mammal species to use tools.
 * **Level ** || **Classification ** ||
 * **Kingdom** || [|//Animalia//] ||
 * **Phylum** || [|//Chordata//] ||
 * **Subphylum** || [|//Vertebrata//] ||
 * **Class** || [|//Mammalia//] ||
 * **Order** || [|//Carnivora//] ||
 * **Suborder** || [|//Caniformia//] ||
 * **Family** || [|//Mustelidae//] ||
 * **Subfamily** || [|//Lutrinae//] ||
 * **Genus** || //Enhydra// ||
 * **Species** || //Enhydra Lutris// ||

=Habitat= The subfamily of otters, //Lutrinae// make up the largest subfamily, out of the //Mustelids//. Consequently, otters are of great abundance worldwide, even though there are many threatened species as a result of the human interaction of hunting their prized fur. Otters can be found in almost every continent, except for Australasia and Antarctica.

Species Distribution

 * **Europe**
 * Eurasian otter //(Lutra lutra)//
 * **Africa**
 * Eurasian Otter //(Lutra lutra)//
 * Cape Clawless Otter //(Aonyx capensis)//
 * Spotted-necked Otter //(Lutra maculicollis)//
 * Congo Clawless Otter //(Aonyx congica)//
 * **Asia**
 * Eurasian Otter //(Lutra lutra)//
 * Smooth-coated Otter //(Lutra perspicillata)//
 * Hairy-nosed Otter //(Lutra sumatrana)//
 * Asian Short-clawed Otter //(Amblonyx cinereus)//
 * **North America**
 * River Otter //(Lontra canadensis)//
 * Sea Otter //(Enhydra lutris)//
 * **South America**
 * Giant Otter //(Pteronura brasiliensis)//
 * Neotropical Otter //(Lontra longicaudis)//
 * Southern River Otter //(Lontra provocax)//
 * Marine Otter or Sea cat //(Lontra felina)//
 * River Otter //(Lontra canadensis)//

General Environment
These semi-aquatic animals tend to live in bodies of water close to land, always generally within a few hundred metres of water. This is because of their diet, which depends largely on aquatic life. Depending on the species, otters survive in both freshwater and saltwater/marine environments. Examples of areas which they reside include many inland waterway systems such as rivers streams and creeks (river otters, genera //Lutra//, //Lontra//, and //Pteronura//), also favouring slow-moving waterways (//Pteronura// genus) and the security of forests and wetlands, enjoying swamp and marsh environments. Additionally, the sea otter (//Enhydra Lutris//) live as fully aquatic mammals, living in the marine environment of the north of the Pacific Ocean //(see below – specific habitat)//. Exclusive of sea otters (//Enhydra lutris//), most otters spend a great deal of their time on land. They are found hiding in their homes, which are burrows or dens called holts or couches, which are permanent. Sometimes, these are previous dens of beavers. Although otters do not tend to be territorial when in the water, they are highly protective of their created land habitat.

Space and Movement
Otters are able to travel great distances, both on land and through the water. Many species of otter undergo seasonal movements; however, they do not migrate extensively. Otters all have a home range, which is the animal’s frequently visited area of land and water and belongs to their entire raft (group of otters). The size of home ranges varies. It depends on the species of otter, their location and the distribution of their resources. However, the home range for males is generally larger than the home range for females. A general size for the home range of an otter is around a 16km straight line length. Home ranges are not the same as an otter’s territory. The territory of an otter is specifically their own, and are therefore, in general, smaller than home ranges. Although not particularly territorial, same-sex territories do not overlap. The territory of an otter can be marked with their scent, and spraint (the scat of an otter).

Sea Otters (//Enhydra Lutris//) – A Specific Example
As sea otters do not have to spend time on land, they have quite a different habitat to other species of otter. The biosphere in which otters live is mainly the north parts of the Pacific Ocean (//see distribution map//). Therefore, they have adapted to live in the cold, temperate waters. They inhabit the aquatic biome of coastal areas, in shallow waters less than approximately 40 metres deep, living less than 1km from the shore. This is for convenience, in order to catch their food.[2] Otter habitats are found as part of the kelp forest ecosystem. Kelp forests are areas which are home to countless other species beside sea otters, including sea urchins, fish, abalone and sea stars. An otter is central to maintaining the nature of kelp forest ecosystems, as they contribute to biodiversity and balance //(refer to food web below)//. This was made clear to scientists when sea otters were hunted and were threatened to become extinct. Being the top predator for sea urchins, without sea otters, the kelp forests were greatly reduced due to the main herbivore, sea urchins. This relationship between sea otters and kelp is two-fold. Sea otters have been found to wrap themselves in kelp when they sleep. They also provide shelter for sea otter mothers and pups. [3]

=Adaptations= Adaptations are inherited special characteristics which are favourable in allowing an organism to survive in the environment that it lives in. An animal is affected by living and non-living factors in the environment. It is a result of these pressures that an animal adapts, in order to survive. There are 3 classifications of adaptations. These are: //The adaptations discussed below are specific to Sea otters (Enhydra Lutris), but some can apply to other species of otters.//
 * Structural adaptations, which are physical, and able to be observed.
 * Functional or physiological, which involves the internal structure of the organism
 * Behavioural adaptations which pertain to the way an animal acts.

1. Fur
Otters live in temperate waters. These can be very cold environments. Otters do not have blubber to insulate them, like other marine mammals that live in similar climatic conditions, such as seals. Instead, the small creatures have dense coats of fur, which made up of fine hairs, with an overall velvety texture, which provides it with insulation, and reduces the loss of body heat in the water. Otters have two types of fur, which is similar to other mammals. Stout guard hairs provide a waterproof covering, outer layer of long hairs. They also have an even more dense covering of short and fine underfur. This adaption is vital for its aquatic survival, as it is 27 times easier for animals to lose heat in water, compared to air.

2. Teeth
As meat eating carnivores, otters must have very strong and sharp teeth to be able to digest their food and survive. The structure of teeth in an otter’s mouth is unique and assists it to survive in its environment. An adult otter has 32 teeth in total. Most of these teeth are molars. All species of otter have 3 pairs of incisors except for the sea otter only has two pairs, in comparison to humans which have 4 pairs. Incisors are used to tear food, however, as the sea otter only has two pairs, they tend to crush and grind their food. An environmental pressure that could have given rise to this particular structure of sea otters could be their diet. In this way, sea otters are more suited to the animals which they consume, for example, being able to crush the shells of invertebrates by using their molars instead of tearing flesh with incisors.

1. Grooming
As explained above, otters must be able to survive in the cold climatic conditions. For an otter to maintain the insulating qualities of their fur coats, they groom themselves frequently, sometimes for a great deal of time. They groom themselves by using their paws to remove debris and their claws to comb over their fur. This adaption is one which would have developed in favour of their physical characteristics. Their flexibility and the feature of loose fitting skin allow it to groom every part of its body. Another technique that otters use to improve insulation of their fur is to aerate it, through blowing air into it, or whipping the water into foam. A research statistic shows that sea otters spend from a minimum of 11% to as much as 48% of their day grooming themselves. River otters also groom their fur, after drying themselves on the land.

Behavioural 2 – Communication
The sea otters have a mostly solitary social structure. Therefore, sea otters must be able to communicate with others, and obtain information about others. This is achieved through visual behaviour and vocalisations. For example, when an individual sea otter approaches a raft (group) of sea otters, it is common for the otter to make a “head jerk”. The otter jerks its head from side to side, while sniffing the other otters when it approaches. Vocalisations are also an important part of otter communication. All species of otter are able to produce sounds to vocally communicate. Through research, 9 different types of vocalisations have been identified. These vocalisations related to emotions. For example, stressed sea otters are able to make whining, hissing and growling noises, and sea otter pups (young) frequently make high pitched squeals to keep in contact with their mother, for when she returns from foraging.

Circulatory System
Otters have another adaption to assist it to survive in their cold environment. To travel in the water, sea otters must move their feet very quickly; more so than the rest of their bodies. This means that this area of the body will suffer from more heat loss. To be more heat efficient, the veins and the arteries in the extremities of an otter are very close together. This adaptation allows for heat from the blood in the arteries to transfer to the de-oxygenated blood in the veins, which are travelling back to the heart. This is called a ‘countercurrent heat exchange system’. This system prevents them from the blood to be lost to the environment, as the otter swims in cold waters.

Links with Other Animals

 * Beavers are also semi-aquatic mammals, and share a possible ancestor, //Castorcauda lutrasimilis[[file:///C:/Users/StudentID/Documents/2011 Year 10/Science/Evolution/Designer Animals.docx#_ftn4|**[4]**]]//; http://designeranimals2011.wikispaces.com/Beaver//
 * //Platypus are also semi-aquatic mammals; http://designeranimals2011.wikispaces.com/Platypus//
 * //The otter is the main predator for sea urchins in the kelp forest ecosystems; http://designeranimals2011.wikispaces.com/Sea+Urchin-modern//

===**Bibliography** ===


 * //SeaWorld Parts & Entertainment. (Unknown).// Otters Infobook Index//. Retrieved June 22, 2011, from []//
 * //Bluske, B. (2004).// Enhydra Lutris The Sea Otter//. Retrieved June 22, 2011, from []//
 * //Gunderson, A. (2002).// "Enhydra lutris" (On-line), Animal Diversity Web. //Retrieved June 22, 2011, from []//
 * //Infoquis Publishing, Co. (2009).// Information and Facts about Otters//. Retrieved June 22, 2011, from []//
 * //Defenders of Wildlife (Unknown).// Sea Otter//. Retrieved June 22, 2011, from, []

// //WoRMS taxon details// Enhydra lutris //[]// // []

// []