Alaska is the largest state in the US, covering 665,400 square miles. It is home to a diverse range of habitats, including mountains, glaciers, forests, tundra, and wetlands, and has an extensive coastline, which is 44,000 miles long. Winter temperatures can fall as low as -20°C (-4°F) in the northernmost regions, while in the summer, maximums of 32°C (90°F) have been reported in Central Alaska. The oceans bordering Alaska provide a variety of habitats too, such as kelp forests, eelgrass meadows, and coral gardens. These support a great abundance of marine life, including that of economic importance – commercial fisheries are a major industry in this state.
Two species of otter can be found in Alaska: the northern sea otter and the North American river otter. These occupy vastly different niches and differ greatly in their ecology.
Alaska Otters
1) Northern sea otter (Enhydra lutris kenyoni)
- Native to the Aleutian Islands, southern Alaska, British Columbia, and Washington
- Family: Mustelidae
- Order: Carnivora
- Conservation status: Endangered
The northern sea otter can grow to lengths of 150 cm (5 ft) and has a dense brown or black coat. Its hind feet are webbed, and it has strong canines and molars to tear and crush its food. This species is well-known for its use of tools; however research has found that sea otters in Alaska use them much less than other populations – this is thought to be due to the prevalence of certain prey types influencing which foraging strategy is needed.
There are three distinct populations of the northern sea otter within Alaska: southeast, south-central, and southwest. They inhabit shallow coastal waters, usually over sandy or rocky substrate, where they feed on sea urchins, crabs, clams, mussels, octopus, and fish. Interestingly, male otters have been found to make longer foraging dives and consume more clams than females. The foraging habits of sea otters affect the communities within its ecosystem: for example, an absence of sea urchins due to otter predation can lead to increased development of macroalgae.
Several factors threaten the northern sea otter, including fishing, storms, and recreational activities such as water sports. Diseases such as phocine distemper virus are also a concern. The sea otter is protected under the Marine Mammal Protection Act, although hunting is still legal in cases where its sole purpose is to provide food to a person or family.
2) North American river otter (Lontra canadensis)
- Native to North America
- Family: Mustelidae
- Order: Carnivora
- Conservation status: Least concern
The North American river otter can grow to lengths of 90 – 120 cm (3 – 4 ft) with males typically being larger than females. These otters have short legs, webbed feet, a long narrow body, and a flattened head – all of which are adaptations to streamline them and maximize their efficiency while swimming. As well as being used as a rudder to help steer the otter through the water, the tail is utilized for fat storage.
This species can be found throughout Alaska, except for the Aleutian Islands. There are coastal populations of the river otter, which occupy timbered areas in close proximity to marine habitat and are rarely reported to move inland. The inland populations reside in lakes, marshes, ponds, and rivers, where they dig dens into banks or use hollow logs for shelter. Lontra canadensis primarily feeds on fish, although coastal populations in southeastern Alaska have also been found to supplement their diet with chitons, limpets, sea urchins, and gastropod mollusks.
Interestingly, male river otters have been discovered to be more social than females, and will often forage in groups. These otters also create latrine sites, where they mark their scent by defecating. The exact social function of this is poorly understood, although it has been suggested to relate to social dominance and marking feeding sites. These sites can provide researchers with a useful, non-invasive method for estimating the sizes of otter populations.
