Sea otter - Hotsprings Cove, Tofino BC
Sea otters off the Aleutian Islands, Alaska, have decreased drastically over the past 15 years. Transient killer whales have been suggested as a cause but sea otters are relatively low in energy reserves versus other marine mammals due to their thin blubber layer. Otters have a very thick fur layer with a million hairs per square inch to keep them warm. Their pelts is why they became extinct off the British Columbia coast during the fur trade and decimated in the Pacific. Sleeper sharks have concurrently increased in population and need to be further investigated as a cause of the sea otter decline. The change in abundance of sea otters is cause for concern as they are a top predator in the kelp forest. Sea otters feed on urchins allowing for the kelp bed to grow. The forest provides protection and is a nursery for many species of fish and invertebrates. Disease and high contaminant levels have not been ruled out as a significant contributor to the sea otter decline.
Paper - A re-evaluation of the role of killer whales Orcinus orca in a population decline of sea otters Enhydra lutris in the Aleutian Islands and a review of alternative hypotheses