Sea otters are a keystone species, a species upon which the health of their entire ecosystem is largely dependent. During the 18th and 19th centuries, sea otters were hunted to near-extinction for their valuable pelts. Before the 1700's, the range of the sea otter extended in a continuous belt around the Pacific, from Japan to Baja California. Today, sea otter numbers are slowly recovering, but their distribution remains fragmented and patchy throughout their former range.
By the early 1900's, excessive hunting left just a handful of southern sea otters (Enhydra lutris nereis) surviving along the Big Sur coast - and nowhere else in California. Monterey Bay was devoid of sea otters, and its biologically rich forests of giant kelp were suffering greatly. The presence of sea otters ensures healthy kelp forests, as the otters prey on sea urchins, which in turn consume kelp. Without the otters, kelp forests are overgrazed by sea urchins and biodiversity plummets. During the early- and mid-20th century, Monterey Bay was something of a barren wasteland - nothing like the thriving kelp forests we see today!
Eelgrass beds, which act as nurseries for many types of fish and mollusks, also require otters in order to thrive. Sea otters prey on crabs, and crabs feed on sea slugs. Sea slugs feed by scraping algae off blades of eelgrass. Without otters, crab populations boom, which causes sea slug numbers to drop and allows algae to thrive, essentially suffocating the eelgrass. Effects of the failure of eelgrass beds can be felt throughout the food web.
In addition to being a keystone species in their ecosystem, sea otters are also an indicator species; the health of the sea otter population reflects the overall health of the greater marine ecosystem.
Sea otters were protected under the Endangered Species Act in 1977. Thanks to herculean efforts by research and conservation groups, sea otter populations in California have risen and these marine mammals can now be found from Half Moon Bay in San Mateo county to Point Conception in Santa Barbara county.
But sea otters are not out of the woods yet (or should I say, not out of the kelp forests yet? Bad pun fully intended). Infectious diseases and parasites still threaten otter populations, and may be caused by highly contaminated coastal waters. Oil spills are absolutely detrimental to sea otters (and other sea life!), as oil destroys the insulating properties of otters' fur and leads to hypothermia (sea otters are the only marine mammals that do not have insulating blubber, and instead rely on well-groomed thick fur). Ingesting and inhaling oil is fatal for marine life as well.
If you get the chance, take time this week to learn more about the role sea otters play in their ecosystem, and to appreciate the efforts conservationists have made over the last few decades to ensure the survival of this incredible species. It is a beautiful time of year to visit Monterey Bay, which is one of the best places to see sea otters in the wild!
For more information about Sea Otter Awareness Week, visit their website: https://www.seaotterweek.org/