Sea otters, sea urchins, and kelp: Nature’s precarious balance
The water taxi from Zeballos dropped us near the outer end of Esperanza Inlet. From there we paddled west into the Nuchatlitz Islands where swells rolling in from the open Pacific send surges of water rushing in and out of rocky clefts crowded with brightly coloured starfish and anemones. We came to this wild, pristine part of the B.C. coast hoping to find sea otters. The lush beds of kelp were a good sign and as I threaded my kayak through the shifting fronds I was soon rewarded by a raft (family group) of eight sea otters, their heads held remarkably high above the water for a better look at my passing boat.
These large marine weasels ( Enhydra lutris ) are totally adapted to life in the water. They breed and spend their entire 10 to 11 year lives in shallow coastal water where they dive for shellfish, urchins, and slow-moving bottom fish. A single pup, born and nursed in the ocean, is carried on the back or chest of its mother who provides food and care for most of its first year. Much of a sea otter's life is spent floating on its back sculling with the webbed feet on its short hind legs while grooming its fur or manipulating food with its dexterous forepaws. One of the few animals to use "tools" sea otters will use a rock to break a shell that is too tough for its powerful jaws. Unlike other marine mammals sea otters have no protective layer of blubber, relying instead on their dense coat of fine underfur and guard hairs to keep them warm and dry.
Once common around the Pacific from the Aleutians to southern California, the demand for their fur saw them hunted to the verge of extinction. By the 1960s only a few small groups remained in isolated bays in Alaska and California. The B.C. otters were gone – and only then did biologists appreciate what a critical role these fur-bearing mammals play in the marine ecosystem.
An adult sea otter weighs more than 60 pounds and will eat a quarter of its body weight per day. With the urchin-eating otters gone, and with no other predators to control their burgeoning numbers, the spiny, algae-eating urchins decimated the marine plant life. Grazing on the bottom they not only devoured the smaller plants they also cut the holdfasts that anchor giant kelp to the bottom. The great underwater "kelp forests" were cut free to wash ashore and rot on the beaches and the diverse fauna they harbour was replaced by barren rock patrolled by hundreds of urchins ready to eat any plant that tried to grow.
In 1968 sea otters were re-introduced from the Aleutians to several spots on the B.C. coast and their population is growing. During our week in the Nuchatlitz we saw several dozen of these charming creatures happily floating among thick beds of healthy kelp. But they are still at risk, particularly from oil-spills which can foul their insulating fur and rapidly lead to death. When faced with danger females will try to protect their young by holding them under water. So as wildlife observers we must keep our distance, and guard against loving them to death.
September 1 — Monthly Bird Walk . Meet at the base of Lorimer Road at 7 a.m. Contact Michael Thompson for more information.
The Whistler Naturalists’ weekly Sunset Nature Walks are now finished for the year, but we’ll be hosting some all-day trips to places such as the Whistler alpine and to Cheakamus Lake in September. Watch this column for more details.
Written by: Jack Souther