Mendocino: Big River Wildlife

Big River is certainly a very special place. Here at Catch a Canoe we have listened to the stories of thousands of paddlers who’ve returned to our dock. Our first question typically is: how was your trip? The answer that invariably comes back more than any other is – “we saw some seals!” or “we saw the family of otters!”

As enjoyable as paddling a canoe or kayak up beautiful Big River is, it’s the wildlife which really grabs us the most. Seeing the marine mammals and abundant bird life is wonderful, but having an opportunity to learn all about them from an experienced local naturalist is the best way to fly/paddle!

big river mendocino harbor seals

Harbor Seals (Phoca Vitulina)

Harbor Seals can be observed in Big River Estuary at almost any time of year. These shy, curious pinnipeds spend much of their time foraging in the ocean as well as in the estuary.

Equally important to the time spent foraging, is the time they spend resting or “hauled out” on offshore rocks, logs or small islands within the estuary. This allows them to thermoregulate or bring their body temperate up. Did you know seals can get hypothermia?

In the early spring it’s possible to quietly observe pups with their ever watchful moms. The mom and pup bond is strong and begins immediately after birth with nose to nose contact. This “kiss” is repeated frequently on land as well as in the water. If you’re lucky enough to observe this, it’s sure to make you smile.

Harbor seal pups are one of the few pinniped newborns that are capable of swimming within hours of birth and are weaned at around six weeks of age. Once weaned, they learn from mom to forage on their own, but may start out dinning on crustaceans and graduate later to faster moving fish as they grow into adept predators.

It’s extremely important to observe seals from a distance. Frequent disturbances can break the bond and cause pups to be abandoned. Please stay back a minimum of 100 feet.

To report a stranded Marine Mammal please contact The Marine Mammal Center @ (415)-289-SEAL (7325)

River Otter (Lontra Canadensis)

River otters are a key indicator of the health of an ecosystem. Just knowing that River Otters make Big River home is a high compliment to the dedicated, hard work of many to protect California’s second longest tidal estuary.

It is pure joy to catch a glimpse of these playful aquatic predators. The quiet observer may hear otter families “chirp” to each other as they cruise the eel grass and repeatedly dive for prey. Look for a trail of “champagne bubbles” on the water surface that escape their dense fur when they dive. Reminiscent of a teenage human they spend a great deal of time eating, grooming, playing and sleeping. These activities however are critical to their survival. Oily, un-groomed fur will not keep an otter warm while foraging for hours each day in very cold water. Because of their high metabolic rate they need to consume close to 20% of their body weight each day. That is a lot of Crayfish! They also prey on a wide variety of other aquatic animals such as fish and frogs and sometime even birds.

River otters can stay under water for up to eight minutes and can close their ears and nostrils to keep the water out. They use their whiskers to detect vibration of their prey in the sometimes dark and murky depths of up to 60 feet.
Always keep in mind that we are the visitors to this wild and scenic place. … please do not interfere with the activities of the animals that make this their home and keep back at least 100 feet.

big river mendocino bird watching


The Birds seen along Big River Estuary vary drastically with the season. Expect to see and hear different types of birds depending on what time of year you visit.

One thing you can count on year round is a kind of quiet seldom found in our busy lives. Once you leave the beach area and head up the estuary, you may become aware of the sound of the wing beats of Ducks, Geese or Cormorants as they wing their way up or down the estuary. There are a number of bird species that choose to raise young along the estuary and if you visit in the early spring you may be treated to a cacophony of birds songs, cries, croaks grunts or “Gaaaks” depending on the bird. Great Blue Herons are year round residents and can be seen patiently awaiting their chance to skewer a fish along the bank or you may witness the adults bringing food to the young in the tree tops high above the first tidal flat. This is a Heron “rookery”. There are also Osprey nests in this area. Further up the estuary there is a Double-crested Cormorant rookery.

Because of the dense forest surrounding the estuary many birds will be heard rather than seen. So listen … There is nothing more beautiful than the song of the elusive Hermit Thrush breaking the silence.

wildlife being respectful guidelines


Sarah Grimes is a naturalist, a teacher, an artist, a mother, a wife, and a rescuer of marine mammals. Sarah leads some of the Big River Guided Tours and also wrote the wildlife descriptions found on this page. Her favorite place is out of doors where nature and wildlife infuse her spirit. She has participated in scientific projects involving marine mammals and birds in many locations along the Mendocino Coast and is intimately familiar with many of the species to be found along Big River.

Sarah has helped youngsters of all ages to discover the unexpected within the obvious. She knows about birds and marine mammals from the classroom but most of all from her experiences rescuing the sick and injured, watching harbor seal pups being born each year, and helping visitors from near and far spot their first whale spout.

Her stories will entertain as you search for marine mammals and the abundant bird life found in and around Big River.

““When nature has work to be done, she creates a genius to do it.” — Ralph Waldo Emerson