Cute but Ferocious: River Otters

A word of warning… this is a post about predation and the pictures reflect that.

River Otters moved into Rodeo lagoon in the Marin Headlands about 4 years ago and the resident birds were ill prepared.

They became instant celebrities and many people went to the lagoon to try and catch a glimpse of the group. They started out seven strong but have since become a quartet.

Like lions on the Serengeti, they carefully stalk their prey. In this instance they were after mallards on the shore. Their main technique seems to be:
1. Locate prey floating in the lagoon
2. Submerge and close the distance underwater
3. Grab the prey from below and asphyxiate with a bite to the neck or drowning
Cute huh?

A juvenile gull snatched from mid-lagoon.

A Heermann’s Gull too slow to react gets caught and brought to a nearby dining spot.

After the hunter gets its fill the meal gets shared with the other otters waiting their turn. The number of feathers stuck in the vegetation nearby is evidence of many meals eaten here. The otter is working on the gull’s head (which, if you decide, you can see by clicking on the image).

One of these otters is an experienced hunter who seems to take on large prey the others pass up.

On rainy morning the gang sees a Great Blue Heron resting on shore and they all submerge and disappear.

30 seconds later the water around the heron boils and an otter lunges at the heron who leaps to safety just in time.

This Pelican wasn’t so lucky. It was one of many that the otters caught as they landed on the lagoon to rest during their meanderings down the coast. As the months went on, fewer and fewer Pelicans spent any time on the water and otters switched to other prey.

7 responses

  1. Excellent documentary post. Thanks!

    October 12, 2011 at 8:05 am

  2. adrianduque89

    nice photos!

    October 12, 2011 at 11:10 am

  3. John Wall

    Outstanding story!

    October 12, 2011 at 12:34 pm

  4. julie beddome

    I’ve been watching nature live for sometime now and it is difficult to watch at times, but everyone needs to eat…

    October 12, 2011 at 4:10 pm

  5. Sarah

    I love the shot of the otter leaping out of the water for the GBHE!!

    October 12, 2011 at 5:31 pm

  6. damn. very educational. and I always thought they only ate fish. and I alwys thought they were cute and entertaining as well. so they must be considered invasive – e.g. not native to the lagoon? someone must have introduced them (?). regardless, any enemy of pelicans and great blues…

    October 12, 2011 at 8:35 pm

    • Well they aren’t invasive as far as I know. They are more accurately referred to as “land” otters to distinguish them from their oceanic counterparts. They probably travelled over land by night to reach the lagoon from another location in the Headlands. There is some evidence that they can sneak along the coastlines too when feeling adventurous. The birds had gotten used to an otter free lagoon and had to make behavioral adjustments to a new predator… but the system seems to have found balance again and the otters are a valued part of the community. They are endemic to North America and have been around since the Bering land bridge so I think that classifies them as locals. I love watching them do their thing and, while they do kill birds, they don’t seem to have the power to adversely impact populations as a whole.

      October 13, 2011 at 5:08 am

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