Delta Wanderings XXVII – Dec 2016 -- “Aquatic Mammals of the Delta"

December 07, 2016 • 2 Comments

Can you tell what kind of aquatic mammals these guys are? They are common in the California Delta

We get 4 types of Aquatic Mammals in Discovery Bay: We have resident Beavers, River Otters and Muskrats and occasionally we get transient California Sea Lions (not Seals) in the Delta coming up from the San Francisco Bay. Sometimes these guys are hard to tell apart especially when most of their body is submerged while swimming. There are of course some tell tale signs; like body shape, size, food type, teeth, tail structure, and behavior. While all the below photos were taken in deep water in Discovery Bay, our resident aquatic mammals can also be found in Willow Lake.

Delta Wanderings Photo Gallery: http://www.DeltaWanderings.com

(A periodic photo blog of our Discovery Bay and Delta Wanderings)

This little guy is a Muskrat often confused with our local Beavers and Otters

Muskrats are rat like, notice the smaller, roundish body and long thin scaly, non-hairy tail. Like Beavers and Otters, these guys live in dens dug into the mud embankments along the Delta shoreline. During low tide you can often see the entrances to these dens, along with foot and tail prints.

Muskrats are rodents (like beavers), notice the classic teeth of a herbivore, plant eating animal. Muskrats are the smallest of our water mammals, up to 4 lbs and 2 feet long

Otters on the other hand are larger and have elongated bodies with a long round, pointy, hairy tail and canine type teeth as they are carnivores eating fish, crabs, clams and crayfish. Adults are 3-4 feet long and 11-30 lbs.

Their long bodies make for sleek swimmers

Of our 3 resident aquatic mammals, Otters seem to be more curious traveling further and exploring their environment during the day often climbing on docks and boats. They are the more playful of our resident aquatic mammals.

BTW Otters often piss and crap on your dock

Beavers are much bigger than Otters and Muskrats, have large ears, a triangular head, roundish body and a large flat platter like tail. 3-4 feet long and 24-70 lbs.

Notice the classic teeth of a herbivore and floating plant stalks (his food) nearby, this Beaver's teeth are similar to those of Muskrats. This Beaver lives along Indian Slough and he is sitting in front of the entrance of his den.

Beavers like their rodent Muskrat cousins are also herbivores, this one is eating some plant material which they do very often given their size and weight

Beaver tails very different than our other aquatic mammals, broad, flat and hairless

(C)Bill Klipp 2012

Beavers can be skittish and when startled or when they want to send you a message like you are in my territory they make a large tail slap on the surface of the water.

Beaver tail slaps can be very loud and startling

Delta Beaver Video Click above photo

We also get transient California Sea Lions (not Seals) in Discovery Bay. The swim up from the San Francisco Bay hunting fish like Bass, Catfish and Carp. Sea Lions travel long distances and are often found in the more open deeper waters of the Delta. Most often seen in the Delta winters but can sometimes be seen all year round. Adult males can be up to 8 feet long and weigh 400-600 lbs while females can be 6 feet long and 200 lbs.

Notice the large canine type teeth of this carnivore

Have you ever wondered about the main differences between Seals and their "second cousins," the Sea Lions? Sea lions have small flaps for outer ears "true" seals lack external ears altogether. Sea lions are noisy, Seals are quieter. Sea Lions vs Seals are more adapted to land as their rear flippers are like feet they can walk on while Seal’s rear flippers angle backward so when on land they wiggle around vs walk. Seals don't like leaving the water unlike Sea Lions who like to lounge in the sun on land

If you missed my last "Delta Wanderings" blog post check it out at: http://billklipp.zenfolio.com/blog/2016/12/delta-wanderings-xxvi-dec-2016---parade-of-lights

For more photos visit Bill’s Discovery Bay & Delta website: http://DiscoveryBay.me

Check out my online Photo Website at: http://www.DiscoveryBay.me or http://www.wkimages.net

* Any use of these images requires the prior written permission of Bill Klipp the photographer, no other uses of any kind including print or electronic are permitted without the prior written permission of the photographer.

Comments

jim spence(non-registered)

As they say on Laugh in Very interresting .

Richard Pontes(non-registered)

Thank you for the wonderful article.

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