The Bay Delta Region

It’s been a while due to the responses we’ve been having, but for this week’s blog, I’d like to get back to our region highlights, with Region 3, the “Bay Delta”. Recall that the California Department of Fish and Wildlife (CDFW) divides the state into 7 functional regions:

  • Region 1: Northern
  • Region 2: North Central
  • Region 3: Bay Delta
  • Region 4: Central
  • Region 5: South Coast
  • Region 6: Inland Deserts
  • Region 7: Marine

Region 3 consists of the Bay Delta counties from Sonoma and Napa in the north, east to San Joaquin, and south to Santa Cruz and Santa Clara  

With 19 Member Organizations within this area, it contains our most represented region: 

  • Sonoma County
    • The Bird Rescue Center in Santa Rosa
    • Wildlife Rescue of Sonoma County in Petaluma
    • Point Blue Conservation Science Headquarters in Petaluma
  • Marin County
    • Point Blue Conservation Science Palomarin Field Station in Bolinas
    • WildCare in San Rafael
    • Estuary and Ocean Science Center in Tiburon
    • The Marine Mammal Center in Sausalito
  • Solano County
    • International Bird Rescue (North) in Fairfield
    • Six Flags Discovery Kingdom in Vallejo
    • The Wild Neighbors Database Project 
  • Contra Costa County
    • Lindsay Wildlife Experience in Walnut Creek
  • San Francisco County
    • Aquarium of the Bay in San Francisco
    • Greater Farallones Association in San Francisco
    • California Academy of Sciences in San Francisco
  • Alameda County
    • Golden Gate Audubon Society in Berkeley
  • San Mateo County
    • Peninsula Humane Society & SPCA in Burlingame
  • Santa Clara County
    • San Francisco Bay Bird Observatory in Milpitas
  • Santa Cruz County
    • University of California – Santa Cruz
    • Marine Wildlife Veterinary Care and Research Center in Santa Cruz
    • Native Animal Rescue in Santa Cruz

While this region is highly populated and urbanized, it is also spread out over large areas of wetlands and mountains that surround the San Francisco Bay.  I got to see more of this area and its wildlife this past weekend when OWCN responded to a spill in the area of Fremont/Coyote Creek.  Thankfully the spill was of gasoline so it dissipated rather quickly, but we could see how difficult the situation could have been as much of the area is a network of vegetation-lined streams and mudflats.  This region is home to many endemic species, including some that I find particularly interesting:

Alameda Island Mole

This Species of Special Concern is found only on Alameda Island.  And even if you were there looking for it, it’s unlikely you will see any because they have a fossorial lifestyle (live most of their life relatively deep underground).  Like other moles, their tunnel openings at the surface have a volcano-like appearance that differs from what you usually see with burrowing rodents (gophers, ground squirrels, voles…).  They also do not typically form collapsing burrow tracts that you see with voles which burrow shallower to feed on the root systems of plants. 



Ground Squirrel

Point Reyes Mountain Beaver

Another seldom seen animal of Region 3, this Mountain beaver is endemic to the Point Reyes area.  Mountain beavers are often considered the most primitive rodent species.  But why are they called “beavers”?  They don’t frequent the water or build dams like the beavers we typically think of, and they don’t look like them either.  Their similarity comes from chewing down trees, or at least stalks and saplings.   

They are nocturnal, active year-round and territorial, remaining close to their burrow to defend it.  Like other Mountain beavers, their primitive kidneys are unable to concentrate urine, so they require a constant source of available water.  Their Preferred Optimum Temperature Zone (POTZ) is a chilly 40-60F.  And they have opposable thumbs!

San Francisco Dusky-footed Woodrat

This endemic Species of Special Concern of the Bay Area can be found from Point Reyes to Santa Cruz, and inland to Mount Diablo and Pleasanton.  This species prefers heavily wooded areas that have a good amount of undergrowth and it builds distinctive large stick houses, usually at the base of or within a tree that is in close proximity to water.

Woodrat Den

Salt-marsh Harvest Mouse

Salt-marsh Harvest Mouse in Pickleweed

There are 2 subspecies of the State and Federally Endangered Salt-marsh harvest mouse, with the South Bay subspecies having a dark brown fur above and a lighter brown fur coat on the belly and the North Bay subspecies having a lighter cream-colored belly.  Like many of our native mice, it has a bicolored tail.  This mouse makes its nests out of grass and sedge on the ground and is usually associated with areas of Pickleweed.

While we were doing our wildlife surveys at Coyote Creek the other day, Scott Buhl had been talking about the elusive Salt-marsh harvest mouse and when Tim Williamson pointed out the Pickleweed lining the banks, it jarred my memory that this was the habitat I had learned about!  Although, we still did not see any of those elusive mice.

San Francisco Gartersnake

This State Threatened and Federally Endangered snake is endemic to the San Francisco Peninsula from San Francisco County to Northern Santa Cruz County.  It is mostly active during the day in wetlands and grasslands near water, often fleeing into the water when threatened.  It is also active at lower temperatures than most other snakes.

California Ridgway’s Rail

Another species that is often associated with Pickleweed habitat is the California Ridgways’ rail.  A State and Federally Endangered species, this large chicken-sized bird is a resident of the San Francisco and San Pablo Bays and Suisun Marsh.  Like many of the other species mentioned here it is very reclusive and not often seen; however they may theoretically be a species easier to catch since they prefer to either freeze and hide under vegetation or run away rather than fly.

Santa Cruz Black Salamander

And we should always include a herp, so the final spotlight species is the Santa Cruz black salamander.  This amphibian inhabits mixed woodland and conifer forests of Santa Cruz, Santa Mateo and Santa Clara counties.  If you were to see this salamander, it would likely be either at night or on the ground in damp areas under rocks, logs or in talus.  It is also aggressively territorial to others of its species!

I hope everyone is having a nice holiday time with family and friends and remembers to think about the really cool wildlife that we are fortunate to live amongst!

Mele Kalikimaka me ka Hau’oli Makahiki Hou!


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