Salt Marsh Harvest Mouse, the Tiniest Endangered Species

Most inhabitants of the Bay Area are aware of threatened species such as the sea otter and harbor porpoise, or even the endangered California clapper rail, but there’s a mammal that’s completely unique to the Bay Area and so tiny most people have never even seen one.This mammal, among the smallest rodents in the U.S., lives only here in the Bay in a very specific habitat, and can be credited with much of the tidal marsh restoration happening now.

In 1970, thanks to the work of Dr. Howard Shellhammer, the Environmental Protection Agency listed the salt marsh harvest mouse as endangered, and kick-started the explosion of San Francisco Bay conservation efforts. The endangered status of the salt marsh harvest mouse halted plans for development, agriculture, and industrialization of natural marsh habitat. US EPA - Endangered Species Facts  - Salt Marsh Harvest Mouse

A salt marsh harvest mouse is about the size of one’s thumb, largely nocturnal, and lives among the reddish pickle weed in the low tidal marsh—an area frequently subject to tidal inundation. Salt marsh harvest mice are adapted to live in this challenging environment, as they can swim short distances and consume food and water with a high salt content.

During high tides and peak flooding by storms, salt marsh harvest mice escape into the upland marsh for protection. It is this safe-haven habitat that has been greatly diminished and is of most concern for the survival of these tiny mammals. Without this high tide refugia, or proper corridors permitting travel to them, salt marsh harvest mice are subject to drowning and predation. The threat of sea level rise makes this an even greater concern

Although some of the habitat of the salt marsh harvest mouse is protected around the Bay, the continuing threats from pollution, poor water quality, invasive species, and habitat fragmentation are driving the population into further decline. Under the umbrella of the United States Fish and Wildlife Service Tidal Marsh Recovery Plan, Save The Bay is working to prevent the loss of the salt marsh harvest mouse by preserving and restoring vital marshland habitat. Harvest mouse habitat is also habitat for hundreds of other species. That’s why Save The Bay works to prevent further filling of Bay tidal marsh, combat pollution, and restore the vital marsh habitat that the salt marsh harvest mice use during winter high tides and storms.

This winter we are planting 45,000 plants to provide suitable marsh habitat for this endangered species. Volunteer with us this season to plant suitable refuge for these unique, adorable rodents!

City’s Plan Would Pave Bay Wetlands with Golf Course, Nearly 500 Houses

Photo of Area 4
Historic Bay tidal marsh, Newark’s “Area 4,” is one of the largest areas of restorable, undeveloped baylands in the South Bay (Photo by Margaret Lewis)

Should a bayside city work to help expand the San Francisco Bay National Wildlife Refuge, restoring more than 400-football fields-worth of Bay wetlands and habitat? Or should they forever destroy that opportunity by filling in the area with an 18-hole golf course and nearly 500 single family houses?

Those are the choices right now in the City of Newark – a shoreline city of 40,000 next to Fremont. Rather than recognize the incredible opportunity to protect the Don Edwards S.F. Bay National Wildlife Refuge, endangered species, and migratory bird habitat, Newark is seeking approval to fill in over 300 acres of historic baylands, including nearly 100 acres of wetlands and aquatic habitat, sprawling the city into a FEMA-designated flood zone.

Environmental organizations and regulatory agencies have long stressed to Newark of the ecological importance of 550-acre “Area 4” – one of the largest areas of restorable, undeveloped baylands in the South Bay:

  • The 1999 Baylands Ecosystem Habitat Goals Project, the scientific roadmap for the restoration of the Bay shoreline, identifies Area 4 as being uniquely situated for the restoration of both tidal marsh and adjacent upland transition zones, two habitats critical to the health of the Bay
  • Area 4 is host to approximately a dozen special status species –including the endangered Salt Marsh Harvest Mouse – and it is directly adjacent to Mowry Slough, a primary breeding ground for San Francisco Bay Harbor Seals
  • The San Francisco Bay Regional Water Quality Control Board has stated that “large expanses of undeveloped uplands immediately adjacent to tidal sloughs are extremely rare in the south and central San Francisco Bay” and that “Area 4 represents a rare opportunity to … provide an area for tidal marsh species to move up slope in response to sea level rise”
  • Similarly, the California Department of Fish and Wildlife have stated that “this wetland is an integral component of the San Francisco Bay ecosystem,” and “critically important to waterfowl and shorebirds.”

Yet Newark has ignored these concerns, proposing to fill in these rare wetlands and wildlife habitat with 2.1 million cubic yards of fill – enough dirt to fill nearly 100 trucks a day for two years straight!

The City should focus future growth within already developed areas, near transit, shops and services, not on ecologically-sensitive, restorable baylands at risk from flooding and sea level rise.

Update 10/11/2013: 

Opposition to Newark’s plan to build as many as 500 houses and an 18-hole golf course on one of the largest pieces of restorable Bay shoreline in the South San Francisco Bay is growing. More than 2,000 Bay Area residents submitted comments to the city on its General Plan. You added your voice to the chorus of opposition from regulatory agencies including the U.S. Fish and Wildlife Service (USFWS), the Bay Conservation and Development Commission (BCDC), and the Water Board.

A letter submitted by Don Edwards San Francisco Bay National Wildlife Refuge (USFWS) staff stated, “the proposed development of Area 4 will only add to the cumulative loss of tidal wetlands in San Francisco Bay and endangered species that are dependent on that habitat.”

Your support also helped us convince several environmental organizations to send letters of opposition, including Center for Biological Diversity, Defenders of Wildlife, and Greenbelt Alliance. Thanks to you, Newark’s plan will not go unnoticed much longer. Sign up here for updates on next steps.

Volunteer Spotlight | Meet Isaac Harrington

Isaac Harrington
Isaac recently volunteered at Ravenswood Pond in Menlo Park.

Meet Isaac, a student from Redwood City.

How many times have you volunteered with Save The Bay?

Do you have a favorite site?

What is the best thing about volunteering with Save The Bay?
It is fun to plant native plants and to take out invasive plants.

If you could be one Bay plant or animal, what would it be and why?
Salt marsh harvest mouse because they can swim in and drink salt water!

What is one thing you do each day to protect the environment?

Volunteer with Save The Bay — register online today

The Luck of the Bay Saver! Save The Bay Educator and Girl Scouts See Rare, Endangered Mouse

What does a Bay Area resident have to do to find the luck-bringing creature, the Salt Marsh Harvest Mouse? For years, I have read the tales of ecologists spotting these tiny creatures in the wee hours of the night and imagined it happening to me. Up until this past Saturday, the only mouse I had ever spotted was the one stuffed in an exhibit at the Palo Alto Baylands Nature Preserve. As one must conclude, I was skeptical and wary of the possibility that I may one day be lucky enough to see one of these elusive creatures.

My luck has changed! Finally after five years leading over 450 educational programs in the San Francisco tidal marshes for Save The Bay, I have successfully spotted a Salt Marsh Harvest Mouse! I am honored to be one of the first with Save The Bay to see this rare and tiny creature that is endemic to the San Francisco Bay.

The mouse was first spotted by a few Girl Scouts this past Saturday at 11:42 a.m. during a Save the Bay Girl Scouts volunteer planting day at the Palo Alto Baylands. One of the girls tugged on my sleeve and said “Jill, there is a mouse in the water, over here! Look!” The other girls were exclaiming all at once “How cuuuuttttee!” Sure enough, there was the Salt Marsh Harvest Mouse swimming at the water’s edge. Cautiously, I signaled to the girls to step back to observe the mouse silently from a distance so as not to scare it away.

What makes spotting the Salt Marsh Harvest Mouse so lucky?
To start with, this creature is incredibly tiny, said to fit on the tip of your thumb and weigh about as much as a nickel or quarter. In addition to being small in size, this creature is endemic to the San Francisco Bay wetlands. With only 10 percent of the Bay wetlands remaining, the population of the Salt Marsh Harvest Mouse has declined over the past century, putting it on the endangered species list with a population under 2000. Finally, this mouse is nocturnal, making it nearly impossible to see the mouse under the sunlight.

So, why did we spot this mouse?
This mouse lives primarily in the pickleweed, a low zone tidal marsh plant that is often submerged under the brackish water during high tide. During the high tide, the mouse usually finds shelter in the mid zone plant species, like alkali heath or gumplant. During extreme high tide events, like this past Saturday, this mouse must find shelter in the higher zone plant species which sometimes do not exist, due to the development of roads, trails and parking lots. Over the past few years, Save The Bay has been working in partnership with the Palo Alto Baylands to restore these high or “transition” zone plant species to provide shelter and habitat for species like the Salt Marsh Harvest Mouse.

What does a Bay Area resident have to do to see a Salt Marsh Harvest Mouse?
Become a Bay Saver and join Save The Bay as a volunteer to protect and restore the habitat for the Salt Marsh Harvest and the hundreds of other animals that call our wetlands home! We cannot guarantee you will be lucky enough to spot this creature, but we can guarantee you will see wildlife and have a great day out on the beautiful San Francisco Bay!

— Jill Jacobson

A Mouse in the House

by Darcie Collins, Ph.D., Habitat Restoration Director

$30 million in the stimulus package for a mouse? That was the claim in last Thursday’s Washington Times. GOP officials, arguing the new stimulus package is stuffed with Democratic pork, charged Nancy Pelosi with earmarking $30 million of the $780 billion package to protect the salt marsh harvest mouse, an endangered animal endemic to the marshes of the San Francisco Bay.

The story evolved like this: last week, a House Republican staffer circulated an email claiming an unnamed Federal Agency would spend “thirty million dollars (of stimulus money) for wetland restoration in the San Francisco Bay Area—including work to protect the salt marsh harvest mouse.” Although there is no specific language in the bill indicating the money would go explicitly to protecting the endangered animal, the staffer held to this claim: “The bottom line is, if this bill becomes law, taxpayers will spend $30 million on a mouse.”

Pelosi’s staff disagreed. “There are no federal wetland restoration projects in line to get funded in San Francisco,” Pelosi spokesperson Drew Hammill said. “Neither the Speaker nor her staff have had any involvement in this initiative. The idea that $30 million will be spent to save mice is a total fabrication.”

In truth, it’s not a total fabrication. But many San Francisco Bay wetland restoration projects—earth-moving, planting, fence and road building, and creating wildlife viewing areas and parking lots—are currently at a stand-still due to inadequate funding. These “ready-to-go” projects are prime for the stimulus package. And they would help protect the salt marsh harvest mouse.

So what is wrong with a project that benefits an endangered species and creates job opportunities? Unfortunately the little mouse has been getting a bit of a bad rap.

In wetland restoration, the salt marsh harvest mouse operates as an “indicator species.” Indicator species are very sensitive organisms that respond to extremely small changes in the environment and are often used to indicate pollution and other impacts in ecosystems. In the case of the salt marsh harvest mouse, the loss of San Francisco Bay tidal wetlands and salt marshes has caused a dramatic decrease in the harvest mouse population, resulting in its addition to the Endangered Species List in 1970.

But just as sensitive species can be indicators of disturbance, they are also indicators of healthy systems, and restoration biologists often use these species as evidence of the successes of restoration work.

So what does the mouse-bashing mean for SF Bay restoration ?

Healthy salt marshes are vital for a sustainable Bay ecosystem, which helps combat the effects of global warming and leads to a sustainable fishing industry, improved water quality, and increased tourism and recreation. GOP officials may bash the little mouse, but a thriving salt marsh harvest mouse population indicates a healthy wetland ecosystem. And since salt marshes are the lungs of the Bay—providing habitat to hundreds of fish and wildlife species, trapping pollutants from urban areas before they reach the Bay, capturing carbon from greenhouse gases and providing flood and erosion control—this is a good thing.

The proposed stimulus package includes $30 million to restore San Francisco Bay wetlands, which ultimately protects the salt marsh harvest mouse. Some call it pork; others call it cheese. I call it a good investment for our Bay.

Learn more about Save The Bay’s wetland restoration program.