Science Spotlight

California leaf-nosed bats. CDFW photo by retired biologist Andy Moore.


Hundreds of bats in flight. ©Dave Feliz, all rights reserved.


Little brown bat with white-nose syndrome. US Fish and Wildlife Service photo.


Townsend's big-eared bat in flight. National Park Service photo.

The last seven days of October are celebrated each year as Bat Week – a time to learn about the importance of bats in our environment.

Bats are nature’s best pesticide. According to a study by the University of California, Davis, Division of Agriculture and Natural Resources, each of these small mammals eats between half and 100 percent of its own weight in insects every night. Some California species consume as many as 600 insects per hour. Imagine living with all the mosquitoes, flies, midges, moths and agricultural pests that are now consumed by bats!

In monetary terms, the natural pest control that bats provide is extremely valuable to the state’s $54 billion per year agriculture and $450 million timber industries. The bats’ appetite reduces the need for chemical pesticides, reduces crop losses and curtails the spread of crop diseases. According to the US Geological Survey, a recent economic analysis indicated that insect suppression services provided by bats to American agriculture is worth something between $4 billion and $50 billion per year.

California Department of Fish and Wildlife (CDFW) Senior Environmental Scientist Scott Osborn notes the estimate’s wide range makes it hard to know exactly how much money bats save farmers. “But even the low estimate, $4 billion, is an impressive amount,” he said. “Bats are an important part of integrated pest management systems.”

As the wildlife trustee agency in California, CDFW is engaged in several activities to help us understand the conservation status of bats in the state, as well as to address threats to bat populations. At statewide, regional and local scales, our scientists have been deploying acoustic bat detectors to determine the distribution of California’s 25 bat species. When CDFW’s bat acoustic data are combined with data collected by partners at other state and federal agencies, academic researchers and non-governmental organizations, we should have more accurate knowledge of where various bat species occur, as well as their seasonal movements.

White Nose Syndrome (WNS) is now a real threat to California’s bats. WNS is a fungal disease that is estimated to have killed more than 6 million bats in eastern North America. With the discovery of WNS for the first time on the west coast (in Washington state) last year, California is bracing for potentially devastating impacts to our bat populations. CDFW is working with the US Fish and Wildlife Service and other partners to conduct surveillance for the fungus that causes the disease, as well as develop plans to manage the disease when it arrives in California. So far, all of the samples collected from bats and their roosts in California have been free of the fungus, but increased vigilance is necessary to help ensure the disease is detected immediately when it arrives. Special measures to reduce the impact of WNS on hibernating bats may include closing caves and other roosts to visitors, because people can unwittingly spread the fungus on their clothing, shoes and gear. Ultimately, it is hoped that ongoing research into the disease will provide tools to either eliminate or control the fungus, both in the environment and in infected bats.

To learn more about the exciting world of bats and how you can “Go to Bat for Bats!” check out the Bat Week 2017 website.

Top photo: A California bat in a crevice. ©Dave Feliz, all rights reserved.

CDFW Seasonal Aid Katie Schroyer determines the age of a dove by examining its wing


A banded mourning dove at a CDFW trap site in northern California


Age and sex data are recorded before the bird is banded and released.


A large kennel trap can catch more than 30 birds at a time.

As the second half of California’s split dove season kicks off, dove hunters may put more than birds in their bags. They may harvest a bird with a band on its right leg – thus getting an opportunity to contribute important data that will help guide future management efforts.

Since 2003, California has been an active partner in a nationwide assessment of mourning dove populations. California is one of 39 states that currently participate in dove banding. During the months of July and August, trained biologists and volunteers trap and band doves throughout the state. The banding of migratory birds requires a Master Banding Permit issued upon approval of a study application by the U.S. Geological Survey. All banders must pass an annual training to participate and are then issued a sub-permit.

Mourning doves are so widely distributed that banding operations can be – and are – located almost anywhere, from rural locations to urban backyards. Larger operations located on Wildlife Areas, ranches and open desert sites may employ the use of a large kennel trap capable of trapping 30 or more birds at a time, while smaller operations (“backyard banders”) use small Kniffin traps that catch just one or two birds at a time.

When a bird is banded, age and sex data are recorded. This information, along with capture location, date, bander name and corresponding band number, becomes part of a massive database managed by the USGS’s Bird Banding Laboratory. The mourning dove banding data is available to any interested party, but is mainly used by the U.S. Fish and Wildlife Service (PDF), university scientists and state agency scientists to analyze and estimate annual survival, harvest rates, recruitment and abundance.

The resulting analysis is used by wildlife managers in setting annual hunting regulations. For instance, in 2015, the USFWS increased the take of mourning doves in the Western Management Unit (which includes the states of California, Oregon, Washington, Idaho, Nevada, Utah and Arizona) from a daily bag limit of 10 to 15. The California Fish and Game Commission followed suit, also increasing the possession limit from two to three times the daily bag limit, in order to accommodate hunters on multi-day hunting trips.

If you harvest or find (encounter) a banded bird, CDFW asks that you report the number directly to the Bird Banding Laboratory. This can be done online at www.reportband.gov, or by calling (800)327-2263. When reporting an encounter you will be asked for the band number and basic information about where and how you obtained the band.

The person reporting is allowed to keep the band, and will receive a certificate with the details about where, when and by whom the bird was banded.

The USGS Bird Banding Lab is the keeper of banding data for both the US and Mexico. As of September 18, 2017 and since 1960, the BBL has received over 64 million banding records. Since the inception of the North American Bird Banding Program, the BBL has received over 4 million encounter records. On average, over the past decade, the BBL received 1.2 million banding and 87,000 encounter records per year.

For more information about mourning dove banding, including the 2017 Mourning Dove Harvest Strategy, visit the Doves and Pigeons page on the FWS website.

CDFW photos by Kloey Helms
Featured photo: CDFW Seasonal Aid Katie Schroyer determines the age of a dove by examining its wing.

A tiny, endangered mammal is the subject of an extraordinary conservation effort near the communities of Shoshone and Tecopa in Inyo County.

The Amargosa vole is unique to the Mojave Desert, and today, scientists estimate there are only about 500 remaining in the wild. Though the Amargosa vole is rarely seen by humans, biologists recognize that it is a key link in the native food chain. Predators, including raptors and water birds, share the desert marshes where they live, and the extinction of the Amargosa vole would have a ripple effect on these and many other species as well.

For a year, a scientific team consisting of CDFW, UC Davis and US Geological Survey biologists have conducted intensive research into the life cycle of this little vole. The team visited every marsh that potentially could be inhabited by voles – they mapped the marshes, assessed habitat quality, and determined whether or not voles were present. In a subset of larger marshes the team conducted more detailed assessments of water inflow-outflow, soil moisture and vegetation, and captured voles to estimate local population numbers, assess the health of the voles and take samples for disease and genetics studies. In addition to the hands-on study in the desert, they also studied satellite data to track the amount of vegetation and water in the area over a period of time. A grim picture emerged of a habitat range in decline, due in large part to climate change and human modification.

Some of the findings included:

• Total available habitat for the voles decreased 37 percent between 2012 and 2015.
• Over decades, global climate change has caused a gradual decrease in water in this region. California’s recent drought has exacerbated the problem.
• Of the more than 80 marshes that were documented at the beginning of the study, about 60 have degraded and/or dried up. Those that remain are almost all too small to sustain vole populations. Just as pandas eat only bamboo, the Amargosa vole survives solely on bulrush, a plant that grows in desert marshes.
• Another important finding was that 80 percent of the individual voles found and tracked during the study were adults. This indicates low birth rates and survival rates for juveniles – more barriers to the species’ recovery.

Scientists believe that the network of springs and marshes in the vole’s natural range has been so extensively modified by humans that the vole’s future existence will depend almost entirely on whether humans continue to supply water where and when needed. They found evidence to support this, as an intensive restoration effort at one of the largest marshes showed signs of successfully supporting and sustaining voles.

The report authors identified several specific measures that could be taken to increase vole habitat and improve their chances of survival – including reconfiguring water inflow and outflow, changing elevations and planting vegetation that would enhance existing marshes and/or better connect adjacent marshes.

This study is part of a larger long-term effort to secure a future for the Amargosa vole and the unique marsh ecosystems it depends upon in the Mojave Desert. In late 2014 vole numbers became so low that scientists initiated a captive breeding program at the UC Davis School of Veterinary Medicine to reduce the risk of extinction. Today more than 100 voles are in the captive colony at UC Davis – providing a potential source of animals for release into restored habitats, and an important insurance population to prevent extinction.

Photos by Don Preisler/UC Davis School of Veterinary Medicine