Wintertime in Vole Country

By Austin Roy – Scientific Aid

Amanda Poulsen, a graduate student from UC Davis and CDFW volunteer, with an Amargosa vole (Microtus californicus scirpensis) after recording demographic data and applying a numbered ear tag.

Amanda Poulsen, a graduate student from UC Davis and CDFW volunteer, with an Amargosa vole (Microtus californicus scirpensis) after recording demographic data and applying a numbered ear tag.

Winter is usually a time to cozy up in front of the fire with a cup of hot chocolate, but winter for the endangered Amargosa vole (Microtus californicus scirpensis) is a totally different story.  These elusive desert rodents do not hibernate like some other mammals.  They work during the cold winter nights (as low as 5F /-15C) and cool days in search of food.  Because of their yearlong activity, the work at WIL doesn’t slow down over winter either.

Researcher looking for predator tracks around known vole habitat near Tecopa, CA.

Greta Wengert Ph.D., a collaborator from the Integral Ecology Research Center, looks for predator tracks around known vole habitat near Tecopa, CA.

Little is known about Amargosa vole behavior and biology.  Most of the information available is derived from the Amargosa vole’s cousin, the California vole (Microtus californicus).  To remedy our lack of knowledge, a team of researchers and volunteers from WIL, UC Davis, and USGS continues to work through the winter to try to learn more about the Amargosa vole.

A track plate box used to record predator tracks

A track plate box used to record predator tracks

Our project involves monitoring the vole population by live-trapping the voles.  This trapping allows for us to assess the health of individual voles, record demographic data (age, sex, weight, etc.), give voles individually marked ear tags, and then release the animals back into their environment.  This type of research allows us to track changes in the population and get an understanding of the geographic range of the vole.  In addition to “hands-on” research, I am also involved with “hands-off” surveillance.  Non-invasive techniques such as looking for vole sign (feces and runways), water sampling, and recording vegetation allow me to gain information about the vole and its habitat while creating as little impact as possible.

A bobcat (Lynx rufus) captured on a trail camera near Tecopa, CA

A bobcat (Lynx rufus) captured on a trail camera near Tecopa, CA

Also, over the winter months I am continuing to gather data on the predators of the Amargosa vole.  Recent findings from USGS suggest that predation might be a limiting factor to the vole’s persistence in its environment.  In response to this finding I began a study to observe and document predators.  I am deploying trail cameras and once a month I conduct point counts to record predator species that utilize vole habitat.  With the help of volunteers, I am also collecting predator feces and pellets.  This allows us to examine the diet of predators and identify which predator species are eating the vole.

The Amargosa vole display recently installed in the Shoshone Museum, in Shoshone, CA.

The Amargosa vole display was recently installed by CDFW and UC Davis in the Shoshone Museum, in Shoshone, CA.

All of this information is well worth the discomfort of working through cold weather.  The data we collect is being applied to the management of the vole  and will aid researchers in understanding how to best help this imperiled animal.  For this reason, we happily bundle up, heat up some tea for our travel mugs, and embrace the weather as we continue to do our best to help the Amargosa vole survive in such an extreme environment.

Drought and the Impact on California’s Wildlife

By Tom Batter, WIL Scientific Aid

California has been experiencing persistent dry conditions since 2012.  According to the National Drought Mitigation Center at the University of Nebraska-Lincoln, 99% of California is currently abnormally dry, 67% of California is in extreme drought, and almost 10% is experiencing exceptional drought — and it may not let up soon.  The implication of a drought emergency is relatively straightforward: there is a severe lack of water.  This lack of water affects Californians in many ways, be it economically or socially.  But how does it affect the state’s wildlife?

Nearly 99% of California is abnormally dry, while 63% of the state is experiencing extreme drought (as of February 4, 2014).  Photo courtesy of the U.S. Drought Monitor.

Nearly 99% of California is “abnormally dry”, 67% of the state is experiencing “extreme drought”, and 10% is experiencing “exceptional drought” (as of February 4, 2014). Photo courtesy of the U.S. Drought Monitor.  Click here for the most up to date drought conditions in California.

California’s wildlife depends on water just as it’s citizens do.  With water resources becoming increasingly rare, a “domino effect” takes place in the ecosystem. Drought conditions negatively impact habitat through resource deterioration and wildfire, causing migration and behavior changes of animals.  Wildlife become concentrated in remaining suitable habitat, increasing chances for disease outbreaks due to close contact.

It begins at the producer level.  As drought intensity increases, vegetation growth is stymied.  Plants that lack necessary water resources respond by reducing new stem growth while previously produced stems will shrivel and die.  The obvious effect from lowered plant production is a reduction in food availability for herbivores.  This in turn reduces populations of insects, reptiles, wild rodents, and hares which many small carnivores and raptors rely upon for food.

Dry conditions in cache creek, Yolo County.  Photo credit: Krysta Rogers, WIL.

Dry conditions at Cache Creek, Lake County, in late December 2013. Photo credit: Krysta Rogers, Wildlife Investigations Lab (WIL).

With lower food availability, animals tap into their body’s fat reserves. Utilizing fat reserves will ultimately lead to starvation for wildlife whose nutritional needs are not eventually fulfilled. Beginning in mid-December, WIL began documenting increased mortality of young red-tailed hawks in central and southern California. Investigation revealed poor body condition, emaciation, and secondary bacterial or fungal infections. A similar event occurred the previous winter, also in dry conditions.

Red tailed hawk.  Photo courtesy of the U.S. Fish & Wildlife Service

Drought impacts all trophic levels, including birds of prey such as the red-tailed hawk (pictured). Photo credit: U.S. Fish & Wildlife Service (USFWS).

Reduced plant growth also negatively affects available cover for wildlife.  Cover is an important element for prey species to evade predators.  As plant life diminishes, landscapes become more open.  For some wildlife, such as ground nesting birds, the likelihood of predation increases as these drought ridden landscapes open up.

With the odds already stacked against them, wildlife in drought conditions are also forced to travel greater distances in search of food and water resources.  Some behavior changes may take place as a result; for example, typically nocturnal species such as raccoons and opossums may remain active well into the daylight hours seeking food.  The extra effort for nutrients puts these animals at an increased risk of exhaustion, starvation, predation, and disease.

As drought conditions persist, animals will seek out alternative habitats that have more favorable conditions for survival.  Areas where food and water are still available will attract many species to a relatively small area.  Predation rates are likely to increase as predators can more easily focus on a centralized group of prey.  Furthermore, large concentrations of wild animals increase the odds for disease outbreaks that could decrease populations.

In fact, this winter WIL has already investigated several avian cholera outbreaks throughout California. Large numbers of ducks, geese, and swans spend the winter on the state’s many ponds and lakes. The current lack of precipitation has reduced the amount of habitat available for these birds, forcing them to become concentrated in locations where water remains. Close contact among waterfowl allows a bacterial disease like avian cholera to spread very rapidly, resulting in the death of hundreds to thousands of birds.

Large concentrations of waterfowl seek out remaining suitable habitat. Photo credit: Scott Flaherty, USFWS Pacific Southwest Region.

A variety of waterfowl species congregate at the Sacramento National Wildlife Refuge.  Photo credit: Scott Flaherty, USFWS Pacific Southwest Region.

While these impacts of drought do indeed create dire circumstances for wildlife, it is important to remember that droughts are natural phenomena.  Wildlife and drought have coexisted for generations upon generations.  Generally speaking, wildlife populations are resilient and are able to bounce back from drought events once typical weather patterns return.  For example, in the early 1960s severe winter drought contributed to extreme deer die-offs in Texas.  When rainfall levels returned to normal, the deer population was able to rebound in only one year.

Many species of wildlife, such as mule deer, are capable of bouncing back after drought once favorable conditions return. Photo credit: T.A. Blake, USFWS

Many species of wildlife, such as mule deer, are capable of bouncing back after drought once conditions return to normal. Photo credit: T.A. Blake, USFWS

During these hard times, it may be tempting to “rescue” or “save” an animal that is seeking food and water.  It is entirely possible that more wildlife will make their way into urban and residential areas in an attempt to find nutrients.  It would be a disservice to both human and animal to offer handouts, for similar reasons it is inappropriate to keep wildlife as pets. This natural drought event will eventually pass, and when it does, CDFW and WIL staff would rather see California’s fauna remain reliant upon themselves rather than their human counterparts.

Got Acorns?

If you have acorns in your area, be on the look out for band-tailed pigeons this winter. Band-tailed pigeons are California’s only native pigeon and this time of year, they will fly great distances to find acorns. Band-tailed pigeons are one of the rare bird species that will actually swallow acorns whole! Unfortunately, this behavior also makes them more susceptible to Trichomonosis, a disease caused by a single-celled microscopic protozoan parasite, Trichomonas gallinae.

Band-tailed pigeon. Photo by Krysta Rogers.

Adult band-tailed pigeon showing the characteristic white crescent and iridescent greenish-bronze patch of feathers on the hind neck and black band on the tail, for which the species was named. Photo by Krysta Rogers, 2013.

The parasite lives in the mouth and throat of infected birds, causing caseous (“cheese-like”) lesions to develop in the bird’s mouth or esophagus. As the lesions become larger, the pigeons can no longer swallow acorns, leading to weight loss and eventually death. The lesions also may cause the pigeon to suffocate, if they block the airway.

Band-tailed pigeons with Trichomonosis. Photos by Jeff Cann & Krysta Rogers.

Fig. 1: A band-tailed pigeon showing signs of infection with Trichomonosis.
Fig. 2: A dead band-tailed pigeon observed during a Trichomonosis die-off in 2012.
Fig. 3: Caseous lesions in the oral cavity of a band-tailed pigeon with Trichomonosis.
Photos by Jeff Cann (Fig. 1) & Krysta Rogers (Fig. 2 & 3).

While this disease can make pigeons sick any time of the year, large-scale die-offs only occur during the winter, in some years. The last series of mortality events were reported in 2012 in California, when up to 10,000 pigeons were estimated to have died between December and March. Recent research by CDFW suggests that these mortality events are more likely to occur in winters with low precipitation, similar to the conditions we’ve been experiencing so far this winter.

So, if you have acorns, be on the lookout for band-tailed pigeons and enjoy watching them comically hang from the branches as they try to reach an acorn. Hopefully, the pigeons will not experience any die-offs this winter. However, if you do happen to see pigeons that appear sick, such as showing signs of weakness, labored breathing, breathing with their bill open, drooling, reluctance to fly when approached, or are dead, you can help by reporting the mortality to the Wildlife Investigations Lab.

If you have any questions, or would like to report sick or dead band-tailed pigeons, contact Krysta Rogers at 916-358-1662.

UC Davis, CDFW and USFWS team up to assess western pond turtle health in California

The western pond turtle (Emys marmorata), the only native species of freshwater turtle in California, has been a species of special concern since 1994. Possible causes for declining western pond turtle populations include urbanization and habitat destruction (which often reduces or eliminates basking and nesting sites available near pond
habitat), poor water quality, and reduced survival of young turtles causing the population to be skewed towards aged turtles that don’t reproduce well.

The western pond turtle is California's only native aquatic turtle and a species of conservation concern. (Image courtesy of CDFW Outdoor California March-April 2011)

The western pond turtle is California’s only native aquatic turtle and a species of conservation concern. (Image courtesy of CDFW Outdoor California March-April 2011)

Another challenge to the survival California’s native western pond turtles has been the introduction and spread of non-native red-eared sliders (Trachemys scripta elegans).  Red-eared sliders were imported for the live food market and are popular in the pet industry, often resulting in illegal pet release. “Sliders” are larger than pond turtles
and outcompete pond turtles for nesting and basking sites.

This is a Red-eared Slider (Trachemys scripta), a common turtle in the pet trade. They compete in the wild with our native Western Pond Turtle, so they should never be released. (CDFW photo by Dave Feliz)

The Red-eared Slider is a common turtle in the pet trade. They compete in the wild with our native Western Pond Turtle, so they should never be released. (CDFW photo by Dave Feliz)

It is not known if disease is playing a role in the observed declines of western pond turtles.   Additionally, introductions of non-native red-eared sliders into pond turtle habitat might also introduce new pathogens (disease causing agents like viruses, bacteria, fungi, and parasites) or strains of pathogens that western pond turtles had not been previously exposed to.

Absolutely nothing was known about the pathogens western pond turtles are exposed to in California, so Janet Foley, Joy Worth and then Master’s student, Connie Silbernagel from UC Davis School of Veterinary Medicine, Deana Clifford from the CDFW Wildlife Investigations Lab, and Jamie Bettasco from the US Fish and Wildlife Service teamed up to conduct the first assessment of pathogen presence in western pond turtles across the state. The team also tested non-native red-eared sliders at study sites where both species were living  to see whether or not red-eared sliders carried different pathogens and whether or not western pond turtles living in the same sites as nonnative sliders were more likely to carry different pathogens.

A western pond turtle is being measured as part of a collaborative study to examine their health. (Photo courtesy of C. Silbernagel)

A western pond turtle is being measured as part of a collaborative study to examine their health. (Photo courtesy of C. Silbernagel)

The team found that both species of turtles carried Mycoplasma spp. bacteria (a cause of respiratory infections) with prevalence being highest at sites in southern California regions. Furthermore native western pond turtles that were infected with Mycoplasma spp bacteria were more likely to weigh less and live in southern California. All turtles tested negative for two common viruses, Herpesviruses and Ranaviruses, and Salmonella bacteria (which can cause gastroenteritis and is a bacteria that can infect people).

Dr. Connie Silbernagel tests the quality of a water sample. Connie earned her Master's degree at UC Davis conducting the western pond turtle health assessment with CDFW and USFWS.

Dr. Connie Silbernagel tests the quality of a water sample. Connie earned her Master’s degree at UC Davis conducting the western pond turtle health assessment with CDFW and USFWS.

This study is the first of its kind to document pathogen prevalence in both native western pond turtles and non-native red-eared sliders and will provide important baseline data as we strive to conserve western pond turtles in California.

Click here to view the abstract:

Silbernagel C, Clifford DL, Bettaso J, Worth S, Foley J. Prevalence of selected pathogens in western pond turtles and sympatric introduced red-eared sliders in California, USA. Diseases of Aquatic Organisms 107:37-47

Disease Surveillance Projects for Bighorn Sheep Completed in November


Dr. Colleen Duncan from Colorado State University and Dr. Ben Gonzales from California Department of Fish and Wildlife collect biological samples from bighorn sheep for disease testing. (Photo courtesy of George Kerr, Society for the Conservation of Bighorn Sheep)

Early November 2013 was a busy time for Wildlife Investigations Laboratory staff.  Two important disease surveillance projects for bighorn sheep were conducted in the Mojave National Preserve in San Bernardino County and the Peninsular Ranges in San Diego and Imperial Counties.  A total of 91 sheep were captured, GPS collared for monitoring and biological samples taken so that a variety of disease tests could be done.  One significant test is for Mycoplasma ovipnenumonia, a bacteria that caused a bighorn die-off in the Mojave earlier this year. Scientists will use the laboratory results (still pending) to determine the cause of the disease and to document the number of animals involved and the geographic extent of the outbreak.

These projects could not have been conducted without the many partners involved including; The National Park Service, the Society for the Conservation of Bighorn Sheep, California Wild Sheep Foundation, United States Fish and Wildlife Service, Bureau of Land Management, Oregon State University and Colorado State University.


Taking blood samples from bighorn sheep for use in disease testing. (Photo courtesy of George Kerr, Society for the Conservation of Bighorn Sheep)


Inspecting bighorn for signs of respiratory distress. (Photo courtesy of George Kerr, Society for the Conservation of Bighorn Sheep)

New publication describes the cause of a skin disease in endangered Amargosa voles

In only 19 square kilometers of the Amargosa basin in the Mojave Desert of California, lives the small, brown Amargosa vole (Microtus californicus scirpensis). This specialized vole lives in bullrush (Scirpus oleyni) dominated marshes that appear when the normally underground Amargosa river reaches the surface.  Conservation of this unique habitat on which this state- and federally-listed endangered vole depends has been a cornerstone of conservation efforts.


A sunset view of one of the unique marshes that provide critical habitat for the endangered Amargosa vole. (Photo by D. Clifford)

While conducting surveys to determine for Amargosa Voles in September 2010, California Department of Fish and Wildlife scientist Tammy Branston discovered unusual deformities on the ears and genitalia of some of the voles which appeared to be associated with the presence of an orange substance on the skin.  Some voles were so severely affected that they were missing their ear pinnae (the visible part of the ear) altogether. Tammy alerted CDFW veterinarian Dr. Deana Clifford, and along with her colleagues Dr. Janet Foley, a small mammal disease ecologist at UC Davis, and Dr. Leslie Woods, a veterinary pathologist at the California Animal Health and Food Safety Lab (CAHFS) at UC Davis, they sampled affected voles and conducted additional tests to determine the cause of the deformities.  They discovered that the orange “stuff” was actually a hard orange mite, a chigger in fact.   Of 151 Amargosa voles examined from February-April of 2011, 40% of the voles had hard orange mites adhered to some part of their bodies, and 47% of voles examined had ear lesions and deformities which included alopecia (hair loss), swelling, tissue death and ulcers at the ear edges, as well as scarring, scabbing, and loss of external ear tissue.

The team’s findings are published in the August 2013 issue of the Journal of Parasitology.


An Amargosa vole with a normal ear is ready to return to the bulrush after its examination. (Photo by D. Clifford)

It is extremely unusual to see such severe damage due to a chigger in a small mammal, which raises concerns that this condition could negatively impact the health and fitness of individual voles.

An interdisciplinary team with members from CDFW, UC Davis, UC Berkeley, the Bureau of Land Management, the US Geological Survey, and the US Fish and Wildlife Service, is studying population dynamics, habitat needs, genetics, and disease in order to ensure that healthy populations of this unique endangered vole of the desert persist well into the future.

To access the paper abstract, click here

Full reference: 2013. Foley J, Branston T, Woods L, Clifford D. Severe ulceronecrotic dermatitis associated with mite infestation in the critically endangered Amargosa vole (Microtus californicus scirpensis). Journal of Parasitology.  Aug;99(4):595-8.

Click here to read more about the Amargosa vole and download recovery documents.

Click here to read about agency efforts to enhance the voles habitat, the Amargosa Area of Critical Environmental Concern (ACEC).

Click here to learn more about the Amargosa Conservancy’s local efforts to protect the Amargosa Basin.

Why is it important to report wildlife mortalities?

Over the past 12 months, the Wildlife Investigations Laboratory has been asking the public for their assistance in reporting wildlife mortality events.  WIL recognizes that mortality reports are an important tool in monitoring the health of the State’s wildlife. Wildlife mortality reports can:

  • help us better understand these phenomena;
  • lead to more effective prevention and control;
  • potentially detect emerging diseases affecting fish and wildlife; and
  • recognize problems that could affect human and domestic animal health.

WIL received 30 mortality reports submitted by the public from July 2012 – June 2013.  These reports documented mortalities in 21 different species and have been added to a permanent record so that we may potentially be able to detect phenomena such as seasonal mortality trends or weather mortality events in the future.

Mortality Reports:  July 2012 – June 2013

CDFW - WIL Wildlife Mortality Reports, 2012-2013

CDFW – WIL Wildlife Mortality Reports, 2012-2013

Public reporting makes a valuable contribution to the information we are trying to collect and is an important source for disease outbreak monitoring and emerging health threats. Please help us monitor the fish and wildlife populations in California.

For more information on wildlife mortality reporting, please follow the links below.

California wildlife mortality reports:

California roadkill tracking:

Wildlife heath information: