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.

Advertisements

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.