In the Spring of 2016, CDFW (WIL and Region 6), UC Davis, BLM, USFWS, and many volunteers partnered to restore a key habitat patch utilized by the Amargosa vole. This habitat patch used to sustain the highest density of Amargosa voles in the world, but in 2010 it began to deteriorate due to changes in hydrology. The Amargosa vole team worked diligently to restore the water supply and reinvigorate vegetation growth at the marsh. Learn more about the Amargosa vole project.
Be on the look out for band-tailed pigeons! Reports this month indicate band-tailed pigeons, California’s only native pigeon, are utilizing areas where they haven’t been in years. Observers have reported flocks of 50 to 100 birds in locations where pigeons haven’t been seen in at least 15 to 20 years. These seemingly erratic movements are directly tied to available food resources. During the winter, band-tailed pigeons feed primarily on acorns. They are one of the few species that actually swallow acorns whole!
Acorn productivity fluctuates among oak species and between years. In some years, oaks may produce large quantities of acorns, in other years acorn production can be spotty. If acorns are not available, pigeons will rely on other food items such as madrone berries or pine nuts. However, the availability of all these plant foods are dependent upon weather conditions including temperature and the timing of rain, which leads to changeable food resources. Band-tailed pigeons must be adaptable to these variable conditions and seek out food resources across the landscape.
The observations of pigeons using “non-traditional” locations this winter may possibly be influenced by recent drought conditions. In Sacramento County, acorn productivity this season was very high and, in fact, bird watchers reported seeing flocks of band-tailed pigeons along the American River during fall migration. In contrast, a recent trip to the Los Padres National Forest in Monterey County, a location known to be especially reliable for both acorns and band-tailed pigeons, revealed neither acorns nor band-tailed pigeons this winter! Instead, pigeons were observed at lower elevations where abundant food was available.
Also likely related to drought, was the increased incidence of Trichomonosis in band-tailed pigeons this summer. Trichomonosis is a disease caused by a single-celled microscopic protozoan parasite, Trichomonas gallinae. The parasite lives in the mouth and throat of infected birds, causing caseous (“cheese-like”) lesions to develop in the birds’ mouth or esophagus. The lesions eventually block the passage of food, causing the bird to become weak and emaciated. Infected birds die from starvation, or suffocation if the lesions block the airway.
Band-tailed pigeons are highly susceptible to infection with Trichomonas gallinae. Traditionally, large-scale die-offs occur during the winter months, in some years. However, this year the Wildlife Investigations Lab received reports of increased mortality of band-tailed pigeons in several locations along the central California coast between May and August. Drought conditions likely resulted in increased contact between individual birds at limited food or watering sites, resulting in rapid spread of disease. This increased mortality of band-tailed pigeons is concerning because the band-tailed pigeon population has been declining for the past 40 years. Die-offs due to Trichomonosis can remove hundreds to thousands of pigeons from the population in a relatively short period of time.
This winter, be on the look out for band-tailed pigeons in your area. If you see pigeons, enjoy the spectacle, it may not occur at that location for another 20 years! And if you happen to observe 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.
By Austin Roy (Scientific Aid)
Reintroductions, translocations, and augmentations are methods of restoring or increasing wildlife populations. These actions require a lot of planning and are often expensive. These methods involve removing animals from a source population and placing them in another location. The goal of these efforts are usually to establish a sustainable population where one did not previously exist, provide new individuals to a site with a low population in hopes of increasing the population, and providing new or rare genes to a population that may need genetic rescue, among other reasons.
This summer our University of California, Davis and California Department of Fish & Wildlife (WIL) research team conducted a population augmentation for the endangered Amargosa vole (Microtus californicus scirpensis). Our goal was to supplement a very small population of voles in one marsh with new individuals and genes from a larger population in another marsh.
We placed radio collars on 3 voles at the source site, 4 voles that we removed from the source site and relocated to the recipient site, and 3 individuals at the recipient site. By collaring both relocated voles and resident voles at source site and the recipient site we could monitor how relocated animals utilized the new site and whether or not resident individuals were impacted by the presence of new individuals in their habitat.
The data we collected will greatly benefit vole recovery and inform how we conduct future releases.
In addition to the augmentation efforts this summer we also continued to study the population cycles of voles and predators in the area. These studies allow us to better understand how voles and predators use the area how the predators may be affecting vole populations. We have also been studying the vegetation and water levels to better understand the needs of the Amargosa vole. These efforts will help us better understand how to restore and improve vole habitat.
The research this summer would not have been possible without the support from our partners at the U.S. Bureau of Land Management, U.S. Fish & Wildlife Service, CA Department of Fish & Wildlife (Region 6), Integral Ecology Research Center, U.S. Geological Survey, Shoshone Village, Inyo County Roads Department, and the Amargosa Conservancy.
[*Note from the lab’s Dr. Deana Clifford: Wev’e been a bit quiet for a while, but not because we’ve disappeared. We are re happy to start back up again with a 3 part special series updating everyone about our exciting multi-agency/academia/NGO effort to save the critically endangered Amargosa vole. Stay tuned-more posts coming from our activities including voles, fishers, and bighorn sheep!]
By Austin Roy (CDFW WIL Scientific Aid) & Anna Rivera (CDFW Volunteer)
Captive breeding can sometimes be an effective conservation method in the toolbox available to wildlife managers. It’s often employed as a last resort when other conservation efforts have not succeeded. Wild-caught animals are brought into a captive environment and mated for the purpose of increasing the species’ numbers and/or to create an insurance population in case the wild population goes extinct. Captive breeding programs have helped in recovery efforts for several endangered species including the California condor, black-footed ferret, island fox, and peregrine falcon.
Our research team from CDFW and UC Davis have been monitoring the population of the endangered Amargosa vole (Microtus californicus scirpensis). In July, we observed that the habitat of the marsh where most remaining voles live was rapidly degrading. At the same time, vole numbers were rapidly increasing as part of a normal birth pulse cycle. The shrinking marsh was not going to be able to support the number of voles being born so we consulted with our collaborators in the Amargosa vole working group (the US Fish and Wildlife Service, Bureau of Land Management, US Geological Survey, and UC Berkeley) and brought 20 young voles (that would have likely died in the wild) into captivity to try to establish an insurance population of voles.
Ten males and 10 females were brought to UC Davis and placed into indoor quarantine in late July 2014. Individuals underwent disease and genetic testing to decide which individuals would be paired for mating. After quarantine, voles were placed into pairs for mating.
In October, we successfully weaned our first litter of Amargosa vole pups! This is the first step to expanding the captive population to the point when animals can begin to be released into the wild to supplement the wild population. The voles are currently being housed indoors, but we are in the process of creating outdoor pens for the voles where they will experience conditions more closely resembling their natural marsh environment.
While a small step has been made towards the recovery of this endangered species and the path forward remains long, our team remains committed to saving the Amargosa vole.
Click on the links below to read about the Amargosa vole captive breeding program and see more pictures:
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?
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.
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.
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.
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.
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.