Posts Tagged: bats
California is in the middle of the Pacific Flyway, a major north-south flyway for migratory birds, and also bats, that extends from Alaska to South America.
“Every autumn, migratory bats, such as the Mexican free-tailed bats, travel to their overwintering grounds in Southern California and Mexico, where there's plenty of bugs to eat; they come back each spring to raise their families,” said Rachael Long, a UC Cooperative Extension advisor who studies bats.
Bats are beneficial because they feed on insects, including mosquitoes and pests such as codling moths that damage fruit and nut crops. The economic value of bats for pest control on farms has been estimated by some studies to exceed $23 billion per year. Long, who serves Sacramento, Solano and Yolo counties, is studying the value of bats for pest control in walnut orchards.
In the city of Davis, officials recently warned people to stay away from bats after bats found on the UC Davis campus tested positive for rabies. Long agrees with the warning, but worries that it might also result in healthy bats being killed.
“This is most unfortunate for people and bats, but not a surprise at this time of year. Right now, thousands of bats are flying through our great Central Valley, migrating south for the winter, just like ducks and geese, so there's a higher chance of contact,” she said “We just don't see bats as much because they are flying at night, using the stars, earth's magnetic field, and landscapes to navigate.”
Their journey south is lengthy, from as far north as Washington state to Mexico, and exhausting, so bats need to rest along the way.
“Sometimes you'll see one or more tucked up in the corner of your house, such as under an eave,” Long said. “If so, use this as an opportunity to share with others the amazing life of a bat that can fly over a thousand miles to their overwintering grounds and back again in the spring. Leave them alone, let them rest, and they will fly away after they've rested and recovered.”
If you have to move a bat, she notes you should wear gloves and not handle a bat with bare hands because they will bite in self-defense.
“If you find a bat on the ground, place a box over the bat and using a piece of card, slip it under, then gently and carefully slide the bat into the box,” Long said. “Place the box at 4 to 5 feet off the ground and open it (bats usually can't take off from the ground). The bat can then crawl out of the box in its own time and fly away.”
“If the bat does not fly away within 30 minutes, it is probably sick or injured. In this case, contact a wildlife rescue unit in your area.”
Long noted that animal control officers have to euthanize bats to test for rabies.
“The bat may be perfectly healthy, just tired,” she said. “If no people or pets have obviously touched the bat, you can call a wildlife rescue organization. If in doubt, call animal control.”
If a bat does have rabies, Long said, “Rabies dies within five to 10 minutes after the bat dies.”
For more information on the benefits of bats, see Long's post in UC ANR's Green Blog, “Bats in the Belfry? No, Bats in Walnut Orchards” at http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=17395.
What's the economic value of bats to the agricultural pest control? It probably exceeds $23 billion per year, according to recent studies. However, very little data exists on the benefits of bats for individual crops, such as walnuts.
UC Agriculture and Natural Resources researchers, together with UC Davis, are launching a survey to better understand the value of bats (and birds) on managed lands. The voluntary survey, focused on growers and landowners in California's Central Valley, may be completed online.
Work is already underway to assess the pest-control impact of bats on walnut production in the Central Valley with a grant from the U.S. Environmental Protection Agency STAR (Science to Achieve Results).
California produces almost all of the nation's walnuts. Farmers grow some 500,000 tons of walnuts on 290,000 acres, with the annual crop valued at $1.8 billion. Due to popular demand, new orchards are planted every year, calling for more intensive farming practices to manage costly crop pests. For walnuts, the key pest is the codling moth, a larva that feeds on developing nuts. The adult moths begin to fly and lay eggs on the nutlets in May and produce up to four generations per year.
Bats forage in walnut orchards for codling moths and other insects. Colonies of bats double their activity on farms when they roost in bat houses attached to barns in the orchards. The Mexican free-tailed bat is the most abundant species, followed by the Yuma and California myotis, and five other species, including the pallid bat.
In an effort to quantify the economic impact of bats' consumption of codling moths, we captured 36 Mexican free-tailed bats over a three-night period in an 80-acre walnut orchard in Yolo County. Some 3,000 bats live in the bat houses in an abandoned shop on the property.
The research procedure: We opened our mist net from 11 p.m. to 2 a.m. to correspond with codling moth flights and bat activity, and captured the bats as they returned to the roost after feeding. We placed the bats individually in sterile cloth sacks and kept them there until they defecated, then we released them. We quickly froze the guano pellets and shipped them to a USDA lab, where scientists genetically tested them for the presence of codling moths.
Our preliminary data suggest that 5 percent of these bats – about 150 bats from this colony of 3,000 – consumed at least one codling moth per night. We calculated 30 nights per generation for the codling moth, and four generations per year, with each female moth laying 60 viable eggs on individual nuts.
The next steps: we are refining our economic data and determining whether these insect-hunting bats help reduce pesticide use in walnut orchards.
Bats provide these pest control services for free while farmers enjoy a decrease of pests in their orchards and an increase in profits.
Co-authors: Rachael Long, UC ANR advisor; and Katherine Ingram, Department of Wildlife, Fish and Conservation Biology, UC Davis.
Wild Campus organization two years ago to conserve wildlife in the greater UC Davis area.
Working with campus experts (such as faculty and staff in the Department of Wildlife, Fish and Conservation Biology) and local environmental and conservation organizations, the volunteer students are improving the habitats for local wildlife and engaging the public in hands-on activities.
This is an extraordinary program that gives the students real-world environmental management skills, along with leadership opportunities and communications experience. Professor John Eadie, Department of Wildlife, Fish and Conservation Biology at UC Davis, said of the Wild Campus program, “Hands-on activity is a huge part of the educational experience.”
Putah Creek Riparian Reserve, the students are establishing wildlife habitat areas and monitoring populations of amphibians, birds, fish, insects, mammals, and reptiles. They will record the changes over the course of time. Recent work in the riparian reserve (aka “the living classroom”) has included planting native oak seedlings, and installing tule plants to provide protection for the Western Pond Turtle, a species of concern.
A past project — Build a Wild Home Day — involved working with the UC Davis Arboretum on a successful public outreach program to build bird and bat boxes for installation on campus. (Great photos of this program are on the group’s Facebook page.)
The Wild Campus organization has a large cadre of eager and dedicated students who are improvising and making the most of limited resources. However, they are in need of donated field equipment (used equipment is fine) and financial contributions.
Visit the Wild Campus website and Facebook page for a feel-good look at what these ambitious students are doing to improve the environment, along with ways you can help them succeed.
California is home to 25 species of bats. All are insectivorous, with the exception of two species in the Southern California desert that feed on pollen and nectar. Here in the Central Valley there are seven common species of bats including red, hoary, pallid, big brown, and Mexican freetailed bats, as well as California myotis, and Yuma myotis, sometimes referred to as little brown bats.
Farmers welcome bats to their farms every year because they are voracious predators of pests including stinkbugs, cucumber beetles, and moths such as cutworms and armyworms that plague crops. Mosquitoes, midges and flies are also a favorite prey. Studies by UC Cooperative Extension in Yolo County and the UC Davis Department of Wildlife, Fish, & Conservation Biology are looking at the impact of bats on codling moth control in walnuts, a serious exotic pest that costs the walnut industry tens of thousands of dollars every year to control. Current data suggest that orchards with colonies of bats have higher bat activity than those without bats.
Yolo County Resource Conservation District in Woodland builds and sells bat houses for those interested in installing them on their farms.
Sometimes bats roost where they are not wanted. If this occurs, excluding them from the area is the best way to remove them. However, this should not be done between the end of May and early August when bats have their young. Generally they have one offspring per year, with many weeks before the pups can fly. Insectivorous bats generally live for at least 10 to 15 years. Contact the UC Cooperative Extension Service in Yolo County for more information on excluding bats from buildings. If one is found in your house, simply turn out the lights and open the doors or windows and it will fly right out (they’re as scared as you are!).
Injured and orphaned bats are occasionally found on the ground. Never touch a bat with bare hands as they can carry rabies. If one is found on the ground, use gloves or a dustpan and broom to gently pick it up and put it in an area where predators such as cats or dogs cannot get to it. The bat will usually fly away at some point. If a bat is obviously injured or sick, contact the California bat rescue unit and someone will come get the bat to try to nurse it back to health to release it back in the wild.
Migration is the most dangerous time for bats because they become concentrated as they move, making them more vulnerable to dangers, such as wind turbines. Since little is known about the migratory movement of bats, it is crucial that we develop a better understanding of their seasonal whereabouts so hazards are minimized. Wind turbines especially should not be placed in their migratory pathways.
For those interested in learning more about bats, contact the Yolo Basin Foundation. Every summer they lead tours to watch several hundred thousand bats leaving their roost at dusk under the Sacramento causeway to forage for insects, helping farmers with natural pest control.
White-nose syndrome, a horrific disease that has killed millions of bats on the East Coast since its identification in 2006, is spreading fast across the United States, warns Rachael Long, UC Cooperative Extension farm advisor for Yolo County. She dreads its arrival in California.
This disease is caused by a fungus that grows most noticeably on a bat’s muzzle, coating it in a white powder, hence the name "white-nose." It primarily affects hibernating bats by causing them to be more active, according to Long.
"As a result they wake up more often during the winter, burn up fat reserves, and die of starvation," Long said. Where the disease is occurring, bats that were relatively common are now rare.
"Like a tsunami on a quiet beach, white-nose syndrome is expected to strike California in the next couple of years," Long said. "With 25 species of bats in our state, the potential loss in the abundance and diversity of bats could be devastating."
Bats are extremely important in our environment. They are voracious predators of insects, often consuming their body weight in insects each night. As a result, they are important allies to farmers, helping to reduce the numbers of insects that damage crops and providing important ecosystem services in agricultural landscapes.
Currently no one knows where white-nose syndrome came from or how to control it. The disease first showed up in New York in 2006 in a cave that is a popular tourist destination, so it may have been introduced by a foreign visitor.
The hope is that enough bats have a strong enough immune system to survive the disease to repopulate the landscape before colonies go extinct. Likewise, researchers hope that the fungus will not adversely affect migratory colonies, that is, those bats that spend the winter in warmer climates and return to more temperate regions in spring and summer. The fungus favors cooler conditions so it may primarily impact bats that hibernate. California is home to both types of bats. For example, the Mexican freetailed bats migrate, but big brown bats hibernate.
Long suggests a number of ways that one can help bats and the white-nose syndrome crisis, including the following:
- Report unusual late-winter bat behavior (for example, bats flying during the daytime) or unexplained bat deaths to your state wildlife agency.
- Adhere to state, federal and local cave advisories and closures to help prevent the transmission of white-nose syndrome. Even though bats carry the fungus, people can also move the disease around and in greater distances than bats.
- Share with family and friends the benefits of bats and information about the white-nose syndrome crisis.
- Encourage state and federal legislators to allocate funding towards the effort to understand and fight white-nose syndrome.
For more information about bats, see Long's research articles published in California Agriculture journal: "Well-placed bat houses can attract bats to Central Valley farms" and "Bats feed on crop pests in Sacramento Valley."
The photo above of the little brown bat with white fungus on his nose is courtesy of Ryan von Linden of the New York Department of Environmental Conservation. The U.S. Fish and Wildlife Service has this photo and other photos showing symptoms and the effects of white-nose syndrome at http://www.fws.gov/WHITENOSESYNDROME/photos.html.