Bats – Friends in the Garden – with Mount Shasta’s Ray Miller

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There’s a lot to love about the garden in winter. But I do miss some things from the summer garden. For instance, I miss my bats. Of course, they are not technically “my” bats, but rather a small colony that roost in the eaves of my family’s home each summer.

The colony has grown over time from just a few shadowy smaller-than-fist-sized dark brown creatures to perhaps ten or twelve. Each sunset in spring, summer and fall, the bats unfold themselves out of a crack less than a quarter of an inch wide and, apparition-like, disappear into the gloaming over our garden and the countryside beyond. Each morning in the dim before sunrise, they return and put themselves carefully back to bed in a seemingly choreographed flight pattern circling beneath the deep eaves of our back porch. Each bat takes its turn – swiftly but carefully folding itself back up into the eave to rest for the day.

As a gardener and observer, I can pace the measure of my days, the circle of the seasons, and in some ways the general health of my little region by the rhythms of these hard working furry mammals – the only mammals to have true flight. After attending a ranger program on bats at Craters of the Moon National Monument in Idaho this past summer and learning of a fungal disease known as White-Nose Syndrome affecting bat populations in much of the country, I was determined to find out what I could do to help or at least not inadvertently harm the bats who so vigilantly patrol my garden for bugs so much of the year.

Northern California is relatively rich with bats. Seventeen distinct species are known to occur in our region, and we have several well-known and helpful bat researchers and resources. I learned a great deal from Northern California Bats, a non-profit organization founded and run by Corky Quirk and dedicated to the rescue, rehabilitation and release of bats throughout Northern California and based out of the Sacramento/Davis area, as well as Ray Miller, a bat researcher and caver from Mt. Shasta, California, with whom I chatted at length about his work with bats. Both regularly give educational presentations on bats.

Worldwide there are about 1,100 species of bats and 70% of those, including all North American bats, eat only insects. While bats primarily navigate by echolocation – a biologically-based built-in sonar sending images to the brain, they are not actually blind and generally see as well as humans, although they see in black and white. Some species do migrate in winter, although some of our Northern California bats also remain in the area and simply seek more secure winter roosts with better protection from the cold and weather. While some hibernate rather than migrate, in warmer areas such as the Valley portions of Northern California, bats can also go into torpor – a shorter-term more temporary form of hibernation. Photo: Courtesy of US Forest Service Celebrating Wildflowers.

My first question to Miller, a retired career Navy man and native of the Mt. Shasta area, was: “Should I worry about them in terms of health or safety living in the eaves of my house?” His response was that the diseases they carry are few and the parasites – such as mites they carry on them — are fairly specific to them, so not much to worry about for humans. “Cold is a problem for bats, and when I capture bats for ongoing studies and to collect data, I frequently put them inside my coat against my skin to keep them warm. In 25 years I have never been bitten by its fleas or mites,” he shared. He has been bitten by bats, but “I get pre-exposure rabies vaccine just as your pets do,” he told me.

He went on to ask me: “Do they bother you: are they damaging the structure of the house or do they have a strong smell?” My small colony roosts in an exterior knee wall of a second story deck and so they are never in our house’s internal structure near wires or air vents. Their guano (poop) does drop on the ground beneath the entrance to their roost, but I have solved this issue by placing a wide container in the spot and every now and then I empty its contents into my compost bins.

Finally, Miller said “the catastrophic fungal white-nose disease is not in our region’s bat community. Research is ongoing, but from what has already been learned spread of this disease to our area is unlikely due to environmental and bat behavior factors.” However, to protect the bats, it is best to not touch or otherwise handle them or where they roost.

My second question to Miller was: What kind of bats do I have? I followed this question with an elaborately vague description of a smallish, medium brown winged animal, its colony size and its seasonal appearance. His response was: “You have just described most of the 17 species that live in Northern California, but if they don’t have a strong smell, they are probably not the Mexican free-tailed bat (Tadarida brasiliensis), which stink,” he assured me. “The largest bat in your area is the Western Mastiff bat (Eumops perotis), but they are very uncommon and generally cliff-dwellers, so they are not likely,” Miller shared. The most common bats in our area are the Mexican free-tailed bat and the Pallid bat (Antrozous pallidus).

My third question to Miller was: What can I do to help them? He had several suggestions, the first of which was if my bats seemed happy and healthy – then leave them alone and just enjoy their many benefits. “A healthy adult bat will eat around their own body weight in bugs each night. The equivalent of us eating 150 hamburgers a night, they just have to work harder to do it.”

One of the best things you can do is reduce or eliminate pesticides from your home and garden. “Pesticides will accumulate in the insect populations and begin to harm the bat populations, which in turn will create a much larger insect problem in our region.” Photo: The yellow blazing star is a wildflower common in the West which opens at night and can be bat pollinated.

Finally, he suggested that if you want to encourage bats into your garden with a bat house you should keep a few things in mind. “Bats are neat little guys,” Miller enthused. His favorite is perhaps the Townsend’s long-eared bat (Corynorhinus townsendii) because it is the “easiest to get along with in a discussion.” If you have ever lived in close proximity to bats you will know what he means, they chirp and chatter quite a bit more than you might think. “But they are little and temperature is critical for them. Their average body temperature is about 107 degrees, so they need it nice and warm.”

He pointed out that most commercial bat houses are fairly thin and the temperature inside of them fluctuates rapidly. If you are going to install a bat house, the best ones are those that are quite tall and have an air vent half way up to help the air circulate and allow for the bats to adjust themselves up and down inside the house and find a warm spot. “The bats come home in the morning cold and tired from the night’s feeding,” he also told me, so orient your house against a flat surface, such as the side of a building facing southeast when the morning sun will provide needed warmth. “Bats will rarely roost in a bat house placed in a tree,” he warned, “because the temperature is too variable and predators such as cats and snakes are able to access the house.” You don’t need to clean a bat house, he told me, as most of the guano falls out the bottom anyway, and “A little poop and pee in the house makes it smell more like home. In fact,” he said, “if you know where to get some guano, smearing it around the base of a new bat house could help to entice some bats in!” Photo: Bat house designs can be found on-line for do-it-yourselfers, and out of Chico also has a wonderful selection to order ready-made.

Beyond a bat house, “a yard light and a small pond of open water are great attractants. Bats drink while in flight,” said Miller.

So while I still don’t know the identity of my bat colony, I do know that they add to the identity and beauty of my garden – and the environmental health of our region. I will look forward to their return in the spring.

If you have unwanted bats in your house, or find an orphaned or injured bat, call a bat advocate before a pest control service for help. While Ray Miller has been handling bats for more than 25 years and never come across a rabid one, he stresses that it is both against the law and unwise to handle a bat, or any “animal living or dead not behaving normally” yourself. Contact a permitted professional.
Ray Miller is not certified to rehabilitate bats, but can be reached with questions or for advice on bat removal or exclusion at: Corky Quirk and Northern California Bats can be found at, or contacted by phone at 530-902-1918.

An edited version of this article first appeared on 1.20.11 in the Chico News & Review, for which I write regularly about gardening and environmental topics.

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Jennifer Jewell
In a North State Garden is a bi-weekly North State Public Radio and web-based program celebrating the art, craft and science of home gardening in Northern California and made possible in part by the Gateway Science Museum - Exploring the Natural History of the North State and on the campus of CSU, Chico. In a North State Garden is conceived, written, photographed and hosted by Jennifer Jewell - all rights reserved In a North State Garden airs on Northstate Public Radio Saturday morning at 7:34 AM Pacific time and Sunday morning at 8:34 AM Pacific time, two times a month.
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