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A bat-ty summer night out

Sit on the edge of a lake at sunset and you're in "bat commuter zone," says one bat expert.

by on August 23, 2012

Townsend's big-eared bat (Corynorhinus townsendii). Photo by Ann Froschauer/USFWS.

Move over, birds. There is another flying – albeit more elusive– species drawing summer crowds.

Warmer weather and longer twilights make it ideal to watch some of the coolest little critters in the Bay Area — bats!

California leaf-nosed bats. Photo from Creative Commons.

Here are the facts. There are 24 species of bats in California and they’ve nudged their way into just about every kind of land habitat — mountains, deserts, and even urban neighborhoods. Between 12 to 16 bat species call the San Francisco Bay Area home.

Not impressed enough by these flying mammals? Well, how about this. Almost one-quarter of the world’s 4,400 species of mammals are bats.

“Bats can really be found anywhere if you’re looking,” says Cat Taylor, a naturalist with the East Bay Regional Park District. “Since they primarily feed on small insects, they are mainly around lakes, rivers and streams, but they’ll hang out around streetlights around your neighborhood or anywhere else there are insects.”

Think of bat watching as a way to appreciate, for a moment, all that these little critters do for us. Dismiss preconceptions about bats being ruthless, bloodsucking harbingers of disease. Yes, there are the occasional cases — such as the recent scare at a Mendocino yoga retreat where some seven Bay Area residents are being treated for possible rabies infection after exposure to bats. At Lake Merced, San Francisco Health officials are warning people about bats that recently tested positive for rabies.

But bats are generally shy, intelligent creatures that are important to our ecosystem and are of considerable benefit to humans. They are natural pest controllers, pollinators and fertilizers.

Dusk and early dawn are the best time to watch bats. The longer twilights of summer make for particularly good viewing conditions, and the warmer weather ensures all the bats are out and about town, instead of in hibernation or migration.

Although bats are everywhere, to guarantee seeing them, head to a body of fresh water at sunset and look to the brightest part of the sky, says Taylor.  Western pipistrelles are among the first bats to come out and even fly in daylight. One of the top spots in the Bay Area to watch bats is Lake Del Valle in Livermore.

Western pipistrelle bat. Photo is Creative Commons.

“If you are sitting on the edge of the lake, 10 to 15 minutes after sunset, you are in a bat commuter zone,” says Taylor. “It’s like being on the Bay Bridge at 7:30 a.m. and everyone’s going to work.”

Bats can also be seen in the wee hours of the morning. If you’ve adopted a semi-nocturnal lifestyle and are heading home around 4 am, you’re in good company. Bats generally feed for brief periods at a time, return home to rest, then head back out to snack before turning in for good at dawn.

And they aren’t just zipping overhead. If you are nearby a body of water, bats are lurking everywhere you imagine: under loose bark, in crevasses of rocks, behind signs, or in rodent holes in the ground.

The pallid bat is one of the few species of ground-dwelling bats. Photo by Keaton Wilson.

Bats are extremely diverse in every possible way: size, how they forage, where they live and what they eat. Some fruit bats pollinate flowers, and the pallid bat hunts scorpions–and is immune to its venom–making it a ground dweller most of the time. Say what? Bats on the ground?!

Know the phrase, “blind as a bat”? Dismiss that one as well. Bats see very well. In fact, the California leaf-nosed bat has night vision far superior to the best man-made night scope. The need for echolocation was born not out of blindness, but to maximize hunting yields in the dark.

Bats’ hearing is so advanced that the high-pitched sound waves that bounce off objects and back don’t just tell the location of an insect or fruit, it tells them whether it is their favorite variety. Since insects can hear the bat calls and evade getting caught, bats will generally rely on their eyes to find prey until the last minute.

Echolocation doesn’t just help bats find their prey, it helps us find bats. Once you identify the high-pitched calls and squeaks, you can track bats in the night sky. When watching bats, be respectful. Be sure to watch quietly and avoid shining flashlights at the animals. The best method is to set up lawn chairs, relax and try not to be obtrusive.

“Be as non-disruptive as possible,” says Taylor. “If you’ve done anything to make an animal change its natural behavior, you’ve done something wrong.”

Here are our top picks on the best places to watch bats in the Bay Area:

East Bay Regional Parks:

Lake Del Valle, Livermore
7000 Del Valle Road, Livermore, CA, 94550, (888) 327-2757
Park gate closes at 9, but curfew is 10 p.m., so you can park and walk in.

Shadow Cliffs Regional Recreation Area, Pleasanton
2500 Stanley Boulevard, Pleasanton, CA 94566, (925) 846-3000

San Francisco:

Lake Merced
Several entrances off Lake Merced Blvd, John Muir Blvd and Skyline Blvd. Suggested trail: Lake Merced Rim

Stow Lake, Golden Gate Park
Stow Lake Drive, SF, CA 94119


Perhaps the best place to see bats in one fell swoop is the Yolo Causeway, halfway between Davis and Sacramento. At the beginning of every June, 250,000 Mexican free-tailed bats migrate to the 3-mile long causeway, where they roost during the daytime and emerge at twilight in massive numbers. It’s one of this species’ largest colonies in California. [The Davis Enterprise]


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Alice Chan on August 23rd, 2012 at 9:20 am

Any suggestions about good places for bat-watching in Sonoma County?

Bay Nature staff on August 23rd, 2012 at 10:30 am

Hi Alice, NorCal Bats has a great calendar listing bat “hot spots” around the Bay. There’s an event listed for Napa:
http://www.norcalbats.org/calendar.shtml Happy batting!

Bay Nature staff on August 30th, 2012 at 3:45 pm

We also contacted Frederique Lavoipierre from Sonoma State University about your query, Alice. She said:

” I know a spot on the side of a building in Sebastopol where the bats emerge every evening – I like to watch them. Other than that, I suggest you contact Pepperwood Preserve and Bouverie Preserve (Audubon). Perhaps the Grape Growers Association could be helpful.”

Angie Felshaw on June 15th, 2014 at 2:25 pm

Where is there Bat watching in Southern California as far north as Bakersfield?

Karen on July 11th, 2014 at 3:29 pm

Not very many locations, what about Alameda or Oakland?

Susan McIntyre on April 5th, 2018 at 9:00 am

Hello, I’m appalled people are encouraged to be around bats. I’d like to share information I learned during my workplace’s outbreak of an airborne infectious disease that can cause malignancies, precancerous conditions, rheumatological diseases, connective tissue diseases, heart disease, autoimmune symptoms, inflammation in any organ/tissue, “mimics” inflammatory bowel disease, causes seizures, migraines, mood swings, hallucinations, etc. and is often undiagnosed/misdiagnosed in immunocompetent people. 80-90+% of people in some areas have been infected, and it can lay dormant for up to 40 years in the lungs and/or adrenals.
My coworkers and I, all immunocompetent, got Disseminated Histoplasmosis in Dallas-Fort Worth from roosting bats, the most numerous non-human mammal in the U.S., that shed the fungus in their feces. The doctors said we couldn’t possibly have it, since we all had intact immune systems. The doctors were wrong. Healthy people can get it, too, with widely varying symptoms. And we did not develop immunity over time, we’d get better and then progressively worse, relapsing periodically and concurrently every year.
More than 100 outbreaks have occurred in the U.S. since 1938, and those are just the ones that were figured out, since people go to different doctors. One outbreak was over 100,000 victims in Indianapolis.

It’s known to cause hematological malignancies, and some doctors claim their leukemia patients go into remission when given antifungal. My friend in another state who died from lupus lived across the street from a bat colony. An acquaintance with alopecia universalis and whose mother had degenerative brain disorder has bat houses on their property.

There’s too much smoke for there not to be at least a little fire.

Researchers claim the subacute type is more common than believed. It’s known to at least “mimic” autoimmune diseases and cancer and known to give false-positives in PET scans. But no one diagnosed with an autoimmune disease or cancer is screened for it. In fact, at least one NIH paper states explicitly that all patients diagnosed with sarcoidosis be tested for it, but most, if not all, are not. Other doctors are claiming sarcoidosis IS disseminated histoplasmosis.

What if this infection, that made me and my coworkers so ill, isn’t rare in immunocompetent people? What if just the diagnosis is rare, since most doctors apparently ignore it? Especially since online documents erroneously state it’s not zoonotic.

Older documents state people exposed to bats are known to get Disseminated histoplasmosis, but at some point this information appears to have been lost, for the most part. And now bat conservation groups encourage people to leave bats in place in public buildings and homes, since they claim they’re harmless and even beneficial. What a horrible mistake they’ve made.

This pathogen parasitizes the reticuloendothelial system/invades macrophages, can infect and affect the lymphatic system and all tissues/organs, causes inflammation, granulomas, and idiopathic (unknown cause) diseases and conditions, including hematological malignancies, autoimmune symptoms, myelitis, myositis, vasculitis, panniculitis, dysplasia, hyperplasia, etc. It causes hypervascularization, calcifications, sclerosis, fibrosis, necrosis, eosinophilia, leukopenia, anemia, neutrophilia, pancytopenia, thrombocytopenia, hypoglycemia, cysts, abscesses, polyps, stenosis, perforations, GI problems, hepatitis, focal neurologic deficits, etc.

Many diseases it might cause are comorbid with other diseases it might cause, for example depression/anxiety/MS linked to Crohn’s.

The fungus is an Oxygenale and therefore consumes collagen. It’s known to cause connective tissue diseases (Myxomatous degeneration?), rheumatological conditions, seizures, and mental illness. Fungal hyphae carry an electrical charge and align under a current. It causes RNA/DNA damage. It’s known to cause delusions, wild mood swings (pseudobulbar affect?), and hallucinations. It’s most potent in female lactating bats, because the fungus likes sugar (lactose) and nitrogen (amino acids, protein, neurotransmitters?). What about female lactating humans…postpartum psychosis (and don’t some of these poor women also have trouble swallowing)? The bats give birth late spring/summer, and I noticed suicide rates spike in late spring/early summer. It’s known to cause retinal detachment, and retinal detachments are known to peak around June-July/in hot weather. A map of mental distress and some diseases appear to almost perfectly overlay a map of Histoplasmosis. Johns Hopkins linked autism to an immune response in the womb. Alzheimer’s was linked to hypoglycemia, which can be caused by chronic CNS histoplasmosis. The bats eat moths, which are attracted to blue and white city lights that simulate the moon the moths use to navigate. Bats feed up to 500 feet in the air and six miles away in any direction from their roost, but not when it’s raining or when the temperature is less than approximately 56° F. Although the fungus grows in bird feces, birds cannot carry the fungus like mammals can, because their body temperature is too high, killing the fungus.
I believe the “side effects” of Haldol (leukopenia and MS symptoms) might not always be side effects but just more symptoms of Disseminated Histoplasmosis, since it causes leukopenia and MS symptoms. What about the unknown reason why beta receptor blockers cause tardive dyskinesia? The tinnitus, photophobia, psychosis “caused” by Cipro? Hypersexuality and leukemia “caused” by Abilify? Humira linked to lymphoma, leukemia and melanoma in children? Disseminated Histoplasmosis is known to cause enteropathy, so could some people thought to have nonsteroidal anti-inflammatory drug enteropathy have it and taking NSAIDs for the pain/inflammation it causes, and the NSAIDs aren’t the actual culprit?
From my experience, I learned that NO doctor, at least in DFW, will suspect subacute and/or progressive disseminated histoplasmosis in immunocompetent people. Some doctors, at least the ones I went to, will actually REFUSE to test for it, even when told someone and their coworkers have all the symptoms and spend a lot of time in a building with bats in the ceiling. Victims will be accused of hypochondriasis. In fact, the first doctor to diagnose me was a pulmonologist, and the only reason he examined me was to try to prove that I didn’t have it, when I really did. No doctor I went to realized bats carry the fungus. And NO doctor I went to in DFW, even infectious disease “experts,” understand the DISSEMINATED form, just the pulmonary form, and the only test that will be done by many doctors before they diagnose people as NOT having it is an X-ray, even though at least 40-70% of victims will have NO sign of it on a lung X-ray. It OFTEN gives false-negatives in lab tests (some people are correctly diagnosed only during an autopsy after obtaining negative test results) and cultures may not show growth until after 12 weeks of incubation (but some labs report results after 2 weeks).
One disease of unknown cause that could be caused by Disseminated Histoplasmosis: I suspect, based on my and my coworker’s symptoms (during our “rare” infectious disease outbreak) and my research, that interstitial cystitis and its comorbid conditions can be caused by disseminated histoplasmosis, which causes inflammation throughout the body, causes “autoimmune” symptoms, and is not as rare as believed. I read that “interstitial cystitis (IC) is a chronic inflammatory condition of the submucosal and muscular layers of the bladder, and the cause is currently unknown. Some people with IC have been diagnosed with other conditions such as irritable bowel syndrome (IBS), fibromyalgia, chronic fatigue syndrome, allergies, and Sjogren’s syndrome, which raises the possibility that interstitial cystitis may be caused by mechanisms that cause these other conditions. In addition, men with IC are frequently diagnosed as having chronic nonbacterial prostatitis, and there is an extensive overlap of symptoms and treatment between the two conditions, leading researchers to posit that the conditions may share the same etiology and pathology.” Sounds like Disseminated Histoplasmosis, doesn’t it?
My coworkers and I were always most ill around April/May/June, presumably since the Mexican Free-tail bats gave birth in Texas during May, and fall/Thanksgiving to December, for some unknown reason (maybe migrating bats from the north?). We had GI problems, liver problems, weird rashes (erythema nodosum, erythema multiforme, erythema annulare, etc.), plantar fasciitis, etc., and I had swollen lymph nodes, hives, lesions, abdominal aura, and started getting migraines and plantar fasciitis in the building, and I haven’t had them since I left. It gave me temporary fecal incontinence, seizures, dark blood from my intestines, tinnitus, nystagmus, benign paroxysmal positional vertigo, what felt like burning skin, various aches and pains (some felt like pin pricks and pinches), tingling, tremors, “explosions” like fireworks in my head while sleeping, temporary blindness, and chronic spontaneous “orgasms”/convulsions. Suddenly I was allergic to pears (latex fruit allergy?). I had insomnia (presumably from the fungus acidifying the blood, releasing adrenaline) and parasomnias. I suddenly had symptoms of several inflammatory/autoimmune diseases, including Fibromyalgia, Sarcoidosis, ALS, MS, Sjogren’s syndrome, etc. that have disappeared since leaving the area and taking nothing but Itraconazole antifungal.
No one, including doctors (we all went to different ones), could figure out what was wrong with us, and I was being killed by my doctor, who mistakenly refused to believe I had it and gave me progressively higher and higher doses of Prednisone (at least 2 years after I already had Disseminated Histoplasmosis) after a positive ANA titer, until I miraculously remembered that a visiting man once told my elementary school class that bats CARRY histoplasmosis….so much of it that they evolved to deal with the photophobia and tinnitus it causes by hunting at night by echolocation. There’s a lot more. I wrote a book about my experience with Disseminated Histoplasmosis called “Batsh#t Crazy,” because bats shed the fungus in their feces and it causes delusions and hallucinations, I suspect by the sclerotia it can form emitting hallucinogens (like psilocybin and dimethyltryptamine) along with inflammation in the CNS. (Schizophrenics have 2X of a chemical associated with yeast, part of the fungal life cycle.)
Thank you for your time,
Susan McIntyre

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