We are reprinting with permission an article about bats in San Francisco’s parks from the San Francisco Forest Alliance. The article reports observations of bats as well as a study of bat populations in San Francisco’s parks. The study found that both the number of bats as well as the number of species of bats was related to the amount of forest edge in each park and the availability of water. The study reports that the forest edge contains more insects which are the primary food of the bats.
We are posting this story today because hundreds of trees in Glen Canyon Park in which bats and many other creatures live are being destroyed as we speak. Here is a video of the destruction which started yesterday and continues today, along with a narrative of how and why this needless destruction is happening. Please watch this moving video to understand why we are so committed to opposing the pointless destruction of our trees by extremist agendas that are damaging the environment and harming the animals that live in our open spaces. (Edited to Add: And here is a video showing the second day of the demolition project.)
The study did not find any relationship between the number of bats nor the number of species of bats with the percent of native plant coverage. We speculate—although the study does not—that the absence of correlation between bat populations and native plant populations suggests that there are not more insects in native plants than at the forest edge. Although native plant advocates claim that more insects are found in native plants, this is yet more evidence that this claim is not true.
Bats are insect-eating machines. According to the USGS, “Bats normally eat about half their weight in flying insects each night.” So even for those who don’t find these night-flying mammals charming, it’s good to know there are bats among us.
San Francisco has at least four species of bats, all of which eat insects. According to research by Jennifer Krauel, which involved recording bat sounds to determine which species they were, Mexican Free-tailed bats are the most common. Parks with water – like Glen Canyon – also have Yuma Myotis bats. The other two species she found (more rarely) were Western Red Bats, and Little Brown Bats, and she found them in just a couple of places.
Her research indicated that “amount of forest edge and distance to water were the factors best explaining species richness and foraging activity.” It also showed that bats in San Francisco remain active through the winter and don’t hibernate or move elsewhere.
If you’re interested in reading her paper, it’s here as a PDF: Jennifer Krauel thesis on bats in SF
BATS IN GLEN CANYON PARK
Glen Canyon’s bats are often visible at dusk. They’re most evident in the Fall, though they’ve been seen at other times of the year. (The pictures above are from February and April, those below from October.)
Here’s a note on bat-viewing from one visitor to Glen Canyon.
“It was late in the afternoon, and late in October. We were standing around the entrance to the park on Alms Rd. As dusk fell, bats emerged from the tall eucalyptus trees. Quite suddenly they were in the air right above us. I pulled out my camera, which is not really good in poor light but I tried to take some pictures anyway. Here’s one:
“They’re difficult to spot in the picture, but all those black smudges are bats that were moving too fast for my pocket-camera. Here’s the same picture, cropped, with the bats circled in yellow:
“They dispersed over the canyon. Here’s another picture from a few minutes later (and the one below it shows where the bats are).
“It was fantastic. I haven’t seen this many bats anywhere in San Francisco.”
LARGE TREES ARE IMPORTANT
We did a little research, and found a Stanford report that emphasized the importance of large trees to a particular species of bats, Yuma Myotis… bats that Krauel’s research had actually found in Glen Canyon Park.
“Yuma bats that forage in the preserve travel several miles to roost in large trees in Portola Valley and Woodside, suburban communities on the San Francisco Peninsula. The average diameter of the bats’ chosen trees is about a yard across — more than three times wider than the average tree in those areas.”
(The link to the abstract of the actual Stanford research paper is HERE.)
That’s the size of the big eucalyptus trees in Glen Canyon Park – including those that SFRPD wants to chop down.
WHY BATS MATTER
Bats are an important part of an eco-system, and fill a role few other creatures do: They hunt night-flying insects like mosquitoes that birds don’t catch because they’re sleeping. This is especially important now as West Nile virus, a mosquito-borne disease, has been spreading.
Having bats in a landscape contributes to its bio-diversity. All species of bats are protected in California.
(Some people are concerned that bats carry rabies – and it’s true no one should handle bats, especially grounded bats that may be sick, with their bare hands. But according to the California Department of Fish and Wildlife, less than 1% of bats are infected. [Click HERE to see their note.] The risk of getting rabies from a bat is less than the risk of being struck by lightning.)
HOW WILL SF RPD ENSURE THE PRESERVATION OF THE BATS?
We’re concerned about the impact of the planned tree removals on Glen Canyon’s bats.
- All species of bats are protected, and removing the trees will impact their habitat by reducing the number of safe roosting spots, especially for Yuma Myotis bats that need both large trees and nearness to water.
- The contractor will be chopping down the trees in the daytime. Bats roosting there are likely to be killed – if not in the process of the tree-felling, by being forced to fly blinded and confused in the daytime and fall prey to hawks, crows and ravens.
How is SF RPD going to ensure the protection of these bats?
And in what ways will felling large trees near the stream alter the ecology of the canyon?
3 thoughts on “Bats in Glen Canyon Park are being evicted NOW!”
This back to native imitation restoration just makes me sick. These ‘restoration’ programs are no different from strip mining operations. This is the same long term plan for the San Leandro Creek.
THE REMOVAL OF THESE MATURE EUCALYPTUS IS INSANE! THE BATS AND THE THE BUTTERFLIES ARE SO IMPORTANT TO THE ECOSYSTEM…..AND THE REMOVAL WILL CREATE SLIDE HAZARDS. ONLY THE SAPLINGS SHOULD BE REMOVED AND GOATS EMPLOYED TO DEAL WITH DEBRIS. THE CITY SHOULD BE SUED FOR THE DESTRUCTION OF HABITAT, AND IN A TIME OF CLIMATE CHANGE, THE LOSS OF TREES CAN RESULT IN LOSS OF GROUND WATER, CREEK HEALTH AND THE POLLUTION PROTECTION AFFORDED BY THE TREES. I WOULD CERTAINLY WANT TO KNOW HOW THE CITY CAN AFFORD TO PAY FOR THIS MASSIVE DESTRUCTION. MOST PARK BUDGETS ARE BEING CUT IN THE BAY AREA. WHERE IS THE MONEY COMING FROM?
CAROLE SCHEMMERLING CO-FOUNDER, URBAN CREEKS COUNCIL OF CALIFORNIA HORTICULTURIST; MEMBER, CITY OF BERKELEY PARKS COMMISSION
Date: Fri, 11 Jan 2013 15:34:11 +0000 To: email@example.com
Webmaster: Thank you for your comment and for describing your credentials for expressing your opinion.
This particular episode of destruction in Glen Canyon Park is being financed by a capital improvement bond, ironically, However, many other sources of funding have been used in other phases of the huge project to return this park to native grassland and dune scrub. One of the most outrageous sources of funding was the State of California, specifically a “Habitat Improvement” grant. This funding is consistent with the absurd fiction that wildlife benefits from the destruction of their homes and their sources of food.
Wow, someone actually read my thesis! And you represented my findings pretty accurately as well. I no longer live in the city, alas, but love Glen Canyon and used to walk my dog there regularly. If you’re going to use my results, want to make a couple of points as caveats here.
First, there is no evidence that Yuma myotis, or any other local bat, roosts in Eucalyptus trees. They are going to look for holes in big trees, or cracks under the bark. It’s possible they might not like the strong odor of eucs; we simply don’t know this. I don’t believe there were any eucs in the Stanford study area, and if there were the bats didn’t use them, so again, we don’t know. However, the Glen Canyon eucs certainly are some of the biggest trees in the area, and Yumas do like big trees, so it’s a reasonable (but completely untested) hypothesis.
Second, the location of my detector in the canyon was next to the stream in the willows, an area that was restored previously and seemed to have the most promising habitat. I never actually saw bats emerge from roosts, so I don’t know where they came from. The Stanford Yumas traveled far enough from their roosts that we can’t assume the Glen Canyon Yumas roost in the canyon, and the same for the freetails. My study was only about foraging, and not about roosts, unfortunately.
Third, while I agree that there is no data to support higher insect counts in native than non-native plants (and believe me I looked hard to find it) I think this is due to a lack of studies, rather than a result of research. So while I wouldn’t let this be a rationale for cutting the trees down, it’s not a rationale for keeping them either.
Finally, while I love big trees, I also think the restored area (under where the owls nested while I lived there) is also lovely, and I think the people promoting natural areas are trying to do the right thing and often produce wonderful results. I wish people weren’t so seriously polarized about this issue. Now that I no longer live in the city, I want to say: take a step back and appreciate what you have. It’s so much better than anyplace else, with or without those trees.
Webmaster: Actually there are many studies that report that native plants do not support more insects than non-native plants. Here is a compendium of such studies: https://milliontrees.me/2012/08/14/doug-tallamy-refutes-his-own-theory-without-changing-his-ideology/.
Thanks for your visit and for providing clarification of your findings.