Zoöp Observations: Bats
27 July 2022
Took a bat detector with me on a two-hour bat safari in The New Garden last night, for the fourth time. For several years two boxes made specially for bats have been hanging on the eastern facade of The New Institute, but I don’t think they are used as a mating, maternity and summer residence. Bats are fairly picky regarding the type of box, the size of the entrance opening, and particularly the location, the microclimate in the box, absence of draft and light.
During my first bat safari, in the early hours of July 2, I immediately noticed a spotlight in the villa garden at 18 Jongkindstraat that permanently illuminates the eastern facade of The New Institute at night. It is completely understandable that bats would avoid the boxes on this facade. Various bat species however do visit the New Garden as a foraging area. I have recorded bat activity on three of my four night safaris.
Both on my first safari on July 2, and on my third safari on July 20, my bat detector picked up echolocation calls of the common pipistrelle (Pipistrellus pipistrellus) and the soprano pipistrelle (Pipistrellus pygmaeus). The peak frequency for the call of the common pipistrelle is 42-49 kHz, while the soprano pipistrelle echolocates at 52-60 kHz. On my second safari on July 9, I only picked up the common pipistrelle. My fourth safari yielded no echo location calls at all. Temperature may play a role in this: the night of July 27-28 was relatively cool, so bats of both species may have chosen to forage somewhere closer to their residences.
On each safari I also searched the ponds of Het Nieuwe Instituut for the aforementioned bats. I was hoping to find Daubenton’s bat (Myotis daubentoni), as this species is also foraging above the nearby pond behind the Boijmans van Beuningen museum. Daubenton’s bat emits echolocation calls at frequencies between 25 and 80 kHz that are loudest at 40 to 45 kHz and are reminiscent of the sound of a machine gun. These bats can often be seen circling just above the water surface. Only during my third safari on July 20 did I spot a Daubenton’s bat over the large pond of The New Institute.
I doubt the other, smaller pond will ever attract a single Daubenton’s bat, as long as this pond is permanently illuminated at night by the white neon letters spelling N-I-E-U-W. Right next to these letters a third bat box has been attached. It's hard to imagine a more ill-chosen spot!
Artist Frank Bruggeman, in collaboration with researcher and author Peter Zwaal, describes what he sees happening in The New Garden since spring 2022, when the Nieuwe Instituut officially became a zoop. In small vignettes, he outlines the dynamics between plants, animals, walkers, staff and other human and other-than-human presences in the outdoor space around the institute. From the return of the moorhen to the unexpected introduction of the cherry tomato.
Read other observations