Bats can hear an insect walking. They eat up to 1,000 mosquitoes in an hour, live as long as 40 years and are the only mammal to truly fly. And one bat species may have a bachelor pad in the San Juan Islands. Rochelle Kelly, a University of Washington doctoral candidate, is studying bats on Shaw and several other islands in the San Juans to add to the limited information on their foraging habits, reliance on forests, and how sensitive they are to fragmented habitats
“One hypothesis was that the more they relied on closed habitats, forests, the less likely they were to cross water. If that’s true, they probably don’t interbreed across islands,” Kelly said, which could affect breeding and diversity of bloodlines.
Kelly could be studying starfish, dragonflies or beetles. Why bats? “I fell into it. I met someone who worked with bats. After quite a bit of research, I realized how incredibly diverse and how many amazing adaptations they have and how underappreciated they are. And once I held my first bat, it was all over for me. I’ve always been a fan of the underdog.”
She’ll return to Shaw next spring.
There are 15 species of bats in Washington, 10 in the San Juans (four on Shaw Island). The small, isolated islands (Sucia, Patos, Jones, etc.) had the fewest bats. Shaw’s resident bats are the big brown bat, Yuma myotis, California myotis, and Western long-eared myotis.
The study’s 2014 pilot program was on San Juan Island. Last summer the survey was expanded. Kelly’s base was on Shaw Island, for logistical reasons. She lived in a small cottage on the University of Washington’s Cedar Rock Preserve. On Shaw, she trapped bats mostly on the preserve, Shaw Island County Park and San Juan Preservation Trust lands, but she wants to expand to other sites. “One of the challenges in a study like this is access to land. (In 2016) I’d like to hook up with more locals for better sampling at more locations.”
Kelly trapped bats on 13 islands, two to 10 nights on each. Bats are difficult to study because they are creatures of the night and fly fairly high off the ground. She uses the extremely lightweight low-tech mist net to catch and release bats. It resembles a volleyball net when attached to poles. She looks for the best foraging areas for bats, which include trees, ponds, open fields next to woods (edge habitats are used by several species), trails or roads with a natural forest overstory.
“One of the highest capture rates was at the preserve (on Shaw). I had nets on the trail to the pond. Having a water source is ideal for many reasons. You can’t get the net over the water but when bats emerge at night, they often go first for a drink of water,” she said.
The research has had a few surprises. She found only two species, about 40 individuals, all male, on 217-acre Vendovi Island, owned by San Juan Preservation Trust. “That was surprising. I called it the bachelor pad. I surveyed in the summer, the highest activity time for bats. Even if a female comes, they’d still be mostly bachelors. Most studies focus on females because of their importance to the population. It may be fidelity to the site to have that sizable of a male colony,” Kelly said.
“One hypothesis was that the more bats relied on unfragmented forests, the less likely they were to cross water. If that’s true, they probably don’t interbreed across islands,” she said. While there are some historical records of bats on the Orcas, Lopez, San Juan and Shaw, there is no data on the smaller islands.” I get a sense of discovery being the first one to survey those islands. It will give the islands a baseline inventory.”
The second surprise was on 564-acre Sucia Island. “It had a really high diversity (of species). The closer, larger islands had more species than the more distant, smaller islands. And Sucia is real isolated. But it two nights I captured five species. That’s a higher number on a few nights sampling relative to other survey efforts on larger islands. They might be more abundant on Sucia because there’s more (unfragmented) forest. It may not be an issue just of how much forest but how much is suitable habitat. I’d need more sampling nights before we could see a pattern of species.”
One bat was the Western long-eared. “It’s a gleaning species that hunts and takes prey off trees and the ground rather than when they’re flying. They move slower, and they’re active all night long. (I) found a higher number on a few nights sampling relative to other survey efforts on larger islands. It may not be an issue just of how much forest but how much is suitable habitat. Lopez Island has less forest but Shaw, Orcas and Suchia have more forest relative to the size of the island.”
Once a bat is captured, it is placed in a small bag and processed. The bag helps keep in body warmth and is a handy fecal matter catcher, important for her study of iguano when back at the Burke Museum in Seattle. Each bat is weighed and several measurements are taken, as well as notes on sex and reproductive condition. Kelly is collecting a variety of data about the bats, including DNA samples that helps identify insect parts to determine what different species bats eat. “Molecular technologies have come a long way, too. The sequencing process is huge. A DNA sequence acts like a bar code for insects.” She also makes audio recordings to listen for calls from all bats in the area—even those who fly higher than the nets can reach.
Bats usually roost in trees and buildings because there are only so many caves to go around. “Some people are happy to have some bats in the house. I suspect that ‘in the house’ translates into attics and under the eaves. Maternity colonies seem to prefer buildings, perhaps as better protection against the elements and predators.”
Despite their speed and agility, bats have a predator: owls. “It’s hard to catch a solo bat, even for an owl. They’re more likely to be caught around the roost when the bats are leaving or returning. Juveniles are not as agile as adults.”
Kelly does not set her nets on a full moon. “Stories of bats at full moons are rampant. But they have reduced activity during a full moon. I don’t sample on a full moon. Maybe they’re less likely to fly in the open where they’re visible in the moonlight and more likely to hunt in darker habitats.”
— Contributed by Sharon Wootton; photographs by the Burke Museum