Counting Free-tailed Bats in Bridges

9/10/18
By Merlin Tuttle

Merlin inspects Brazilian free-tailed bats (Tadarida brasiliensis) moments after removing them from their bridge crevice roost for counting.

For many years we’ve wondered just how many Brazilian free-tailed bats (Tadarida brasiliensis) could cram into a single 18-inch-deep bridge crevice. Accurate counts of large colonies are difficult no matter how they’re made. However, when estimating bridge colonies, it would help if we knew the number, using an average horizontal foot of crevice.

The solution seemed easy. Two years ago, Glen Novinger, an MTBC member and I, inserted two, three-quarter-inch-thick wooden frames, each encompassing a square foot of interior space, into bridge crevices of the same width while the bats were out feeding. The idea was to later slowly remove them, forcing those roosting inside to exit into a cloth-lined bag from which we would count them.

However, the bats were full of surprises. The first night we waited patiently till half an hour after we’d seen the last ones leave—or at least that was what we thought! But when we approached to install our devices, roughly half remained inside. I couldn’t help but wonder how many emergence counts had missed those that, for whatever their reasons, didn’t emerge at sundown. (more…)

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Texas Department of Transportation Celebrates Bats

8/28/18
By Merlin Tuttle

 

The Texas Department of Transportation (TxDOT) has set world records when it comes to helping bats, and that special help is paying big dividends for Texans and for countless visitors. Thanks to the enthusiastic early leadership of Supervising Bridge Engineer, Mark Bloschock and the continuing efforts of Stirling Robertson, now in charge of Strategic Projects, and John Young, an Environmental Specialist, TxDOT is taking great pride in its accomplishments.

On August 21, Stirling and John organized a special bat evening for 30 of TxDOT’s most important media and public information officers. They each received a copy of Department’s new guide to bat watching at state bridges, attended my 20-minute presentation at TxDOT headquarters, then joined me for a special Congress Avenue Bridge bat watching evening. We were delighted when we learned that Mark, who is now retired, would be able to join us.

Merlin speaking to TxDOT media and public relations staff.
Merlin entertaining TxDOT staff with bat facts while waiting for Congress Ave Bridge bats to emerge.

The bats performed beautifully, and Stirling reported, “There has been overwhelming positive response to your talk and the whole event. Good stuff!” A big thank you to Stirling for making this event possible! We look forward to future collaboration and many more bats in Texas bridges.

 

 

Emerging bats providing America’s most famous urban wildlife spectacle.

 

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Mosquito Eating in Bats

8/9/18
By Merlin Tuttle

For decades, bat biologists have debated the extent to which bats prey on, and potentially reduce mosquito populations. However, recent research suggests bats may be eating far more mosquitoes than yet suspected. Amy Wray and associates (2018) relied on newly refined techniques that provide greater sensitivity. In their paper, titled “Incidence and taxonomic richness of mosquitoes in the diets of little brown and big brown bats,” they reported that these common species eat a greater variety of mosquitoes, and catch them more frequently than previously suspected.

A little brown myotis (Myotis lucifugus) in Wisconsin. Just one of these bats can catch 1,000 mosquito-sized insects in a single hour.

They tested guano samples from 22 locations in a range of habitats, across the State of Wisconsin, from May 17 through July 29. Seventy-two percent of little brown myotis (Myotis lucifugus) samples contained mosquitoes representing 15 species, more than twice as many as big brown bats (Eptesicus fuscus). But even the larger big brown bats, previously thought to feed mostly on beetles and moths evidenced mosquito-eating in 33 percent of samples. Frequency of mosquito-eating remained constant throughout the active season in big brown bats but declined slightly in little browns.

Little brown myotis (Myotis lucifugus) from Tennessee.
A third of big brown bats (Eptesicus fuscus) in Wisconsin fed on mosquitoes.

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Bats and Chocolate Production

By Merlin Tuttle
6/6/18

While conducting her Ph.D. thesis research, Bea Maas and her team (Maas et al. 2013) collected data that would surprise even her. When insect-eating bats and birds were excluded from cacao trees in Sulawesi, Indonesia, the crop yield fell by 31 percent. And when she compared losses due to night versus daytime exclusion, bats versus birds, she discovered that bats accounted for 22 percent of the prevented losses.

A control site in the same study (poles without netting).

To obtain such data, Bea selected 15 plantations where she enclosed 120 cacao trees in 60 exclosures (like huge, mesh cages) constructed of nylon mesh. There were four exclosure treatments per plantation, one daytime, one nighttime, one day and night, and one always left open as a control.

A bat/bird exclosure in Sarawak, Indonesia, built with bamboo poles and commercial nylon monofilament netting with a mesh size of 2 x 2 cm. These were opened and closed like curtains daily.

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Success in Panama!

During both weeks of our workshops, we encountered periodic rain showers, keeping the normally hot, dry-season temperatures far more comfortable than anticipated. The downside was that we had poor netting results on three nights during the second week. We shared the forest with some interesting characters, such as a black jaguar, which fortunately left us alone, though it likely observed our activities. This one was photographed on a trail camera near one of our netting sites.

 

We set up a triple-high mist net almost every night, both weeks.

Departing to net bats over the nearby river. Daniel Hargreaves is carrying the triple-high net rig in the red bag. His team of skilled instructors from the U.K., Steve and Fiona Parker and Daniel Whitby, were superb.

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More Bats from Cocobolo

During our two-week stay in Panama’s Cocobolo Nature Reserve, we recorded more than 600 bats of 53 species, more than half the total number known for the entire country. Additional species were netted nearly every night, including two on our final evening. Over our two-weeks of workshops, common vampire bats (Desmodus rotundus) and greater fishing bats (Noctilio leporinus) were participant favorites, though an incredible variety of fruit-, nectar-, and insect-eating species were seen. The hardiest of our group members often worked till dawn, bringing in a steady stream of species for portrait photos, especially during the first week. By the second week much more time was devoted to training bats to come on call, especially to locations where Merlin could photograph natural behavior, such as catching katydids.

Merlin Tuttle training a hairy big-eared bat (Micronycteris hirsuta) to come on call to a leaf to catch katydids (its natural prey) in front of bright video lights needed for high speed video shooting.

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Some non-bat Cocobolo critters

We found dozens of creatures while out netting for bats, and even at base camp. We don’t have species names for all of them but here’s a small collection of some of Cocobolo’s non-bat critters…

 

Jen Shallman with a Mussurana snake (Clelia clelia) Photo: Los Naturalistas
Gladiator tree frogs (Hypsiboas rosenbergiPhoto: Los Naturalistas
Eyelash viper (Bothriechis schlegeliiPhoto: Los Naturalistas
Brown blunt-headed vine snake (Imantodes cenchoaPhoto: Los Naturalistas
Photo by Daniel Whitby
Photo by Daniel Whitby
Photo by Daniel Whitby
Photo by Daniel Whitby
Photo by Daniel Whitby
Photo by Daniel Whitby
Bullet ants Photo by Daniel Whitby
Kind toad Photo by Daniel Whitby
Photo by Daniel Whitby
Photo by Daniel Whitby
Photo by Daniel Whitby
Photo by Daniel Whitby
Photo by Daniel Whitby
Whip scorpion Photo by Daniel Whitby
Photo by Daniel Whitby
Coral snake (Mircrurus clarkii), this was the first one of this species ever seen on Cocobolo Nature Reserve! So many discoveries to be made here.

 

 

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MTBC’s Bat Adventures continue: Panama – Week 2!

The new group arrived successfully and with bells on for Week 2.

We have three bats in training. Merlin trained a hairy big-eared bat (Micronycteris hirsuta) for photography. Within 15 minutes it was flying to his hand on call, rewarded with meal worms. Janell Cannon, the famous author of  Stella Luna, trained a white-throated round-eared bat (Lophostoma silvicolum) to eat from her hand. Her bat has a very calm temperament. Alexis and Amy trained a Niceforo’s big-eared bat (Trinycteris nicefori) for photography, a very sweet and eager gal.

Merlin guiding Janell in training the (Lophostoma silvicoluma) in a small tent provided for this purpose.
Merlin guiding Janell’s bat training.
Merlin guiding Alexis in training a (Trinycteris nicefori).

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Bats from Cocobolo

We’re just finishing up an incredible first week at Cocobolo and already caught 44 species of bats, everything from fishing bats to vampires, not to mention a wide variety of fruit, nectar, and insect eaters. Merlin added 10 additional species to his collection! Pygmy fruit-eating bats were found roosting in leaves they had cut to form “tents”.

Pygmy fruit-eating bat (Artibeus phaeotis)

Chestnut short-tailed bats were all around camp, feeding on piper fruit.

Chestnut short-tailed bat (Carollia castanea)

We caught more than 20 Common vampire bats. Frontier campesinos keep a few livestock not too far away, explaining the presence of so many vampires. Most of these seem to have lots of personality, enabling Merlin to get this cool photo. The trip participants had loads of fun shooting videos of the vampires running around on the ground on all fours.

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Hike to the Continental Divide and back!

MTBC’s Bat Adventures in Panama Week 1 group started out from our base camp for an energetic hike to the top of the mountain ridge. Some did it in 3.5 hours, some 6.5 hours, and everything in between. My GPS said I hiked 19,190 steps (about 10 miles!) and burned 2,701 calories. Some will go back at night to net for bats in this cloud forest where they hope to find different species than the ones found at the Cocobolo Nature Reserve banana plants, and along the lower river forest.

Merlin in the lead for our hike from camp straight up the vertical climb to the ridge top of the Continental Divide, about halfway between the Pacific and Caribbean.

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