Mexican Long-tongued bat

Sugar Bats

Among the long list of interesting creatures that call southern Arizona home are a couple of species of nectar-feeding bats, the Mexican Long-tongued bat and the Lesser Long-nosed bat.  Unlike most bats that feed on insects, nectar-feeding bats feed on the nectar of large flowers of cacti.  They are well-known to most southern Arizonans that put out hummingbird feeders to attract hummingbirds, as come August and September, suddenly the feeders are completely empty first thing in the morning.  Recently, someone on Facebook posted a cool little video of bats swooping into their hummingbird feeder, taken from a trail camera.  I thought this was a great use of a trail camera, so I dug mine out, filled up the hummingbird feeder and waited to see what would happen.  I normally don’t like to feed animals sugar water, which is sorely lacking in nutrients compared with the flower nectar they should be feeding on.  The sugar may provide them with an extra source of energy if flowers are scarce, so I try to limit it to times when I think the critters are desperate.  Or, totally selfishly, when I want to draw the animals in for photographs.  I also set out an ultrasonic recorder to hear what the bats were saying.  Although I wouldn’t expect them to be echolocating around the feeders (bats can see in the dark, after all), I thought they might be talking to each other.   Setting up and collecting the recorder meant walking through a cloud of whirling, swirling, fluttering bat wings, which I found quite enthralling.

Sugar Bats from Christine Hass on Vimeo.

Mobile users: click on the words “Sugar Bats” above to view video.

The bats found the feeder right away. There were at least half a dozen bats the first night, with more in subsequent nights. How did they find it so quickly? My guess is that smell has a lot to do with it. And, although they weren’t as talkative as I would expect a small crowd of careening animals to be, they did give me some nice recordings – including different calls by the different species. I spliced together some of the sample videos for you, and added some of the bat sounds – slowed down into audible range. The lower chirpy one is probably the Lesser Long-nosed bat, and the higher, pippy one is probably the Mexican Long-tongued bat. The faint rattling sound is made by some ultrasonic crickets, probably a variety of tree cricket. When the bats were flying around, I could also hear some chirps, but these didn’t appear in the recordings.

calls of bats

Spectrogram of different calls around the hummingbird feeder at night. The scale on the right side is frequency, ranging from zero to 100 kHz. Across the bottom is time, which here spans 2.5 seconds.

These two bat species share similar life histories.  Both spend most of their time in Mexico and Central America.  In the spring, the females head north along the coast of the Sea of Cortez, following the blooming columnar cacti (cardon, saguaro, organ pipe, and etcho).  The females give birth in maternity roosts in mines and caves in northern Sonora and southern Arizona.  After a few weeks, the youngsters are able to fly, but often hitch a ride on mom as they resume their search for cactus blossoms.

Saguaro blossoms

Saguaro blossoms

They follow the blooming cacti east across Arizona.  As late summer approaches, they shift from blossoms on columnar cacti, and some cactus fruits, to agave (century plant) blossoms found at higher elevations.  Aided, no doubt, by hummingbird feeders.  They follow the Sierra Madre back to their winter roosts, where they rejoin the males who stayed in Mexico and Central America.

The Lesser Long-nosed bat sticks to this pattern.  It is considered federally endangered, both in the US and in Mexico, under threat due to habitat loss that threatens columnar cacti habitats and the caves and mines they need for maternity roosts.   Overharvesting of agave for tequila is also impacting these bats.

Lesser Long-nosed Bat

Lesser Long-nosed bat approaches the feeder. It is distinguished by it’s shorter nose and the lack of tail or membrane between its hind legs.

Although Mexican Long-tongued bats have similar habits, they appear to be more flexible.  They are also less social and are not so picky about their maternity roosts.  They are also vulnerable to habitat loss, but currently they have no federal protection.

Mexican Long-tongued Bat

Mexican Long-tongued bat flies away from the feeder. They are distinguished by their longer nose and the membrane between their hind legs.

Soon the bats will continue on their journey south.  I’ve enjoyed spending the evenings with them, feeling their wings fluttering by my head and watching their crazy acrobatics in and around the hummingbird feeder.  Be safe on your journey, my little friends.

 

Video recorded with a Bushnell trail camera.  Audio recorded with a Dodotronics Ultramic and Samsung Galaxy S3.

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