Nectar feeding bats

In southeastern Arizona hummingbird feeders may be emptied during the night by nectar-drinking bats that cross over into the U.S. from Mexico, where they have their main population centers. If you find your hummingbird feeders drained absolutely dry at dawn for several days running, you have probably been visited by these bats. They feed on blooming and fruiting plants such as agave and saguaro cactus. These bats have very good eyesight and forage by night, roosting during the day in caves, abandoned mine tunnels and drainage culverts. Like most bats they use echolocation to navigate, emitting ultrasonic pulses from their mouths or noses, and locating obstacles or food by the sounds that bounce off objects and are reflected back to the bats' ears. Nectar bats are excellent long-distance fliers who migrate long distances to follow the blooming seasons of their favored plants.

The three species of long-nosed, nectar-feeding bats that may be seen in the U.S. are: the Mexican long-tongued bat (Choeronycteris mexicana), the lesser long-nosed bat (Leptonycteris curasoae), and the Mexican long-nosed bat (Leptonycteris nivalis). All three are a little over three inches long and weigh from seven-tenths to four-fifths of an ounce. Although all three species overlap in range in Mexico, the Mexican long-nosed bat is not likely to be found in Arizona since it generally appears in the U.S. only in Texas around the Big Bend area. The bats of nearby Kartchner Caverns State Park are not nectar-feeding bats, but rather myotis bats which eat insects. The pregnant myotis bats arrive at the cavern in April and give birth to a single young in June. The babies remain in the roost while their moms forage for insects in the surrounding area, consuming half a ton of bugs before they leave in mid-September for their winter hibernation roost.

The lesser long-nosed bat is on the endangered species list, so if you have a mind to leave some nectar out at night you may help these little fellows survive. If you turn out all the lights and watch out the window on a night of bright moonlight, you may be able to see these bats. Ours come in mid- to late-August, arriving shortly after sunset, generally about 8 p.m. Arizona time. (Binoculars can help even at night, especially if you are looking for the bats silhouetted against a cloudy sky.) These bats are an amazing sight, flying swiftly and quite silently. The hummingbirds don't seem to mind sharing as long as you refill the feeders promptly at dawn.

Bats have been surrounded by myths and superstititions which have often led to persecution by humans, though they are almost always harmless and often beneficial to human interests. For example, these nectar-feeding bats are important pollinators of desert flowers and are essential to the desert ecosystem, but beyond that these fascinating little creatures are worth protecting and preserving for their own sake. Bat Conservation International aims to educate public perceptions and support the conservation of bats. Their website contains excellent photos and interesting information about bats.

Bat Conservation International has the following statement about the conservation status of the Leptonycteris species, which includes the lesser long-nosed bat and the Mexican long-nosed bat. See their website for more information.

The U.S./Mexico border is home to some of the world’s largest remaining bat colonies. Several species migrate from summer nursery sites in the U.S. to northern Mexico each winter, meaning they cannot survive without protection on both sides of the border. Because some species of Borderland bats can form enormous, conspicuous colonies in relatively few locations, they are exceptionally vulnerable to humans who often fear and persecute them or simply fail to recognize their values and needs. These bats will never be secure until their key roosts are identified, protected and periodically monitored.

Traditional conservation efforts have focused on well known, publicly accessible sites. However, initial evidence documents the existence of additional critical roosts that are more immediately threatened than previously recognized. It is imperative that we identify these caves and collaborate on their protection before countless more bats are lost. The continued loss of Mexican free-tailed (Tadarida brasiliensis) and long-nosed (Leptonycteris sp.) bats, species that rank among our continent’s most ecologically and economically valuable, could seriously harm desert ecosystems and human agriculture.

Because these bats migrate seasonally across our shared border, a binational approach to their conservation is essential. For more than a decade, BCI has coordinated a wide range of educational programs and exhibits and achieved great progress in protecting known bat caves on both sides of the border. Yet much remains to be done on the vast private holdings where caves are poorly reported and seriously threatened by neglect or mismanagement.

Recommended reading:

Bowers, Nora, et al. Mammals of North America. New York: Houghton Mifflin Co., 2004.

Chambers, Nina et al. Pollinators of the Sonoran Desert: A Field Guide. Tucson: Arizona-Sonora Desert Museum, 2004. Good information on the most common Arizona hummingbirds: Anna's, Black-chinned, Broad-billed, and Rufous. There are also excellent descriptions and photos of Lesser long-nosed bat and Mexican long-tongued bat.