Imagine you want to create a hummingbird haven in your yard. Besides planting native plants, you start hanging up feeders, only to find them drained before dawn. Are there special nocturnal hummingbirds, or is your neighbor having midnight nectar cravings? If you live in the southwest United States or Central/South America, the answer may be a few species of bats doing the sugar heist. Bats around the world eat a wide variety of goodies, from insects to frogs to blood. In southeastern Arizona, there are two species of more flower-focused bats: Lesser Long-nosed Bats (Leptonycteris yerbabuenae, previously L. sanborni or L. curasoae) and Mexican Long-tongued Bats (Choeronycteris mexicana). Both are members of the New World leaf-nosed bat family, Phyllostomidae, a diverse family containing everything from these nectar-feeding bats to the famous vampire bat. They have a "nose leaf" on the end of their snout, which is a neat skin projection around their nose. While the function of nose leaves for echolocation is not fully understood, they do affect the directionality of sound, and their shape seems to differ based on what the bat species eats (Bogdanowicz et al., 1997). Telling Lesser Long-nosed from Mexican Long-tongued bats can be tricky, but up close the differences are clearer. Mexican Long-tongued bats have a longer, more narrow snout, a larger "U shaped" uropatagium (interfemoral membrane between the legs), and a visible small tail (Morgan et al., 2019). Lesser Long-nosed bats have no visible tail (although apparently you can feel it), a shorter snout, and a smaller uropatagium, which make some "V shaped" pantaloons. I like using the uropatagia to identify them with the "UV method": U for Mexican Long-tongUed, V for Lesser Long-nosed (it's not perfect). Researchers come to the Southwestern Research Station (SWRS) in the Chiricahua Mountains to see and survey bats, because the mountains are a mega hotspot for bat diversity in the United States! The two nectarivorous or nectar-feeding bats are monitored by many groups of scientists. This fall (2019), there were three groups that caught and released bats to look at tongue mechanisms, novel diets, and take general measurements to estimate population size and health. The mammalogy class from the University of Arizona learned how to survey bats over water with a mist net - a common research tool to catch bats. Disclaimer: All bats were caught and released under the supervision of a certified bat scientist. For the safety of the bats and people, no bats may be handled or caught without a license. Many researchers come to the station to study the 14+ species of hummingbirds at its feeders. However, once the sun sets, the mammals replace their bird counterparts and begin to drain the uncaged feeders. Mexican Long-tongued bats seem to arrive first to feed, with Lesser Long-nosed bats coming later in the evening. When not frequenting the hummingbird feeders, these bats feed on nectar, pollen, and fruit. A couple lucky researchers were even looking through the poop of the bats to see if they ate bugs. The biggest implication of feeding on nectar is what makes these two bats so special: they are pollinators. Lesser Long-nosed bats pollinate agave plants and large cacti like the iconic Saguaro (Carnegiea gigantea) and Organ Pipe Cactus (Stenocereus thurberi). Organ pipe is a rare columnar cactus in the United States, only found commonly in Mexico or in Organ Pipe Cactus National Monument, which straddles the border in southwest Arizona (there is a great podcast about this special place by In Defense of Plants, link below). Called pitahaya in Mexico or chuhuis by the native O'odham people, the Organ Pipe cactus is a vital symbol of desert life for people and animals. Its desert habitat is being threatened by climate change and the prolonged fight over the border wall. Lesser Long-nosed bats were endangered as well until recently, delisted in 2015 in Mexico and 2018 in the US. Both plant and animal are important parts of the desert pollinator network. Lesser Long-nosed bats are great pollinators because they can travel super far (up to 100 kilometers a night!) to visit the night-blooming flowers of the big columnar cacti (Medellin et al. 2018). The bats get pollen all over their upper bodies, so when they jam their little noses into the next flower, they pollinate that plant. Pollen from the bats can be sampled and imaged to determine what plant it is from, or its DNA sequenced to more easily determine the species. We sampled pollen off of two Lesser Long-nosed bats at the research station, stained the pollen fuchsia to see better, and determined it was agave pollen, probably from the local Palmer's agave (Agave palmeri). Both nectarivorous bats are examples of the amazing biodiversity of the Chiricahuas. Research on bats and much more continues every year at the station. A new mural, drawn by Jen Schlauch in 2019, showcases many of these endemic study animals. In May of most years, Bat Conservation International (BCI) holds a workshop at the station for a weeklong dive into bat conservation. More info can be found about the bat species and the course on the SWRS website, linked below in Further Reading. Further Reading
Mexican Long-tongued Bat: https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/mexican-long-tongued-bat.shtml Lesser Long-nosed Bat: https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/lesser_long-nosed_bat.shtml SWRS courses: https://www.amnh.org/research/southwestern-research-station/education In Defense of Plants podcast on Columnar Cactus: http://www.indefenseofplants.com/podcast/2018/4/1/ep-154-the-columnar-cacti-trifecta-my-first-sonoran-experience References Bogdanowicz, W., Csada, R. D., and Fenton, M. B. (1997) Structure of Noseleaf, Echolocation, and Foraging Behavior in the Phyllostomidae (Chiroptera). Journal of Mammalogy, 78(3): 942-953. Medellin, R. A., Rivero, M., Ibarra, A., de la Torre, J. A., Gonzalez-Terrazas, T. P., Torres-Knoop, L., Tschapka, M. (2018). Follow me: foraging distances of Leptonycteris yerbabuenae (Chiroptera: Phyllostomidae) in Sonora determined by fluorescent powder, Journal of Mammalogy, Volume 99, Issue 2, Pages 306–311, https://doi.org/10.1093/jmammal/gyy016 Morgan, C., Ammerman, L., Demere, K., Doty, J., & Nakazawa, J., and Mauldin, M. (2019). Field Identification Key and Guide for Bats of the United States of America. Occational Papers, Museum of Texas Tech University, 360.
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