By Laura A. Nájera Cortázar

Bats are one of the most successful groups among mammals, for they can be found in five continents (except Antarctica) and in most types of habitats worldwide.

They are the only flying mammals, which makes them special, and range in all kinds of sizes from the Bumblebee Bat (Craseonycteris thonglongyai) weighing 0.7 oz and with a wingspan of 1 in, to the Golden-crowned Flying Fox (Acerodon jubatus) with a body weight of 2.6 lbs and a wingspan of 66.9 in.

A small group of Pallid Bats (Antrozous pallidus) hanging. Photo by Alan Harper.

Contrary to the popular belief, nocturnal bats are not blind. In addition to vision, they possess a navigation system called echolocation. Bats emit sound waves that bounce off objects enabling them to forage and feed, this also provides them with greater maneuverability and efficiency.

There are approximately 1,300 bat species worldwide. They feed on different things, but most of the species are fruit bats or insectivores (they feed on insects). Some others are nectar-feeding bats (flower nectar); and others are carnivorous (they feed on arthropods, fish, and small reptiles). The least common bats are hematophagous (blood), only three endemic species of the American continent feed on blood, and their preys are mostly cattle and birds – not humans.

Mist nets are used to sample bats. They get caught in them when they forage or leave their caves.  Campo Mosqueda, Mexicali, B.C. Photo by Laura A. Nájera.

The diversity of bat guilds is as great as their importance to the ecosystem and agriculture. They serve as seed-dispersers, pollinators, and as agents of biological control, which is crucial for harvests. Without bats, harvests would be vulnerable to plagues –and more mosquitoes!­

In Mexico we have around 140 species of bats, and at least 69 of them are partially or totally distributed in northwest Mexico. The 807-mile long Baja California peninsula (the second largest in the world) is almost entirely isolated from the continent, and connected only on the northern part. Due to its latitudinal gradient, it possesses a wide variety of vegetation and weather. These characteristics, along with a complex geological history, have made of the peninsula a source of endemic plants and animals.

The Pallid Bat (Antrozous pallidus) widely occurs along the Baja California peninsula. Oasis San Fernando, Ensenada, B.C. Photo by Alan Harper.

At least 25 bat species (mostly insectivores) inhabit the entire peninsula or parts of it. One of the most common, the Brazilian free-tailed Bat (Tadarida brasiliensis), is known for forming large group colonies of millions, and eating up to 250 tons of insects a night.

The Pallid Bat (Antrozous pallidus) occurs in most of the Baja California peninsula. It has big ears and enjoys eating scorpions and crickets for dinner. According to a study by the researcher Winifred Frick and collaborators, it was discovered that the pallid bat feeds occasionally at the flowers of Mexican giant cactus (Pachycereus pringlei). This makes it a very efficient pollinator, at times and in some places even better than the Lesser Long-nosed Bat (Leptonycteris yerbabuenae), a completely nectar-feeding species that is famous for being the main pollinator of several agave species in Mexico –that’s right… tequila!

  There is a great diversity of bat ectoparasites. Here, a Lesser Long-nosed Bat (Leptonycteris yerbabuenae) and an agave fly in its nose. El Rebaje, Mulegé, B.C.S. Photo by Laura A. Nájera.

Another interesting individual is the Fishing Bat (Myotis vivesi), an endemic species of the coasts and islands of northwestern Mexico that uses its enormous claws and uropatagium (the membrane that stretches between the lower limbs and tail or parts of it) to feed on fish and crustaceans. Currently it is enlisted in the IUCN (International Union for Conservation of Nature) as an endangered species. The fishing bat has a high genetic diversity in the Mexican islands, but it is susceptible to introduced species predators (i.e. cats and rats).

Research on bats in the Baja California peninsula goes back to a few decades ago, from the findings and descriptions of the species that occur here, to complex biogeographic and genetic analysis. Several researchers and naturalists are working towards the conservation of bats by generating useful information for the protection and promotion of the importance of these mammals to the ecosystem.

The Peninsular Myotis (Myotis peninsularis) is an endemic bat from the Cabo region. Santa Anita, Los Cabos, B.C.S. Photo by Laura A. Nájera.

I began my research on this group in 2011, as a master’s degree project, in which I studied the taxonomic status of an endemic bat of the Cabo region: the Peninsular Myotis (Myotis peninsularis). Currently, I am working on my PhD project on a group of myotis that co-occur along the peninsula, focusing on the genetic limits between species and if their distribution corresponds to the genetic subdivision I find between them. Furthermore, I am collecting information to learn about the diversity and distribution of their pathogens.

Research is essential to help and propose strategies towards the conservation of natural resources. Laura Najera observing the morphological characteristics of a Long-legged Myotis (Myotis volans). Campo Mosqueda, Mexicali, B.C. Photo by Eduardo F. Aguilera.

About the author

Laura A. Nájera Cortázar is a biologist graduated from the University of Guadalajara and holds a Master’s Degree from the Northwestern Center of Biological Research (CIBNOR). Currently she is pursuing her PhD studies at the University of Leeds in England. She has participated in fauna monitoring, along with the University of Guadalajara, working with mammals, reptiles, and birds. She has collaborated with Terra Peninsular and researchers from the United States in the search for bats along the Baja California peninsula.

References

  • Altringham, J.D. 2011. Bats. From evolution to conservation, 2nd ed. Oxford University Press, New York, U.S.A.
  • Álvarez-Castañeda, S.T. & Murphy, R.W. 2014. The endemic insular and peninsular species Chaetodipus spinatus (Mammalia, Heteromyidae) breaks patterns for Baja California. PLoS One 9: e116146.
  • Álvarez-Castañeda, S.T. & Patton, J.L. (eds). 1999. Mamíferos del Noroeste de México. Centro de Investigaciones Biológicas del Noroeste, S. C., México.
  • Betke, M., Hirsh, D.E., Makris, N.C., McCracken, G.F., Procopio, M., Hristov, N.I., et al. 2008. Thermal imaging reveals significantly smaller Brazilian Free-tailed bat colonies than previously estimated. J. Mammal. 89: 18–24.
  • Floyd, C.H., Flores-Martínez, J.J., Herrera M., L.G., Mejía, O. & May, B. 2010. Conserving the endangered Mexican fishing bat (Myotis vivesi): Genetic variation indicates extensive gene flow among islands in the Gulf of California. Conserv. Genet. 11: 813–822.
  • Frick, W.F., Price, R.D., Heady Iii, P.A. & Kay, K.M. 2013. Insectivorous bat pollinates columnar cactus more effectively per visit than specialized nectar bat. Source Am. Nat. Am. Nat. 181: 137–144.
  • IUCN. 2017. Myotis. The IUCN Red List of Threatened Species.
  • Nájera-Cortazar, L.A., Álvarez-Castañeda, S.T. & De Luna, E. 2015. An analysis of Myotis peninsularis (Vespertilionidae) blending morphometric and genetic datasets. Acta Chiropterologica 17: 37–47.