When thirty-five year old C. Hart Merriam came to the Colorado Plateau in 1890 he was already an accomplished zoologist, mammalogist, ethnographer and naturalist. He had helped found the National Geographic Society in 1888 but he was now back in the field to explore the virgin regions around the Flagstaff, Arizona Territory area. He was especially interested in a nearby inactive volcanic mountain range known as the San Francisco Mountains with its 12,633 foot high (3,851 m) Humphreys Peak, shown above. Four years of field work in this region resulted in Merriam publishing his “lifezone” concept of biogeographical elevation gradients based on the distribution patterns of terrestrial plants and animals. Merriam’s lifezone model suggested seven distinct lifezones in North America from the earth’s equator to the north pole. According to Merriam the Arizona Territory itself contain six of those seven lifezones. Over the years modern biologists have made significant adjustments to C. Hart Merriam’s lifezone theory now referring to such regions as ecoregions with various biomes or habitat types. But Merriam’s early work was ground breaking in the ways scientists would look at the relationships between elevation, slope, soil types and the amount of moisture that falls upon the land to the plants and animals that make their homes there.
The Pallid bat, Antrozous pallidus, range across much of the American West and along the Pacific coast from Canada to Mexico. With eyes larger than most North American bats, the pallid bats is unique in that they catch most of their arachnid prey while moving across the ground in a variety of gaits and steps. Their ears are exceptionally large allowing these bats to actually hear crickets, scorpions, beetles, etc. walking on the ground. Since pallid bats forage on the ground, they too become susceptible to predators such as cats, frogs, coyotes, raccoons and snakes. Owls have been known to take pallid bats from the air while both are in flight. Pallid bats only live to 10 years in the wild and are sensitive to human habitat encroachment. In a single night of hunting, a pallid bat can eat half of its body weight.
A big family
Bats make up nearly 20 percent of all living mammal species. Historically bats have been classified into two primary suborders — the Megachiroptera and the Megachiroptera. Large, Old World, fruit-eating bats were placed into the sub-order Megachiroptera. Bats of the Megachiroptera sub-order generally find their food by using their eye sight. Bats which find their food by echolocation were placed into the sub-order Microchiroptera. Microchiroptera bats tend to be smaller and feed primarily on insects. Because of the great diversity within the bat species, modern taxonomist are currently suggesting changes to the suborders of classifying the world’s bats. A juvenile Mariana fruit bat, Pteropus mariannus, also called the flying fox is shown above and is a member of the Megachiroptera suborder. It is native to Guam, American Samoa and the Northern Mariana Islands.
Flying in for a snack
The 28 species of bats that make their colonies in Arizona all belong to the Microchiroptera sub-order. Most are insectivores with their colonies consuming thousands of flying insects each and every night. But two of Arizona bat species are consumers of nectar and pollen and not insects. They are the Mexican long-tongued bat, Choeronycteris mexicana, and lesser long-nosed bat, Leptonycteris yerbabuenae, shown above approaching a saguaro cactus, Carnegiea gigantea, bloom. Both of these gentle bats travel through the dark, summer sky of Arizona in search of food from the many night-blooming cereus cacti and agave plants found in southern Arizona. Almost all the desert night-blooming flowers are whitish in color making it easier for the bats to see. They do the work of oversized bees as they poke their heads into the flowers in search of nectar while grains of pollen attach to their fur. As they move from flower to flower, the bats pollinate the many spectacular night-blooming floral bouquets found during the early summer nights of the Sonoran Desert. These two species of bats will also ingest seeds and disperse in their droppings such seeds as they travel about from plant to plant.