The saguaro cactus (Carnegia gigantea) is important to many desert animals. It provides habitat for the Gila woodpecker (Melanerpes uropygialis), gilded flicker (Colaptes chrysoides), red-tailed hawk (Buteo jamaicensis), and various insects and lizards. Many birds, bats, and insects feed on saguaro nectar and fruit. However, these relationships are not one-sided. The saguaro depends on these very same critters to fertilize it because it requires cross-pollination, pollen being delivered to a flower of a different plant. The saguaro has developed several characteristics to ensure that animals pollinate it. The cactus flowers on cooler desert nights in May and June when lesser long-nosed (Leptonycteris curaseae) and Mexican long-tongued (Choeronycteris mexicana) bats are migrating through the cacti's range, and the flowers remain open until mid-day allowing insects time to feed on the remaining nectar. Its flowers are creamy-white colored and have a strong scent, which attracts the nectarivorous bats. Its stamens form a circle at the top of a tube and sweet nectar accumulates at the bottom of this tube. This forces the pollinators to reach deep into the blossoms, causing their heads to be covered with pollen that they then transfer to other flowers while feeding. Other pollinators of the saguaro cactus include the white-winged dove (Zenaida asiatica), bees such as the saguaro cactus bee (Diadasia opuntiae) and honey bee (Apis mellifera), wasps, and butterflies. In fact the white-winged dove visits the saguaros more frequently than all other pollinators - all other pollinators, that is, except the honey bee which is believed to be the most frequent saguaro visitor. Interestingly, saguaros are the largest cactus in the United States, growing up to 50 feet, and living up to 200 years.
The lesser long-nosed (Leptonycteris yerbabuenae) and Mexican long-tongued (Choeronycteris mexicana) bats are specifically adapted for feeding on and pollinating columnar cacti species throughout their ranges. Adaptations include an elongated muzzle, narrow snout, reduced dentition, and a brush-tipped tongue, all of which better enable the bats to reach inside the flowers to collect nectar. Also, the bats have specialized hairs on the face and neck that are flattened to carry pollen. These hairs become covered in large amounts of pollen as the bats reach deep inside the flowers. After returning to their roosts, the bats lick off and eat this pollen. However, during foraging the pollen is transferred from flower to flower. Columnar cacti have also evolved adaptations to attract the bats. Adaptations include flowers that are light in color making them easy for the bats to see; flowers that are erect, bowl-shaped, large-mouthed, and located at the top of the branches making it easier for the bats to feed on them; flowers that have a strong odor that the bats can smell; flowers that open nocturnally (known as dehiscense) when the bats are out foraging; and flowers that have high levels of pollen protein with relatively low levels of nectar sugar concentrations.
These bats feed and pollinate many different cacti species including saguaro (Carnegiea gigantea), organ-pipe cactus (Stenocereus thurberi), agaves (Agave spp.), and cardon (Pachycereus pringlei). It has been demonstrated that the lesser long-nosed bat and Palmer's agave have a mutualistic relationship. Studies have also shown that viejo (Cephalocereus hoppenstedtii) and the branched columnar cactus tetecho (Neobauxbaumia tetetzo) only produce fruit when pollinated by one or both of these bat species.
Description:The Mexican long-tongued bat has short ears, a long, narrow rostrum, big eyes, a minute tail, and a leaf-like projection of skin above the nostrils called a nose leaf. It is a medium sized bat that weighs about 25 grams and is between 3 and 3.5 inches long. The fur is gray to brown above and lighter on the underside. The tongue of the Mexican long-tongued bat extends up to 1/3 of its body length.
Life History:Mexican long-tongued bats migrate northward beginning in May and breed in the summer in the northern part of their range. A single pup is born in late June or early July, and females use caves, mines, rock crevices, and abandoned buildings as maternity roosts. The pup stays with its mother until it can fly, about two to three weeks after birth. Migration southward occurs in October and November. These bats typically roost individually or in groups of 15 or fewer. However, roosts with up to 50 bats have been documented. During cooler temperatures the bats hang in a cluster; during warmer temperatures they remain one to two inches apart in the roost. The bats are most active 1.5 hours after sunset and then again 3 hours after sunset.
These bats feed primarily on the nectar and pollen of night blooming flowers of agaves and columnar cacti. Their long tongues aid in removing flower nectar. They may also eat the fruit of columnar cacti and take incidental insects. They have also been seen at hummingbird feeders and eating ornamental vegetation.
Habitat:This bat lives in a variety of habitats, including desert, semidesert grassland, montane, riparian, tropical deciduous forests, and urban environments. The bat is most frequently found roosting in desert canyons, but also in deep caves, mines, rock crevices, and abandoned buildings.
Distribution:This species is common throughout Mexico. Its range extends through Central and northern South America and to the southern parts of Texas, New Mexico, Arizona, and California. However, it is rare in the United States.
Status:The Mexican long-tongued bat is listed as near threatened by the International Union for Conservation of Nature and Natural Resources (IUCN) and is listed as a species of concern by the United States Fish and Wildlife Service. It is the only nectarivorous bat that is not endangered. However, fewer than 400 bats of this species have been seen in the United States in the last 100 years. Caving, mine closures, mine reclamation, and loss of food sources due to development, prescribed fires, and grazing threaten this species.
Mammalian Species: Choeronycteris mexicana (J. Arroyo-Cabrales, R. R. Hollander, J. K. Jones, Jr. In: Mammalian Species, No. 291, pp. 1-5, August 12, 1987, The American Society of Mammalogists)
