Lesser Long-nosed Bat, Leptonycteris yerbabuenae

Lesser Long-nosed Bat, Leptonycteris yerbabuenae. Photograph taken in the greater Alamos area, Alamos, Sonora, December 2016. Photograph and identification courtesy of David F Smith, Alamos, Sonora.

The Lesser Long-nosed Bat, Leptonycteris yerbabuenae, is a member of the Phyllostomidae family of American Leaf-nosed Bats. The Phyllostomidae family consists of one hundred sixty species placed in fifty-five genera. There are three species in the Leptonycteris genus. The Lesser Long-nosed Bat are also known as Sanborn’s Long-nosed B and the Mexico as Murciélago de Nariz Larga Menor.

Lesser Long-nosed Bats are yellow-brown or cinnamon gray in color dorsally, with rusty brown hair on their ventral side. Their ears are small and they have a short tail. They measure up to 7.6 cm (3.0 inches) in snout-to-vent length  and have wingspans of 25 cm (10 inches). They weigh up to 23 g. Their tongue measures approximately the same length as their body, providing access to nectar of deep desert flowers. They have a small noseleaf, which is a fleshy leaf-shaped structure on the tip of their nose that likely assists in echolocation.

Lesser Long-nosed Bats are migratory animals. They spend the winter in central Mexico, and follow the scent of blooming flowers, often referred to as the “nectar trail”, as far north as southern Arizona and New Mexico. While they travel, they gather by the thousands in roosts where they rest and give birth to their young. Lesser Long-nosed Bats are sensitive to their environment, so roosts must have the right temperature and humidity level to accommodate them. Therefore, individuals typically return to the same spots each year. Roosts are often in caves or abandoned mines. For Lesser Long-nosed Bats that migrate northward during the summer, their breeding season lasts from November to December. The breeding season for those that give birth in the south is May to June. Despite the presence of two distinct mating seasons, individuals mate only once a year. While little is known about the mating system and behavior of Lesser Long-nosed Bats, it is known that females converge to form mating colonies to birth and care for their young. The timing of these colonies varies by population. In the northern Sonoran Desert and Arizona, females converge in mid-to-late April. Maternity colonies consist of anywhere from several thousand to over one hundred thousand pregnant females, which collectively trap metabolic heat. This metabolic heat reduces the energetic cost to females and increases growth rates in the young. Females do not come to the colony at the same time or during the same stage of pregnancy. After a gestation period of approximately 6 months, females give birth to a single pup during the time of local peak flower availability. Births are typically spread out over a one-month period. Each female cares for her pup alone. No attempts are made by mothers to nurse or feed each other’s pups. However, mothers do exhibit behaviors such as visiting, touching, and nosing other pups. Newborn pups weigh 4 to 7 grams and are fully weaned at four to eight weeks of age. They can fly after one month, but do not begin to leave the maternity roost for another 2 to 3 weeks. Lesser long-nosed bats have life spans of twelve years in the wild. 

Lesser long-nosed Bats are nocturnal and spend their days in roosts, leaving only at night to forage for night-blooming flowers. They typically forage between mid-night and 02:00 a.m., when flowers have accumulated substantial amounts of nectar. They follow the scent from night-blooming plants such as Saguaro, Organ Pipe Cactus, and Agave. They are agile fliers and hover over the blossoms as they poke their slender noses deep within. Then, using their long, brush-tipped tongues, they lap up the sweet nectar. They emerge from feeding covered in pollen that has been trapped in their fine hair. As they continue to feed, they unwittingly pollinate flower after flower. As the season progresses, the Lesser Long-nosed Bats diet focuses on the sweet fruit produced by desert cacti. While they are able to consume the pulp of the fruit, the seeds pass through their digestive tract intact, thus aiding in the dispersal of cactus plant seeds. They are preyed upon by owls, snakes, and bobcats. Predators will wait at cave entrances or interiors looking for individuals who have fallen to the ground, or those that they can catch in flight. 

Lesser Long-nosed bats inhabit semi-arid grassland, scrub, or forest habitats below 550 m (1,800 feet). They are able to tolerate unusually high temperatures of up to 41°C (106°F), due in part to their low metabolic rate. They do not enter torpor or hibernation, and are not able to survive ambient temperatures below 10°C (50°F).

The Lesser Long-nosed Bat may be confused with the Greater Long-nosed Bat, Leptonycteris nivalis (smaller in stature, longer shorter grayish fur, and proportionally shorter wings). 

From a conservation perspective, Lesser Long-nosed Bats are considered to be Near Threatened because they face significant threats from disturbance and vandalism at roost sites and loss of food resources. Land clearing and anthropogenic development has led to a loss of food sources throughout their range. Habitat loss in caves, used for mining and recreation, remains an issue. Additionally, they are deliberately killed by humans who are frightened or mistake them for Common Vampire Bats, Desmodus rotundus, which can transmit rabies.