HORSESHOE BATS

Horseshoe bats make up the bat family Rhinolophidae. In addition to the single living genus, Rhinolophus, one extinct genus, Palaeonycteris, has been recognized. The closely related Hipposideridae are sometimes included within the horseshoe bats as a subfamily, Hipposiderinae. Both families are classified in the suborder Yinpterochiroptera or Pteropodiformes and were previously included in Microchiroptera.

Appearance

The lancet and sella in profile

All horseshoe bats have leaf-like, horseshoe-shaped protuberances called noseleafs on their noses. The noseleafs are important in species identification, and are composed of several parts. The lancet is triangular, pointed, and pocketed, and points up between the bats' eyes. ^[1] The sella is a flat, ridge-like structure at the center of the nose, rising from behind the nostrils, that points out perpendicular from the head.^[1] The sella usually has less hair than the lancet or the noseleaf.^[1]
In the related Hipposideridae, these protuberances are leaf- or spear-like. They emit echolocation calls through these structures, which may serve to focus the sound. Their hind limbs are not well developed, so they cannot walk on all fours; conversely, their wings are broad, making their flight particularly agile. Most rhinolophids are dull brown or reddish-brown in color. They vary in size from 2.5 to 14 cm in head-body length, and 4.0 to 120 g in weight.^[2] Their dental formula is 1.1.1-2.32.1.2-3.3.
The females have a pair of mammary glands and two "false nipples" above and to the side of the genital opening, to which newborn bats cling for a few days after birth.

Ecology

Rhinolophids inhabit temperate and tropical regions of southern Europe, Africa, and Asia south to northern and eastern Australia. All species are insectivorous, capturing insects in flight. Their roost habits are diverse; some species are found in large colonies in caves, some prefer hollow trees, and others sleep in the open, among the branches of trees. Members of northern populations may hibernate during the winter, while a few are known to aestivate; at least one species is migratory. Like many Vespertilionidae bats, females of some rhinolophid species mate during the fall and store the sperm over the winter, conceiving and gestating young beginning in the spring.

Classification

Horseshoe bats are closely related to the family Hipposideridae, which is often included within the Rhinolophidae; however, it is now considered a separate family.^[3][4] In addition to the sole living genus, Rhinolophus, the family Rhinolophidae contains one extinct genus, Palaeonycteris.^[5] Many species are extremely difficult to distinguish.
Although horseshoe bats have traditionally been included in the suborder Microchiroptera ("microbats"), genetic evidence suggests they and a few other microbat families are more closely related to Pteropodidae, the only family of "megabats" (Megachiroptera). Therefore, Pteropodidae, horseshoe bats, and related families are now placed in a single suborder, called Yinpterochiroptera or Pteropodiformes.^[4]

Medical significance

In September 2005, four Rhinolophus species (R. sinicus, R. ferrumequinum, R. macrotis, R. pearsoni) were identified as natural reservoirs of SARS coronavirus-like viruses, the causative agent of SARS outbreaks in 2002–2004.^[6][7]