Family Rhinolophidae
horseshoe bats

Rhinolophidae is a large family of bats, including approximately 130 species in 10 genera. It is sometimes divided into two families, Rhinolophidae (horse-shoe bats) and Hipposideridae (Old World leaf-nosed bats). There is little question that these two groups of bats are closely related. Here they are treated as two subfamilies (Hipposideridae, with 8 genera, and Rhinolophidae, with the single genus Rhinolophus) in the family Rhinolophidae. Many species are extremely difficult to distinguish. (Vaughan, Ryan, and Czaplewski, 2000)

Rhinolophids inhabit temperate and tropical regions of southern Europe, Africa, Asia, parts of Australia, and many Pacific islands. All species are insectivorous, hawking insects in flight or gleaning them from surfaces. Their roost habits are diverse; some species are found in large colonies in caves, some prefer hollow trees; others sleep in the open, among the branches of trees. Members of northern populations may hibernate during the winter; at least one species is migratory. Females of some rhinolophid species mate during the fall and store sperm over the winter, conceiving and gestating young beginning in the spring. (Hill and Smith, 1984; Nowak, 1991a; Nowak, 1991b; Vaughan, Ryan, and Czaplewski, 2000)

Rhinolophids are widely distributed throughout both temperate and tropical regions of the Old World. They inhabit southern Europe, Africa, Asia, northern and eastern Australia, and many Pacific islands. (Hill and Smith, 1984; Nowak, 1991a; Nowak, 1991b; Vaughan, Ryan, and Czaplewski, 2000)

Rhinolophids are found in a variety of temperate, tropical and desert biomes at both high and low elevations. They forage both within forests and in open spaces. Their roosting habits are also diverse: rhinolophids use caves, tree holes, foliage, mines, and buildings. Species that hibernate may use different roost types in the summer and winter months. While a cave may be used for hibernation in the winter, a tree hole may be used as a summer roost. (Nowak, 1991a; Nowak, 1991b; Vaughan, Ryan, and Czaplewski, 2000)

It is clear from both molecular and morphological data that rhinolophids (Rhinolophidae) and hipposiderids (Hipposideridae) are closely-related taxa, and are likely sister groups. Many authors consider them to be separate families, the Hipposideridae, or Old World leaf nosed bats, and Rhinolophidae, or horseshoe bats. In this system, only members of the genus Rhinolophus (with about 70 species) constitute the family Rhinolophidae. Others consider both groups to be subfamilies within the single family Rhinolophidae, the classification scheme followed by the Animal Diversity Web. (Hill and Smith, 1984; Nowak, 1991a; Nowak, 1991b; Teeling et al., 2002; Vaughan, Ryan, and Czaplewski, 2000)

Several morphological features distinguish rhinolophines from hipposiderines. These include differences in dental formulae and the morphology of the noseleaf, feet, shoulder girdles, and hip girdles. Hipposiderines lack a lower small premolar that is present in Rhinolophus. Both groups bear noseleaves, but several features differ consistently between groups. For example, the noseleaves of Rhinolophus have a more prominent lancet (a spear-shaped projection of skin) than those of hipposiderines. Also, hipposiderine noseleaves do not bear a pointed projection above the nostrils (the "sella") as in Rhinolophus. Hipposiderines have only two phalanges in each of their toes, whereas rhinolophines have three phalanges in four of the five toes. (Hill and Smith, 1984; Nowak, 1991b)

Bats have traditionally been divided into two suborders, the Megachiroptera (Old World fuit bats, Pteropodidae) and the Microchiroptera (all other bats), which includes Rhinolophidae. Several recent studies have concluded that not all microchiropterans evolved from a single, common ancestor (i.e., Microchiroptera is not a monophyletic clade). In particular, the Rhinolophidae, Megadermatidae and Rhinopomatidae form a clade that is most closely related to megachiropteran and not other microchiropterans. Increasing amounts of evidence support this hypothesis of relationships and its implication are yielding exciting scientific inquiry and debate, particularly with respect to the evolution of echolocation. All microchiropterans use laryngeal echolocation as a primary means of navigation, whereas no megachiropterans use laryngeal echolocation. If Microchiroptera is truly paraphyletic, then laryngeal echolocation either evolved once and was subsequently lost in what we traditionally recognize as Megachiroptera, or echolocation evolved twice within Chiroptera: once in the lineage leading to "true" microchiropterans, and once in the lineage leading to Rhinolophidae, Megadermatidae, and Rhinopomatidae. (Teeling et al., 2002)

All rhinolophids have leaf-like protuberances on their noses. In hipposiderine species, these are more rounded; in Rhinolophus, they are leaf or spear-like. The projection beneath the nostrils is horse-shoe shaped and, while it is present in hipposiderines, this feature is more pronounced in rhinolophines. Echolocation calls are emitted through these nasal structures, which may serve to focus the sound. The ears of these bats vary in size and lack a tragus. Most rhinolophids are dull brown or reddish brown in color. Their fur has a tendency to become bleached, so some individuals may become a bright reddish-orange. They vary in size from small to moderately large (6 to 150 grams). Males may be slightly larger than females. Their wings are broad and rounded, making them highly maneuverable in flight in cluttered spaces. (Hill and Smith, 1984; Nowak, 1991a; Nowak, 1991b; Vaughan, Ryan, and Czaplewski, 2000)

Rhinolophids have distinctive premaxillae, with palatal branches only. The premaxillae on opposite sides of the skull are neither fused with each other nor are they fused with the maxillary bones. Rhinolophid skulls often have distinct sagittal and lambdoidal crests. The palate is unusually short due to deep indentations at both ends. The molars are dilambdodont, and the dental formula is 1/2, 1/1, 1-2/2-3, 3/3 = 28-32. (Nowak, 1991a; Nowak, 1991b)

Rhinolophids, like many bats, can live exceptionally long lives for such small animals. The longest known lifespan of a wild rhinolophid is 30 years. (Nowak, 1991a)

Rhinolophids have broad, rounded wings that permit excellent maneuverability at very slow speeds. Many rhinolophids can hover in place, which is helpful when they are picking prey from the surfaces of leaves or out of spider webs. All rhinolophids also capture flying insects; many species do so while in continuous flight, but others search for insects as they hang from a perch and then make short pursuit flights when prey is detected. Upon capturing food, they land and wait for another insect to fly nearby. Even those bats that do not hunt from perches will land to consume an especially large insect. (Hill and Smith, 1984; Nowak, 1991a; Nowak, 1991b; Vaughan, Ryan, and Czaplewski, 2000)

While some species are solitary, most rhinolophids roost in colonies. Members of some colonial species even forage in small groups (e.g., Hipposideros), but most forage alone. These bats do not defend feeding territories, however. Rhinolophids are all nocturnal and are active later in the evening than many other groups of bats. (Nowak, 1991a; Nowak, 1991b)

Horseshoe bats have a roosting posture thas is unique among bats. Instead of hanging with their wings folded at their sides, they wrap their wings and tail membranes around their bodies, enshrouding themselves. (Nowak, 1991a)

All rhinolophids in temperate regions hibernate during the winter. Even during the active season, these bats enter daily torpor to conserve energy. Some species and populations migrate seasonally. (Hill and Smith, 1984; Nowak, 1991a)

All rhinolophids use echolocation as a primary means of navigating and finding food. Rhinolophid echolocation calls typically have two components: a constant frequency portion and a frequency-modulated sweep. The constant-frequency portion is usually 1 to 7 milliseconds in Hipposideridae and much longer (about 20 milliseconds) in Rhinolophidae. Unlike many other microchiropterans, rhinolophids can tolerate considerable overlap between outgoing calls and returning echoes. This tolerance allows them to spend more time calling, thus increasing their chances of detecting prey. Rhinolophids emit calls through their nasal passages, which lets them continue calling as they chew. Their echolocation calls are directed using motions of the head and the noseleaf. The calls of many species have several harmonics, which increases their frequency range and thus the size distribution of detectable targets. (Hill and Smith, 1984)

Vision, olfaction, and touch are also important to varying degrees in bats. Scent plays an important role in many social interactions, such as in mating and in mother-infant bonding. Scent glands are common in many bats (as they generally are in mammals).

These bats either catch insects in flight or take insects and spiders from surfaces. Hipposiderine bats typically catch insects in the air, while rhinolophine bats take both flying and non-flying prey. Rhinolophines typically forage near the ground or near dense foliage, which allows them to detect non-flying prey. Some species in this family hunt in a manner similar to many flycatchers. They hang among foliage waiting for prey to fly by, at which point they make a short pursuit flight and return to their perch, awaiting their next opportunity. Rhinolophids are capable of extremely maneuverable flight, including the ability to hover. Bats that are capable of hovering can exploit prey sources on surfaces, a resource most bat species cannot exploit. (Hill and Smith, 1984; Nowak, 1991a; Nowak, 1991b; Vaughan, Ryan, and Czaplewski, 2000)

Predation on bats generally appears to be low, and this probably is true for rhinolophids as well. Most knowledge of bat predators comes from anecdotal observation of predation events or bat remains in scat. Groups that are known to eat bats are owls and other birds of prey, many carnivores, other bats, snakes, and other opportunistic vertebrate scavengers that encounter an injured or juvenile bat.

Bats are probably most vulnerable to predators while they roost or as they emerge in the evening to forage. Some predators (e.g., snakes or hawks) may wait near cave entrances at dusk, attacking bats as they emerge. Juvenile bats that cannot fly are also at risk if they fall to the ground and are not quickly retrieved by their mothers. (Hill and Smith, 1984)

All bats in the family Rhinolophidae eat only insects and other small arthropods. Their primary ecosystem function is probably to limit populations of insects and spiders. Bats harbor parasites such as fleas, mites and trematodes; thus, rhinolophids also serve as a resource for parasites. Bats are not typically important prey for other animals, but they are preyed upon by nocturnal birds of prey and snakes. (Hill and Smith, 1984)

Some rhinolophids may become household pests if they form large colonies in human dwellings. The buildup of guano from a large colony can produce a foul odor.

Rhinolophids are all insectivorous and are likely to control populations of insect pests. Large guano deposits can be harvested commercially for fertilizer.

Many bats are declining worldwide, and this is true for many rhinolophids as well (e.g., Rhinolophus hipposideros and Rhinolophus ferrumequinum). Disturbance of roosts, particularly winter hibernacula, can threaten a large number of bats in a short time. Habitat destruction (e.g., the reduction of appropriate forest habitat) is also a problem. Many insectivorous species are threatend by widespread pesticide use. Individual bats can eat hundreds of insects in an evening. If those insects have ingested harmful chemicals, the bats may suffer as a result. The International Union for the Conservation of Nature and Natural Resources (IUCN) currently lists 13 species of rhinolophids as endangered or critically threatened, and an additional 66 that are vulnerable or near threatened. Data is insufficient to evaluate the status of many other species, so this may be an underestimate of the groups overall vulnerability. (Hill and Smith, 1984; IUCN, 2004)