Setirostris
Setirostris eleryi is a species of small insectivorous bat found in inland eastern Australia. It is the sole species of the molossid genus Setirostris, a name that refers to the coarse bristles on their faces. Earlier common names have referred to this unique feature, and the 'free-tail' that is a common feature of its microchiropteran family, the Molossidae; no single common name emerged during the taxonomic revisions that identified what was referred to as the bristle-faced freetail.
Setirostris eleryi differs from all other bats in the family by possessing unique dentition and genital morphology, a distinctive echolocation call structure, and notably smaller body size of around. The presence of stout bristles on the thin muzzle and face of S. eleryi distinguishes them from similar genus Ozimops, once regarded as "Mormopterus species", that previously included parts of the population. The description, first published in 2008, emerged from a comparison of morphological features with an earlier phylogenetic analysis that had indicated cryptic species amongst this poorly-known group of bats.
Setirostris eleryi may be widely distributed across inland Australia, ranging from very arid to moister subtropical regions. However, it is locally uncommon across its range, and only known to inhabit riparian zones and floodplains. During the day these bats roost in tree hollows of mature eucalypts, but are noted as squeezing themselves into other tiny crevices. They form colonies of up to twenty individuals, which often include bats of other species.
Taxonomy
A 1988 genetic study of species boundaries in Australian free-tailed bats indicated that species Setirostris eleryi, referred to as 'form sp 6', was one of eight distinct and unresolved genetic groups in the Australian population of Mormopterus. Mormopterus sp 6 was genetically distinct from all other types; however, only a single specimen from central Australia was included in the study. The acquisition of twenty-four additional specimens, from museum collections and by targeted trapping, facilitated a working description of Mormopterus sp. 6 in 2008 using a multi-locus analysis of morphology, the results of allozyme electrophoresis and investigation of echolocation call signatures. Referenced as an undescribed taxon, Mormopterus sp. 6 was cited by authors until its recognition as species Mormopterus ''eleryi in publications after 2011.Resolution of Australian Molossidae systematics showed that this species, and the east-coast Micronomus norfolkensis, are only distantly related to other Australian mollosid taxa. The differences between these two species and remaining taxa in the Mormopterus planiceps group', or planiceps–beccarii–loriae complex', previously published as an interim arrangement, led to the erection of four new subgenera in 2014. Prior to 2014, two subgenera were recognized within Mormopterus: subgenus Mormopterus and subgenus Micronomus. The two new subgenera included Setirostris, isolating this species as a monotypic taxon, and Ozimops, a subgenus containing seven other Australian taxa, as well as several Indo-Papuan taxa, all formerly in the planiceps group. Other mollosid populations were separated to the monotypic genus Micronomus and those outside of the same austral region remained within the subgenus Mormopterus. Subsequently, the rank of subgenus Mormopterus was itself revised, excluding the Australasian species, and elevated to the rank of genus.
The type specimen was collected at an elevation of near Eringa, a cattle pastoralist lease close to the northern state border of South Australia.
The name Setirostris is derived from a combination of the Latin seta, meaning bristle, and rostrum, beak or snout, and refers to the characteristic bristles on the face; the gender is feminine. The specific name eleryi is for Elery Hamilton-Smith in recognition of contributions to bat research and conservation.
Common names for the species include hairy-nosed—or hairy-rostrum—free-tailed bat, bristle-faced freetail bat and Mormopterus'' sp. 6.
Description
Setirostris eleryi is a very small microchiropteran, with a light build, and was regarded as tiny when compared to species of Mormopterus, the genus of smaller bats in which they were variously placed. They have a mean weight of, a maximum weight of and a forearm length from. The face and muzzle are relatively long and narrow. The muzzle and face are sparsely covered in fine hair, with the exception of a unique series of 26 to 30 conspicuous bristles on each side and a fringe of fur on the upper lip.The ears are triangular and are not joined across the forehead and the tragus is rounded. The dorsal colour ranges from sandy-brown to grey-brown with lighter coloration on the ventral surface.
A prominent long and slender genital projection is present in both the male and female of the species. The function of the projection is unknown and these features are not shared by any other Australian Chiroptera with the exception of Micronomus norfolkensis. Males of the species also possess unique serrated lateral flanges on the acutely pointed glans penis. Features of the dentition are also unique to this species.
As the type and sole species of genus Setirostris, S. eleryi is distinguished from other Molossid species, in particular those formerly placed in Mormopterus, by the absence of a developed gular sac, possessing two lower incisors and two upper premolars.
Range and distribution
Setirostris eleryi is uncommon and widely dispersed across broad areas of inland Australia, with specimens and records from central Australia and the remote southwestern corner of the Northern Territory, northern South Australia, western and central Queensland and northwestern and northern inland New South Wales. The distribution of S. eleryi is notable in that it ranges from extremely arid areas of the central Australian interior, where average annual rainfall is less than, to areas of the northeastern Queensland dry tropics where average annual rainfall can exceed. The eastern component of its distribution range occurs to the west of the Great Dividing Range within the Brigalow Belt, Mulga Lands, Darling Riverine Plains and Nandewar Biogeographic Regions.In the western component it occurs within the Finke, MacDonnell Ranges, Simpson Strzelecki Dunefields and Central Ranges Bioregions.
The presence of outlying records for S. eleryi at Kaltukatjara, Mount Isa and in the area south of Bourke indicate that the species may have a more extensive distribution in the arid and semi-arid regions of NSW, Queensland, the Northern Territory and Western Australia than available records indicate. However its range and status remain relatively poorly known. By 2008 it had been recorded at 26 localities and few additional locations have been recorded in subsequent years.
Habitat
Records of S. eleryi are of individuals captured in mist nets or harp traps in riparian habitats on ephemeral streams, floodways, pools or dams, usually at sites supporting a large fringe of eucalypt trees. Capture sites are consistently associated with riparian and floodplain habitats that support a canopy of eucalypts, including Eucalyptus camaldulensis, E. coolabah, E. microtheca, E. populnea, E. polyanthemos and E. citriodora. At Gundabooka National Park in western NSW the species was only trapped along drainage lines with eucalypts E. camaldulensis and E. populnea. During radio tracking studies at the Gundabooka site the species was observed to preferentially forage along drainage lines and open channels, rarely moving into adjacent mulga vegetation dominated by Acacia aneura. All the roost sites identified were in tall eucalypts within, or adjacent to, riparian zones.The preference of this species for riparian habitats is consistent across its known range. At the type locality in northern South Australia S. eleryi was captured on a floodway in Acacia cambagei low woodland with emergent Eucalyptus coolabah. At Idalia National Park in western Queensland two specimens were captured in riparian woodland near open water, with a canopy of Eucalyptus camaldulensis and Eucalyptus populnea. At a site in northeastern NSW the bat was captured on a riparian terrace adjacent to a river, with trees at the location including Eucalyptus camaldulensis, Eucalyptus blakelyi and rough-barked apple, species Angophora floribunda.