Letteratura scientifica selezionata sul tema "Chalinolobus gouldii"

The taxonomic status of the New Caledonia Wattled Bat Chalinolobus neocaledonicus Revilliod, 1914 has remained uncertain since its synonymy with mainland Australian Gould’s Wattled Bat C. gouldii (Gray, 1841) in 1971. Although Chalinolobus neocaledonicus is now widely accepted as a valid species, this was based on a tentative taxonomic opinion published in 1995. We examined most of the original material used to justify synonymy with C. gouldii, which included the type series of C. gouldii venatoris, a small northern Australian form that superficially resembles C. neocaledonicus but is currently not generally recognised as a valid subspecies. We found consistent differences in key diagnostic external and cranial criteria that support species status for C. neocaledonicus. We also review the taxonomic status of venatoris. Contrary to previous assessments, our re-interpretation of the taxonomic literature supports subspecific recognition of venatoris. Nevertheless, we are unable to conclusively resolve the status of venatoris because a more complex pattern of variation than a simple latitudinal size cline is apparent in C. gouldii. We argue that recognition of venatoris as the northern subspecies of C. gouldii has merit, pending a comprehensive analysis of variation in mainland C. gouldii to test for the presence of cryptic taxa.

Bat boxes are often used to provide supplementary roosting habitats; however, little is known of their impacts on community composition. Data collected from a 25-year box-monitoring and 31-year harp trapping case study provides preliminary evidence that the installation of boxes may have contributed to one species, Gould’s wattled bat (Chalinolobus gouldii), dominating the bat community of a periurban park in Melbourne. This highlights the need for systematic monitoring and empirical assessment of conservation-focused bat box programs.

Gould’s wattled bat (Chalinolobus gouldii) is one of only three native Australian mammals with an Australia-wide distribution. However, currently no data are available on the thermal physiology of free-ranging C. gouldii. Therefore, we aimed to quantify the effect of roost choice on daily skin temperature fluctuations during winter in C. gouldii living in an agricultural landscape in a temperate region. Ambient conditions consisted of long periods below 0°C and snow. Some individuals roosted high in dead branches whereas one individual roosted in a large cavity located low in a live tree. Torpor was employed on every day of the study period by all bats, with bouts lasting for over five days. The skin temperature of individuals in the dead branches tracked ambient temperature, with skin temperatures below 3°C on 67% of bat-days (lowest recorded –0.2°C). In contrast, the individual in the tree cavity maintained a larger skin-ambient temperature differential, likely influenced by the internal cavity temperature. Our study presents the lowest skin temperature recorded for a free-ranging Australian microbat and reveals that roost choice affects the thermal physiology of C. gouldii, ensuring survival during periods of cold weather and limited food supply.

Echolocation calls were recorded from six species of microchiropteran bats (Rhinolophus megaphyllus, Miniopterus australis, M. schreibersii, Eptesicus pumilus, Chalinolobus gouldii and Scotorepens greyii) in the Brisbane area. All species were recorded in free-flight when searching for prey in the wild, with some also recorded in roosts and in the hand. Sonagrams are presented for use in species identification.

Univariate and bivariate analyses were used to demonstrate that C. gouldii increases in size from north to south and, to a lesser extent, from west to east. There is little difference between the sexes in most dimensions. Although significant differences exist between animals from localities widely separated geographically, multivariate analyses suggest that C. gouldii once occurred over most of mainland Australia, Tasmania, Norfolk I. and New Caledonia. The species appears to have become extinct or very rare in recent times on Norfolk I.; the possibility of re-introduction is discussed.

Bat activity was surveyed at Belair National Park, Adelaide and an adjacent house in Glenalta, March 1996 to March 1997, using the Anabat system. 44 bats of 6 species (Chalinolobus gouldii, C. morio, Vespadelus darlingtoni, V. regulus, V. vulturnus, and Nyctophilus geoffroyi) were captured, providing positive identification of calls. Three additional species were recorded (Tadarida australis, Mormopterus planiceps and an unidentified species). At Playford Lake, Belair, 2522 bat calls were recorded in 35 h, with most calls from V. darlingtoni (76.3% of total). At Glenalta, 1521 calls were recorded in 238 h, with most calls from C. gouldii (69.2% of total). V. darlingtoni, V. regulus and M. planiceps showed significantly more activity at Playford Lake, Belair, a wooded site beside a lake, than at Glenalta, a suburban site with artificial lighting, while activity of C. gouldii and T. australis was similar at the two sites. Most bats showed significant lower activity in winter, apart from V darlingtoni, which was active all year round at Belair. Nocturnal temperatures during the study varied from 6-31°C. The activity of most bat species showed no significant correlation with temperature, apart from C. gouldii at Belair, which averaged 1.2 passes per hour below 13°C and 9.3 passes per hour above l3°C.

Bat boxes are frequently used as conservation and habitat-offset measures, yet their effectiveness is equivocal, particularly in Australia. Boxes used in Australia are largely voluminous-type boxes with Chalinolobus gouldii (Gould’s wattled bat) frequently dominating their use. We tested multichambered boxes comprising fissure-type cavities made from either plywood (~20000cm3) or woodcement (~7400cm3). We investigated whether occupancy was influenced by box colour (white boxes facing morning sun versus black boxes facing afternoon sun), box material/size, chamber width (15mm versus 20mm) and box host (tree versus pole). Boxes were monitored over 1.8 years. Overall, 245 bat observations were recorded. Boxes were frequently used (15% of 1088 box checks) by Nyctophilus geoffroyi (lesser long-eared bat), a species uncommonly reported to use boxes, which used 50 of the 64 boxes (78%), including for maternity roosting (n=6). In comparison, C. gouldii was rarely detected (1% of box checks). Two other species were also found in boxes at low frequencies. Modelling showed a preference by N. geoffroyi for black boxes, the larger plywood box and boxes installed on poles. Fissure-type boxes appear to meet the roost requirements of N. geoffroyi but not that of C. gouldii, the species principally detected in voluminous-type boxes and postulated to gain a competitive advantage. The black woodcement box was the second most frequently used design, demonstrating that this long-lasting box material can be a suitable alternative to the less durable plywood material. Given that just one species commonly used boxes, there is a need for further research on box designs.

Tree-roosting bats are highly social mammals, which often form fission–fusion societies. However, extensive, fine scale data is required to detect and interpret these patterns. We investigated the social structure of Gould’s wattled bats, Chalinolobus gouldii, roosting in artificial roosts (bat-boxes) over a continuous 18-month period. Network analyses revealed non-random associations among individuals in the roosting population consistent with a temperate zone fission–fusion social structure. Females generally showed stronger associations with roost-mates than did males. Two distinct sub-groups within the larger roosting population were detected. There was also evidence of smaller subunits within these larger roosting groups in spring and summer, with broader mixing at other times of the year. The extensive roost occupancy data collected across all seasons was critical in defining this fine scale, and otherwise cryptic, social structure, and in particular indicating that associations observed during peak activity periods may not be maintained across the year.

Day-roosts are an essential resource for tree-hole roosting microbats (Microchiroptera), providing shelter, protection from predators and an appropriate microclimate for energy conservation and reproduction. Microbats often make use of multiple roosting sites, shifting between roosts frequently. Conservation of tree-hole roosting microbats requires an understanding of roost selection and fidelity to enable the protection of sufficient suitable roosting sites. In Australia, as in other countries, habitat loss, particularly in the form of large hollow-bearing trees, is threatening the survival of microbat populations. In addition, the renewal of natural roosts in Australia is very slow, as trees may need to be 100 years old for hollows to form. Where roosting resources are limited, such as in urbanised areas, batboxes may be used as a substitute. As bat-boxes are also accessible to researchers, these roosting sites can help to improve our understanding of roosting behaviour.
This thesis investigates the roosting behaviour of two sympatric microbat species: Gould’s wattled bat (Chalinolobus gouldii) and the white-striped freetail bat (Tadarida australis). These are insectivorous tree-hole roosting species, which naturally occur in urban Melbourne, Australia. Both species make use of bat-boxes at three sites in Melbourne, often sharing roosts with members of the other species. This provided an opportunity not only to study their use of bat-boxes for conservation management purposes, but to investigate factors influencing bat roost selection and fidelity. This study incorporated PIT tags (microchips) and a detector array at the bat-boxes, in addition to monthly manual bat-box inspections, as a method for monitoring roost-use. This approach enabled the collection of long-term, fine-scale roosting data. These data, along with captive and field-based experiments were used to examine the influence of parasites, microclimate and social structure on roost selection patterns and roost fidelity. The specific questions posed were whether tree-hole roosting bats: select roosts based on physical characteristics; perceive a cost of carrying ectoparasites and avoid infested roosts; select roosts to maintain social associations; and select for specific beneficial microclimates.
The patterns of roost selection, ectoparasite diversity, social structure, and the selection of roost microclimate differed between the two species. Microclimate of the bat-boxes was a strong influence on roost selection for both species, as it is for microbats generally. White-striped freetail bats preferred warmer roosts with stable humidity. For Gould’s wattled bats, the selection of roost microclimate differed between the sexes and even between separate, but adjacent, roosting groups. Patterns of preference indicated that individuals had knowledge of the available roosting sites.
The presence of parasites had no obvious influence on roost selection patterns in either species. The white-striped freetail bat was found to support lower ectoparasite diversity, which may be influenced by characteristics of the pelage and may partially explain why parasite load was not a useful predictor of roost selection in this species. In contrast, Gould’s wattled bat supported a larger diversity of ectoparasites, which showed clear patterns of distribution through the bat populations, and intra-specific and spatial variability. A radio-tracking study indicated that parasites in the roost and on the Gould’s wattled bat may influence their roosting behaviour. Additionally, experimental assessments of the bats’ grooming response to parasites indicated that the perceived costs of these parasites differed with parasites that remained permanently attached to the host eliciting a stronger response than those also found in the roost. The defensive mechanism against parasites that completed part of their life-cycle in the roost was expected to be avoidance behaviour, yet, in both captive and field experiments, these parasites did not strongly influence roost selection or fidelity.
Social associations among white-striped freetail bats appeared to be random, and did not explain roosting patterns. This may reflect the restricted sampling of roosting sites, and the possible role of the bat-boxes in this study as ‘satellite’ roosts, separate from a larger communal roost, likely to be in a large tree-hollow. Unlike white-striped freetail bats, Gould’s wattled bats showed fission-fusion social structure, driven by stronger female associations. The distribution and abundance of parasites was correlated with the social structuring of the host species, and host selection appeared to facilitate transmission. These patterns suggest that female Gould’s wattled bats, in particular, are choosing roosts based on the benefits of social association despite the cost of increased parasite risk, and may provide an explanation for sexual segregation in temperate tree-roosting bats.
This study demonstrates the species-specificity of roosting behaviour, and the importance of investigating several factors that influence roost selection, to better understand roost requirements. It also highlights the inherent complexity in roost selection by tree-hole roosting microbats, which may be making trade-offs between the benefits of social associations and the cost of parasitism, as well as choosing an optimal microclimate. Further investigation into interactions between these factors will greatly advance our understanding of roost selection and fidelity in tree-hole roosting bats.