Lisa Cawthen

Bat fatalities at two wind farms in Tasmania, Australia: bat characteristics, and spatial and temporal patterns

Abstract Bat carcasses from two wind farms in Tasmania (2002–2010) were assessed to determine the species, sex, age, reproductive state, morphometrics, presence of food in the gastrointestinal tract, and evidence of spatial and seasonal patterns. Thirty-eight of the 54 carcasses were Goulds wattled bats, with another 14 likely to be, and two Vespadelus sp. All but two were adults, with an equal ratio of females and males. None were actively breeding when found, and five of the six bats tested, had not been recently feeding. Mortalities predominantly occurred in autumn, with a small difference between sites. There was no pattern in the location of carcasses. There appear to be particular ecological, morphological and behavioural characteristics associated with bat collision risk—tree roosting bats with high wing aspect ratios that forage in the open air at high altitude appear to be susceptible. Seasonal patterns may be associated with specific behaviours.

The use of hollow-bearing trees retained in multi-aged regenerating production forest by the Tasmanian common brushtail possum (Trichosurus vulpecula fuliginosus)

Context Hollow-bearing trees are frequently retained in timber-production areas as part of measures to mitigate against the impacts of forest harvesting on fauna, yet few studies have investigated the effectiveness of such measures. Such studies are essential for adaptive forest management. Aims The main aim of the present study was to evaluate the use of hollow-bearing trees retained in harvested and unharvested forest as den sites by the Tasmanian common brushtail possum. In particular, we examined the distribution and types of hollow-bearing trees used as den sites and whether or not their use in harvested sites was influenced by time since harvest. Methods Thirty brushtail possums were radio-tracked to their day-time den sites between March 2007–July 2007 and July 2008–October 2008, at five dry Eucalyptus forest sites (three regenerating after partial harvest with hollow-bearing trees retained inside the coupe and two in relatively undisturbed forest) in south-eastern Tasmania, Australia. Key results The brushtail possums tracked in the study denned primarily in hollow-bearing trees at both the harvested and unharvested sites. At sites regenerating 8 and 10 years after harvest, most den site locations were in trees retained outside the harvest area, in large patches. In contrast, at the site regenerating 17 years after harvest, isolated trees and small patches within the harvested area were used. Conclusions Hollow-bearing trees retained within harvest areas do provide habitat for hollow-dependent fauna such as the common brushtail possum and enable recolonisation of harvested areas in the medium term. However, in the short term these trees may not be used and hollow-bearing trees retained in the surrounding landscape are important for providing refuge as the harvested area regenerates. Implications The retention of hollow-bearing trees in harvested areas may be an effective measure at enabling recolonisation of harvested areas once suitable habitat regenerates, but it is also important to ensure that large patches of mature forest (containing hollows) are retained in the surrounding landscape to ensure the persistence of hollow-using fauna.

The design and testing of linen thread weak-links in brushtail possum radio-collars

Linen thread was built into radio-collars as a weak-link to trial its effectiveness at ensuring that radio-collars did not remain indefinitely on animals if they were not recaptured. Eighty percent of collars with weak-links broke or degraded, resulting in the collars dropping off within 12–45 days. This method may be useful for short-term studies of some species of mammal that are difficult to recapture in order to remove collars.

Insectivorous bat activity in timber production forests in the headwaters of the South Esk River, North East Tasmania

Riparian zones are an important habitat for a range of bat species and, as a consequence, understanding whether land use practices such as timber harvesting influence their use is important for conservation and management. This small-scale study used bat activity as a measure of the use of riparian and up-slope zones along headwater streams by bats, and to determine whether past timber harvesting influenced the use of these areas by bats by comparing regrowth with no retained riparian buffers and mature forest. This study found no significant differences in bat activity between treatments, but did find a trend of higher bat activity in riparian zones compared to up-slope zones, particularly in regrowth forest. However, many sites had little to no bat activity indicating activity was influenced by factors not measured in this study. Despite limited data, this study highlights the potential value of retaining riparian habitat in harvested forests for bats, as is practised elsewhere in Australia, and the need for future research into the effectiveness of forest retention measures for wildlife.

White-striped freetail bat in Tasmania – resident, vagrant or climate change migrant?

The white-striped freetail bat (Austronomus australis) is distributed throughout mainland Australia, but historically has not been known from the island of Tasmania, off south-eastern mainland Australia. Between 2009 and 2012, echolocation calls identified as those of A. australis were recorded in Tasmania during bat call surveys. There are three hypotheses that could explain the discovery of this species in Tasmania: that A. australis is a previously undetected resident; it is a vagrant; or it is undergoing a southwards range expansion or shift. Based on the limited evidence available, including this species’ long-range flight capabilities (including over open water out to sea), I suggest that this species is a periodic vagrant to Tasmania and that monitoring is necessary to identify whether this species is undergoing a southwards range extension into Tasmania.