Linda F. Lumsden

How well do ecosystem-based planning units represent different components of biodiversity?

There are many proposals for managing biodiversity by using surrogates, such as umbrella, indicator, focal, and flagship species. We use the term biodiversity man- agement unit for any ecosystem-based classificatory scheme for managing biodiversity. The sufficiency of biodiversity management unit classification schemes depends upon (1) wheth- er different biotic elements (e.g., trees, birds, reptiles) distinguish between biodiversity management units within a classification (i.e., coherence within classes); and (2) whether different biotic elements agree upon similarities and dissimilarities among biodiversity management unit classes (i.e., conformance among classes). Recent evaluations suggest that biodiversity surrogates based on few or single taxa are not useful. Ecological vegetation classes are an ecosystem-based classification scheme used as one component for biodiversity management in Victoria, Australia. Here we evaluated the potential for ecological vegetation classes to be used as biodiversity management units in the box-ironbark ecosystem of central Victoria, Australia. Eighty sites distributed among 14 ecological vegetation classes were surveyed in the same ways for tree species, birds, mammals, reptiles, terrestrial invertebrates, and nocturnal flying insects. Habitat structure and geographic separations also were measured, which, with the biotic elements, are collectively referred to as variables. Less than half of the biotic element-ecological vegetation class pairings were coherent. Generalized Mantel tests were used to examine conformance among variables with respect to ecological vegetation classes. While most tests were not significant, birds, mammals, tree species, and habitat structure together showed significant agreement on the rating of similarities among ecological vegetation classes. In this system, use of ecological vegetation classes as biodiversity management units may account reasonably well for birds, mammals, and trees; but reptiles and invertebrates would not be accommodated. We conclude that surrogates will usually have to be augmented or developed as hierarchies to provide general representativeness.

Location of roosts of the lesser long-eared bat Nyctophilus geoffroyi and Gould's wattled bat Chalinolobus gouldii in a fragmented landscape in south-eastern Australia

The location of roosts of two species of vespertilionid bats, the lesser long-eared bat (Nyctophilus geoffroyi) and Gould’s wattled bat (Chalinolobus gouldii), was investigated in a remnant vegetation-farmland mosaic and adjacent floodplain forest in south-eastern Australia. A total of 45 individuals of N. geoffroyi and 27 C. gouldii were fitted with radio transmitters, which resulted in the location of 139 and 89 roosts respectively. Selection of roosting habitat showed both inter- and intra-specific differences. At the landscape level, locations of roosts used by male and female N. geoffroyi differed markedly. Most males roosted in the farmland mosaic within 3 km (mean 1.9±2.9 km) of where they were captured while foraging in remnant vegetation. In contrast, roost sites of females were predominantly in the floodplain forest, 6–12 km from their capture site in farmland (mean for all females, 6.7±2.9 km). All maternity roosts were in the extensive floodplain forest, 4–10 km from foraging areas. Distances moved by this species were greater than previously recorded and further than predicted by flight morphology. Most C. gouldii roosted in the floodplain forest, 4–10 km from their capture site (6.9±1.6 km). Within the floodplain forest, both species roosted in areas that had higher densities of hollow-bearing trees than generally available; dead hollow-bearing trees for N. geoffroyi and large, live trees for C. gouldii. The scale of movements undertaken by these species means that they can obtain resources from multiple landscape elements. Both species used different habitats for roosting and foraging despite the energetic costs of commuting relatively large distances. Conservation of bat populations in rural environments needs to be considered at the landscape scale, with particular attention to identifying landscape elements that provide key resources.

Day roost selection by female little forest bats (Vespadelus vulturnus) within remnant woodland on Phillip Island, Victoria

The day roosting behaviour of the little forest bat (Vespadelus vulturnus), Australia’s smallest bat, was investigated in the context of the planned removal of dead timber within managed woodlands on Phillip Island, Victoria. Between August 1999 and March 2000, 14 female little forest bats were fitted with VHF microtransmitters and tracked to a total of 16 roost trees. All roosts were located in dead timber, 11 in severely decayed remains of eucalypt trees, and five in dead sections of live trees. Roost trees were compared with randomly chosen trees from within the available habitat, for a range of tree characteristics. Female little forest bats selected roosts in trees with dead timber offering many hollows and reduced canopy cover. Furthermore, roost trees were located in areas (0.1-ha plots) with higher densities of these types of trees than in the available habitat. However, there was no difference in the height or diameter of roost trees or roost plots compared with available habitat. Emergence time from roosts was strongly associated with civil twilight (when the centre of the sun is 6° below an ideal horizon), and the number of bats exiting a single roost tree ranged from 1 to 120 (median = 20). Dead trees provide critical roosting habitat and we recommend retention of dead standing trees for conserving little forest bat roosts in managed woodlands.

Surface reflectance drives nest box temperature profiles and thermal suitability for target wildlife

Thermal properties of tree hollows play a major role in survival and reproduction of hollow-dependent fauna. Artificial hollows (nest boxes) are increasingly being used to supplement the loss of natural hollows; however, the factors that drive nest box thermal profiles have received surprisingly little attention. We investigated how differences in surface reflectance influenced temperature profiles of nest boxes painted three different colors (dark-green, light-green, and white: total solar reflectance 5.9%, 64.4%, and 90.3% respectively) using boxes designed for three groups of mammals: insectivorous bats, marsupial gliders and brushtail possums. Across the three different box designs, dark-green (low reflectance) boxes experienced the highest average and maximum daytime temperatures, had the greatest magnitude of variation in daytime temperatures within the box, and were consistently substantially warmer than light-green boxes (medium reflectance), white boxes (high reflectance), and ambient air temperatures. Results from biophysical model simulations demonstrated that variation in diurnal temperature profiles generated by painting boxes either high or low reflectance colors could have significant ecophysiological consequences for animals occupying boxes, with animals in dark-green boxes at high risk of acute heat-stress and dehydration during extreme heat events. Conversely in cold weather, our modelling indicated that there are higher cumulative energy costs for mammals, particularly smaller animals, occupying light-green boxes. Given their widespread use as a conservation tool, we suggest that before boxes are installed, consideration should be given to the effect of color on nest box temperature profiles, and the resultant thermal suitability of boxes for wildlife, particularly during extremes in weather. Managers of nest box programs should consider using several different colors and installing boxes across a range of both orientations and shade profiles (i.e., levels of canopy cover), to ensure target animals have access to artificial hollows with a broad range of thermal profiles, and can therefore choose boxes with optimal thermal conditions across different seasons.

Urban bat communities are affected by wetland size, quality, and pollution levels

Abstract Wetlands support unique biota and provide important ecosystem services. These services are highly threatened due to the rate of loss and relative rarity of wetlands in most landscapes, an issue that is exacerbated in highly modified urban environments. Despite this, critical ecological knowledge is currently lacking for many wetland‐dependent taxa, such as insectivorous bats, which can persist in urban areas if their habitats are managed appropriately. Here, we use a novel paired landscape approach to investigate the role of wetlands in urban bat conservation and examine local and landscape factors driving bat species richness and activity. We acoustically monitored bat activity at 58 urban wetlands and 35 nonwetland sites (ecologically similar sites without free‐standing water) in the greater Melbourne area, southeastern Australia. We analyzed bat species richness and activity patterns using generalized linear mixed‐effects models. We found that the presence of water in urban Melbourne was an important driver of bat species richness and activity at a landscape scale. Increasing distance to bushland and increasing levels of heavy metal pollution within the waterbody also negatively influenced bat richness and individual species activity. Areas with high levels of artificial night light had reduced bat species richness, and reduced activity for all species except those adapted to urban areas, such as the White‐striped free‐tailed bat (Austronomus australis). Increased surrounding tree cover and wetland size had a positive effect on bat species richness. Our findings indicate that wetlands form critical habitats for insectivorous bats in urban environments. Large, unlit, and unpolluted wetlands flanked by high tree cover in close proximity to bushland contribute most to the richness of the bat community. Our findings clarify the role of wetlands for insectivorous bats in urban areas and will also allow for the preservation, construction, and management of wetlands that maximize conservation outcomes for urban bats and possibly other wetland‐dependent and nocturnal fauna.

Divergent Microclimates in Artificial and Natural Roosts of the Large-Footed Myotis (Myotis macropus)

The thermal environment of day roosts is considered one of the most influential factors affecting the survival, growth and reproduction of microbats. The use of torpor is a common energy saving strategy employed by microbats in temperate regions. The efficiency of entry into, and arousal from, torpor is governed by roost microclimate, primarily roost temperature. The large-footed myotis Myotis macropus roosts in both tree cavities and a man-made tunnel at Yan Yean reservoir in Victoria, Australia. We investigated the thermal properties of both roost types in comparison to available tree cavities and ambient temperature over four time periods from October 2003 to May 2005. Tree cavities and tunnel roosts remained significantly warmer at night, cooler during the day, and were more stable than ambient temperatures. In addition, roost tree cavities were significantly cooler between 10:00–13:00 h compared to available tree cavities, and there was a trend for roost tree cavities to be slightly warmer at night and slower to reach maximum temperature relative to available tree cavities during the breeding season (October–January). In contrast, there was little difference in roost and available tree cavity temperatures outside of the breeding season (April–May). Temperatures inside tunnel roosts were more stable and were significantly cooler during the afternoon compared to roost tree cavities during both the breeding and non-breeding seasons. Myotis macropus may actively trade-off the enhanced thermoregulatory benefits of warm roosts for reduced predation risk associated with the tunnel roosting environment.

Hypersalinity reduces the risk of cyanide toxicosis to insectivorous bats interacting with wastewater impoundments at gold mines

Wildlife and livestock that ingest bioavailable cyanide compounds in gold mining tailings dams are known to experience cyanide toxicosis. Elevated levels of salinity in open impoundments have been shown to prevent wildlife cyanide toxicosis by reducing drinking and foraging. This finding appears to be consistent for diurnal wildlife interacting with open impoundments, however the risks to nocturnal wildlife of cyanide exposure are unknown. We investigated the activity of insectivorous bats in the airspace above both fresh (potable to wildlife) and saline water bodies at two gold mines in the goldfields of Western Australian. During this study, cyanide-bearing solutions stored in open impoundments at both mine sites were hypersaline (range=57,000-295,000 mg/L total dissolved solids (TDS)), well above known physiological tolerance of any terrestrial vertebrate. Bats used the airspace above each water body monitored, but were more active at fresh than saline water bodies. In addition, considerably more terminal echolocation buzz calls were recorded in the airspace above fresh than saline water bodies at both mine sites. However, it was not possible to determine whether these buzz calls corresponded to foraging or drinking bouts. No drinking bouts were observed in 33 h of thermal video footage recorded at one hypersaline tailings dam, suggesting that this water is not used for drinking. There is no information on salinity tolerances of bats, but it could be assumed that bats would not tolerate salinity in drinking water at concentrations greater than those documented as toxic for saline-adapted terrestrial wildlife. Therefore, when managing wastewater impoundments at gold mines to avoid wildlife mortalities, adopting a precautionary principle, bats are unlikely to drink solutions at salinity levels ≥50,000 mg/L TDS.

Continuous predictors of species distributions support categorically stronger inference than ordinal and nominal classes: an example with urban bats

Understanding of how species distributions are driven by landscape-level processes has been obscured by null or inconsistent findings from poorly designed studies. We explore how differences in the way potential drivers of species distributions are defined can influence their perceived effects. Specifically, we evaluate how much statistical power is lost when continuous variables are discretised, and how the use of qualitatively defined nominal variables impacts biological interpretation of results. We fitted generalized linear models to dependent variables relating to bat distribution (species richness, diversity, relative abundance of functional groups and individual species) obtained from 36 sites across Melbourne, Australia, and independent variables that were continuous (percentage tree cover, dwelling density), ordinal (dichotomised continuous variables) or nominal (land-use, urban context). We found that models fitted with continuous predictors had better fit and explanatory power than those fitted with ordinal predictors for all response variables. Ordinal models failed to detect statistically significant effects for 4 of the 11 response variables that were successfully modelled with continuous data, suggesting Type II errors had occurred. Models fitted with nominal data explained a comparable amount of variation in some dependent variables as continuous models. However, interpretation of the mechanisms behind responses to nominal categorical levels was obscured because environmental conditions within them were confounded and not homogenous. To gain better understanding from nominal predictors would therefore require further investigation. Our findings show that careful consideration must be given to the choice of environmental variables used for species distribution modelling and how those variables are defined.

Bat boxes are not a silver bullet conservation tool

Nest boxes are often promoted as substitute structures for hollow-dependent fauna, but are they generally effective? In a long-term bat-box monitoring project in south-eastern Australia, box occupancy was dominated by one common and widespread urban-adapted species, Goulds wattled bat Chalinolobus gouldii. In contrast, the 13 other bat species in the area made little or no use of the boxes. Policymakers, land managers and conservation professionals working in the field of biodiversity offsets should be aware that bat boxes are unlikely to compensate adequately for the broad-scale loss of tree hollows caused by various forms of human disturbance.

Virus survey in populations of two subspecies of bent-winged bats (Miniopterus orianae bassanii and oceanensis) in south-eastern Australia reveals a high prevalence of diverse herpesviruses

While bats are often viewed as carriers of infectious disease agents, little research has been conducted on the effects these potential pathogens may have on the bat populations themselves. The southern bent-winged bat (Miniopterus orianae bassanii) is a critically endangered subspecies endemic to south-eastern Australia. Population numbers of this bat have been declining for the past 50 years, but the reasons for this are unclear. As part of a larger study to determine if disease could be a contributing factor to this decline, 351 southern bent-winged bats from four locations were captured, and oral swabs were collected and tested for the presence of potentially pathogenic viruses. Results were compared with those obtained from 116 eastern bent-winged bats (Miniopterus orianae oceanensis) from three different locations. The eastern bent-winged bat is a related but more common and widespread subspecies whose geographical range overlaps partly with southern bent-winged bats. Herpesviruses were detected in bent-winged bats from all seven locations. At least six novel herpesviruses (five betaherpesviruses and one gammaherpesvirus) were identified. The prevalence of herpesvirus infection was higher in eastern bent-winged bats (44%, 51/116), compared to southern bent-winged bats (27%, 95/351), although this varied across the locations and sampling periods. Adenoviruses and a range of different RNA viruses (lyssaviruses, filoviruses, coronaviruses and henipaviruses) were also tested for but not detected. The detected herpesviruses did not appear to be associated with obvious ill health, and may thus not be playing a role in the population decline of the southern bent-winged bat. The detection of multiple novel herpesviruses at a high prevalence of infection is consistent with our understanding of bats as hosts to a rich diversity of viruses.