Magnitude of Canopy Dieback and Implications for Conservation of Southern Rata-Kamahi (

The amount of conspicuous canopy dieback in all central Westland southern rata-kamahi forests east of the Alpine Fault, between 500 m altitude and treeline, was assessed and mapped from aerial photographs taken in 1984-85 and verified by aerial reconnaissance of selected areas in 1988. At least 20% of all canopy trees, predominantly southern rata (Metrosideros umbellata) and Hall's totara (Podocarpus hallii), were dead in 1984-85. Major catchments with their headwaters east of the Alpine Fault comprised 78% of the study area and were worst affected (5%-44% canopy mortality). Because affected trees decay and eventually disappear from the canopy, the extent of visible dieback underestimated total canopy depletion, particularly where mortality occurred more than c. 15 years ago. Geographical variation in canopy dieback reflected the intensity and duration of browsing by the introduced brush- tailed possum (inferred from patterns of invasion from their liberation sites) and the influences of forest composition and timing of dieback. Although 29% of the forests showed light dieback (<10% mortality), only 11% had not experienced heavier past dieback and could be classified as having canopies largely unmodified by possums. Such widespread and continuing forest depletion, and declining possum control effort over the last decade, indicate the urgent need for a coordinated rata-kamahi forest conservation strategy, involving long-term possum control and monitoring in representative tracts.     

Ecology of Ship Rats (

The impact of browsing by introduced brushtail possums on mixed beech—broadleaved forests in South Westland was estimated from the amount of conspicuous canopy dieback present in 1989- 1990. Aerial and ground-based reconnaissance in all catchments indicated most canopies (84%) were intact. The remaining 16% of canopies were affected by conspicuous dieback, principally of southern rata (Metrosideros umbellata) and/or fuchsia (Fuchsia excorticata). Major dieback nuclei were located in the three areas with the longest history of browsing by possums, which had spread from three known liberation centres. At each dieback nucleus, the amount of dieback reflected the abundance of possum-preferred canopy species. Because South Westland forests contain lower proportions of such species, they are less susceptible to dieback than the conifer-broadleaved forests of central Westland. However, the present low amounts of dieback in South Westland mainly reflect low overall possum densities and a short period of occupation. The occurrence of key possum- preferred species indicates that about one-third of the forests could develop conspicuous canopy dieback if possum numbers increase and 44-94% are susceptible to canopy and/or understorey depletion. By 1992, the few areas selected for sustained possum control effort in Westland under-represented the range of forest composition. However, recently boosted funding for possum control has provided the opportunity to protect representative forest tracts before the onset of widespread ecosystem depletion in South Westland.     

Mistletoe (

The condition of 79 plants of the loranthaceous mistletoe Tupeia antarcticain a podocarp-hardwood forest in the central North Island, New Zealand, was monitored over 4 years during a period of increasing possum density, following previous possum control. Mistletoe comprised 1.2% of total possum diet during the three years following possum control. Incidence of possum browse on mistletoe plants increased from 2.6% of plants when the trap-catch index of possum density was < 3%, to 75.9% of plants when trap-catch rates reached 4.6%. Mistletoe foliage cover declined from 49.8% to 15.6% and mean plant size declined by about 55% over the same period. The mistletoe population was dominated by plants with large haustoria, located in heavily shaded locations in the lower crown of their Carpodetus serratus hosts. Most plants established more than 20 years ago, and the current potential for recruitment of new individuals into the population is severely limited by possum browsing and the senescent nature of the mistletoe population. Intensive management of host crowns and possum populations will be necessary to ensure the long-term viability of mistletoe at the study site.     

Spatial variation in impacts of brushtail possums on two Loranthaceous mistletoe species

Browsing by introduced brushtail possums is linked to major declines in mistletoe abundance in New Zealand, yet in some areas mistletoes persist, apparently unaffected by the presence of possums. To determine the cause of this spatial variation in impact I investigated the abundance and condition (crown dieback and extent of possum browse) of two mistletoes (Alepis flavida, Peraxilla tetrapetala) and abundance and diet of possums in two mountain beech (Nothofagus solandri var. cliffortioides) forests in the central-eastern South Island of New Zealand. Mistletoe is common and there are long-established uncontrolled possum populations in both forests. Mistletoes were abundant (216?1359 per hectare) and important in possum diet (41?59% of total diet), but possum density was low (c. 2 per hectare) in both areas. Possum impacts were slight with low browse frequencies and intensities over much of the study sites. However, impacts were significantly greater at a forest margin, where possum abundance was highest, and at a high-altitude site where mistletoe density was lowest. Mistletoe crown dieback was inversely proportional to intensity of possum browsing. These results suggest that the persistence of abundant mistletoe populations at these sites is due to mistletoe productivity matching or exceeding consumption by possums in these forests of low possum-carrying capacity, rather than low possum preference for the local mistletoe populations.     

Seasonal variation in the impacts of brushtailed possums (

The seasonal variation in possum browse and foliage cover of five possum-preferred species was quantified and studied in northern Westland, New Zealand over a 24 month period. Four of the five species (Pseudopanax simplex, P. colensoi, Aristotelia serrata, and Elaeocarpus hookerianus) showed marked seasonal patterns in both browse and foliage cover, with maximum browse evident in winter/spring when foliage cover was at a minimum. There was very little browse and no seasonal pattern in foliage cover for the fifth species, Pseudopanax crassifolius. In the season of maximum browse there were significant negative correlations between browse and foliage cover for the four impacted species suggesting that the changes in foliage cover were caused by possum browsing. Mortality was highest in the two most heavily browsed species (P. simplex and P. colensoi). This seasonality in possum browse needs to be, accommodated when designing long-term surveys of possum impacts.     

Browse on mahoe and kamahi leaf-fall as a trigger for possum control

Introduced brushtail possums (Trichosurus vulpecula) are controlled over large parts of New Zealand to protect canopy trees. The condition of canopy trees is one of the cues used to trigger possum control, but selecting an indicator of canopy tree condition is difficult because many factors unrelated to possum browsing can affect canopy condition, and indices based on canopy scoring may not always quickly detect real changes in possum herbivory. We therefore investigated the usefulness of the percentage of fallen mahoe (Melicytus ramiflorus) and kamahi (Weinmannia racemosa) leaves browsed by possums (‘fallen-leaf browse’ or ‘FLB’) as a trigger for control aimed at protecting these tree species. We collected leaves falling from kamahi and mahoe trees every two months for two years at two study areas in the central North Island, one with initially high possum abundance (Oriuwaka) and the other with low possum abundance (Otupaka). We classified each of 92 384 leaves as either not-browsed, possum-browsed or insect-browsed. There was a strong and similar seasonal pattern in the mean number of fallen leaves per tree for both mahoe and kamahi at both study areas; fewest leaves fell in winter, and the most leaves fell in spring and early summer. Mahoe and kamahi FLB exhibited a similar seasonal pattern at both areas, being lowest in winter and highest in spring and early summer. FLB for both mahoe and kamahi declined following control of possums to low densities at Oriuwaka. The proportion of fallen mahoe and kamahi leaves browsed by possums was small compared with those browsed by insects or not browsed. We show that spring/early summer (i.e. September–December) is the best period for sampling FLB and that the mean FLB can be estimated with a CV of 20% if one trap is randomly placed under the canopy of each of 24 randomly located trees. However, CVs were much larger in other seasons and when possum abundance was low. We consider FLB to be a sensible trigger for initiating possum control when the objective of control is to protect canopy trees, but further work is needed to determine the relationships between possum abundance, FLB, canopy condition, and key tree demographic rates.     

The relationship between possum density and browse damage on kamahi in New Zealand forests

To minimize the impacts of introduced pests and to justify and prioritize pest control, managers need to know the relationship between pest density and damage. This relationship can be difficult to quantify because pest impacts can be highly variable. In New Zealand, introduced brushtail possums (Trichosurus vulpecula) browse a wide range of native forest species. However, possum browse is extremely patchy making it difficult to quantify the relationship between density and damage, meaning the benefits of reducing possum densities are poorly understood. We quantified patterns of possum browse on kamahi (Weinmannia racemosa), a common canopy tree species, at 21 forest sites that were repeat‐measured over an 8‐year period in the North Island, New Zealand, during which time possum densities fluctuated widely. We fitted a multilevel statistical model in order to quantify the relationship between possum density and browse damage while simultaneously quantifying how browse varied among trees, sites and years. Higher possum densities were associated with greater browse damage, but browse was also patchily distributed among trees at the same site, and among sites and years for a given possum density. This heterogeneity meant there was no simple density damage relationship, with the relationship differing from tree to tree and among sites and years. Our results show that at most sites reductions in possum density would have little benefit in reducing the probability of heavy browse on kamahi trees, but at a few sites there would be substantial benefits. This approach provides insights into the pattern and potential causes of variability in possum impacts, and a quantitative basis for prioritizing sites for possum control.     

Diet and impacts of brushtail possum populations across an invasion front in South Westland, New Zealand

Impact of the irruptive fluctuation in abundance of brushtail possum populations since their initial colonisation was investigated in the forests of South Westland, New Zealand. Possum abundance, fecundity, and diet, the condition of common possum-palatable tree species, and the abundance of common forest birds were measured at three sites occupied by possums for c. 10, 20, and 30 years. Possum densities were highest at the site where possums had been present for c. 20 years. Possum fecundity was higher at the site they had recently colonised than at the two sites where they had been present for c. 20–30 years. Diet of possums where they had recently colonised was dominated by highly preferred foods (72% of total diet), whereas these same foods contributed just 36% of total diet at the site where possums had been present for more than two decades. Canopy condition of common possum-preferred trees was scored progressively lower in areas with increasing length of possum occupation, especially at the site where the possum population had apparently declined from its maximum density. Native forest bird abundance also declined with increasing length of possum occupation. The implications of these results for management are discussed.     

The impact of brodifacoum on non-target wildlife: gaps in knowledge

To assess the effect of possum browse on plant growth, an index of the amount of foliage on about 50 trees of Fuchsia excorticata and the number of trees that died or were completely defoliated was measured at five sites in South Westland over 5 years. This index was compared to possum density indices taken at each site each year. At one site, possums were reduced from a high density about 6 months before the final measurement. The degree of defoliation of fuchsia was significantly related to the density of possums at each site. Possums defoliate and kill fuchsia within two years once the catch-rate index of their density exceeds about 25%. However, this impact can be halted and quickly reversed by reducing possum density.     

Possum (

To assess the effect of possum browse on plant growth, an index of the amount of foliage on about 50 trees of Fuchsia excorticata and the number of trees that died or were completely defoliated was measured at five sites in South Westland over 5 years. This index was compared to possum density indices taken at each site each year. At one site, possums were reduced from a high density about 6 months before the final measurement. The degree of defoliation of fuchsia was significantly related to the density of possums at each site. Possums defoliate and kill fuchsia within two years once the catch-rate index of their density exceeds about 25%. However, this impact can be halted and quickly reversed by reducing possum density.     

Crown dieback events as key processes creating cavity habitat for magellanic woodpeckers

Abstract Woodpeckers are considered keystone species for webs of cavity nesters and habitat and resource specialists that strongly depend on availability of trees suitable for cavity excavation. Most studies carried out in northern hemisphere temperate coniferous forests emphasize the importance of old growth stages of forests or large dead trees as habitat for cavity builders. We present a study of Nothofagus pumilio tree selection by the magellanic woodpecker (Campephilus magellanicus) that incorporates dendroecological data on long‐term growth trends of trees that provides new insights into the processes that create suitable habitat for cavity excavating species. We analysed 351 cavity and neighbouring control trees in terms of age and radial growth patterns, as well as external tree characteristics. In addition, from a subsample of these trees we developed tree‐ring chronologies for each group using standard methods in order to analyse potential differences in radial growth patterns between cavity and non‐cavity trees. Multivariate models that account for differences between paired cavities versus control trees indicated that growth decline and the degree of crown dieback were the primary variables explaining magellanic woodpecker tree selection for cavity building. In contrast to previous work, neither diameter (above a certain threshold) nor age, were important determinants of selection. Furthermore, trees that became present cavity are those that had synchronously declined in radial growth during the 1943–44 and 1956–57 droughts and the 1985–86 massive caterpillar defoliation. Insect outbreaks and extreme climatic events may episodically reduce vigour, induce partial crown mortality, trigger increased fungal attack and heart rot formation at different tree heights on the bole in a group of trees and thus increase availability of soft substrate and their likelihood of cavity excavation by the magellanic woodpecker. These results underscore the importance of drought/biotically‐induced canopy dieback events in creating habitat for woodpeckers and their dependent cavity users.     

Variation in woody plant mortality and dieback from severe drought among soils, plant groups, and species within a northern Arizona ecotone

Vegetation change from drought-induced mortality can alter ecosystem community structure, biodiversity, and services. Although drought-induced mortality of woody plants has increased globally with recent warming, influences of soil type, tree and shrub groups, and species are poorly understood. Following the severe 2002 drought in northern Arizona, we surveyed woody plant mortality and canopy dieback of live trees and shrubs at the forest–woodland ecotone on soils derived from three soil parent materials (cinder, flow basalt, sedimentary) that differed in texture and rockiness. Our first of three major findings was that soil parent material had little effect on mortality of both trees and shrubs, yet canopy dieback of trees was influenced by parent material; dieback was highest on the cinder for pinyon pine (Pinus edulis) and one-seed juniper (Juniperus monosperma). Ponderosa pine (Pinus ponderosa) dieback was not sensitive to parent material. Second, shrubs had similar mortality, but greater canopy dieback, than trees. Third, pinyon and ponderosa pines had greater mortality than juniper, yet juniper had greater dieback, reflecting different hydraulic characteristics among these tree species. Our results show that impacts of severe drought on woody plants differed among tree species and tree and shrub groups, and such impacts were widespread over different soils in the southwestern U.S. Increasing frequency of severe drought with climate warming will likely cause similar mortality to trees and shrubs over major soil types at the forest–woodland ecotone in this region, but due to greater mortality of other tree species, tree cover will shift from a mixture of species to dominance by junipers and shrubs. Surviving junipers and shrubs will also likely have diminished leaf area due to canopy dieback.     

Patch dieback of Colophospermum mopane in a dysfunctional semi‐arid African savanna

Abstract Patch dieback occurred in an almost monospecific Colophospermum mopane (Kirk ex Benth.) Kirk ex J. Léonard woodland in the Northern Province, South Africa, following severe droughts in 1988–1989 and 1991–1992. Discrete patches of dieback and adjacent paired areas of ‘healthy’ vegetation lost an average of 87 and 13% of basal area to mortality, respectively. Whole trees mostly died on ‘dead’ plots, while single‐stem mortality prevailed on ‘live’ plots. Tree mortality decreased with increasing stem number per tree. Patch dieback did not occur on sandy soils. On fine‐textured soils, variation in soil type, topography or slope did not affect dieback. Dieback was influenced by vegetation structure, soil surface condition and soil chemistry. Intense intertree competition, shown by self‐thinning occurring prior to dieback, was a precondition for dieback. Intertree competition had heightened during the 30 years prior to dieback because of an increase in woody cover. Dieback patches had changed from functioning as sinks of water and sediment to sources of these as a result of loss of perennial herbaceous cover, decreased water retention on bared surfaces, and accelerated erosion during 50 years of livestock ranching. Vegetation had thus become increasingly drought‐prone, exacerbated in places by soils with a high sodium concentration. Dieback had occurred because the water requirements of C. mopane could no longer be met during drought years on the dysfunctional patches.     

Declining carbohydrate content of Sitka-spruce treesdying from seawater exposure

Increasing sea levels associated with climate change threaten the survival of coastal forests, yet the mechanisms by which seawater exposure causes tree death remain poorly understood. Despite the potentially crucial role of nonstructural carbohydrate (NSC) reserves in tree survival, their dynamics in the process of death under seawater exposure are unknown. Here we monitored progressive tree mortality and associated NSC storage in Sitka-spruce (Picea sitchensis) trees dying under ecosystem-scale increases in seawater exposure in western Washington, USA. All trees exposed to seawater, because of monthly tidal intrusion, experienced declining crown foliage during the sampling period, and individuals with a lower percentage of live foliated crown (PLFC) died faster. Tree PLFC was strongly correlated with subsurface salinity and needle ion contents. Total NSC concentrations in trees declined remarkably with crown decline, and reached extremely low levels at tree death (2.4% and 1.6% in leaves and branches, respectively, and 0.4% in stems and roots). Starch in all tissues was almost completely consumed, while sugars remained at a homeostatic level in foliage. The decreasing NSC with closer proximity to death and near zero starch at death are evidences that carbon starvation occurred during Sitka-spruce mortality during seawater exposure. Our results highlight the importance of carbon storage as an indicator of tree mortality risks under seawater exposure.

Decline in carbohydrate storage is strongly associated with progressive mortality of trees under frequent seawater exposure, and starch is almost completely consumed at crown death.     

Benefits of aerial 1080 possum control to tree fuchsia in the Tararua Range, Wellington

The Department of Conservation established tree fuchsia (Fuchsia excorticata) monitoring in the Tararua Range in 1994 to determine the effectiveness of large-scale (66 000 ha) possum control for protecting fuchsia. We present results from data collected from 39 permanent plots on fuchsia tree stem survival, growth, and canopy condition between 1994 and 2004 using standard permanent plot and foliar assessment methods. Plots were established in four areas where possums were controlled or treated by aerial application of sodium monofluoroacetate (1080) poison, and in one untreated area. More fuchsia stems died in the untreated area (29.8%) than in the treated areas combined (mean of 7%) over the duration of the study. Stem mortality was offset by a mean 3% (+ 1.1% SEM) increase in fuchsia basal area in the treated areas, whereas basal area declined by 15% in the untreated area. Stem mortality occurred largely in smaller size-classes (<21 cm diameter) in all areas. Mean foliar cover showed a greater decline (42%) in the untreated area than in the treated areas (range 0 to 26%). Within two of the four treated areas, foliar cover declined as the interval between possum control operations lengthened. Our results clearly show that the conservation goal of preventing 25% mortality of tree fuchsia between 1994 and 2004 was successfully achieved in upland possum control areas.     

The impact of defoliation on the foliar chemistry of southern rātā (

Brushtail possums (Trichosurus vulpecula) tend to eat young canopy foliage in southern rätä (Metrosideros umbellata), and browsing tends to be concentrated on only a few trees. Samples collected as part of an artificial defoliation experiment were analysed for NPK (nitrogen, phosphorus, and potassium), carbohydrate, and polyphenolic concentrations to determine whether changes in foliar chemistry associated with defoliation provide an explanation for these patterns of browsing. In non-defoliated trees, NPK concentrations were highest in young leaves and declined with age, while concentrations of carbohydrates and polyphenolics were independent of leaf age. Nitrogen, phosphorus and polyphenolic concentrations were consistently higher in canopy (sun) versus subcanopy (shade) foliage regardless of leaf age, a trend that was reversed for potassium. Partial (50%) defoliation had little effect on foliar chemistry, regardless of its timing. Total (100%) defoliation stimulated NPK concentrations and depressed condensed tannin concentrations of new foliage produced by the surviving shoots. These results suggest that brushtail possums may focus their feeding on only a few trees because of nutritional changes to leaves as a result of browsing.     

Direct and indirect effects of marsupial browsing on a foundation tree species

Plant‐mediated indirect effects can be important ecological drivers in plant communities, especially in systems where extended genetic effects of foundation species can shape communities and influence ecosystem dynamics. Here we investigate the direct and indirect effects of uncontrolled browsing by marsupial herbivores including the common brushtail possum Trichosurus vulpecula, Bennetts wallaby Macropus rufogriseus and the red‐bellied pademelon Thylogale billardierii, in a Eucalyptus system known to have extended community and ecosystem genetic effects. In a common garden trial containing 525 full‐sib families from an incomplete diallel crossing program located in northeastern Tasmania, Australia, we assessed the genetic basis to herbivore preferences, the impact of a single and repeated marsupial browsing event on tree fitness and morphological traits and the associated indirect plant‐mediated effects on a subsequent herbivore, autumn gum moth Mnesampela privata. Marsupial browsing was not influenced by plant genetics, but spatial components instead affected the pattern of damage across the trial. Marsupial browsing had significant impacts on tree development, morphology and survival, resulting in reductions in survival, height and basal area, an increase proportion in multiple stems, delays in flowering as well as delays in phase change from juvenile to adult foliage. Fitness impacts were minimal in response to a once‐off browsing event, but effects were exacerbated when trees suffered repeated browsing. We demonstrate clear plant‐mediated indirect effects of marsupial browsing on subsequent tree use by an invertebrate herbivore, through induced changes in plant morphology. Such indirect effects have the potential to influence biotic community structure on a foundation species host‐plant, and the evolutionary interactions that occur between organisms and the host‐plant themselves.     

Comparative dietary ecology of two congeneric marsupial folivores

Knowledge of species diets is critical to assisting our understanding of their ecology. Using microhistological analysis of faecal samples, we described and compared the diets of sympatrically occurring folivorous congenerics, common and mountain brushtail possums (Trichosurus vulpecula and T. cunninghami, respectively). Throughout the 28‐month study period, common brushtails relied heavily on eucalypt foliage, particularly very young leaves, which is consistent with data from captive studies on their dietary physiology. In contrast, eucalypt foliage formed only a small part of the diet of mountain brushtails, which instead relied heavily on silver wattle foliage. The mean number of plant groups per faecal sample was significantly greater for common brushtails than mountain brushtails. No significant differences in diet between male and female mountain brushtails were detected. However, intraspecific differences in diet occurred for common brushtails: the diet of females included significantly less eucalypt foliage and significantly more foliage of the exotic, tree lucerne, than that of males during the Wet Season (April–November), but not during the Dry Season (December–March). Diets varied temporally for both species, with some individuals feeding on seasonally available resources. The diets described for common and mountain brushtails are consistent with those of a dry‐adapted and mesic‐adapted species, respectively. We discuss how our results contribute to our understanding of the evolutionary history of both study species, and more broadly the family Phalangeridae to which they belong. We also consider the diet of our study species in the context of recent advances in our understanding of interactions between plants that produce secondary metabolites, and mammals specialized to feed on them.     

Predicting Summer Site Occupancy for an Invasive Species,the Common Brushtail Possum (Trichosurus vulpecula), in an Urban Environment

Invasive species are often favoured in fragmented, highly-modified, human-dominated landscapes such as urban areas. Because successful invasive urban adapters can occupy habitat that is quite different from that in their original range, effective management programmes for invasive species in urban areas require an understanding of distribution, habitat and resource requirements at a local scale that is tailored to the fine-scale heterogeneity typical of urban landscapes. The common brushtail possum (Trichosurus vulpecula) is one of New Zealand’s most destructive invasive pest species. As brushtail possums traditionally occupy forest habitat, control in New Zealand has focussed on rural and forest habitats, and forest fragments in cities. However, as successful urban adapters, possums may be occupying a wider range of habitats. Here we use site occupancy methods to determine the distribution of brushtail possums across five distinguishable urban habitat types during summer, which is when possums have the greatest impacts on breeding birds. We collected data on possum presence/absence and habitat characteristics, including possible sources of supplementary food (fruit trees, vegetable gardens, compost heaps), and the availability of forest fragments from 150 survey locations. Predictive distribution models constructed using the programme PRESENCE revealed that while occupancy rates were highest in forest fragments, possums were still present across a large proportion of residential habitat with occupancy decreasing as housing density increased and green cover decreased. The presence of supplementary food sources was important in predicting possum occupancy, which may reflect the high nutritional value of these food types. Additionally, occupancy decreased as the proportion of forest fragment decreased, indicating the importance of forest fragments in determining possum distribution. Control operations to protect native birds from possum predation in cities should include well-vegetated residential areas; these modified habitats not only support possums but provide a source for reinvasion of fragments.     

Microbat responses to forest decline

Tree declines have been recorded across forests and woodlands on most continents, causing tree mortality over thousands of square kilometres, yet the impact of tree declines upon mammals have only rarely been quantified. Once the dominant tree over the western parts of the Swan Coastal Plain in Western Australia, tuart (Eucalyptus gomphocephala) forest has been reduced to less than a third of its former range through clearing for agriculture and urban development. Additionally, over the last 30 years, the remnant population has been heavily impacted by a decline that has an unknown cause, but is likely related to a root pathogen coupled with abiotic factors (reduced rainfall, increased salinity and elevated temperatures). Tuart decline is evident as marked canopy dieback, replacement with epicormic growth and increasing bare branches, while leaf litter is lost from the tree surrounds. We examined the effect of tuart decline and other vegetation measures upon bat activity using auditory monitoring. Vegetation structure was correlated with Vespertilionidae bat activity. Falsistrellus mackenziei were more likely to forage around healthy canopies (activity positively correlated with tuart crown density and negatively correlated with tuart crown dieback). By contrast, the other three taxa were more often encountered in declining rather than healthy tuart sites. Chalinolobus gouldii was positively associated with tuart crown dieback. Activity of Vespadelus regulus and Nyctophilus spp. (species not distinguishable from their calls) were significantly positively correlated with an open tall canopy (positively with cover of plants >10 m tall and negatively with overall canopy cover density). There were no vegetation measurements that were strong predictors of activity of two Molossidae species (Ozimops kitcheneri and Austronomus australis), which intercept insects above the forest canopy. This study clearly reveals different factors influencing the activity of bat taxa, which are likely related to where they feed and their manoeuvrability around tree canopies.