Queensland northern quolls are not immune to cane toad toxin

The release of the highly toxic South American cane toad (Bufo marinus) to the toad-free Australian continent in 1935, and their subsequent rapid spread over large areas of tropical Australia, has resulted in a massive decline of predators such as yellow-spotted goannas (Varanus panoptes) and northern quolls (Dasyurus hallucatus). In spite of dramatic declines of northern quoll populations in the Northern Territory, a few populations still persist in areas of Queensland where northern quolls have co-existed with toads for several decades

Analysis of trade-offs between biodiversity, carbon farming and agricultural development in northern Australia reveals the benefits of strategic planning

Australia's northern savannas are one of the few remaining large and mostly intact natural areas on Earth. However, their biodiversity and ecosystem values could be threatened if proposed agricultural development proceeds. Through land-use change scenarios, we explored trade-offs and synergies among biodiversity conservation, carbon farming and agriculture production in northern Australia. We found that if all suitable soils were converted to agriculture, habitat at unique recorded locations of three species would disappear and 40 species and vegetation communities could lose more than 50% of their current distributions. Yet, strategically considering agriculture and biodiversity outcomes leads to zoning options that could yield >56,000 km2 of agricultural development with a significantly lower impact on biodiversity values and carbon farming. Our analysis provides a template for policy-makers and planners to identify areas of conflict between competing land-uses, places to protect in advance of impacts, and planning options that balance agricultural and conservation needs.

Landscape pattern, countryside heterogeneity and bird conservation in agricultural environments

This study confirms the valuable contribution that agricultural landscapes make to bird conservation in Australia. While native vegetation is critical to conservation efforts, careful management of production land-use types may provide additional benefits. Results show that productive farm enterprises can make real contributions to the success of broader conservation goals.

Ecology and conservation of insectivorous bats in rural landscapes

Throughout the world, the increasing use of land for agriculture has been associated with extensive loss and fragmentation of natural habitats and, frequently, the degradation of remaining habitats. The effects of such habitat changes have been well studied for some faunal groups, but little is known of their consequences for bats. The aim of this study was to investigate the ecology and conservation of an assemblage of insectivorous bats in a rural landscape, with particular focus on their foraging and roosting requirements. This increased knowledge will, hopefully, assist the formulation of policy and management decisions to ensure the long-term survival of bats in these altered environments. The distribution and abundance of insectivorous bats in the Northern Plains of Victoria was investigated to determine the impacts of land-use change and to identify factors influencing the distribution of bats in rural landscapes. Thirteen species of insectivorous bats were recorded across the region by sampling at 184 sites. Two species were rare, but the remaining 11 species were widespread and occurred in all types of remnant wooded vegetation, ranging from large blocks (≥200 ha) to small isolated remnants (≤5 ha) and scattered trees in cleared farm paddocks. There was no significant difference between remnant types in the relative abundance of bat species, in species richness, or in the composition of bat assemblages at study sites. In a subsequent study, no difference in the activity levels of bats was found between remnants with different tree densities, ranging from densely-vegetated blocks to single paddock trees. However, sites in open paddocks devoid of trees differed significantly from all types of wooded remnants and had significantly lower levels of bat activity and a different species composition. In highly cleared and modified landscapes, all native vegetation has value to bats, even the smallest remnant, roadside and single paddock tree. Roost sites are a key habitat requirement for bats and may be a limiting resource in highly modified environments. Two species, the lesser long-eared bat Nyctophilus geoffroyi and Gould's wattled bat Chalinolobus gouldii, were investigated as a basis for understanding the capacity of bats to survive in agricultural landscapes. These species have different wing morphologies, which may be influential in how they use the landscape, and anecdotal evidence suggested differences in their roosting ecology. Roosting ecology was examined using radio-tracking to locate 376 roosts in two study areas with contrasting tree cover in northern Victoria. Both species were highly selective in the location of their roosts in the landscape, in roost-site selection and in roosting behaviour, and responded differently to differing levels of availability of roosts. The Barmah-Picola study area incorporated remnant vegetation in farmland and an adjacent extensive floodplain forest (Barmah forest). Male N. geojfroyi roosted predominantly within 3 km of their foraging areas in remnants in farmland. However, most female N. geoffroyi, and both sexes of C. gouldii, roosted in Barmah forest up to 12 km from their foraging areas in farmland remnants. These distances were greater than previously recorded for these species and further than predicted by wing morphology. In contrast, in the second study area (Naring) where only small remnants of wooded vegetation remain in farmland, individuals of both species moved significantly shorter distances between roost sites and foraging areas. There were marked inter- and intra-specific differences in the roosts selected. C. gouldii used similar types of roosts in both areas - predominantly dead spouts in large, live trees. N. geoffroyi used a broader range of roost types, especially in the farmland environment. Roosts were typically under bark and in fissures, with males in particular also using anthropogenic structures. A strong preference was shown by both sexes for roosts in dead trees, and entrance dimensions of roosts were consistently narrow (2.5 cm). In Barmah forest, maternity roosts used by N. geoffroyi were predominantly in narrow fissures in large-diameter, dead trees, while at Naring maternity roosts were also found under bark, in buildings, and in small-diameter, live and dead trees. The number of roost trees that are required for an individual or colony is influenced by the frequency with which bats move between roosts, the proportion of roosts that are re-used, the distance between consecutive roosts, and the size of roosting colonies. Both species roosted in small colonies and regularly shifted roost sites within a discrete roost area. These behavioural traits suggest that a high density of roost sites is required. There were marked differences in these aspects of behaviour between individuals roosting in Barmah forest and in the fragmented rural landscape. At Naring, N. geqffroyi remained in roosts for longer periods and moved greater distances between consecutive roosts than in Barmah forest. In contrast, C. gouldii used a smaller pool of roosts in the farmland environment by re-using roosts more frequently. Within Barmah forest, there is an extensive area of forest but the density of hollow-bearing trees is reduced due to timber harvesting and silvicultural practices. Individuals were selective in the location of their roosting areas, with both species selecting parts of the forest that contained higher densities of their preferred roost trees than was generally available in the forest. In contrast, in farmland at Naring, where there were small pockets of remnant vegetation with high densities of potential roost sites surrounded by cleared paddocks with few roosting opportunities, little selection was shown. This suggests that in Barmah forest the density of trees with potential roosts is lower than optimal, while in farmland roosting resources may be adequate in woodland remnants, but limiting at the landscape scale since more than 95% of the landscape now provides no roosting opportunities. Insectivorous bats appear to be less severely affected than some other faunal groups by habitat fragmentation and land-use change. A highly developed capacity for flight, the spatial scale at which they move and their ability to cross open areas means that they can regularly move among multiple landscape elements, rather than depend on single remnants for all their resources. In addition, bats forage and roost mainly at elevated levels in trees and so are less sensitive to degradation of wooded habitats at ground level. Although seemingly resilient to habitat fragmentation, insectivorous bats are fundamentally dependent on trees for roosting and foraging, and so are vulnerable to habitat loss and ongoing rural tree decline. Protection of the remaining large old trees and measures to ensure regeneration to provide ongoing replacement of hollow-bearing trees through time are critical to ensure the long-term conservation of bats in rural landscapes.

Foraging ecology of ground-feeding woodland birds in temperate woodlands of Southern Australia

Ground-foraging birds of temperate woodlands of southern Australia are prominent among bird species considered to be susceptible to population decline. We examined the foraging ecology, including foraging substrates, actions and heights, of 13 ground-foraging species at four woodland sites in northern Victoria. Nine species are regarded as declining in southern Australia and four are considered common. Ten foraging substrates were identified, of which leaf-litter (54% of observations) and bare ground (17%) were most frequently used. In all woodland sites, litter was used more frequently than expected from its proportional cover. Bare ground was frequently used as a substrate by individual species, and fallen timber and grass were important for some species. Most species were generalists in their use of substrates. Six foraging actions were observed, of which gleaning and pouncing were most frequently recorded. All species foraged close to the ground and four foraged almost entirely at ground level. For pouncing birds, dead branches and fallen timber were the most important launch substrates from which pouncing actions were initiated. Eight of the 13 species differed in some aspect of their foraging ecology between woodland sites, especially in relation to the use of substrates (seven species). Fewer species (four) displayed differences in foraging ecology between seasons, with the greatest seasonal variation being in use of foraging substrates (three species). Overall, no significant differences were evident in the foraging ecologies of common and declining species. Species in both groups encompassed a wide range of foraging behaviours. Owing to this range in foraging ecology, the conservation of diverse assemblages of ground-foraging birds requires the maintenance of heterogeneous ground layers and careful management of disturbance processes.

Challenges for native grassland conservation on Victoria's Northern Plains

Discusses some of the challenges faced in attempting to retain and conserve grasslands on Victoria's Northern Plains over the past decade. The development of a strategic vision and directions and opportunities for the future are highlighted.

Conservation ecology and breeding biology of the white-browed treecreeper, Climacteris affinis

The White-browed Treecreeper Climacteris affinis is one of many woodland-dependent birds that are at risk from the encroachment of human-dominated land-uses into natural landscapes. The White-browed Treecreeper inhabits semi-arid woodlands in north-west Victoria, Australia, a vegetation community that has undergone extreme modification in the last century due to the expansion of agriculture in the region. Extant woodlands represent only 10% of the original woodland cover in the region, and are highly fragmented and disturbed in many districts. Thus, the survival of the White-browed Treecreeper may depend on active management. However, current knowledge of the ecology and biology of this species is virtually non-existent, and inadequate for informed and effective conservation actions. The aim of this thesis is to redress this situation and provide the ecological basis for sound conservation management of the species. The thesis consists of two parts: an investigation of habitat use at three spatial scales and a study of the social organization, nesting requirements, breeding behaviour and reproductive success of a population of White-browed Treecreepers. Fifty-six patches of remnant woodland in north-west Victoria were surveyed to determine the factors affecting the occurrence of the White-browed Treecreeper at the regional scale. It was detected in 16 patches, and was largely confined to two core districts - Yarrara and, Wyperfeld (Pine Plains). The floristic composition of the dominant tree species was an important determinant of patch occupancy, with the results providing quantitative support for the previously suspected affinity for Belah Casuarina pauper and Slender Cypress-pine Callitris gracilis — Buloke Allocasuarina luehmannii woodlands. However, the absence of the White-browed Treecreeper from several districts was due to factors other than a lack of appropriate habitat. Demographic isolation - the distance from the focal patch to the nearest population of the White-browed Treecreeper - was the most important variable in explaining variation in patch occupancy. Patches isolated from other treecreeper populations by more than 8.3 km in landscapes of non-preferred native vegetation, and 3 km in agricultural landscapes, were unlikely to support the White-browed Treecreeper. The impact of habitat loss and fragmentation on the capacity of individuals to move through the landscape (i.e. functional connectivity) is considered in relation to disruption to dispersal and migration, and the potential collapse of local metapopulations. Habitat use was then examined in a network of patches and linear strips of Belah woodland embedded in a predominantly cultivated landscape. A minimum area of 18.5 ha of Belah woodland was identified as the most important criterion for patch occupancy at the local scale. This landscape appeared to be permeable to movement by the White-browed Treecreeper, facilitated by the extensive network of linear habitat, and clusters of small to medium fragments. The third scale of habitat use investigated the frequency of use of 1-ha plots within tracts of occupied woodland. It is important to discriminate between habitat traits that operate at the population level, and those that act as proximate cues for habitat selection by individuals. Woodlands that have high tree density, extensive cover of low-stature shrubs, abundant lichen, a complex vertical structure, and relatively low cover of grass and herbs are likely to support larger populations of the White-browed Treecreeper. However, individuals appeared to be using tree dominance (positive) and tall shrub cover (negative) as proximate environmental stimuli for habitat selectivity. A relatively high cover of ground lichen, which probably reflects a ground layer with low disturbance and high structural complexity, was also a reliable indicator of habitat use. Predictive models were developed which could be used to plan vegetation management to enhance habitat for the White-browed Treecreeper. The results of the regional, landscape and patch-scale investigations emphasise that factors operating at multiple spatial scales influence the suitability of remnant vegetation as habitat for the White-browed Treecreeper. The White-browed Treecreeper is typical of many small Australian passerines in that it has high annual survival, small clutches, a long breeding season, multiple broods and relatively low reproductive rates. Reproductive effort is adjusted through the number of clutches laid rather than clutch size. They occupy relatively large, all-purpose territories throughout the year. However, unlike many group territorial birds, territory size was not related to the number of occupants. The White-browed Treecreeper nests in tree hollows. They select hollows with a southerly orientation where possible, and prefer hollows that were higher from the ground. At Yarrara, there was considerable spatial variation in hollow abundance that, in concert with territorial constraints, restricted the actual availability of hollows to less than the absolute abundance of hollows. Thus, the availability of suitable hollows may limit reproductive productivity in some territories, although the magnitude of this constraint on overall population growth is predicted to be small. However, lack of recruitment of hollow-bearing trees would increase the potential for hollow availability to limit population growth. This prospect is particularly relevant in grazed remnants and those outside the reserve system. Facultative cooperative breeding was confirmed, with groups formed through male philopatry. Consequently, natal dispersal is female-biased, although there was no skew in the sex ratio of the fledglings or the general adult population. Helpers were observed performing all activities associated with parenting except copulation and brooding. Cooperatively breeding groups enjoyed higher fledgling productivity than simple pairs, after statistically accounting for territory and parental quality. However, the difference reflected increased productivity in the 1999-breeding season only, when climatic conditions were more favourable than in 1998. Breeding commenced earlier in 1999, and all breeding units were more likely to attempt a second brood. However, only breeders with helpers were successful in fledging second brood young, and it was this difference that accounted for the overall discrepancy in productivity. The key mechanism for increased success in cooperative groups was a reduction hi the interval between first and second broods, facilitated by compensatory reductions in the level of care to the first brood. Thus, females with helpers probably achieved significant energetic savings during this period, which enabled them to re-lay sooner. Furthermore, they were able to recommence nesting when the fledglings from the first brood were younger because there were more adults to feed the dependent juveniles. The current utility, and possible evolutionary pathways, of cooperative breeding is examined from the perspective of both breeders and helpers. Breeders benefit through enhanced fledgling productivity in good breeding conditions and a reduction in the burden of parental care, which may impart significant energetic savings. Further, breeders may facilitate philopatry as a means for ensuring a minimum level of reproductive success. Helpers benefit through an increase in their inclusive fitness in the absence of opportunities for independent breeding (i.e. ecological constraints) and access to breeding vacancies in the natal or adjacent territories (i.e. benefits of philopatry). However, the majority of breeding unit-years comprised unassisted breeders, which suggests that pairs are selectively favoured under certain environmental or demographic conditions.

Flowering ecology of a Box-Ironbark Eucalyptus community

Box-Ironbark forests occur on the inland hills of the Great Dividing Range in Australia, from western Victoria to southern Queensland. These dry, open forests are characteristically dominated by Eucalyptus species such as Red Ironbark E. tricarpa, Mugga Ironbark E. sideroxylon and Grey Box E. microcarpa. Within these forests, several Eucalyptus species are a major source of nectar for the blossom-feeding birds and marsupials that form a distinctive component of the fauna. In Victoria, approximately 83% of the original pre - European forests of the Box-Ironbark region have been cleared, and the remaining fragmented forests have been heavily exploited for gold and timber. This exploitation has lead to a change in the structure of these forests, from one dominated by large 80-100 cm diameter, widely -spaced trees to mostly small (≥40 cm DBH), more densely - spaced trees. This thesis examines the flowering ecology of seven Eucalyptus species within a Box-Ironbark community. These species are characteristic of Victorian Box-Ironbark forests; River Red Gum E. camaldulensis, Yellow Gum E. leucoxylon, Red Stringybark E. macrorhyncha, Yellow Box E. melliodora, Grey Box E. microcarpa, Red Box E. polyanthemos and Red Ironbark E. tricarpa. Specifically, the topics examined in this thesis are: (1) the floral character traits of species, and the extent to which these traits can be associated with syndromes of bird or insect pollination; (2) the timing, frequency, duration, intensity, and synchrony of flowering of populations and individual trees; (3) the factors that may explain variation in flowering patterns of individual trees through examination of the relationships between flowering and tree-specific factors of individually marked trees; (4) the influence of tree size on the flowering patterns of individually marked trees, and (5) the spatial and temporal distribution of the floral resources of a dominant species, E. tricarpa. The results are discussed in relation to the evolutionary processes that may have lead to the flowering patterns, and the likely effects of these flowering patterns on blossom-feeding fauna of the Box-Ironbark region. Flowering observations were made for approximately 100 individually marked trees for each species (a total of 754 trees). The flower cover of each tree was assessed at a mean interval of 22 (+ 0.6) days for three years; 1997, 1998 and 1999. The seven species of eucalypt each had characteristic flowering seasons, the timing of which was similar each year. In particular, the timing of peak flowering intensity was consistent between years. Other spatial and temporal aspects of flowering patterns for each species, including the percentage of trees that flowered, frequency of flowering, intensity of flowering and duration of flowering, displayed significant variation between years, between forest stands (sites) and between individual trees within sites. All seven species displayed similar trends in flowering phenology over the study, such that 1997 was a relatively 'poor' flowering year, 1998 a 'good' year and 1999 an 'average' year in this study area. The floral character traits and flowering seasons of the seven Eucalyptus species suggest that each species has traits that can be broadly associated with particular pollinator types. Differences between species in floral traits were most apparent between 'summer' and 'winter' flowering species. Winter - flowering species displayed pollination syndromes associated with bird pollination and summer -flowering species displayed syndromes more associated with insect pollination. Winter - flowering E. tricarpa and E. leucoxylon flowers, for example, were significantly larger, and contained significantly greater volumes of nectar, than those of the summer flowering species, such as E. camaldulensis and E. melliodom. An examination of environmental and tree-specific factors was undertaken to investigate relationships between flowering patterns of individually marked trees of E. microcarpa and E. tricarpa and a range of measures that may influence the observed patterns. A positive association with tree-size was the most consistent explanatory variable for variation between trees in the frequency and intensity of flowering. Competition from near-neighbours, tree health and the number of shrubs within the canopy area were also explanatory variables. The relationship between tree size and flowering phenology was further examined by using the marked trees of all seven species, selected to represent five size-classes. Larger trees (≥40 cm DBH) flowered more frequently, more intensely, and for a greater duration than smaller trees. Larger trees provide more abundant floral resources than smaller trees because they have more flowers per unit area of canopy, they have larger canopies in which more flowers can be supported, and they provide a greater abundance of floral resources over the duration of the flowering season. Heterogeneity in the distribution of floral resources was further highlighted by the study of flowering patterns of E. tricarpa at several spatial and temporal scales. A total of approximately 5,500 trees of different size classes were sampled for flower cover along transects in major forest blocks at each of five sample dates. The abundance of flowers varied between forest blocks, between transects and among tree size - classes. Nectar volumes in flowers of E. tricarpa were sampled. The volume of nectar varied significantly among flowers, between trees, and between forest stands. Mean nectar volume per flower was similar on each sample date. The study of large numbers of individual trees for each of seven species was useful in obtaining quantitative data on flowering patterns of species' populations and individual trees. The timing of flowering for a species is likely to be a result of evolutionary selective forces tempered by environmental conditions. The seven species' populations showed a similar pattern in the frequency and intensity of flowering between years (e.g. 1998 was a 'good' year for most species) suggesting that there is some underlying environmental influence acting on these aspects of flowering. For individual trees, the timing of flowering may be influenced by tree-specific factors that affect the ability of each tree to access soil moisture and nutrients. In turn, local weather patterns, edaphic and biotic associations are likely to influence the available soil moisture. The relationships between the timing of flowering and environmental conditions are likely to be complex. There was no evidence that competition for pollinators has a strong selective influence on the timing of flowering. However, as there is year-round flowering in this community, particular types of pollinators may be differentiated along a temporal gradient (e.g. insects in summer, birds in winter). This type of differentiation may have resulted in the co-evolution of floral traits and pollinator types, with flowers displaying adaptations that match the morphologies and energy requirements of the most abundant pollinators in any particular season. Spatial variation in flowering patterns was evident at several levels. This is likely to occur because of variation in climate, weather patterns, soil types, degrees of disturbance and biotic associations, which vary across the Box-Ironbark region. There was no consistency among sites between years in flowering patterns suggesting that factors affecting flowering at this level are complex. Blossom-feeding animals are confronted with a highly spatially and temporally patchy resource. This patchiness has been increased with human exploitation of these forests leading to a much greater abundance of small trees and fewer large trees. Blossom-feeding birds are likely to respond to this variation in different ways, depending upon diet-breadth, mobility and morphological and behavioural characteristics. Future conservation of the blossom-feeding fauna of Box-Ironbark forests would benefit from the retention of a greater number of large trees, the protection and enhancement of existing remnants, and revegetation with key species, such as E. leucoxylon, E. microcarpa and E. tricarpa. The selective clearing of summer flowering species, which occur on the more fertile areas, may have negatively affected the year-round abundance and distribution of floral resources. The unpredictability of the spatial distribution of flowering patches within the region means that all remnants are likely to be important foraging areas in some years.

Ecology of Powerful Owls (Ninox strenua) in contrasting habitats of the Yarra Valley Corridor, Victoria, Australia

In this research I investigated ecological attributes of Powerful Owls (Ninox strenua) in a continuum of habitats throughout the Yarra Valley corridor of Victoria, Australia. These habitats ranged from a highly urbanized parkland (the Yarra Valley Metropolitan Park) to a relatively undisturbed closed forest (Toolangi State Forest). Different aspects of the owls' ecology were investigated at six sites to determine whether their behaviour changed when they occupied habitats with different levels of urbanization and disturbance. The ecological attributes investigated were habitat utilization and habitat requirements (for both roosting and nesting), adult behaviour (through radio-tracking), juvenile behaviour and dispersal (through radio tracking), diet (through analysing regurgitated food pellets) and breeding success rates. A number of methods were used to capture adult Powerful Owls. These are described and their effectiveness discussed. The types of radio-transmitters and colour bands used for identification of owls are also described. The results showed that Powerful Owls are present and successfully breed in urban and suburban areas and that they can tolerate moderate levels of disturbance. However, Powerful Owls do require sites with high prey densities, roost trees and trees with suitable breeding hollows. In comparison with Powerful Owls living elsewhere in forests, the urban owls displayed higher tolerance levels to disturbance and were less selective in terms of habitat usage and diet. Home range sizes of urban Powerful Owls also appeared much smaller than those of the forest-dwelling Powerful Owls. This is probably due to the high prey densities in the urban areas. The ecology of the Powerful Owl is compared with that of two owl species from North America, the Northern Spotted Owl (Strix occidentalis caurind) and the Great Horned Owl (Bubo virginianus). In particular, I compared the similarities and differences in habitat requirements and breeding successes in different habitats for the three species. Overall, it would appear that urban areas can support Powerful Owls providing some old-growth trees are maintained to provide nest hollows. Implications for the long-term management of Powerful Owls in urban areas are also discussed.

Ecology of mistletoe parasitism in rural landscapes

This study examined the distribution of native mistletoes in agricultural landscapes. Mistletoes occur in all types of wooded habitat, and provide resources for many species. Landscape structure, particularly the overall extent of tree cover, is vital for conserving mistletoes. Their future status depends on effective management across different land tenures.

Southern Boobook Ninox novaeseelandiae feeding on the Fungus Pislithus albus in North Queensland

This note describes an observation of a Southern Boobook Ninox ovaeseelandiae pecking at the fruiting body of a terrestrial fungus in northern Queensland.

Ecology / economy

This work speaks to ideas of nurturing and embodiment. In one half of the screen we see a father massaging his child with coconut oil, a common practice in Fijian families, and an early investment in the health and spiritual wellbeing of the child. In the next frame we see the other end of the life cycle and an imagined re-enactment of the folding of the Fijian flag, as in the American military tradition for fallen service people. Here Bolatagici refers to the number of Fijians fighting for foreign armies, including the United States.

Increased mortality of naive varanid lizards after the invasion of non-native can toads (bufo marinus)

Exotic animal and plant species introduced into the Australian continent often imparted catastrophic effects on the indigenous fauna and flora. Proponents of biological control introduced the South American Cane Toad (Bufo marinus) into the sugar cane fields of Queensland in 1935. The Cane Toad is one of the most toxic bufonids and when seized by naive Australian predators, the toxin usually kills the attacker. One group of Australian squamate reptiles that are very susceptible to Cane Toad toxins is varanid lizards. Prior to Cane Toad invasion of our study area, the Adelaide River floodplain of the Northern Territory of Australia, annual mortality of adult male radio-tagged yellow-spotted Goannas (Varanus panoptes) was very low. After the arrival of toads in October 2005, all radio-tracked goannas were found dead in August 2006, most likely attempting to feed on the toads. Our results suggest that invasive Cane Toads place naive adult male Yellow-spotted Goannas at risk of possibly >90% mortality. This increase in mortality could reduce the genetic diversity and hamper long-term survival of these large carnivorous lizards.