To read the full-text of this research, you can request a copy directly from the authors.
When native herbivores are enclosed in fenced reserves without predators or dispersal options then overgrazing can occur, leading to damage to vegetation and co‐occurring fauna species. One‐way gates that allow medium‐sized herbivores to exit fenced reserves may be an effective management tool to address overabundance or facilitate population expansion. We tested the use of one‐way gates to facilitate the movement of the reintroduced burrowing bettong (Bettongia lesueur) from inside to outside a fenced reserve in arid South Australia. One‐way gates were installed in the exterior fence of the reserve and assessed using remote motion‐sensor cameras. The influence of gate position (dune, swale or corner) and provision of food were assessed in relation to gate visits and exits. Animals were trapped inside and outside the gates to determine any population bias in gate exits. Baited gates recorded significantly more exits than unbaited gates and dune gates had higher exit rates than interdunal swale gates. When gates were unbaited, those installed in corners of the reserve showed significantly higher visitation by bettongs and a non‐significant trend towards more exits compared to gates placed in straight sections of fence along dunes or swales. There was no sex or age bias of burrowing bettongs using the gates and bettongs travelled between 75 m and 1535 m from their warrens to use the gates. No non‐target species gained access to the reserve through the one‐way gates and only two non‐target animals used the gates to exit the reserve confirming gate specificity for bettongs. During the same period, 96 burrowing bettongs exited the reserve through the one‐way gates. One‐way gates may be a management strategy for facilitating passive movement of medium‐sized herbivores outside of fenced reserves for the purposes of reducing overpopulation or facilitating population expansion outside reserves.
To read the full-text of this research, you can request a copy directly from the authors.
... Similarly, bump gates in VCFs have proved successful in allowing free movement of stock whilst restricting wildlife movement (see Ver-Cauteren et al., 2009;Barasona et al., 2013). One-way gates such as those used for burrowing bettongs (Bettongia lesueur) (Butler, Paton, & Moseby, 2019), while worth mentioning, are not a true mitigation of this impact. One-way gates do not allow the bidirectional movement of species and therefore do not fulfil the requirements outlined in our definition of barrier to movement. ...
... As a flow-on effect to barrier to movement, similar mitigation strategies to those mentioned above can be utilised. Species-specific gates and gaps can be used to mitigate overpopulation of some species within fences, but notably for this effect, one-way gates (Butler et al., 2019) could be utilised as well. Overpopulation may also be mitigated through active population management, for example the relocation of individuals to other suitable locations (Treydte et al., 2001), contraception (e.g. ...
... One-way gates have been used successfully in Australia (Crisp & Moseby, 2010;Butler et al., 2019) and worldwide (Schumann et al., 2006) to help mitigate over-abundance and the dispersal of individuals to outside populations whilst still excluding the target species, although this would not alleviate genetic pressures on animals within fences (Dickman, 2012). As previously stated, the optimal scenario would be fence gaps or gates designed to allow non-targets free bidirectional movement, while effectively restricting the target species. ...
Exclusion fencing is a common tool used to mitigate a variety of unwanted economic losses caused by problematic wildlife. While the potential for agricultural, ecological and economic benefits of pest animal exclusion are often apparent, what is less clear are the costs and benefits to sympatric non‐target wildlife. This review examines the use of exclusion fencing in a variety of situations around the world to elucidate the potential outcomes of such fencing for wildlife and apply this knowledge to the recent uptake of exclusion fencing on livestock properties in the Australian rangelands. In Australia, exclusion fences are used to eliminate dingo (Canis familiaris dingo ) predation on livestock, prevent crop‐raiding by emus (Dromaius novaehollandiae ), and enable greater control over total grazing pressure through the reduction of macropods (Macropodidae) and feral goats (Capra hircus ). A total of 208 journal articles were examined for location, a broad grouping of fence type, and the reported effects the fence was having on the study species. We found 51% of the literature solely discusses intended fencing effects, 42% discusses unintended effects, and only 7% considers both. Africa has the highest proportion of unintended effects literature (52.0%) and Australia has the largest proportion of literature on intended effects (34.2%). We highlight the potential for exclusion fencing to have positive effects on some species and negative effects on others (such as predator exclusion fencing posing a barrier to migration of other species), which remain largely unaddressed in current exclusion fencing systems. From this review we were able to identify where and how mitigation strategies have been successfully used in the past. Harnessing the potential benefits of exclusion fencing while avoiding the otherwise likely costs to both target and non‐target species will require more careful consideration than this issue has previously been afforded.
... Closed populations, such as those found in fenced reserves or on islands, can be particularly resource-limited as natural processes that regulate populations in response to resource availability, such as compensatory dispersal into surrounding areas, are unable to occur. The removal of predators and competitors, both native and introduced, can further increase the risk of overpopulation due to a reduction in the incidence of density-dependent mortality (Butler et al. 2019). Occasionally, translocations to closed environments have resulted in local extinctions due to resource depletion (Saifuddin et al. 2017). ...
... Macropod overpopulation in fenced reserves is a widespread issue in Australia, with government departments and organisations implementing control programs such as fertility control and one-way gates to lower population size (Willers et al. 2015;Butler et al. 2019;Moyses et al. 2020). At Arid Recovery in South Australia, Boodie (Burrowing Bettong; Bettongia leseuer) populations have been observed increasing within a fenced environment until overabundant, resulting in vegetation damage (Linley et al. 2017;Moseby et al. 2018 Ecosystems comprise many species with spatially and temporally dynamic relationships. ...
Translocations to closed systems such as fenced reserves are commonly used for conservation of threatened fauna species worldwide; however, resources are limited in these areas, and natural processes that regulate populations in response to resource availability are unable to occur. This can result in overabundance followed by overuse of resources, potentially resulting in extreme declines or local extinctions. Resource exhaustion can negatively impact other fauna in the closed environment that exploit similar resources, through inter-specific competition. This paper discusses the reintroduction of Boodie (Bettongia lesueur) and Mala (Lagorchestes hirsutus) to a fenced reserve on the Matuwa Indigenous Protected Area, Western Australia, and raises the concern of potential competition between the two threatened species.
... A strategy tested at AR is bettong-specific one-way gates: small rectangular walk-ways with a vertical Perspex flap allowing animals to push their way out of the fence (Crisp & Moseby 2010). The current model of one-way gates has proven effective in allowing bettongs to disperse outside the fence, with very low rates of non-target species using the gates and no incursions of introduced species (Butler et al., 2019). ...
... One-way gates were open for 41 nights each on the West and East boundaries in 2017 and 12 nights on the West boundary and 22 nights on East boundary in 2018 (Fig. 1c). We deployed two Reconyx HC600 cameras at each gate while gates were open, one camera facing the inside part of the gate and one facing the exit point, with the following settings: high sensitivity, RapidFire, no delay between triggers and one image per trigger (Butler et al. 2019). ...
Understanding the conditions under which small native Australian mammals can persist in the presence of introduced predators remains a key challenge to conservation ecologists. Bettong‐specific one‐way gates were used at a predator‐free reserve in South Australia to allow the burrowing bettong (Bettongia lesueur ) – a small potoroid, listed as ‘vulnerable’ nationally – to disperse out of the reserve. We conducted a field experiment to explore the conditions affecting residence time of bettongs that left the reserve. We monitored bettong and mammalian predator activity outside the fence using track surveys across 18 sites over two seasons. We examined the effect of supplementary feeding as a strategy for increasing residence time, as well as the influence of predator presence and habitat quality, using linear mixed models. Bettong activity was positively associated with supplementary feeding, midstorey vegetation cover and shelter availability. After gates were closed, bettong activity near gates declined to almost zero the following weeks, likely either due to death from predation or due to movement away from the sites. To a small extent, mammalian predators were more likely to be present at sites with high bettong activity. Further research on conditions to support persistence of burrowing bettongs and other small mammals, including understanding minimum necessary predator control effort, is required before successful establishment of populations outside of fences can occur.
... One-way spear gates effectively allowed more than 50 Red Kangaroo individuals directional passive passage through fences without re-entry, injury or other welfare issues. To our knowledge, this is the first published trial of such management tools for use with large macropods, although devices have been developed for conservation-dependent small macropod species in fenced reserves (Butler et al. 2019). Not all kangaroos left the exclosures through one-way gates over the 3-week trial period. ...
Kangaroo populations have increased significantly across Australia’s arid rangelands where the Dingo (Canis dingo) is excluded, with some of the highest concentrations in western New South Wales. Novel adaptive management tools are needed to conserve kangaroo (Macropus and Osphranter spp.) populations and avoid negative impacts to biodiversity, agricultural production and animal welfare associated with their overabundance. Kangaroo densities within the Wild Deserts ecosystem restoration project within Sturt National Park in western New South Wales exceeded 100/km2 in mid‐2016, during an 18‐year regional population high. Following mass population declines attributed to emigration, an estimated 7,700 (±2,100 SE) kangaroos died within the 350‐km2 Wild Deserts site over an 8‐month period during drought (December 2017–August 2018). Population trends recorded at Wild Deserts were similar to population declines recorded during annual aerial survey counts across western New South Wales over the same period. With New South Wales (NSW) National Parks and Wildlife Service, Wild Deserts developed a kangaroo management plan to avoid future catastrophic mortality from starvation and mitigate associated ecosystem impacts. Conservation management centred upon a 104‐km2 Adaptive Management Zone, fenced to trial adaptive management of sustainable kangaroo populations and restore habitats for the reintroduction of locally extinct mammals. Kangaroos were removed from two 20‐km2 exclosures, adjacent to the Adaptive Management Zone, to provide baselines against which kangaroo populations could be assessed under variable environmental conditions. To effect this management, we assessed the effectiveness of one‐way weldmesh spear and flap gates to provide passive unidirectional movement through fences. Of 171 approaches by adult Red Kangaroos to spear gates, 57 resulted in successful exits, while none of 51 approaches resulted in return movements, supporting the utility of spear gates as a practical and effective tool for directional exits of kangaroos through fences.
... Overpopulation is a potential risk for translocated taxa, particularly when predators are absent. However, we found no records of conservation translocations resulting in overpopulation in the U.S. In a few foreign examples, reintroduced populations reached ecologically concerning numbers within fenced reserves (Druce, Mackey, & Slotow, 2011;Moseby, Lollback, & Lynch, 2018); however, mitigation strategies were successfully deployed, preventing damaging consequences (Butler, Paton, & Moseby, 2019;Druce et al., 2011;West, Tilley, & Moseby, 2019). The constraints of fenced reserves do not apply to expansive and connected open habitats, rendering overpopulation a lowrisk outcome when individuals have the ability to expand their range or emigrate to other populations. ...
Conservation translocations (reintroductions, reinforcements, ecological replacements, and assisted colonization) have played a vital and necessary role in conserving endangered species and ecosystems. Yet concerns over potential unintended ecological consequences frequently hinder the progress of translocation activities. We reviewed the history of U.S. translocations to ask: how often were intended benefits the result versus harmful unintended consequences? We found that translocations played a key role in recovery for 30% (14 of 47) of U.S. delisted taxa. Translocations have been performed, are planned, or are part of continuing recovery actions for 70% (1,112 of 1,580) of listed threatened and endangered taxa. Of the 1,014 total taxa we found with recorded conservation translocations spanning 125 years, we found only one restricted instance that caused a loss of biodiversity. All other reports of negative consequences were caused by translocations performed for economic and cultural interests in the absence of conservation‐based governance. Examples included fish stocking for sport and biological control programs for agricultural pests. We included biological control programs in this analysis because they can be and often are used as conservation tools, to directly benefit ecosystems. In addition, they are often raised as examples of harmful unintended results during the conservation planning process. However, only 1.4% (42) of 3,014 biological control agents released globally have caused ecosystem‐level deleterious impacts. All of these were initially released before the 1980s and conservation‐based practice and governance in recent decades have reduced off‐target impacts from biological control practice. Two themes emerged from our review: (a) conservation translocations routinely yielded their intended benefits without producing unintended harm, and (b) when ecological damage did occur, it was in the absence of conservation practice and regulation. This evidence shows that well‐planned translocation efforts produce ecosystem benefits, which should be weighed against the costs of inaction when deliberating conservation strategies.
... With the short training times to learn to use the door, potential applications for these doors include the following: supplementary feeding stations where predators and competitors are excluded; supplementary nestboxes or refuges that limit access to only the intended animals; targeted gate systems that allow targeted dispersal of chosen individuals outside of fenced reserves or soft-release areas, without compromising the integrity of the fence (similar to Butler et al. (2018)); and enrichment for wild-caught animals in captivity with limited human-animal interaction. Given that wildlife faces increasing challenges such as predation, competition and habitat loss, microchip-automated technology may help alleviate pressures on our native wildlife. ...
Context. Soft-release involving supplementary feeding or shelter is commonly used in wildlife reintroduction and rehabilitation projects. However, competition for nestboxes and supplementary feed, as well as predation at feed stations or nestboxes, can reduce the benefits of soft-release. The use of microchip-automated technology can potentially alleviate these concerns, by providing targeted supplementation to only the intended, microchipped animals.
Aims. We aimed to train wild-caught northern brown bandicoots, Isoodon macrourus, to use microchip-automated doors to access safe refuge.
Methods. Bandicoots were trapped from the wild and brought to the Hidden Vale Wildlife Centre, where eight were trained to use the doors in a six-stage process, and then six were trained in a three-stage process, using a peanut butter reward.
Key results. Bandicoots learned to use the doors in as few as 3 days. The duration of visits to the door generally increased during training, although the number of visits decreased.
Conclusions. The bandicoots successfully learned to use the microchip-automated doors, which shows that this technology has great potential with wildlife, particularly given the short training times required.
Implications. The use of these microchip-automated doors with wildlife has many potential applications, including supplementary feeding stations, nestboxes, monitoring in the wild, as well as enrichment for wild animals in captivity.
... ( Burns et al. 2012;Roy 2018). In Australia, fences are already trialling the use of species-specific one-way gates to regulate populations within multi-partition fences, with plans to allow the one-way movement of over-abundant herbivores into the surrounding landscape ( Butler et al. 2019;Crisp and Moseby 2010). ...
Terrestrial fauna of the southern hemisphere, particularly Australia and New Zealand, have suffered significant declines and extinctions due to predation by introduced red foxes Vulpes vulpes and cats Felis catus. Predator-exclusion fences offer protection to these threatened species and allow their populations to persist and even flourish within their boundaries. These fences have traditionally been designed to stop the movement of both the invasive predators (into the fence), and the native animals (out of the fence). However, recent theory and evidence suggest that when native animals are able to move across the fence, they can create a population beyond the fence boundary. This phenomena has been called a 'halo effect', and has the potential to both expand the direct and indirect benefits of predator-exclusion fences, and to reduce their negative effects. However, the conditions under which such an effect can be achieved are uncertain. They include questions about which native species could support a meaningful halo, what levels of predation outside the fence can be tolerated, and how permeable the fence would need to be. Here, we formulate this problem as both a simple two-patch model and a spatial partial differential equation model. We use the two approaches to explore the conditions under which a halo can deliver conservation benefits, and offer clear insights into the problem.
... Future studies should test improved fence permeability and the intensity of threat abatement required to maximize the establishment of spillovers. Increasing the permeability of the fence could be achieved through one-way gates (Butler et al. 2018), bridges, or ramps, methods used to assist the passage of wildlife across other anthropogenic structures (Mata et al. 2005;Glista et al. 2009). We found that conservation fences can create a zone of influence composed of species-specific internal and external activity gradients. ...
Spillover effects are an expansion of conservation benefits beyond protected areas through dispersal of species that reside within. They have been well documented in marine but not terrestrial systems. To understand the effects on wildlife created by conservation fences, we explored the internal and external gradients of activity in mammal, reptile, and bird species at a conservation reserve in arid Australia that is fenced to exclude invasive rabbits (Oryctolagus cuniculus), cats (Felis catus), and foxes (Vulpes vulpes). Two methods were used: counts of animal tracks along transects on sand dunes and captures at pitfall‐trapping sites. In both cases, sites were spaced at different distances from the reserve fenceline inside and outside the reserve. We recorded a range of spillover, source‐sink, step, and barrier effects that combined to create a zone within and around the reserve with fence‐induced species‐specific wildlife gradients. Two endemic rodents but none of the 4 mammal species reintroduced to the reserve showed positive spillover effects. Barrier effects, where activity was highest close to the fence, were recorded for the feral cat and native bettong (Bettongia lesueur), species that could not breach the fence. In comparison, some reptiles and native mammal species that could permeate the fence displayed source‐sink effects; that is, their activity levels were reduced close to the fence likely due to constant emigration to the side with lower density. Activity of some reptiles was lowest at core sites in the reserve and increased as distance toward the outside increased, a gradient likely related to trophic cascades triggered by predator exclusion. Our result show that fenced reserves can create overlapping layers of species‐specific gradients related to each species’ ability to permeate the fence and its varying susceptibility to threats. Managers should be aware that these gradients may extend for several kilometers either side of the fence and that not all contained species will increase in abundance. Creating wider conservation benefits may require increased fence permeability and threat reduction outside the fence. This article is protected by copyright. All rights reserved Article impact statement: Conservation fences create species‐specific internal and external wildlife gradients that don't always generate positive conservation benefits.
... By limiting movement, barrier fences can prevent breeding between animals on either side of the fence Williamson 2009, Linnell 2016), block routes us by seasonally migrating animals (Hailey and DeArment 1969, Johnson 2006b, Russell and Cohn 2012, Bradby et al. 2014, Madani et al. 2016. Fence designs that allow movement of selected non-target species can overcome this problem in some circumstances (Beckmann 1990, Lehnert and Bissonette 1997, Finch et al. 2006, Crisp and Moseby 2010, Coates 2013, Butler et al. 2019), but may still limit movement of animals (Olsson and Widen 2008). ...
... These findings are encouraging because there are many ways in which microchip-automation could benefit conservation efforts, such as: providing shelter or feeding opportunities to vulnerable wildlife; and assisting in dispersal outside of fenced areas (e.g. Butler et al. 2018). Further investigation into the use of microchip-automated devices with a larger sample size and with other wild-caught animals is recommended. ...
Microchip-automated feeders and doors allow individualised access to supplementary food and shelter during soft-release of wildlife. A wild-caught brush-tailed phascogale was used to test whether a wild animal could be trained to use microchip-automated devices. The phascogale was trained to use each device in less than a month.
ContextFenced reserves from which invasive predators are removed are increasingly used as a conservation management tool, because they provide safe havens for susceptible threatened species, and create dense populations of native wildlife that could act as a source population for recolonising the surrounding landscape. However, the latter effect might also act as a food source, and promote high densities of invasive predators on the edges of such reserves. AimsOur study aimed to determine whether activity of the feral cat is greater around the edges of a fenced conservation reserve, Arid Recovery, in northern South Australia. This reserve has abundant native rodents that move through the fence into the surrounding landscape. Methods
We investigated (1) whether feral cats were increasingly likely to be detected on track transects closer to the fence over time as populations of native rodents increased inside the reserve, (2) whether native rodents were more likely to be found in the stomachs of cats caught close to the reserve edge, and (3) whether individual cats selectively hunted on the reserve fence compared with two other similar fences, on the basis of GPS movement data. Key resultsWe found that (1) detection rates of feral cats on the edges of a fenced reserve increased through time as populations of native rodents increased inside the reserve, (2) native rodents were far more likely to be found in the stomach of cats collected at the reserve edge than in the stomachs of cats far from the reserve edge, and (3) GPS tracking of cat movements showed a selection for the reserve fence edge, but not for similar fences away from the reserve. Conclusions
Invasive predators such as feral cats are able to focus their movements and activity to where prey availability is greatest, including the edges of fenced conservation reserves. This limits the capacity of reserves to function as source areas from which animals can recolonise the surrounding landscape, and increases predation pressure on populations of other species living on the reserve edge. ImplicationsManagers of fenced conservation reserves should be aware that increased predator control may be critical for offsetting the elevated impacts of feral cats attracted to the reserve fence.
Burrowing bettongs (Bettongia lesueur) reached high densities within the fenced Arid Recovery reserve. Grazing pressure was assessed by comparing the vegetation inside and outside the reserve during April in 2012, 2013 and 2014. Mean numbers of bettong tracks crossing small 10 m 1 m plots overnight in the main exclosure were 20 in 2012, decreasing to 4 in 2013 and 3 in 2014. Similar declines were present in the second expansion, where tracks decreased from 7 in 2012 to 3 in 2013 and 2 in 2014. Perennial plant species richness decreased significantly over the study period. Acacia aneura, Acacia ligulata, Atriplex vesicaria, Crotalaria eremaea, Dodonaea viscosa, Enchylaena tomentosa, Maireana astrotricha and Sida ammophila were the most heavily grazed species within the reserve. Overall, more than 25% of plants showed some form of conspicuous grazing. C. eremaea and E. tomentosa showed little damage outside the reserve. Inside the reserve many C. eremaea were dead and heavily browsed and few E. tomentosa remained. Recent recruitment of A. ligulata and D. viscosa was also much higher outside the reserve. High densities of burrowing bettongs were associated with declines in vegetation condition potentially impacting other species and the ecosystem as a whole.
As evidence mounts that the feral Cat (Felis catus) is a significant threat to endemic Australian biodiversity and impedes reintroduction attempts, uncertainty remains about the impact a residual population of cats following control will have on a mammal reintroduction programme. Also, behavioural interactions between cats and their prey continue to be an area of interest. Within the framework of an ecosystem restoration project, we tested the hypotheses that successful reintroductions of some medium-sized mammals are possible in locations where feral cats are controlled (but not eradicated) in the absence of European Red Fox (Vulpes vulpes), and that hare-wallabies that dispersed from their release area are more vulnerable to cat predation compared with those that remain at the release site. We used radiotelemetry to monitor the survivorship and dispersal of 16 Rufous Hare-wallabies (Lagorchestes hirsutus spp.) and 18 Banded Hare-wallabies (Lagostrophus fasciatus fasciatus) reintroduced to four sites within Shark Bay, Western Australia. Nearly all foxes were removed and feral cats were subject to ongoing control that kept their indices low relative to prerelease levels. All monitored hare-wallabies were killed by cats within eight and 10 months following release. Significant predation by feral cats was not immediate: most kills occurred in clusters, with periods of several months where no mortalities occurred. Once a hare-wallaby was killed, however, predation continued until each population was eliminated. Animals remaining near their release site survived longer than those that dispersed. The aetiology of predation events observed offers new insights into patterns of feral cat behaviour and mammal releases. We propose a hypothesis that these intense per capita predation events may reflect a targeted hunting behaviour in individual feral cats. Even where feral cats are controlled, the outcome from consistent predation events will result in reintroduction failures. Managers considering the reintroduction of medium-sized mammals in the presence of feral cats should, irrespective of concurrent cat control, consider the low probability of success. We advocate alternative approaches to cat-baiting alone for the recovery of cat-vulnerable mammals such as hare-wallabies.
By 2001, elephants had been translocated (mainly from Kruger National Park) to 58 small, fenced reserves in South Africa. All but two introductions took place since 1989. We document important aspects of the population dynamics of elephants in these reserves using data collected in a survey conducted in 2001. The mean population size was 45 elephants, with an average density of 0.25 lephants/km(2). Populations have a female bias with 0.79 males to females. Populations have 19% adult males, and 31% adult females. On average, almost 50% of the population comprises adult and subadult females, indicating an immanent potential for large population growth. Births were not significantly different from a 1:1 sex ratio. When two extreme populations were removed, mean mortality rate was 0.4% per annum. Population growth rates averaged 8.3%, but five reserves had growth rates above 13%, and the highest annual growth rate was 16.5% per annum. Twenty-seven populations already have densities above 0.2 elephants/km(2), and eight reserves have densities above 0.4 2 elephants/km(2). Assuming a 12% per annum growth (feasible given the data presented), over half the reserves will have densities above 0.33 elephants/km(2) within five years. These results indicate that the translocation of elephants has been successful, with most populations reproducing at a rate far exceeding expectations. This has serious implications for owners and managers, as some form of population control (contraception, removals, culling etc.) needs to be urgently planned for implementation as soon as possible in most, and probably all small reserves.
Overabundant populations of ungulates have caused environmental degradation and loss of biological diversity in ecosystems throughout the world. Culling or regulated harvest is often used to control overabundant species. These methods are difficult to implement in national parks, other types of conservation reserves, or in residential areas where public hunting may be forbidden by policy. As a result, fertility control has been recommended as a non-lethal alternative for regulating ungulate populations. We evaluate this alternative using white-tailed deer in national parks in the vicinity of Washington, D.C., USA as a model system. Managers seek to reduce densities of white-tailed deer from the current average (50 deer per km2) to decrease harm to native plant communities caused by deer. We present a Bayesian hierarchical model using 13 years of population estimates from 8 national parks in the National Capital Region Network. We offer a novel way to evaluate management actions relative to goals using short term forecasts. Our approach confirms past analyses that fertility control is incapable of rapidly reducing deer abundance. Fertility control can be combined with culling to maintain a population below carrying capacity with a high probability of success. This gives managers confronted with problematic overabundance a framework for implementing management actions with a realistic assessment of uncertainty.
Habitat loss and fragmentation are among the major drivers of population declines and extinction, particularly in large carnivores. Connectivity models provide practical tools for assessing fragmentation effects and developing mitigation or conservation responses. To be useful to conservation practitioners, connectivity models need to incorporate multiple scales and include realistic scenarios based on potential changes to habitat and anthropogenic pressures. This will help to prioritize conservation efforts in a changing landscape.
The goal of our paper was to evaluate differences in population connectivity for lions (Panthera leo) across the Kavango-Zambezi Trans-frontier Conservation Area (KAZA) under different landscape change scenarios and a range of dispersal distances.
We used an empirically optimized resistance surface, based on analysis of movement pathways of dispersing lions in southern Africa to calculate resistant kernel connectivity. We assessed changes in connectivity across nine landscape change scenarios, under each of which we explored the behavior of lions with eight different dispersal abilities.
Our results demonstrate that reductions in the extent of the protected area network and/or fencing protected areas will result in large declines in the extent of population connectivity, across all modeled dispersal abilities. Creation of corridors or erection of fences strategically placed to funnel dispersers between protected areas increased overall connectivity of the population.
Our results strongly suggest that the most effective means of maintaining long-term population connectivity of lions in the KAZA region involves retaining the current protected area network, augmented with protected corridors or strategic fencing to direct dispersing individuals towards suitable habitat and away from potential conflict areas.
Despite a vigorous reintroduction program between 1985 and 2010, numbat populations in Western Australia are either static or declining. This study aimed to document the population ecology of numbats at two sites that are going against this trend: Scotia Sanctuary in far western New South Wales and Yookamurra Sanctuary in the riverland of South Australia. Scotia (64 659 ha) and Yookamurra (5026 ha) are conservation reserves owned and managed by the Australian Wildlife Conservancy and where numbats were reintroduced in 1999 and 1993 respectively. Both sites have large conservation-fence-protected introduced-species-free areas where there are no cats (Felis catus) or red foxes (Vulpes vulpes). Numbats were sourced from both wild and captive populations. From small founder populations, the Scotia numbats are now estimated to number 169 (113–225) with 44 at Yookamurra. Radio-collared individuals at Scotia were active between 13 and 31°C. Females had home ranges of 28.3 ± 6.8 ha and males 96.6 ± 18.2 ha, which leads to an estimated sustainable population or carrying capacity of 413–502 at Scotia. Captive-bred animals from Perth Zoo had a high mortality rate upon reintroduction at Scotia due to predation by raptors and starvation. The habitat preferences for mallee with a shrub understorey appear to be driven by availability of termites, and other reintroduced ecosystem engineers appear to have been facilitators by creating new refuge burrows for numbats. This study shows that numbats can be successfully reintroduced into areas of their former range if protected from introduced predators, and illustrates the difficulties in monitoring such cryptic species.
Kaka (Nestor meridionalis), red-crowned parakeet (Cyanoramphus novaezelandiae), whitehead (Mohoua albicilla), tomtit (Petroica macrocephala), and bellbird (Anthornis melanura) have all recently been reintroduced to sites in or near Wellington city. Prior to or concurrent with these translocations, unmarked individuals of all five species were detected in forested reserves on Wellington peninsula. Based on the number of birds seen, and frequency of sightings, we suggest that red-crowned parakeets, whiteheads and bellbirds have established resident populations in some reserves independent of translocations. We attribute these successful re-establishments to the effective control of possums (Trichosurus vulpecula) and rats (Rattus sp.) undertaken by Greater Wellington Regional Council and the Department of Conservation.
Wild cats (Felis spp.) are difficult to monitor because of their cryptic lifestyle and usually low numbers. Hair-snaring is a promising non-invasive method being used increasingly to estimate mammal populations.
Our aim was to carry out pilot trials of a simple hair-snare designed to capture hair from wild cats in arid environments.
Roughened wooden stakes were set at multiple sites on the crests of sand dunes and in swales in western Queensland, Australia, and in mostly sandy habitats of the Namib and Kalahari Deserts, Namibia. In Australia, stakes were sprayed with cat urine, extracts of catnip or valerian herbs as lures, or left untreated; in Namibia, alternate stakes were sprayed with a food lure of tuna emulsion oil. The stakes were checked for hair, usually daily, for 2–14 days, and the surrounding ground was inspected for tracks. Remote cameras also were used at some sites to confirm the identity of visitors to stakes.
In Australia, feral cats (Felis catus) were attracted to, and left hairs on, stakes sprayed with cat urine six times more frequently than to unsprayed stakes irrespective of whether snares were on dune crests or in swales, and showed no response to catnip or valerian. Tracks and photos showed that cats, dingoes or wild dogs (Canis lupus ssp.) and foxes (Vulpes vulpes) also approached and sniffed the stakes. In Namibia, F. catus, F. lybica and F. nigripes left hair on stakes, with deposition rates two and a half-fold higher at stakes with the food lure than without it. At least five other species of predators visited the hair-snare sites.
Simple wooden stakes provide a cheap and simple method of snaring hairs from wild cats, especially if used in conjunction with appropriate lures. Our results broadly support previous work, and extend the utility of the method to different Felis spp. in arid habitats. Further research is needed on snares to investigate the seasonal efficiency of different lures. If DNA also is to be extracted to identify individuals, more work is needed to confirm that snares yield hair of sufficient quality to allow this.
Additional keywords: Felis catus, F. lybica, F. nigripes, F. silvestris, hair sampling, odour.
1. Translocations have become an increasingly popular tool in threatened macropod conservation in Australia. Although previous evaluations of Australian macropod translocations have been published, the number of contemporary translocation programmes awaiting analysis, and new data regarding historic translocations, required a new assessment of macropod translocation programmes.
2. We aimed to assess trends in the way macropod translocations were conducted during the period 1969–2006, determine the number of successful translocations and identify factors common to successful translocations.
3. Data regarding macropod translocations were obtained from a wide variety of sources, including peer-reviewed journals, ‘grey’ literature and popular interest publications. Questionnaires were also sent to translocation managers to acquire detailed information. Specific aspects of macropod translocation methodology were analysed, and classification tree analysis was conducted to identify methodological and environmental factors common to successful translocations.
4. We identified 109 macropod translocations for which sufficient data could be collected to permit analysis. Using the presence of a population on 1 January 2007 as a simple criterion, 61% of translocations were successful. Of these translocations, 66% were also considered successful by Short et al.’s criteria (population persisted for five years and is deemed likely to continue to persist); the remainder could not be assessed due to lack of data or insufficient elapsed time since release. Classification tree analysis suggested methodological and environmental factors common to successful translocations; the overriding factor determining success was the absence of cats and foxes at the release site.
5. Although Australian macropod translocation proponents are faced with myriad methodological options when designing a translocation protocol, the primary consideration should be whether or not cats or foxes are present at the release site. Managers should be aware that there may be no safe population level of such predators for some translocation candidate species. Ignoring this fact will inevitably lead to a repeat of past translocation failures.
Despite once being described as common, digging mammal species have been lost from the Australian landscape over the last 200 years. Around half of digging mammal species are now extinct or under conservation threat, and the majority of extant species have undergone marked range contractions.Our aim is to identify the role of digging mammals in ecosystem processes throughout Australia. We highlight how the actions of digging mammals are vital for maintaining ecosystem functioning and how their extirpation has led to loss of ecosystem functions.A review of the literature indicates that many aspects of the influence of bioturbation on ecosystem functioning have been studied. The role of digging mammals in arid and semi-arid zones has been previously established. We collate and review a broader scope of studies, including those carried out in the mesic woodlands and forests of Australia. We identify roles of digging mammals in the context of ecosystem functioning and conservation management.Bioturbation significantly alters soil processes, increasing soil turnover and altering the chemical and structural properties of soil. Greater water infiltration and decreased surface run-off and erosion alter soil hydrophobicity and increase soil moisture. Diggings capture organic matter, provide habitat for a diversity of microscopic and macroscopic organisms, and increase nutrient cycling. Mycophagous mammals disperse fungi (e.g. mycorrhizae), while all diggings can create suitable sites for fungal growth. Diggings also capture plant seeds, increasing seedling germination, recruitment and plant growth. The overall effect of mammal diggings is therefore increased plant vigour and resilience, increased biodiversity and consequently improved ecosystem functioning.We propose that the loss of digging mammals has contributed to the deterioration of ecosystems in Australia. Recognising the roles of digging mammals will inform potential management options such as species translocations or reintroductions.
Ten reintroduction attempts were conducted in and around the Arid Recovery Reserve in northern South Australia between 1998 and 2008. Five locally-extinct mammal species and one reptile species were reintroduced into a fenced Reserve where cats, foxes and rabbits were excluded. Reintroductions of the nationally threatened greater stick-nest rat, burrowing bettong, greater bilby and western barred bandicoot were all considered successful based on short and medium-term success criteria. These criteria included continued survival after 8 years, increased distribution across the large Reserve and, most importantly, recovery after a drought event. The trial reintroductions of the numbat and woma python into the Reserve were unsuccessful due to predation by native avian and reptilian predators respectively. Outside the Reserve, where cats and foxes were present but controlled through poison baiting, reintroduction attempts of the greater bilby and burrowing bettong were unsuccessful. High mortality was attributed to cat and fox predation with dingoes also contributing to post-release mortality in bettongs. However, a reintroduction of burrowing bettongs into a fenced area with low rabbit and cat abundance has, to-date, met short-term and medium-term success criteria. Results suggest that the absence or severe restriction of exotic mammalian predators was the critical factor responsible for the success of the mammal reintroductions. Determining thresholds of predator activity below which successful reintroduction of threatened species can occur, are needed to improve the science of reintroduction biology in Australia.
Over-abundance of native herbivores is a problem in many forests worldwide. The abundance of native macropod wallabies is extremely high at Booderee National Park (BNP) in south-eastern Australia. This has occurred because of the reduction of exotic predators through an intensive baiting program, coupled with the absence of other predators. The high density of wallabies at BNP may be inhibiting the recruitment of many plant species following fire-induced recruitment events. We experimentally examined the post-fire response of a range of plant species to browsing by wallabies in a forest heavily infested with the invasive species, bitou bush Chrysanthemoides monilifera. We recorded the abundance and size of a range of plant species in 18 unfenced (browsed) and 16 fenced (unbrowsed) plots. We found the abundance and size of bitou bush was suppressed in browsed plots compared to unbrowsed plots. Regenerating seedlings of the canopy or middle storey tree species Eucalyptus pilularis, Acacia implexa, Allocasuarina littoralis, Breynia oblongifolia and Banksia integrifolia were either smaller or fewer in number in grazed plots than treatment plots as were the vines Kennedia rubicunda, Glycine tabacina and Glycine clandestina. In contrast, the understorey fern, Pteridium esculentum increased in abundance in the browsed plots relative to unbrowsed plots probably because of reduced competition with more palatable angiosperms. Twelve months after plots were installed the community structure of the browsed and unbrowsed plots was significantly different (P = 0.023, Global R = 0.091). The relative abundance of C. monilifera and P. esculentum contributed most to the differences. We discuss the possible development of a low diversity bracken fern parkland in Booderee National Park through a trophic cascade, similar to that caused by overabundant deer in the northern hemisphere. We also discuss its implications for broad scale fox control in southern Australian forests.
Pest mammals are completely excluded from Maungatautari Ecological Island, New Zealand, by a 47-km Xcluder pest-proof fence; however, they are commonly sighted directly outside, along the fenceline. Permanent pest exclusion relies on maintaining fence integrity, and enhancing knowledge of pest activity and behaviour at fenced reserves. We describe summer and winter periods of activity and behaviour of mammalian pests directly adjacent to the pest-proof fence. We (1) tested for the effects of adjacent habitat type, breach type and season on the rate of mammalian pest sightings directly at the fence, (2) determined how quickly pest mammals may locate a fence breach, and how likely they are to exploit it, and (3) developed a predictive model to help assess the probability of a pest gaining entry to the sanctuary if repair to a fence breach is delayed. Observations inside the rolled fence hood provided firm evidence that rats travel and forage extensively in this artificial although highly acceptable aboveground habitat, much more than on the ground. We confirm and emphasise that mammalian pests are constantly testing the pest-proof fence. Pests are very common directly outside the fence, and within 24h there is a very high likelihood that a fence breach will be located and exploited. The greatest threat of reinvasion comes (1) nocturnally, (2) from rodents and (3) in the summer; however, these results also confirm that there is constant risk from multiple pest species, regardless of time of day or season.
The home range, reproductive condition and warren and habitat use of reintroduced female burrowing bettongs was compared within two enclosures in the Arid Recovery Reserve at estimated densities of 2.75 and 7.5 bettongs km–2. Bettongs at both densities exhibited similar behaviour, with females using an average of 2.7 warrens over six months and home ranges averaging 29 and 35 ha in the low- and high-density enclosure respectively. All five female bettongs studied in the low-density enclosure were carrying pouch young at the beginning and end of the six-month study but only one of the five females in the high-density enclosure was carrying pouch young after six months. Higher food availability may have accounted for the higher reproductive effort and slightly smaller home ranges observed in the low-density enclosure. Female bettongs at both densities favoured dune habitat over chenopod swales and all burrows were in dune habitat. Although some differences in reproductive output were observed, it is likely that densities are not yet high enough to cause significant behavioural changes.
The absence of top-level predators in many natural areas in North America has resulted in overabundant ungulate populations, cascading negative impacts on plant communities, and the loss of biodiversity and ecosystem processes. Meanwhile, distinct population segments of the gray wolf (Canis lupus) have been removed from the list of endangered and threatened species, implying an end to wolf recovery and reintroductions. We propose another paradigm for wolf conservation, one that emphasizes ecosystem recovery instead of wolf recovery. Improvements in technology, an enhanced understanding of the ecological role of wolves, lessons from other countries, and changing public attitudes provide a new context and opportunity for wolf conservation and ecosystem restoration. Under this new paradigm, small populations of wolves, even single packs, could be restored to relatively small natural areas for purposes of ecosystem restoration and stewardship. We acknowledge the complications and challenges involved in such an effort, but assert that the benefits could be substantial.
The northern bettong ( Bettongia tropica ) (Potoroidae), is an endangered macropod with a restricted distribution. We combined radio-tracking and trapping data with microsatellite genotypes to infer the mating system and local dispersal patterns of this species, and discuss their relevance to translocations. We defined the mating system as ‘overlap promiscuity’ (sensu Wittenberger 1979), though we cannot rule out serial monogamy. We found significant effects of proximity (average distance between parents = 190 m) and male weight, but not size, on the likelihood of paternity, suggesting that closer, heavier males have greater mating success. The average distance between putative pairs of relatives suggested that most dispersal occurred over short distances, with the distance between ‘related’ females significantly lower than that between related males (0.9 km versus 1.3 km). A spatial autocorrelation analysis showed high female relatedness across distances of up to 435 m, equivalent to half an average home range width. Conversely, male pairs had low relatedness across 0 to 870 m. These results suggested that female young often settle next to their mother, while males avoid nesting within their father’s home range. Both limited natal and ‘mating’ dispersal may have contributed to the strong genetic structure previously reported for this species.
Radio-tracking of spotted-tailed quolls Dasyurus maculatus (Marsupialia: Dasyuridae) in the forested ranges of north-eastern New South Wales revealed that home ranges were extensive, with males occupying large, overlapping ranges [minimum convex polygon (MCP) up to 757 ha] and females occupying smaller, non-overlapping territories (MCP up to 175 ha). Quolls were partly arboreal, although most activity occurred on the ground or on fallen logs. Hollow logs were most frequently used as dens, but rock crevices, burrows, tree hollows and artificial structures were also used. Individual quolls were located in up to nine different dens and, with the exception of maternal dens, rarely sheltered in the same location on successive days. The large home ranges of the spotted-tailed quoll and the non-overlapping nature of female ranges necessitate very large areas of habitat to support viable populations. Fallen timber, used extensively for shelter and in travelling, may serve to enhance the quality of habitat for the species, and should be retained by forest and wildlife managers.
Predator-exclusion fencing and repeated use of baits containing the toxin sodium monofluoroacetate (1080) have been used widely
for conservation purposes. Prior to implementation, the relative merits of each are rarely examined. We reviewed the general
and specific advantages and disadvantages of each option and provided five case studies from Western Australia examining the
outcomes of fencing and repeated baiting. There was a dearth of monitoring data and quantitative analyses of the effects from
predator exclusion and repeated baiting. Despite the limited quantitative analyses, feral cats were an issue for areas baited
for fox control. Both feral cats and foxes were an issue for fenced areas where incursions occurred and where eradication
had not been achieved. There were clear long- and short-term advantages and disadvantages for each option and there was a
need to identify the objectives and desired outcomes before deciding between the use of fencing and repeated baiting. Irrespective
of the decision to use fencing, repeated baiting or both, there is a requirement to commit a non-trivial amount of resources
to long-term maintenance and monitoring of the effectiveness of the approach adopted. Integrated control of foxes and feral
cats is desperately required, as is a long-term management philosophy recognising the evolutionary potential of introduced
predators and native fauna.
Getting information on terrestrial large mammals is particularly difficult in tropical rainforests and in altered landscapes,
since the traditionally used method (line-transect census) presents low efficiency in dense vegetation, and is difficult to
standardize among heterogeneous, fragmented areas where the small size of patches restricts the length of transects. Aiming
to generate information to guide the choice of field protocols for surveying terrestrial large mammals in heterogeneous rainforest
remnants, we compared the performance and the correlation between the results of two alternative techniques (track counts
and camera trapping), and of two types of bait, in 24 forest remnants in a fragmented Atlantic forest landscape. Techniques
resulted in similar observed and estimated richness and species composition at the study landscape, including medium-sized
and nocturnal species usually poorly represented in line-transect censuses. Although camera trapping resulted in a higher
recording rate of the most common species (Didelphis aurita) and track counts in higher recording rates of some less common species (e.g. Dasypus novemcinctus), observed richness and recording rates of most species were correlated across the 24 sites between techniques. Conversely,
the use of different baits strongly influenced results, indicating the importance of standardizing baits in comparative studies.
Our results suggest that the two alternative techniques present similar performance and are suitable for studying the factors
affecting the distribution of large mammals in altered rainforest landscapes. The choice of field protocols should then focus
on the available resources and infrastructure, and on particularities of the study area.
KeywordsAnimal signs–Baits–Biodiversity surveys–Biodiversity monitoring–Field protocols–Non-invasive techniques–Sampling efficiency–Sampling methods–Scent lures–Tropical forest
The failure of broadscale management to protect some threatened species has led to an increase in the use of islands and fenced reserves as translocation sites or foci for intensive threat mitigation. Although highly successful at excluding some threats, these sites may be prone to ecosystem imbalance due to the absence or removal of predators and competitors. We documented population trends and environmental impacts of the burrowing bettong, (Bettongia lesueur), a threatened herbivorous macropod reintroduced to a 1400 ha fenced reserve in arid Australia for 17 years after release. The population increased from 30 individuals to an estimated 1532 individuals (1.09 per ha), a density up to ten times higher than wild populations. There was little evidence that population growth was density dependent, the average intrinsic rate of increase (r) was 0.125 and population size was unrelated to rainfall, body condition or reproductive output.
Browse damage on palatable plant species increased, and cover of palatable shrub species decreased, with increased abundance of bettongs. Activity of another reintroduced herbivore, the greater stick-nest rat, (Leporillus conditor), declined as bettong abundance increased while a reintroduced species not reliant on herbage was unaffected.
The burrowing bettong has been successfully reintroduced to the Arid Recovery fenced reserve but the positive average intrinsic rate of increase, inflated population density and impacts to resident plant and animal species suggests the population is now overabundant. This is the first documented case of overpopulation of a reintroduced species at a restricted site in Australia, highlighting the importance of preparing overpopulation management plans and considering reintroductions of species from all trophic levels including native predators.
Two segments of 2. 4-m fence with one-way gates along new Interstate highways in Minnesota were evaluated for 18 months for their effectiveness. The fences were 4 and 5. 1 km long with 9 and 10 pairs of gates, respectively. Passage by deer through the one-way gates was monitored by the use of baler counters and track beds. Sixty-nine percent of 51 passages through the gates were in a positive direction (from inside the fenced highway corridor to the outside). The reported number of deer hit was reduced 60 and 93 percent from the expected number in the two segments. Recommendations are made for design considerations in any future such fence construction.
Twenty four Holstein Friesian cows were kept in a loose housing system with one-way traffic from the lying area to the feeding area through an automatic milking system (AMS) and from the feeding area to the lying area through a one-way gate. The AMS consisted of a double-compartment selection unit (SU), one milking stall (MS), a passage from the SU to the MS, a passage from the MS to the feeding area, and a passage directly from the SU to the feeding area. During the sixth month of automatic milking, cows were observed for 24 h once a week for three weeks. On average, cows came to the AMS 12.5 times per day: 3.4 times with milking and concentrate in the SU and MS, 1.6 times with no milking but with concentrate in the SU, and 7.5 times with no milking and no concentrate. Leaving the SU took the cows 24.4 s when they went to the MS during milking visits and 143.5 s for the remaining visits. Cows that were quicker to leave the SU in the direction of the MS were slower to leave the MS (P < 0.01). Cows placed their hind hoofs inside the MS voluntarily in 65% of the visits; in the remaining visits the closing gate forced them to do this. The average duration of leaving the MS was 51.4 s. This increased with milk yield and daily concentrate allotment and also when the cow kept her head in the trough when the exit-gate of the MS opened. Cows stayed on average 238 s in the passage between the MS and the feeding area. Statistically significant differences between individual cows were found in the durations of leaving the SU and the MS, in passing between the SU and the MS, and in standing in the passage between the MS and the feeding area. It might be possible to increase the capacity of the AMS by accelerating the movement of cows through it. Cows that are not milked would get some concentrate after passing through the SU. Cows that are milked would get some concentrate during milking and some after leaving the AMS.
The ratio of immature to mature males was significantly greater than for females. Males were slightly larger in size than females but the sexes did not differ significantly in weight. Females were, on average, in better condition than males. -from Author
Broad-scale Australian mammal declines following European settlement have resulted in many species becoming regionally or globally extinct. Attempts to reintroduce native mammals are often unsuccessful due to a suboptimal number of founders being used, high rates of predation and a lack of knowledge of the reintroduction biology for the species concerned. We trialled predator swamping and supplementary feeding in an attempt to offset predation and improve reintroduction success for the burrowing bettong (Bettongia lesueur) in arid South Australia. We compared population longevity of a large release group (1266 animals) with five releases of smaller groups (∼50 animals at each). We compared release sites with (n≤5) and without (n≤1) supplementary food to determine whether site fidelity, body condition and reproduction were affected, and whether these traits aided population establishment. Predator swamping did not facilitate reintroduction success, with no bettongs detected more than 122 days after release. While supplementary food increased site fidelity and persistence at release sites, bettongs failed to establish successfully at any site. Neither predator swamping nor supplementary feeding enhanced reintroduction success at our sites but results suggested that supplementary feeding should be explored as an aid to reintroduction success for Australian mammals.
Many Namibian farmers are diversifying from exclusive livestock farming to mixed farming, resulting in a sharp increase in the number of game-fenced areas. However, animals such as warthog (Phacochoerus aethiopicus), porcupine (Hystrix africaeaustralis) and aardvark (Orycteropus afer) dig holes under game fences, allowing access to predators such as cheetah (Acinonyx jubatus). Swing gates were installed along a 4800 m section of game fencing in the Otjiwarongo district of Namibia. The fence was monitored before and after gate installation and trip cameras were used to identify species that used the gates. Warthog, aardvark and porcupines commonly used the gates and the number of holes under the fencing was significantly reduced following gate installation. No predators were observed using the swing gates and the cost was substantially lower than fence electrification This initial research suggests that swing gates could be an important non-lethal predator exclusion technique, although further studies will be needed to confirm their long-term effectiveness. Using techniques such as swing gates, which effectively and economically reduce the frequency with which animals dig holes under fences may not only benefit farmers, but also reduce the unnecessary destruction of non-target wildlife species resulting from unselective trapping.
Because of the ubiquitous and intractable threat posed by fox predation in many parts of south-east Australia, exclusion fences are increasingly seen as playing an important role in the long-term management of some biodiversity reserves. However, while fences can help to reduce predation pressure on populations of small to medium-sized vertebrates, they may also restrict the movement of non-target species and require maintenance to ensure their continued effectiveness. One of the challenges facing conservation agencies is to construct fences that reduce maintenance costs while reliably and selectively controlling the movement of desirable and undesirable species into and out of areas of conservation significance. In this study 10 custom-designed 'wombat gates' were monitored with motion-detecting cameras to determine whether they remained an effective barrier to foxes and other taxa after more than a decade of operation. Wombats and echidnas frequently passed through gates while foxes and black wallabies were apparently unable or unwilling to use them. This type of gate may prove valuable in the management of fenced conservation reserves.
Gates designed to allow passage of mule deer (Odocoileus hemionus hemionus) in only one direction were tested under controlled and field conditions. Two gate types had significantly (P < 0.02) different frequencies of use under controlled conditions. Eight gates of the type deemed most effective were installed in 8-foot (2.44-m) fences adjacent to Interstate Highway 70 near Vail, Colorado. A total of 558 passages were recorded through these gates during 1970-72 and 96 percent of these were in the one-way direction for which the gate was designed. Based on track counts, we estimated these gates permitted about 223 deer to escape the immediate highway right-of-way.
Microtus pennsylvanicus and M. ochrogaster are sympatric in southern Indiana grasslands. From June 1965 to August 1967 four populations were lived trapped, three of them in 0.8-hectare (2-acre) outdoor pens. Both species increased during 1965 and reached peak densities in summer 1966. Microtus ochrogaster declined abruptly that fall and remained low; M. pennsylvanicus declined the following spring. One of the fenced populations increased to a density about three times that of its unfenced control. By early fall 1966 it had nearly destroyed its food resources and then suffered a severe decline associated with obvious overgrazing and starvation. No such overgrazing has been seen on any unfenced grasslands in this area. Dispersal is probably necessary for normal population regulation in these voles, since fenced populations seem unable to regulate their density below the limit set by starvation. Both species bred extensively in the winter of 1965-66 during the phase of population increase. There was little or no breeding during the winter after the peak. Survival of females in the trappable population of both species was high and relatively constant until the end of the cycle. In males, periods of low survival punctuated the increase and peak phases, and these periods of low male survival did not occur at the same time in the two Microtus species. Some mortality processes are thus highly specific for sex and species. In the fenced populations survival rates were very high and no sporadic male losses occurred. Increasing and peak populations of M. pennsylvanicus and M. ochrogaster are characterized by adults of large body size. During the increase and peak phases some voles stopped growing at low weights (30-40 g) while others reached high asymptotic weights (45-55 g). The demography of these Microtus species in southern Indiana is similar to that of other cycle voles and lemmings in temperate and arctic areas.
Burrowing animals such as warthog (Phacochoerus africanus), Cape porcupine (Hystrix africaeaustralis) and aardvark (Orycteropus afer) are able to compromise the integrity of fenced-in farmlands by digging holes under game fences. These holes provide access for predators to enter the farm where they can kill livestock or captive game animals. Data collected from the use of swing gates (n = 263) installed along a 23.93 km game fence in the Otjozondjupa region of Namibia was analysed to determine the factors that influenced their efficacy at reducing hole creation along the fence by digging animals. Statistical analyses revealed that soil substrate, grass height, vegetation density, distance to the nearest permanent water source and season influenced digging activity along the fence line. The number of holes created and reopened decreased over time from the start of the study period, probably demonstrating that burrowing animals had learnt to use the swing gates rather than dig holes under the fence. These factors can inform the correct future usage of swing gates as a large predator exclusion method to ensure that they do not enter game farms, which will reduce the need to lethally control carnivores and burrowing animals.
Field trials were conducted in central Australia to evaluate the ability of
various olfactory lures to attract feral cats
(Felis catus L.). Ten food-based lures, one plant
extract and two scent-based lures (anal-gland preparations from male and
female cats) were evaluated on the basis of visitation rates and elicited
behavioural responses. A visual lure composed of bird feathers was also tested
in conjunction with the scent-based lures. One food-based lure (sun-rendered
prawn) and both of the scent-based lures were found to attract feral cats. The
visual lure did not enhance the attractiveness of the scent-based lures. The
possible uses and relative advantages of these lures in control programmes and
in ecological studies of cats are discussed.
When kangaroo populations reach high numbers in reserves and parkland near urban areas
there are a number of implications. The animals may pose a risk to their own welfare as the
population expands, have a negative effect on other aspects of the local biodiversity or impinge
on human activities. In such cases active management of the population may be sought to
ameliorate the negative effects. Traditional control techniques such as culling are often out of
the question in these circumstances due to social pressures and concerns for human safety. In
this paper I review three fertility control techniques that are potential management tools for
these situations. Surgical sterilisation is a fertility control technique that has been used in a
number of high profile situations. It is probably the most well established method of fertility
control, is permanent, but is invasive and stressful. New biotechnological approaches to fertility
control, such as the use of steroidal and non-steroidal contraceptives, are currently being
trialled on kangaroos. These include the synthetic progestin levonorgestrel and the GnRH
agonist deslorelin. These contraceptive agents are capable of successfully reducing the fertility
of kangaroos for a range of durations depending on the agent used. Such contraceptive agents
are likely to be a useful tool to manage both captive kangaroo populations and those in
parkland areas. The development of a remote delivery technique will increase their efficacy for
use in wild populations.
Large mammalian herbivores are major drivers of the structure and function of terrestrial ecosystems worldwide, and changes in their abundance have resulted in many populations being actively managed. Many empirical studies have identified that abundant mammalian herbivores can have negative impacts on biodiversity, but there has been no specific review of the impacts of native mammalian herbivores.We assessed the peer-reviewed literature on the effects of large native herbivores on other animals. We aimed to quantitatively synthesise current knowledge, identify gaps and limitations in the literature, and highlight priorities for future research.Most empirical studies of herbivory effects compared only two levels of herbivory (76%), and meta-analysis showed that very high densities of herbivores, when compared with very low densities, had mostly negative effects on other animal species. These negative effects were usually attributed to changes in the quantity and/or structure of vegetation. Only 24% of papers studied animal responses across a gradient of herbivore densities; and non-linear responses to herbivory, as well as responses to low and moderate herbivore densities, remain poorly understood.The literature also was dominated by short-term studies (76% sampled animal responses for 2 years or less) and there was a high incidence of confounding factors among studies (38% of studies). In addition, many studies used only coarse metrics to assess effects (e.g. only 33% of studies assessed species composition) and few included community-level synthesis (only 31% of studies reported results from more than one animal class).Synthesis and applications. Critical questions remain for both basic ecology and the management of large native herbivores for biodiversity. Key knowledge gaps include (1) non-linear responses to herbivore pressure, (2) how responses differ between different herbivores, (3) the spatial and (4) the temporal variation of responses, (5) how the effects of herbivores interact with other land management activities, and (6) the mechanisms driving cascading effects through ecosystems. We identify ways to address these gaps and emphasise the need for studies which employ contrasts over a gradient of ecologically relevant herbivore densities and biologically meaningful timeframes.This article is protected by copyright. All rights reserved.
Many species of herbivorous mammals declined to extinction following European settlement of inland Australia. The rufous bettong, Aepyprymnus rufescens (a macropodoid marsupial), is ecologically similar to many of these species. We used analysis of microsatellite markers to determine dispersal patterns and mating system characteristics in a cluster of local populations of A. rufescens , with the aim of gaining a better understanding of regional population dynamics in such species. Particularly, we asked whether the rufous bettong showed sourcesink dynamics, as Morton (1990) hypothesized that many mammals may have been made vulnerable to extinction through such processes. We compared populations separated by distances of up to 12 km, and detected significant genetic differentiation among local populations ( F ST =0.016). Females displayed greater genetic structuring than males, suggesting that females dispersed over shorter distances or less frequently than males. Geographic distance was weakly related to genetic distance between populations suggesting some gene flow at this scale, and paternity assignment indicated that dispersal can occur over distances of up to 6.5 km. Our study populations varied widely in density, but density did not explain the pattern of genetic differentiation observed. These findings of significant structure among populations, some influence of distance on genetic divergence and that density explains little of the divergence among populations, suggested that source-sink dynamics did not play a large role among these populations. Variance in male mating success was low (maximum assigned paternity for an individual male was 14% of offspring). While data on multiple maternity were limited, roughly half of repeat maternity was assigned to the same male, suggesting that the mating system of the rufous bettong is not purely promiscuous.
ABSTRACT People construct fences to delineate land ownership and to control access to land. Fences accomplish several purposes, notable among them are containing livestock or wildlife raised for profit or subsistence, excluding use of vegetation within areas to be conserved, and reducing conflicts between wildlife and humans. In addition to these intended purposes, fences may also offer unanticipated benefits, such as vegetation within hedgerow fences providing cover to wildlife, or grazing by confined herbivores promoting native flora. However, because fences limit mobility of large herbivores, fenced areas become fragments within the landscape, sometimes with undesirable results. We review of the positive and negative consequences of fencing landscape patches for large herbivores, using examples from livestock production and wildlife conservation. Fences allow grazing to be controlled, to control grazing intensity or rest parcels. Fences may entangle or electrocute herbivores, truncate migratory routes, excise important resources needed by large herbivores, and allow resident herbivore populations to become too high and harm vegetation. More subtly, fencing parcels may reduce the carrying capacity of a landscape, irrespective of habitat loss. Eliminating access to heterogeneous forage patches within a landscape reduces options available to herbivores or their herders, both at a given time and across seasons. Normalized difference vegetation indices, derived from satellite images and reflecting green vegetation biomass, are used to suggest potential effects of fencing upon herbivore stocking rates. Ecosystem modeling quantified the decrease in herbivore stocking rate as a 300 km, parcels, 19% fewer cattle could be supported, compared to the block being unfenced.
The female reproductive tract is described and compared with that of other
Macropodidae. It is shown that the characters considered to be diagnostic of the
Potoroinae are more variable than hitherto supposed and occur also in the Macropodinae.
For the greater part of the oestrous cycle the lateral vaginae are probably
occluded and the pseudovaginal canal closes within a day of parturition, so that the
contents of the vaginal smear are derived mainly from the posterior vaginal sinus.
B. lesueur is polyoestrous and monovular. The oestrous cycle has a modal
length of 23 days and gestation modal length of 21 days, post-partum oestrus following
about 1 day later. The reproductive cycle is delayed during lactation and
embryonic diapause occurs. The young leaves the pouch at 115 days and the delayed
embryo is born a few days later. Experimental removal of the pouch young results in
resumption of development and birth 20 days after removal. The young weighs 0.317 g
at birth and it reaches an adult weight at about 280 days, when sexual maturity is
attained. Animals less than 1 yr old can be distinguished by the presence of the sectorial
premolar 3 in the upper jaw, which is shed at 1 yr. The full adult dentition is attained
by 18 months.
In close confinement females bred regularly from February to September but
about 70% spontaneously lost their young by the age of 3 weeks. In large pens young
were carried through lactation to independence.
Reproduction in Bettongia is compared to that of Potorous, a closely related
rat-kangaroo, and a general hypothesis is developed to reconcile several disparate
observations of marsupial reproduction. It is postulated that most marsupials have a
period of obligatory diapause interposed in the development of the embryo, and this is
followed by a short and relatively constant period of embryogenesis. The diapause
may be short, as in Perameles, or long as in Potorous, and, in the special conditions of the
Macropodidae may be greatly extended during lactation. This latter phenomenon may
be secondarily advantageous to the species ecologically but it is emphasized that its
primary adaptive significance is likely to be found in the need to synchronize embryonic
and uterine development for intra-uterine nourishment of the embryo.
Population structure, reproduction, condition, morphology, movements, habitat
preference, and dynamics of the burrowing bettong were assessed on Dorre and
Bernier Islands between 1988 and 1995. The data come from 982 captures of
bettongs in 2661 trap-nights (an average of 37 captures per 100 trap-nights).
Recaptures within a trip made up 39% of bettong captures. Bettongs were
more abundant, as indexed by trap success, than were western barred bandicoots
(the other species caught in considerable numbers on trapping grids). Sex
ratio of bettongs (excluding recaptures) were skewed heavily towards males at
1.43: 1 despite approximate parity in pouch young. Production of young was
concentrated in the wetter winter months and appeared to fall well below their
theoretical capacity of 3 young per year. Bettong females were capable of
producing young at 880–900 g (approximately 7–8 months of age) but
incidence of females with pouch young or showing signs of recent lactation
increased from 40% for females of 881–1000 g to 62% for
females > 1000 g. The incidence of sub-adult bettongs in the population
peaked in spring, but varied between years (range 0–14% of the
population). There was an excess of males over females in the sub-adult
population. Bettongs showed little sexual dimorphism but there were
significant differences in morphology between the two island populations.
Bettongs appeared to suffer substantial reductions in numbers in a prolonged
drought extending from October 1986 to April 1989, reducing trap success for
this species to 19% in the 1989 survey. Numbers grew strongly on both
islands after the breaking of the drought in May 1989, showing an observed
rate of increase of r = 0.75 on Dorre Island.
Trap success had increased to 45% in September 1991. There was a high
turnover of bettongs on trapping grids – 25–40% over 6
months to 80% over 3 years. Movements of bettongs appeared limited: the
median distance moved by bettongs captured more than once within an 8-day
trapping session was 160 m. Only 4% of recorded movements were greater
than 1 km. There was no significant difference in movements between the sexes.
Bettongs were widely dispersed in winter through the four habitats surveyed
but tended to concentrate in dune and Triodia sandplain
habitat in autumn and spring.
This study describes the use of warrens and aspects of the social organisation
of a population of the burrowing bettong, an endangered potoroid. Observations
were made on 14 animals, maintained in a 4-ha enclosure of natural vegetation
at Shark Bay, Western Australia. The population divided into three social
groups, each of one male and one to many females. Individual bettongs used
1–10 warrens over a period of five months. Males changed warrens more
often than females. Some females regularly shared warrens with other females.
Many of these associations appeared to be mothers with their daughter or
daughters. Sharing of warrens occurred regularly until the daughters were
about 10 months old and occasionally after that. Day ranges of males were
larger than those of females, exclusive of other males, and overlapped those
of 1–6 females. Males shared warrens with the females within their day
range. At night bettongs were not constrained to their day range and made use
of the whole enclosure. Equal numbers of agonistic interactions between and
within day-range groups, as well as the absence of feeding associations,
indicated that bettongs operated independently of their day-range groups at
night while feeding. Bettongs formed a weak dominance hierarchy with the
oldest female on top and a young male at the bottom. Male–male
interactions tended to be more aggressive than male–female interactions.
Males were involved in significantly more agonistic interactions, particularly
chases, than were females; chases usually entailed chasing another male away
from a female. Use of space and social behaviour suggested a polygynous mating
The brush-tailed bettong formerly ranged over much of southern Australia, but is now extinct except
in the south-west of Western Australia and northern Queensland. A small colony was obtained from
the Perth Zoo in 1975 and these were bred successfully at the Para Wirra Recreation Park near Adelaide
and provided stock for a re-establishment program in South Australia. Details of the breeding program
are given. Bettongs were kept in small colonies, usually one male and two or three females; the young
were removed when they reached 550 g, or, with very intensive breeding, at a lower weight. The animals
were fed principally on commercial kangaroo pellets with a range of supplements. Usually two offspring
per year were produced although up to three were produced with intensive breeding. Females commenced
breeding when approximately 4 months old. Techniques for re-establishment were tested on small islands.
One island, Island A in Venus Bay, provided apparently ideal habitat and the captive-bred stock released
there established quickly. Bettongs bred in the wild on two small and two large islands. However, the
introduction to St Francis I., their last stronghold before extinction in South Australia, was least successful.
Possible reasons for this are discussed.
A national trap–catch monitoring protocol been developed to standardise the settingand luring of leg-hold traps for monitoring brushtail possum control operations in New Zealand. The methods recommended were initially developed for use in forest and scrub areas, but a suitable luring system was needed to monitor possum populations in grassland (tall tussock) areas. A backing board in a metal frame was developed to which the standard dry flour and icing sugar lure could be applied. Because this added cost to monitoring operations, a trial was carried out to assess whether backing boards could be omitted and the lure placed directly on the ground. Results showed that traps with groundset lure had a capture rate of only about 50% of the rate achieved with lured backing boards. Traps with backing boards are more visually attractive, which probably explains their higher capture rate. To increase the capture efficiency of trapping, we recommend further research on improved visual lures rather than olfactory ones.
Australian arid zone mammal species within the Critical Weight Range (CWR) of 35 g–5.5 kg have suffered disproportionately in the global epidemic of contemporary faunal extinctions. CWR extinctions have been attributed largely to the effects of introduced or invasive mammals; however, the impact of these threatening processes on smaller mammals and reptiles is less clear. The change in small mammal and reptile assemblages after the removal of rabbits, cats and foxes was studied over a 6-year period in a landscape-scale exclosure in the Australian arid zone. Rodents, particularly Notomys alexis and Pseudomys bolami, increased to 15 times higher inside the feral-proof Arid Recovery Reserve compared with outside sites, where rabbits, cats and foxes were still present. Predation by cats was thought to exert the greatest influence on rodent numbers owing to the maintenance of the disparity in rodent responses through dry years and the differences in dietary preferences between rabbits and P. bolami. The presence of introduced Mus domesticus or medium-sized re-introduced mammal species did not significantly affect resident small mammal or reptile abundance. Abundance of most dasyurids and small lizards did not change significantly after the removal of feral animals although reductions in gecko populations inside the reserve may be attributable to second order trophic interactions or subtle changes in vegetation structure and cover. This study suggests that populations of rodent species in northern South Australia below the CWR may also be significantly affected by introduced cats, foxes and/or rabbits and that a taxa specific model of Australian mammal decline may be more accurate than one based on body weight.
Summary Eight Greater Stick-nest Rats (Leporillus conditor S.) were re-introduced into a 8 ha release pen within the Arid Recovery Reserve, South Australia, in September 1998. Their weight, reproductive condition, activity, habitat use and grazing impacts were investigated during the 8 month experimental trial. Greater Stick-nest Rats increased in weight and bred successfully after the end of summer (April 1999). They consumed native vegetation including Bladder Saltbush (Atriplex vesicaria), Ruby Saltbush (Enchylaena tomentosa) and Sturt's Pigface (Gunniopsis quadrifida) but Sturt's Pigface was most heavily browsed and no monitored plants died from over-browsing during the trial. Rats preferred dune habitat and the two largest female rats maintained discrete activity areas and shelter sites. Nocturnal activity of adult male rats was centred around adult females with both sexes generally staying within 150 m of daytime shelter sites. Shelter sites were commonly within dead Umbrella Wattle (Acacia ligulata) or Narrow-leafed Hopbush (Dodonaea viscosa) shrubs covered in low vegetation, and rats also adapted burrows of other species to use as below-ground components. Although supplementary water was provided and may have ensured survival over the hot summer months, the trial release was considered a success and a full-scale re-introduction of the Greater Stick-nest Rat was conducted in 1999.
European badgers Meles meles and their setts are legally protected in the UK. If setts are to be damaged or destroyed as part of development, humane exclusion of badgers is usually required in advance of works. Exclusion can be achieved by erecting one-way gates over sett entrances which allow badgers to exit but not regain entry. Natural England (the governmental conservation advisory body in England) recommends that exclusion is maintained for 21 days before construction work begins to ensure that the sett has been vacated. In this study, a large diameter (400 mm) water main was installed through a badger sett without exclusion of animals due to discovery of the sett only after construction work had commenced. The sett location and the presence of numerous European rabbit Oryctolagus cuniculus burrows interspersed with sett entrances would have made exclusion difficult. As an emergency mitigation measure, a 1.4 m deep, 40 cm wide trench was excavated 6 m from the sett entrances (located mostly in a lapsed field boundary using a combination of hand-augering (to detect badger tunnels and chambers; these were then excavated by hand), followed by mechanical excavation. Subsequent to this, work to excavate the trench, lay the pipe through the sett and back-fill the trench took one week. Despite the disturbance caused by this approach, badgers were not excluded from the entire sett and the risk of killing badgers which may have been present below ground was significantly reduced; no badger or other large mammal activity was evident during the mitigation works. All works were carried out under Natural England licence and under the supervision of an ecologist and a Natural England Wildlife Management Adviser.
Summary • Owing to the detrimental impacts of invasive alien species, their control is often a priority for conservation management. Whereas the potential for unforeseen consequences of management is recognized, their associated complexity and costs are less widely appreciated. • We demonstrate that theoretically plausible trophic cascades associated with invasive species removal not only take place in reality, but can also result in rapid and drastic landscape-wide changes to ecosystems. • Using a combination of population data from of an invasive herbivore, plot-scale vegetation analyses, and satellite imagery, we show how a management intervention to eradicate a mesopredator has inadvertently and rapidly precipitated landscape-wide change on sub-Antarctic Macquarie Island. This happened despite the eradication being positioned within an integrated pest management framework. Following eradication of cats Felis catus in 2001, rabbit Oryctolagus cuniculus numbers increased substantially although a control action was in place (Myxoma virus), resulting in island-wide ecosystem effects. • Synthesis and applications. Our results highlight an important lesson for conservation agencies working to eradicate invasive species globally; that is, risk assessment of management interventions must explicitly consider and plan for their indirect effects, or face substantial subsequent costs. On Macquarie Island, the cost of further conservation action will exceed AU$24 million.
The effect of different levels of cattle grazing on an arid Australian small terrestrial mammal and lizard assemblage was assessed in a long-tem series of cross-fence comparisons. Cross-fenced sites were closely matched for edaphic and vegetation characteristics and experienced near identical weather patterns, to ensure that cattle grazing pressure was the principal determinant of any differences in fauna assemblages. In addition, the effects of removal of cattle, cats, foxes and rabbits from three of these long-term monitoring sites were assessed to determine the relative impacts of cattle grazing and feral animals. Small mammal captures, with the exception of Mus musculus, revealed a significant negative response to cattle grazing pressure but this response was of a considerably lower magnitude than the dramatic increase in rodent captures and species richness within the feral animal-proof Arid Recovery Reserve. Higher kangaroo numbers in ungrazed controls, compared with treatments grazed by cattle, possibly negated the benefits to small mammals of removing cattle grazing. No reptile species responded significantly to the grazing treatments although reptile richness and captures of geckos and skinks were the lowest and agamid captures were the highest at heavily grazed sites. Nephrurus levis was the only reptile species to increase significantly, while captures of some smaller geckoes declined, within the feral-proof treatment. Feral predation exerted a more significant effect on most small mammal species than the levels of cattle grazing assessed in this study, yet reptile responses to grazing or feral animals were less apparent and were likely primarily driven by changes in vegetation cover or secondary trophic impacts.
Summary Many early Australian records indicate that at the time of European settlement there were extensive tracts of highly productive, and species-rich, grassy communities and chenopod shrublands. Topsoils in many areas were soft and friable. The rapid development of livestock industries led to most changes to the environment being simplistically ascribed to domestic stock grazing, land clearance, introduced pests (such as rabbits) or changed burning practices. It has also commonly been assumed that the hoof action of domestic stock was the principal cause of the compaction and surface sealing of soils in many areas. However, the rapid soil deterioration also coincided with the dramatic decline or complete extinction of many small native ground-foraging mammals and the consequent cessation of the soil disturbances and interactions that they created. This paper reviews the role of small mammals in disturbing soils, and implications for incorporation of organic matter, aeration, improvement in infiltration and the provision of suitable sites for seed germination and seedling establishment. This can aid topsoil formation and health by providing substrate for microorganisms, improved water balance and mineral cycles and enhanced soil structure. Seeds and mycorrhizal fungi, that are integral to the establishment and growth of many plants, are spread. Such intermittent disturbance may be an important driving force in determining the pathway of succession and lead to greater biodiversity. Further ongoing research on Australia's small mammals is needed, especially in areas where they are able to move freely in a natural environment and are protected from introduced predators.
Fencing for conservation is an acknowledgement that we are failing to successfully coexist with and, ultimately, conserve biodiversity. Fences arose during the Neolithic revolution to demarcate resource-rich areas (food sources) and exclude threats (intruders). Fencing for conservation can be viewed as fulfilling a similar function. The aims of this paper were to identify when fencing can and is used to conserve biodiversity; highlight the costs and benefits of fencing for conservation; and make recommendations to ensure appropriate use of fencing for conservation in the future. The IUCN identifies ten major threatening processes and the impacts of eight of these can be mitigated via the use of fencing, however avoiding human–animal conflict and reducing the impact of introduced predators are the two most common uses. Fences implemented to achieve a conservation benefit are not necessarily physical barriers, but can also include ‘metaphorical’ fences of sound, smoke and smell, or even actual islands. Fences provide defined units for managers and separate biodiversity from threatening processes including human persecution, invasive species and disease. Conversely, they are costly to build and maintain; they have ecological costs through blocking migration routes, restriction of biodiversity range use which may result in overabundance, inbreeding and isolation; restriction of evolutionary potential; management; amenity and ethical costs. Despite these problems, fencing for conservation is likely to become increasingly utilized as biodiversity becomes increasingly threatened and methods of ameliorating threats lag behind. In the long-term, fences may ultimately prove to be as much a threat to biodiversity as the threats they are meant to exclude, and a new research agenda should arise to ensure that conservation fences do not remain a permanent part of the landscape.