Rewilding lite: Using traditional domestic livestock to achieve rewilding outcomes

The vision of rewilding is to return ecosystems to a “natural” or “self-willed” state with trophic complexity, dispersal (and connectivity) and stochastic disturbance in place. The concept is gaining traction, particularly in Europe where significant land abandonment has taken place in recent years. However, in reality, the purest form of rewilding (Rewilding Max) is constrained by a number of context-specific factors whereby it may not be possible to restore the native species that form part of the trophic structure of the ecosystem if they are extinct (for example, mammoths, Mammuthus spp., aurochs, Bos taurus primigenius). In addition, populations/communities of native herbivores/predators may not be able to survive or be acceptable to the public in small scale rewilding projects close to areas of high human density or agricultural land. Therefore, the restoration of natural trophic complexity and disturbance regimes within rewilding projects requires careful consideration if the broader conservation needs of society are to be met. Here we highlight the importance of herbivory as a key factor in rewilding. We argue that the use of the suite of livestock species, and in particular traditional breeds, offers the opportunity, under both land sharing/sparing strategies, to reinstate a more “natural” form of herbivory but still retain the option for management interventions (Rewilding Lite). It will even be possible to gain economic returns (ecotourism, sale of livestock products) from these systems, which will make them more acceptable to state and private landowners. We develop our case based on the advantages of using landraces versus de-domestication strategies, and on the implementation of eco-shepherding herbivory as a restoration tool in fine mosaics of agriculture/natural patches. If this approach is adopted, then larger areas can be given over to conservation, because of the potential broader benefits to society from these spaces and the engagement of farmers in practices that are closer to their traditions

The effect of pre-release captivity on post-release performance in reintroduced eastern bettongs Bettongia gaimardi.

Reintroductions are used to re-establish populations of species within their indigenous range, but their outcomes are variable. A key decision when developing a reintroduction strategy is whether to include a temporary period of confinement prior to release. Pre-release confinement is primarily used for the purpose of quarantine or as a delayed-release tactic to influence the performance or behaviour of founders post-release. A common difference between these approaches is that quarantine tends to be conducted in ex situ captivity, whereas delayed releases tend to involve in situ confinement at the release site. Although these practices are commonly viewed independently, it may be possible for a single confinement period to be used for both purposes. We tested whether temporarily holding wild eastern bettongs Bettongia gaimardi in ex situ captivity for 95-345 days prior to release (delayed release) influenced their body mass, pouch occupancy or survival during the first 1.5 years post-release, compared to founders released without confinement (immediate release). Our results suggest that exposing founders to captivity did not alter their body mass or performance post-release, despite being heavier and having fewer pouch young when released. We conclude that, for this species, ex situ captivity does not represent a tactical opportunity to improve post-release performance but can be used for quarantine without affecting the probability of establishment

Domestic livestock and rewilding: Are they mutually exclusive?

Human influence extends across the globe, from the tallest mountains to the deep bottom of the oceans. There is a growing call for nature to be protected from the negative impacts of human activity (particularly intensive agriculture); so-called “land sparing”. A relatively new approach is “rewilding”, defined as the restoration of self-sustaining and complex ecosystems, with interlinked ecological processes that promote and support one another while minimising or gradually reducing human intervention. The key theoretical basis of rewilding is to return ecosystems to a “natural” or “self-willed” state with trophic complexity, dispersal (and connectivity) and stochastic disturbance in place. However, this is constrained by context-specific factors whereby it may not be possible to restore the native species that formed part of the trophic structure of the ecosystem if they are extinct (e.g., mammoths, Mammuthus spp., aurochs, Bos primigenius); and, populations/communities of native herbivores/predators may not be able to survive or be acceptable to the public in small scale rewilding projects close to areas of high human density. Therefore, the restoration of natural trophic complexity and disturbance regimes within rewilding projects requires careful consideration if the broader conservation needs of society are to be met. In some circumstances, managers will require a more flexible deliberate approach to intervening in rewilding projects using the range of tools in their toolbox (e.g., controlled burning regimes; using domestic livestock to replicate the impacts of extinct herbivore species), even if this is only in the early stages of the rewilding process. If this approach is adopted, then larger areas can be given over to conservation, because of the potential broader benefits to society from these spaces and the engagement of farmers in practises that are closer to their traditions. We provide examples, primarily European, where domestic and semi-domestic livestock are used by managers as part of their rewilding toolbox. Here managers have looked at the broader phenotype of livestock species as to their suitability in different rewilding systems. We assess whether there are ways of using livestock in these systems for conservation, economic (e.g., branded or certified livestock products) and cultural gains

Birds of a feather flock together: Using trait-groups to understand the effect of macropod grazing on birds in grassy habitats

Restoration of appropriate disturbance regimes is a high conservation priority. However, for most species, little is known about appropriate disturbance regimes to achieve defined conservation outcomes. In this context, trait-based approaches can offer a means to generalize responses to environmental change across multiple species. Here, we investigated the potential of a trait-based approach to predict the preference of birds utilizing the grassy layers for different levels of grazing by a native grazer within grassy habitats in south-eastern Australia. We tested three hypotheses: 1) birds with particular traits (i.e. large ground-foraging, small ground-foraging, aerial insectivore, and ground-nesting/concealment) will show preferences for certain levels of grazing: 2) species within the same trait group will show preferences for a similar level of grazing intensity: and 3) different bird trait groups will favor different grazing intensities Overall, we found a significant relationship between grazing intensity and the richness of aerial insectivore and large ground-foraging trait groups utilizing the grassy layer, but not for the richness of small ground-foraging and ground-nesting/concealment trait groups. We also found that the likelihood of 3/3 aerial insectivores, 4/7 large ground-foragers, 3/10 small ground-foragers, and 1/3 ground-nesting/concealment species using the grassy layer was significantly related to grazing intensity. However, we found no significant relationship between the probability of 12 species using the grassy layer and grazing intensity, with other environmental factors potentially masking grazing response. Importantly, species within the same trait group showed a preference for similar grazing intensities, and different trait groups showed preference for different grazing intensities. For example, aerial insectivores, and a single ground-nesting/concealment species were more likely to use the grassy layer at lower grazing intensities, whereas large ground-foraging birds and small ground-foraging birds were more likely to use the grassy layer at higher grazing intensities. To maintain optimal grass structure for birds with varying grass structure preferences, landscapes should contain a heterogeneous mosaic of grazing intensities

Returning a lost process by reintroducing a locally extinct digging marsupial

The eastern bettong (Bettongia gaimardi), a medium-sized digging marsupial, was reintroduced to a predator-free reserve after 100 years of absence from the Australian mainland. The bettong may have the potential to restore temperate woodlands degraded by a history of livestock grazing, by creating numerous small disturbances by digging. We investigated the digging capacity of the bettong and compared this to extant fauna, to answer the first key question of whether this species could be considered an ecosystem engineer, and ultimately if it has the capacity to restore lost ecological processes. We found that eastern bettongs were frequent diggers and, at a density of 0.3-0.4 animals ha , accounted for over half the total foraging pits observed (55%), with echidnas (Tachyglossus aculeatus), birds and feral rabbits (Oryctolagus cuniculus) accounting for the rest. We estimated that the population of bettongs present dug 985 kg of soil per ha per year in our study area. Bettongs dug more where available phosphorus was higher, where there was greater basal area of Acacia spp. and where kangaroo grazing was less. There was no effect on digging of eucalypt stem density or volume of logs on the ground. While bettong digging activity was more frequent under trees, digging also occurred in open grassland, and bettongs were the only species observed to dig in scalds (areas where topsoil has eroded to the B Horizon). These results highlight the potential for bettongs to enhance soil processes in a way not demonstrated by the existing fauna (native birds and echidna), and introduced rabbit. -

Personality and plasticity predict postrelease performance in a reintroduced mesopredator

Reintroductions involve the relocation of animals into their historical range following extinction or extirpation. In this context, individuals with certain personalities may be more successful than others. For example, proactive individuals may dominate by being bolder, exploratory and more willing to take risks in familiar, stable environments (i.e. the source environment). Reactive personalities, in contrast, may thrive in novel, unstable environments (i.e. the release site) by being vigilant and risk averse. In addition, an individual's ability to adjust its behaviours over time (plasticity, or responsiveness) can play a pivotal role in determining postrelease performance. There is uncertainty, however, surrounding which behavioural measures translate to reintroduction success. We conducted behavioural assays and postrelease monitoring for eastern quolls, Dasyurus viverrinus, to determine whether behavioural measures (e.g. latency to emerge, time spent vigilant) could predict postrelease survival and dispersal in a fenced sanctuary. Using the ‘behavioural reaction norm’ approach, we found that personality derived from time spent exposed or vigilant during the assays had significant associations with postrelease den sharing and home range, while plasticity derived from latency (i.e. time delay) to reach food had a significant association with mean distance between consecutive dens. We recommend that proactive and rigid founders be preferred for initial trial reintroductions, and that reactive and plastic founders be used to supplement the population in later translocations. Our study demonstrates that, by including novelty, innovative behavioural assays offer significant value as a conservation tool to provide the fastest pathway to reintroduction success

Coexistence conservation: Reconciling threatened species and invasive predators through adaptive ecological and evolutionary approaches

Invasive predators are responsible for declines in many animal species across the globe. To redress these declines, conservationists have undertaken substantial work to remove invasive predators or mitigate their effects. Yet, the challenges associated with removal of invasive predators mean that most successful conservation programs have been restricted to small islands, enclosures (“safe havens”), or refuge habitats where threatened species can persist. While these approaches have been, and will continue to be, crucial for the survival of many species, in some contexts they may eventually lock in a baseline where native species vulnerable to invasive predators are accepted as permanently absent from the wild (shifting baseline syndrome). We propose an explicit theme in conservation biology termed “coexistence conservation,” that is distinguished by its pursuit of innovative solutions that drive or enable adaptive evolution of threatened species and invasive predators to occur over the long term. We argue evolution has a large role to play but using it to adapt native species to a new environmental order requires a shift in mindset from small, isolated, and short-term leaps to deliberate, staged steps within a long-term strategy. A key principle of coexistence conservation is that predation is treated as the threat, rather than the predator, driving a focus on the outcome rather than the agent. Without a long-term strategy, we face the permanent loss of many species in the wild. Coexistence conservation is a complementary approach to current practice and will play an important role in shifting our current trajectory from continued and rapid invasive predator-driven defaunation to a world where invasive predators and native prey can coexist

Adapting reintroduction tactics in successive trials increases the likelihood of establishment for an endangered carnivore in a fenced sanctuary

Threatened species recovery programs are increasingly turning to reintroductions to reverse biodiversity loss. Here we present a real-world example where tactics (techniques which influence post-release performance and persistence) and an adaptive management framework (which incorporates feedback between monitoring and future actions) improved reintroduction success. Across three successive trials we investigated the influence of tactics on the effective survival and post-release dispersal of endangered eastern quolls (Dasyurus viverrinus) reintroduced into Mulligans Flat Woodland Sanctuary, Australian Capital Territory. Founders were monitored for 42 days post-release, and probability of survival and post-release dispersal were tested against trial, origin, sex, den sharing and presence of pouch young. We adopted an adaptive management framework, using monitoring to facilitate rapid learning and to implement interventions that improved reintroduction success. Founders released in the first trial were less likely to survive (28.6%, n = 14) than those founders released the second (76.9%, n = 13) and third trials (87.5%, n = 8). We adapted several tactics in the second and third trials, including the selection of female-only founders to avoid elevated male mortality, and post-mating releases to reduce stress. Founders that moved dens between consecutive nights were less likely to survive, suggesting that minimising post-release dispersal can increase the probability of survival. The probability of moving dens was lower in the second and third trials, for females, and when den sharing with another founder. This study demonstrates that, through iterative trials of tactics involving monitoring and learning, adaptive management can be used to significantly improve the success of reintroduction programs

Baseline health and disease assessment of founder eastern quolls (Dasyurus viverrinus) during a conservation translocation to mainland Australia

We evaluated the health of 31 (eight males, 23 females) founder eastern quolls (Dasyurus viverrinus), translocated to a fenced reserve in the Australian Capital Territory between February 2016 and July 2017. Quolls were wild caught in Tasmania (16 animals) or captive bred at Mount Rothwell Biodiversity Interpretation Centre, Victoria (15 animals). Quolls were assessed for the presence of selected potential pathogens (Toxoplasma gondii, herpesviruses, Salmonella serovars, hemoprotozoa, and ectoparasites). We assessed the relationships among sex, provenance (captive or free ranging), T. gondii or herpesvirus infection, weight, and hematologic and biochemical variables. Six of 21 quolls (29%) tested were seropositive for antibodies to T. gondii. Seropositive quolls weighed significantly more and had significantly lower potassium levels, anion gaps, and urea and triglyceride levels than seronegative quolls had. Eighteen of 31 (58%) combined conjunctival-pharyngeal-cloacal swabs collected from quolls were PCR positive for a newly identified gammaherpesvirus, tentatively named dasyurid gammaherpesvirus 3. There were no significant differences among hematologic and biochemical variables or body weights from PCR-positive and PCR-negative quolls. Eighteen of 18 (100%) of rectal-swab samples were culture negative for Salmonella serovars. Three species of tick (Ixodes tasmani, Ixodes fecialis, and Ixodes holocyclus), two species of mite (Andreacus radfordi, one unidentified), and four species of flea (Pygiopsylla hoplia, Acanthopsylla rothschildi rothschildi, Uropsylla tasmanica, and Stephanocircus dasyuri), were detected on wild-caught quolls, whereas a fifth species of flea, Echidnophaga myremecobii, was detected only on captive-bred quolls. Five of 15 blood samples (33%) were positive for hemoprotozoan DNA via PCR, a novel Hepatozoon species, a novel Theileria species, Theileria paparinii, and Trypanosoma copemani were detected. Despite the presence of several potential pathogens known to be associated with disease in other marsupials, the quolls were considered to be in good general health, suitable for translocation, and a viable population was subsequently established

The ‘Goldilocks Zone’ of predation: The level of fox control needed to select predator resistance in a reintroduced mammal in Australia

A large component of the anthropogenic biodiversity crisis is the loss of animal species. In response, there has been significant investment in reintroductions of species to their historical ranges. Predation by native and exotic predators, however, remains a barrier to success. Over the past 200 years, Australia has seen the highest rate of mammal extinction on earth, with mammals within a critical weight range (CWR: 35 g–5.5 kg) most affected due to predation by exotic predators. Populations of some threatened species now exist only in Tasmania, offshore islands, or predator-proof sanctuaries. The next critical step is to return native populations outside of predator-free areas, ‘beyond-the-fence’, on the continental mainland. Given our current inability to completely remove exotic predators from mainland ecosystems, how can we achieve successful mammal reintroductions? A potential solution is to drive adaptation of reintroduced animals towards predator-resistance by exposing them to low levels of predation. We propose the concept of a ‘Goldilocks Zone’—the ‘just right’ levels of predation needed to drive selection for predator-resistant native species, while ensuring population viability. We experimentally reintroduced a mammal, the eastern bettong (Bettongia gaimardi), to mainland Australia, 100 years after its local extinction. Using an intense baiting regime, we reduced the population density of the red fox (Vulpes vulpes), the main factor behind the eastern bettong’s extirpation from the continent. Reducing bait take to 15% of previous levels allowed differential survival among bettongs; some surviving under 100 days and others over 450 (~ 4 times longer than some similar trials with related species). Surviving individuals were generally larger at release than those that died earlier, implying selection for larger bettongs. Our results suggest that reducing predation could establish a Goldilocks Zone that could drive selection for bettongs with predator-resistant traits. Our work contributes to a growing body of literature that explores a shift towards harnessing evolutionary principles to combat the challenges posed by animal management and conservation