Doug P. Armstrong

Reversing defaunation: Restoring species in a changing world

The rate of biodiversity loss is not slowing despite global commitments, and the depletion of animal species can reduce the stability of ecological communities. Despite this continued loss, some substantial progress in reversing defaunation is being achieved through the intentional movement of animals to restore populations. We review the full spectrum of conservation translocations, from reinforcement and reintroduction to controversial conservation introductions that seek to restore populations outside their indigenous range or to introduce ecological replacements for extinct forms. We place the popular, but misunderstood, concept of rewilding within this framework and consider the future role of new technical developments such as de-extinction.

Invasive mammal eradication on islands results in substantial conservation gains.

Significance Global conservation actions to prevent or slow extinctions and protect biodiversity are costly. However, few conservation actions have been evaluated for their efficacy globally, hampering the prioritization of conservation actions. Islands are key areas for biodiversity conservation because they are home to more than 15% of terrestrial species and more than one-third of critically endangered species; nearly two-thirds of recent extinctions were of island species. This research quantifies the benefits to native island fauna of removing invasive mammals from islands. Our results highlight the importance of this conservation measure for protecting the worlds most threatened species. More than US

Successful island reintroductions of New Zealand robins and saddlebacks with small numbers of founders

21 billion is spent annually on biodiversity conservation. Despite their importance for preventing or slowing extinctions and preserving biodiversity, conservation interventions are rarely assessed systematically for their global impact. Islands house a disproportionately higher amount of biodiversity compared with mainlands, much of which is highly threatened with extinction. Indeed, island species make up nearly two-thirds of recent extinctions. Islands therefore are critical targets of conservation. We used an extensive literature and database review paired with expert interviews to estimate the global benefits of an increasingly used conservation action to stem biodiversity loss: eradication of invasive mammals on islands. We found 236 native terrestrial insular faunal species (596 populations) that benefitted through positive demographic and/or distributional responses from 251 eradications of invasive mammals on 181 islands. Seven native species (eight populations) were negatively impacted by invasive mammal eradication. Four threatened species had their International Union for the Conservation of Nature (IUCN) Red List extinction-risk categories reduced as a direct result of invasive mammal eradication, and no species moved to a higher extinction-risk category. We predict that 107 highly threatened birds, mammals, and reptiles on the IUCN Red List—6% of all these highly threatened species—likely have benefitted from invasive mammal eradications on islands. Because monitoring of eradication outcomes is sporadic and limited, the impacts of global eradications are likely greater than we report here. Our results highlight the importance of invasive mammal eradication on islands for protecting the worlds most imperiled fauna.

Mortality and behaviour of hihi, an endangered New Zealand honeyeater, in the establishment phase following translocation

Populations established with a small number of founders are thought to have a high risk of extinction due to Allee effects, demographic stochasticity, inbreeding and reduced genetic variation. We tested whether the initial number of birds released was related to persistence in reintroductions of saddlebacks (Philesturnus carunculatus) and robins (Petroica australis) to New Zealand offshore islands. Data were analysed for 31 populations that had been observed for at least 3 years since reintroductions. The numbers released ranged from 5–188. Most of the populations (26) survived and grew, including five from less than 15 founders, and four out of the five extinctions were attributable to introduced mammalian predators. The number of individuals released did not significantly affect extinction probability. The ability of these small releases to establish populations can be attributed to the closed nature of the islands (allowing birds to find mates), low mortality rates following release and high growth rates at low density. Stochastic simulation models based on data from two reintroduced populations suggested that populations with four founders (two male, two female) would have a negligible chance of extinction through demographic stochasticity and would be able to grow even if there were high rates of egg failure through inbreeding.

Effects of familiarity on the outcome of translocations. II: A test using New Zealand robins

We analysed mortality and behaviour of hihi, an endangered New Zealand honeyeater, in the first three months after translocation to 135 ha Mokoia island. Our aims were to assess: (1) whether mortality and behaviour were affected by the translocation process or post-release management, and (2) whether the fate of birds during this establishment phase affected the viability of the population. Forty hihi were translocated from the wild population on Little Barrier Island, released immediately in three different locations, and provided with sugar water feeders. Many of the birds suffered leg injuries due to the bands initially used, and up to 7 birds may have died from these injuries. Nevertheless, the mortality rate over the first three months was similar to the average rate over the first 3 years. Therefore, except for the bands used, there was no evidence of post-release mortality associated with translocation stress. Most hihi discovered the feeders quickly. However, feeder use varied greatly among birds and there was no evidence that access to feeders reduced mortality. Access to feeders also did not affect overall time spent foraging. However, birds using feeders allocated most of their foraging effort to invertebrate feeding, whereas birds not using feeders foraged mostly on flowers and fruits. Hihi dispersed quickly after release, and moved all over the island. Transmitters increased re-sighting rates over the first 3 weeks, but intensive observation during that period provided no useful information relevant to subsequent survival and reproduction. There was a slight tendency for birds to settle closer to their release sites than expected by chance, but there was no tendency for birds released together to form breeding pairs. We conclude that the viability of this population was not affected by any problems in the establishment phase. However, the population has had a consistently high mortality rate over the first 3 years, and its long-term viability appears poor. Our subsequent research is, therefore, addressing the factors that might be limiting the population in the long-term.

Strategic monitoring of reintroductions in ecological restoration programmes

Abstract Research on birds has shown that familiarity between mates and neighbours leads to lower aggression and higher reproductive success. This study addresses the hypothesis that founder groups used for translocations will do better if made up of individuals that are familiar with one another. The study involved a translocation of a territorial forest bird, the North Island robin Petroica australis longipes to an offshore island. I created both ‘familiar groups’ (made up of birds that had been adjacent to one another at the source location) and ‘unfamiliar groups’ (made up of birds that had been widely separated). I released the groups in separate forest patches on the island, and assessed the effects of familiarity on aggression, dispersal, survival and pair bonding. While the study was limited by the sample sizes possible, there was no indication that ‘familiar groups’ performed differently than ‘unfamiliar groups’, or that familiarity at the source location affected behavioural interactions following translocation. Post-translocation familiarity was clearly important, for aggression declined according to how long birds had been neighbours at the new location. There was little aggression in general over the first two to five weeks, the period when an effect of prior familiarity on aggression may have been most important. In addition, breakup of ‘familiar’ groups by dispersal meant that there was limited opportunity for interaction among familiar birds. These results suggest that familiarity within founder groups is unlikely to have strong effects following translocation.

Floater males gain reproductive success through extrapair fertilizations in the stitchbird.

Abstract It is well recognized that reintroductions have previously suffered from insufficient monitoring, and as a result reintroduction protocols and guidelines now have stringent monitoring requirements. It is important, however, that monitoring is done strategically. To be cost efficient, monitoring must be designed to address key questions relevant to reintroduction success and must be allocated to reintroductions where monitoring will have the greatest value. While the traditional aim of reintroductions was to recover endangered species, there is now a much greater emphasis on reintroduction as part of ecological restoration programmes. This often means that whole suites of species are re-introduced, including common as well as endangered species. We recommend the following approach for strategically monitoring reintroductions in restoration programmes. First, monitoring should be allocated not just to the rarest species, but to focal species chosen based on restoration objectives. Second, monitoring should primarily aim to assess the suitability of the habitat for supporting the species in the long-term, rather than the short-term effects of different release strategies (e.g., soft versus hard release). Third, an experimental approach should be used where possible to test the extent to which habitat factors such as food and predators are limiting population viability. We provide examples from our research on 2 species of New Zealand forest birds being reintroduced as part of ecological restoration programmes.

When do we need more data? A primer on calculating the value of information for applied ecologists

We used minisatellite DNA profiling to assign parentage to stitchbird, Notiomystis cincta, chicks from a breeding population on Tiritiri Matangi Island off the coast of the North Island of New Zealand. The small population size allowed samples to be collected from all potential parents and nearly (33/34 nestlings) complete assignment of paternity. Analysis revealed that 35% of nestlings (12/34) were the result of extrapair copulation and that extrapair young were present in 80% of nests (8/10). About half of the extrapair nestlings were the offspring of unpaired males. This is substantially higher than predicted from the literature, which suggests that extrapair paternity is typically gained by paired males. Copyright 1999 The Association for the Study of Animal Behaviour.

Effects of familiarity on the outcome of translocations, I. A test using saddlebacks Philesturnus carunculatus rufusater

Summary Applied ecologists continually advocate further research, under the assumption that obtaining more information will lead to better decisions. Value of information (VoI) analysis can be used to quantify how additional information may improve management outcomes: despite its potential, this method is still underused in environmental decision-making. We provide a primer on how to calculate the VoI and assess whether reducing uncertainty will change a decision. Our aim is to facilitate the application of VoI by managers who are not familiar with decision-analytic principles and notation, by increasing the technical accessibility of the tool. Calculating the VoI requires explicit formulation of management objectives and actions. Uncertainty must be clearly structured and its effects on management outcomes evaluated. We present two measures of the VoI. The expected value of perfect information is a calculation of the expected improvement in management outcomes that would result from access to perfect knowledge. The expected value of sample information calculates the improvement in outcomes expected by collecting a given sample of new data. We guide readers through the calculation of VoI using two case studies: (i) testing for disease when managing a frog species and (ii) learning about demographic rates for the reintroduction of an endangered turtle. We illustrate the use of Bayesian updating to incorporate new information. The VoI depends on our current knowledge, the quality of the information collected and the expected outcomes of the available management actions. Collecting information can require significant investments of resources; VoI analysis assists managers in deciding whether these investments are justified.

The Risks of Assisted Colonization

Translocation, the intentional release of a species in a new location, plays an important role in the conservation of endangered species. Consequently, there is a critical need for research on factors affecting the outcome of translocation attempts. This study addresses the hypothesis that founder groups will do better if they are made up of individuals that are familiar with one another. The hypothesis is based on research on birds showing that familiarity between mates and neighbours leads to lower aggression and higher reproductive success. Our test involved a translocation of the North Island saddleback Philesturnus carunculatus rufusater, a New Zealand forest bird restricted to islands free of mammalian predators. We created two founder groups of 18 birds each, one made up of birds from a single small forest patch, and including five known pairs, and the other a mixture of birds from several patches, with no pairs. We released the groups in different parts of an island, and assessed the effects of familiarity on survival, dispersal, pair bonding, and reproduction. The two groups showed similarly high survival, and both dispersed widely. Pair bonds formed more quickly among the familiar birds, even though only one of the five original pairs stayed together after translocation. While pairing among unfamiliar birds tended to be delayed, they achieved a similarly high rate of pairing by the start of the breeding season, and reproductive output was similar for familiar and unfamiliar pairs. We therefore found no evidence that using familiar individuals would improve the outcome of bird translocations. We note that familiarity could be more important with other species and/or in other circumstances. However, we also note the potential costs of using familiar individuals.