Reversing functional extinction of mammals prompts a rethink of paradigms about seed fate in arid Australia

Evaluating the success of functional restoration after reintroduction of a lost avian pollinator

Conservation translocation is a common method for species recovery, for which one increasingly frequent objective is restoring lost ecological functions to promote ecosystem recovery. However, few conservation translocation programs explicitly state or monitor function as an objective, limiting the ability to test assumptions, learn from past efforts, and improve management. We evaluated whether translocations of hihi (Notiomystis cincta), a threatened New Zealand passerine, achieved their implicit objective of restoring lost pollination function. Through a pollinator-exclusion experiment, we quantified, with log response ratios (lnR), the effects of birds on fruit set and seed quality in hangehange (Geniostoma ligustrifolium), a native flowering shrub. We isolated the contributions of hihi by making comparisons across sites with and without hihi. Birds improved fruit set more at sites without hihi (lnR = 1.27) than sites with hihi (lnR = 0.50), suggesting other avian pollinators compensated for and even exceeded hihi contributions to fruit set. Although birds improved seed germination only at hihi sites (lnR = 0.22-0.41), plants at sites without hihi had germination rates similar to hihi sites because they produced 26% more filled seeds, regardless of pollination condition. Therefore, although our results showed hihi improved seed quality, they also highlighted the complexity of ecological functions. When an important species is lost, ecosystems may be able to achieve similar function through different means. Our results underscore the importance of stating and monitoring the ecological benefits of conservation translocations when functional restoration is a motivation to ensure these programs are achieving their objectives.

New evidence of seed dispersal identified in Australian mammals

ContextMammal–seed interactions are important for structuring vegetation communities across a diverse range of ecosystems worldwide. In Australia, mammals are typically considered to be seed predators and to play insignificant roles in seed dispersal. However, very few studies have investigated endozoochorous seed dispersal in Australian species. The translocation of Australian mammals for the purposes of ecosystem restoration is increasing. Digging mammals (i.e. species that dig to obtain food or create shelter) are commonly the focus of these translocations because they are considered to be ecosystem engineers, but an understanding of their role in seed dispersal is lacking. AimsThe aim of the present study was to expand the understanding of endozoochory in Australian digging mammals by determining whether seeds consumed by select species remain viable and able to germinate. MethodsScat samples were collected from five digging mammal species, known to consume seeds or fruit, across nine sites in Western and South Australia. The samples were searched for seeds, with the recovered seeds identified and tested for viability and germination capacity. Key resultsThe abundance of intact seeds in scats was generally low, but 70% of the retrieved seeds appeared viable. Five species of seed germinated under laboratory conditions. These seeds were retrieved from bilby (Macrotis lagotis), boodie (Bettongia lesueur), golden bandicoot (Isoodon auratus) and quenda (I. fusciventer) scats. ConclusionsSeeds consumed by Australian digging mammals can remain viable and germinate, indicating that digging mammals play a more important role in seed dispersal than previously considered. ImplicationsDigging mammals have the potential to contribute to ecosystem restoration efforts through the dispersal of viable seeds, but there is also a risk that non-native species could be dispersed. These costs and benefits should be considered by practitioners when planning reintroductions of digging mammals.

Echolocation and foraging ecology of the bristle-faced free-tailed bat, Setirostris eleryi, in central Australia

We document the spectral characteristics of echolocation sequences of Setirostris eleryi recorded from riparian zones in the Central Ranges in Western Australia, near Warakurna. These are the first records of this species in Western Australia. The sequences are comparable to reference S. eleryi sequences from near Alice Springs, as well as to sequences from a nearby vouchered specimen locality (Hull River in the Northern Territory), yet distinct from Scotorepens greyii sequences from Western Australia, including locations in the Central Ranges. The central Australian S. eleryi sequences average 3kHz higher in frequency than reference S. eleryi recordings from eastern Australia. We deduce the species’ foraging strategy, microhabitat, wing beat frequency and flight speed from the echolocation sequences, then show that these deductions are consistent with calculations based on an airframe analysis of museum specimens, and with available field observations. The echolocation recordings provided a quick, passive, cost-effective characterisation of foraging niche, useful for conservation planning.

An Australian perspective on rewilding

Rewilding is increasingly recognized as a conservation tool but is often context specific, which inhibits broad application. Rewilding in Australia seeks to enhance ecosystem function and promote self-sustaining ecosystems. An absence of large-bodied native herbivores means trophic rewilding in mainland Australia has focused on the restoration of functions provided by apex predators and small mammals. Because of the pervasive influence of introduced mesopredators, predator-proof fences, and establishment of populations on predator-free islands are common rewilding approaches. This sets Australian rewilding apart from most jurisdictions and provides globally relevant insights but presents challenges to restoring function to broader landscapes. Passive rewilding is of limited utility in arid zones. Although increasing habitat extent and quality in mesic coastal areas may work, it will likely be necessary to undertake active management. Because much of Australia's population is in urban areas, rewilding efforts must include urban areas to maximize effectiveness. Thus rewilding is not synonymous with wilderness and can occur over multiple scales. Rewilding efforts must recognize human effects on other species and benefit both nature and humans. Rewilding in Australia requires development of a shared vision and strategy and proof-of-concept projects to demonstrate the benefits. The repackaging of existing conservation activities as rewilding may confuse and undermine the success of rewilding programs and should be avoided. As elsewhere, rewilding in Australia should be viewed as an important conservation tool.

Habitat associations of zoophagic bat ensembles in north-western Australia

North-western Australia comprises the Kimberley Craton and parts of three adjacent sedimentary basins. It has a tropical climate and habitats that range from semiarid plains supporting grasslands to mesic uplands supporting woodlands as well as narrow riparian forests and patches of rainforest; mangrove forests occur along the coast. Its bat fauna comprises three obligate phytophages and 27 obligate zoophages. Analysis of zoophagic bats at 171 sites scattered throughout this study area revealed two compositionally distinct ensembles. One, comprising 19 species, occupies mangrove forest and includes three species known only to occupy mangroves in Western Australia. The other, comprising 20 species, occupies landward habitats and includes four species that are found only in landward ecosystems. Both ensembles are structured in terms of resource allocation, but nestedness observed in assemblage composition can be explained by environmental factors, implying the influence of environmental controls. Sixteen species belong to both ensembles, but seven of these require cave roosts and occur only near cavernous country while three others are confined to rocky riparian habitats. The richest assemblages were recorded in rugged cavernous landscapes in complex vegetation structures near permanent freshwater pools in the most mesic areas.

What can echolocation recordings reveal about the foraging ecology of Saccolaimus saccolaimus (Emballonuridae) in north-western Australia?

Echolocation sequences reveal aspects of the foraging ecology of Saccolaimus saccolaimus (Emballonuridae). In combination, pulse peak-frequency and fineness-of-tuning values derived from free-flying search-mode echolocation sequences emitted by S. saccolaimus in north-western Australia imply that it generally forages in uncluttered airspaces using an air superiority foraging strategy. Wing-beat frequency values, derived from pulse repetition rates in these sequences, reveal that it has a maximum aerobic level-flight speed of 8.1 m s–1 (used for foraging). These predictions are consistent with deductions based on airframe design parameters taken from museum specimens, and with available field observations. The echolocation recordings provided a quick, passive, cost-effective characterisation of foraging niche, useful for conservation planning.