A Bat's End: The Christmas Island Pipistrelle and Extinction in Australia

By John Woinarski

On the evening of 26 August 2009, the last known pipistrelle emerges from its day-time shelter on Christmas Island. Scientists, desperate about its conservation, set up a maze of netting to try to catch it. It is a forlorn and futile exercise – even if captured, there is little future in just one bat. But the bat evades the trap easily, and continues foraging. It is not recorded again that night, and not at all the next night. The bat is never again recorded. The scientists search all nearby areas over the following nights. It has gone. There are no more bats. Its corpse is not, will never be, found. It is the silent, unobtrusive death of the last individual. It is extinction.

This book is about that bat, about those scientists, about that island. But mostly it is an attempt to understand that extinction; an unusual extinction, because it was predicted, witnessed and its timing is precise.

A Bat's End is a compelling forensic examination of the circumstances and players surrounding the extinction of the Christmas Island pipistrelle. A must-read for environmental scientists, policy-makers, and organisations and individuals with an interest in conservation.

Recipient, 2019 Whitley Awards Certificate of Commendation: Conservation Biology

• Language: English
• Publisher: CSIRO PUBLISHING
• Release date: Sep 1, 2018
• ISBN: 9781486308651

Book preview

1

Introduction

This book is an obituary and an inquest. Its subject is a small bat, the Christmas Island pipistrelle Pipistrellus murrayi, whose last individual died on the night of 26 August 2009.

This book is an exploration of the shortcomings in research, monitoring, management and policy that led to the conservation management failure that is extinction. It is about the individuals who fought for this species, and those whose responsibility included the protection of this species: for the fate of any species may rest haphazardly and insecurely on the interest, expertise, care or neglect of but a few people.

It is a consideration of our society’s preparedness to countenance extinction, to accept the loss of less consequential species as collateral damage to our progress. ‘Extinction’ itself is an odd and inadequate word, whose grammatical passivity distracts from its immediacy and totality. Species ‘become extinct’, as if that is an abstraction, a progression, or a fate long reserved for them. The sometimes used alternative ‘disappear’ is perhaps worse, suggesting a conjuring trick, and the vague promise of return. The death of (human) individuals is not so neutered: we ‘die’, or are ‘killed’: sharper words that speak of directness and loss. This book seeks to deconstruct a case of ‘extinction’ and to give feeling to that loss.

It is a plot with a beautiful setting, soured by our deliberate, inadvertent or uncaring manipulation of its nature. It is a requiem for the loss of island life, that most baroque and wonderful of evolutionary dealings. It is a mark of respect, that the loss of any species should not go unrecognised. Beyond the specific fate of the pipistrelle, it is a plea to manage our environments with more care and empathy, to accept greater responsibility for the life around us.

This case highlights many of the weaknesses in our capability for environmental management. It would not have been unreasonable to assume that this species could have been successfully conserved. In general – other than a few cases of direct exploitation or intensive disturbance at roost and maternity sites – bat species are reasonably resilient and have not featured prominently in the world’s rollcall of extinctions. More specifically for the pipistrelle: it occurred in a remote island largely protected within a national park managed by Australia’s premier conservation agency; its decline was long noted and recognised in inclusion on Australia’s list of threatened species, ostensibly qualifying it for protection, targeted resourcing and management; it was the subject of a specific and well-considered recovery plan, the primary management mechanism to forestall extinction; the relevant experts warned of the likelihood of its extinction; and its plight was publicised by an informed lobby group. This package of conservation mechanisms failed.

This case interests and disturbs me most because it is so recent. European settlement of Australia, in 1788, brought with it a ‘shock of the new’ set of ecosystem-altering factors that led rapidly to the extinction of uncomfortably many native species. But one could hope that those reverberations have by now largely subsided, that we now care more and have explicit legislative protection for our natural environment and its distinctive biodiversity, and that we have gained sufficient expertise in the management of Australian environments. The pipistrelle’s extinction suggests that such presumptions may be misplaced. Indeed, the pipistrelle is the first species known to have become extinct in Australia since the introduction of Australia’s landmark Environment Protection and Biodiversity Conservation Act 1999, and so may be considered to be the first irredeemable failure of that Act.

This case also interests me because it represents a particularly challenging ecological puzzle, whose (now academic) solution may never be known. Like most deaths, extinction may result from a complex interplay of contributing causal factors, acting immediately or long before, the better management of any one of which may have averted the fatality. A man jumps off a pier and drowns: his death may be due in part to the chance of wild seas and undertow, in part due to inadequate warning signs, in part due to rejection from his lover, in part due to being served too much alcohol, in part due to lack of opportunity to learn to swim, in part due to insufficient funding to allow for a permanent lifeguard, in part due to heavy traffic slowing the ambulance. Likewise, in most cases of extinction, it is often simplistic to blame a single cause. For example, even if an introduced predator consumed all individuals until none remained, causality must also encompass the quarantine policy and practice that allowed the predator to be introduced, the management that failed to reduce predator numbers to safe levels, the research inadequacy that may have failed to identify in sufficient time the problem or its remedy, and the recovery planning that failed to respond to imminent extinction with translocation or other ex-situ measures. Failure in any of these aspects may subvert the species, and cause the conservation attempt to fail. The particular case of the pipistrelle is especially intriguing, because the immediate drivers of its extinction remain poorly defined; and, hence, the management response to decline proved so difficult to prescribe.

This particular extinction event has been summarised pithily as a ‘conservation bureaucratic process working more slowly than an extinction process’.¹ There is some aptness in that description, and perhaps the rest of this book is superfluous. But I am seeking to understand why this particular extinction process was so rapid, and why the conservation bureaucratic process was so slow, or inadequate. This story seeks also to show that extinction is defined by context: it is rarely so very simple. The pathway to extinction, or its prevention, may be a maze. I’ve followed many tangents in this account, on the basis that many of the drivers of this process, or the responses that could or should have been made, operate indirectly, synergistically or uncertainly. Some of these threads may have turned out to lead nowhere, to be uninvolved in this extinction. But the evidence needs to be compiled in order to make such a judgement; and it may be relevant for other cases.

There may be many building blocks that lead to extinction. Happily, our society typically does not seek to deliberately cause extinction: extinctions are more generally the unintended, sometimes unforeseen, by-product of our actions. Governments and others may often make choices, especially in relation to exploitation of our nature, that can predictably or not lead to biodiversity decline. With many such choices made, the cumulative likelihood of significant biodiversity loss – including extinctions – increases. But the makers of any particular resource exploitation decision can argue that it wasn’t their decision alone that sprang the trap.

This is a eulogy for a species that most humans would consider inconsequential: a feeble irrelevance to the more important matters of our life. Indeed, in the Australian media this extinction rated little mention, rapidly eclipsed by far more pressing interest in the details of injuries to key players in the lead-up to the football finals, or the latest batting collapse of the Australian cricket team. I would argue that an extinction event should be far more notable; that it should be a key marker of our nation’s integrity, sustainability, progress and worth. I would argue that every extinction event should be given exposure, reflection and expression of remorse, such as I have sought to do here. But I would hope that there are few such volumes in this series.

The pipistrelle was an obscure species lacking any particular distinction and occurring in a place remote from most population centres. Such ‘anonymous’ species may be those most likely to slip away unnoticed or unmourned. To some extent, such species are the victims of the advertising mode of many conservation organisations and conservation biologists, who sell their message to an attention-limited public using the brightest, largest and most appealing species, in part on the premise that conservation efforts devoted to such species will also benefit the less charismatic, as if pandering to supermodels would assist the destitute. An alternative approach is to tell the stories about even the obscure, to recognise their existence, and give them profile:

… you cannot love what you do not know. If a bird goes extinct before anyone has ever photographed it, or written about it, you do not really care. But once you have seen how beautiful and fascinating it is, you do care.²

The pipistrelle’s extinction was not entirely dismissed in the Australian media, with the most notable contemporary commentary given by Tim Flannery, who explicitly linked its demise to political failure, accusing the federal Environment Minister of abandoning policy for political expediency, and of failing to save this species. Flannery also voiced a personal response, which finds echoes in this book:

I have not seen a mammal extinction in Australia in my lifetime until this year and when it happened it really shocked me … it is appalling, it is horrifying.³

Was the pipistrelle’s extinction an aberration: a freak case fated by the unusual circumstances of its location or ecology? Or is it a forerunner to many others, of increasing spread across the nation, of increasing taxonomic breadth, of increasing public profile and environmental significance? My interpretation and concern is that it is the latter, that there are likely to be many more extinctions in Australia.

This book is a memento mori – a physical reminder of fate and doom, of the proximity of death. It aims to serve as a warning that extinction may be the unwelcome and irreversible end-point of the inadequacy of conservation management effort and legislative scope: the inevitable consequence of us caring too little about the world around us. I would like this story to be memorable: if we mark as inconsequential the extinction of this species then such lack of concern will corrode our moral fabric, reduce to threadbare the standards that our society considers to be environmentally acceptable, and render it more likely that we will accept mutely the next extinction.

I would like this story to be discomforting. Metaphorically, I would disinter the pipistrelle’s neglected corpse, and walk hand-in-wing with the tiny bat ghost, knocking at the door of those policy makers who wheedled the words to avoid any obligation for commitment or accountability, those politicians who too readily sanction and steer our unsustainable use of natural resources and who provide too little in return for the conservation of our nature, those environmental managers who too little cared or tried, and our society itself that without regard countenances such shortcomings in our consideration of nature. Metaphorically, I would like to leave them, and all of us, with an indelible trace, the faint foetid smell of the bat ghost’s decay.

I would also like the bat ghost to salute those who tried desperately to avert its fate, to salve their sense of failure. I would like then to re-bury the bat ghost with respect and sorrow, with the hope that the ceremony would reverberate enough to reduce the likelihood of similar loss.

This is a retrospective assessment of a conservation failure. But it is also an attempt to draw lessons that may reduce the likelihood of such examples recurring, in particular for the many other threatened species on Christmas Island, but more generally for other species on islands, and for the conservation of Australian biodiversity more widely. Already there is some hope that such lessons have been heeded, with some current success in the conservation management of some threatened reptile species on Christmas Island, and a refreshed avowal by the Australian Government to seek to prevent further extinctions. Such benefit may be the pipistrelle’s enduring legacy.

This is a story with many parts: it is about history, biology, ethics, policy, legislation, management, sustainability, individuals and emotion. I try to view this problem from many perspectives, and this narrative accordingly seeks to weave together many disparate threads. Recognising that the demise of the pipistrelle involved a complex ecological package of factors, this story starts with contextual chapters relating to the biodiversity conservation values and challenges of islands in general, and the setting and history of Christmas Island. In part, this story is as much about the environmental decline of a place, Christmas Island, as it is of a species: the two are intimately connected, linked by the environmental and management factors driving these declines. The bat itself makes its appearance (and disappearance) later in the narrative.

Some stylistic conventions

I have attempted to make this book accessible to both the scientifically nimble and those with a general interest in our natural world. But it is to the latter that I am most trying to communicate, because the care and loss of biodiversity should not be seen as a matter left only to the academic elite, or to the ostensibly responsible officers of government departments. So, at the beginning I should explain a few conventions that I employ subsequently.

Following normal practice in scientific writing, I give the common name (where available) and scientific name of any plant or animal species at its first use, and thereafter use only a common name (or scientific name only in those cases where there is no generally accepted common name).

Over the course of the pipistrelle’s decline, the agency primarily responsible for its management was the environment department of the Australian Government (and/or the parks service component of that agency). Typical of government departments, it has undergone numerous re-structures and name changes. In most cases, I refer to it simply as the environment department or, where relevant, the parks service. Likewise, there has been change in the function and name of the Australian Government department primarily responsible for external territories (including Christmas Island) over the period considered in this book. That particular responsibility is small in the ambit of government, and it is typically tacked onto some grab-bag of other ministerial duties. As at December 2017, responsibility for most Australian external territories (including Christmas Island) lies within the Department of Infrastructure and Regional Development.

Table 1.1. Changes over time in the company involved in the mining of phosphate on Christmas Island

The ownership, management and name of the entity that has monopolised phosphate mining on Christmas Island has also changed (Table 1.1), albeit less frenetically than that of the government departments involved in this story.

With this particular story, there is some challenge in accessing primary sources. Most of the information relating to the pipistrelle is compiled in unpublished reports. Although some of these are not readily accessible to the public, I have referenced them as if they were formally published. Where there is uncertainty about content, I have attempted to clarify or verify with those individuals who were primarily responsible for the compilation of the reports.

Disclaimer

I write mostly as a conservation biologist who had little direct involvement in this case. However, I did have some peripheral participation, and it is proper to disclose that role, given that this book includes consideration of the roles and responsibilities of others, and provides some assessment of how well those responsibilities were met.

My role in this case was two-fold. From 2003 to 2012, I was a member of Australia’s Threatened Species Scientific Committee, charged with advising the Australian Minister for the environment on the compilation and maintenance of a national list of species and ecological communities considered to be threatened with extinction, and the endorsement of recovery plans for those species and communities. I was also a member of the Minister’s ‘Expert Working Group’ on the conservation management of Christmas Island biodiversity, established in January 2009, in part to provide advice on the conservation of the Christmas Island pipistrelle. That group arrived on the scene of this story well into the final act, and was dissolved at the completion of its final report, in April 2010. This book germinated from my involvement in the workings of that group, and in particular at frustration, but fascination, with its failure in the particular case of the pipistrelle. Notwithstanding these tangential connections, the opinions in this book are my own (except where explicitly stated to be those of others), and should not be taken to represent the views of the committees or working groups to which I have belonged.

2

The conservation value and challenge of islands

This story is particularly about one bat species on one island. But it relates to biodiversity conservation on islands (and elsewhere) generally; and the characteristics of island ecology and conservation more broadly provide a reference and framework for contextualising this particular case.

There are two general features that characterise island ecology and conservation. One of these is that islands provide much that is most distinctive of the world’s biodiversity. They contribute a far higher proportion of the total species pool of the planet than would be expected from their combined relatively small total area (Kier et al. 2009). The second feature is that island biodiversity has proven particularly susceptible to decline and extinction. Species that are restricted to islands comprise an unrepresentatively high proportion of the world’s threatened and extinct plant and animal species (Alcover et al. 1998; Loehle and Eschenbach 2012; McCreless et al. 2016). Over the last 400 years, more species have become extinct on small islands than on continents. This propensity is particularly marked for birds, for which 87% of recent extinctions have been island endemics, but it applies generally for all animal and plant groups (Blackburn et al. 2004; Brooke et al. 2007; Sax and Gaines 2008; Tershy et al. 2015; Doherty et al. 2016). This is a pattern readily evident in Australia. For example, although islands smaller than Tasmania comprise less than 0.5% of Australia’s land area, 21 of 54 (i.e. 39%) animal taxa listed as extinct in Australia occurred only on such islands (Woinarski et al. 2018).

There are two fundamentally different classes of islands. Continental islands (such as Tasmania, New Guinea, and Ireland) were formerly part of a larger (continental) land mass from which they have since been isolated. In many cases, the connections have repeatedly been severed and re-formed as sea levels rise and fall over time. In contrast, oceanic islands have never had land bridge connections to mainland areas; they have been isolated since birth. Examples include the Hawaiian islands and the Galapagos islands. Many oceanic islands are volcanic in origin, and many have grown, shrunk or disappeared in response to sea level changes and the extent and consequences of volcanic activity.

The two main classes of islands dictate very different biodiversity patterns. When formed, as rising sea levels cut the mainland connection, continental islands supported a ‘mature’ biota, a well-developed subset of that present on their parental mainland. Over time, the continental island biota may diverge from that of its mainland equivalent, through species loss from either the island or mainland, through arrival of new species from other source areas, or through evolutionary divergence of once-shared species.

In contrast, oceanic islands are blank slates at their origin, and assemble gradually over time a completely idiosyncratic complement of colonising species. Many of these colonising species have traits that make for effective dispersal. For plants, these traits include buoyant and resilient seeds that can survive long periods of immersion in the sea, light or fluffy seeds that can be blown extensively by wind, or viscous seeds that may stick to the bodies of birds, hitching rides over long distances. Animal colonisation of oceanic islands may be even more haphazard, and involves a lottery-scale likelihood of success. Some animals raft to islands, unwillingly trapped on flood debris or other floating vegetation. The probability of success is not entirely random: some types of species will be far more tolerant of salt water than others – for example, frogs are notoriously poor colonisers through overseas dispersal. Some animals, such as many spiders, have young that can disperse widely (if aimlessly) on wind currents. Many birds and butterflies disperse long distances through regular migrations, and may be most likely to encounter new islands if they stray from their normal dispersal routes. Storms and cyclones can force many birds, bats and insects to become unsought-for discoverers of new islands.

However, newly arriving at an island does not equate to successful immigration. The colonisers must include individuals capable of reproduction; the island must contain appropriate food resources, habitat, and climate; and it should not already have closely similar species that may be competitively superior, or a severe existing predator or consumer regime. These are formidable constraints, and most would-be colonisers fail. Conversely, islands may offer extraordinary new opportunity for the fortunate or adaptable species, because they can exploit new habitats or resources unhindered by the competitive constraints or predator regimes of their more cluttered source areas.

Over time, the descendants of colonists will diverge from their home stock, transforming to increasingly more distant taxonomic states (forming endemic subspecies, species, genera or even families). This may be due in part to adapting to exploit these novel environments, and gradually losing those previous adaptations that fitted better their source context. It may be a forced consequence of the relatively low complement of the species’ overall genetic variation brought to the island within the typically small number of individuals in the founder stock. It may be due to genetic drift: the random working of time on genetic composition, which will almost inevitably draw two segregated populations further apart.

Older, more isolated, larger and more topographically complex islands tend to have the most distinctive biotas (higher rates of endemism, and higher order endemism), forming separate and strange self-contained worlds in the laboratory of evolution. Remote clusters of islands may be particularly fertile arenas for speciation, where an original colonist to one island may subsequently colonise other islands in the group, with each of these immigrant stocks diverging in subsequent isolation to form a kaleidoscopic radiation of related, but different, species: the classic examples are Darwin’s finches and land tortoises in the Galapagos islands. In some cases, these isolated and divergent forms may then re-colonise other islands in the group and, if they are then sufficiently distinct from their resident relative, the outcome may be multiple related species co-existing on single islands.

Partly due to the hurdle of isolation, the overall number of species on islands is typically fewer than on mainland areas of comparable size, and island ecology may have a relatively simple pattern. In many cases, the uncluttered island ecosystems are characterised by very strong functional linkages between highly evolved species (co-adaptation), where two or more long-established species become mutually dependent upon each other. This intimacy may be efficient in stable and predictable situations, but it may become a fatal flaw under environmental change: if one of the linked species succumbs to a novel introduction or land use change, the other will follow inexorably (Cox and Elmqvist 2000; Mortensen et al. 2008).

The patterning of species richness on islands has been a fertile area of scientific thinking, notably through the theory of island biogeography, developed by Robert MacArthur and E.O. Wilson in the 1960s (MacArthur and Wilson 1963; MacArthur and Wilson 1967). This emphasised the dynamic nature of island ecology, noting that island species’ complements were an uneasy balance between immigrations and localised extinctions, with island species’ tallies largely fixed at an equilibrium value that is determined by island area, moderated by the probability of immigration, itself dependent upon the distance of the island from source areas. The theory, with its later finessed variants (Whittaker 1998; Brown and Lomolino 2000; Lomolino 2000; Hubbell 2001; Kalmar and Currie 2006; Heaney 2007; Whittaker et al. 2008), has been influential in understanding the workings of ecology generally, but more particularly in conservation management and the design of conservation reserves (seen as island analogues, surrounded by a hostile ‘sea’ of unfavourably transformed lands) (Diamond 1975; Lindenmayer et al. 2008).

In general, larger islands support more species than smaller islands, but – comparable to mainland patterns – species richness is also influenced by geographic location, with tropical islands more species-rich than temperate or polar islands. Island fertility or productivity (itself a combination of rainfall and soil type) also influences species richness.

Unsurprisingly, islands may be critically important for many marine species – such as seabirds, marine turtles and seals – that need to breed or roost on land. This is particularly the case for islands that are distant from other land masses, and that have few predators. In such cases, the number of breeding individuals may be extraordinary. In turn, those species may transport and concentrate the sea’s fertility to the islands through nutrient deposition in faeces. One consequence is that many islands have been targeted by humans for their rich guano deposits, exporting the nutrients to build agricultural productivity elsewhere.

Across most of the world, humans have brought much change – in many cases, destruction – to island life. This susceptibility arises from the geographic characteristics of islands themselves, from the evolutionary pressures (or lack of pressures) that have shaped island-adapted plants and animals, and from the caprice associated with the human discovery and use of islands. Writ more large than most other situations, islands epitomise the pattern of homogenisation we have directed at the world’s natural systems (Loope and Mueller-Dombois 1989; Sax and Gaines 2008; Woinarski 2010; Longman et al. 2018). Where once every island contained a different constellation of species, with a propensity to support endemic species, our impacts have since blurred and reduced such distinctiveness, through the deliberate or inadvertent introduction of cosmopolitan species that have, along with other threats we have crafted, dealt the end to many endemic species, and greatly reduced the proportion of native species, often to a minority component in the new hybrid ecology (Christian et al. 2009).

Geography predisposes island species to decline and extinction, once new threatening factors are introduced. By definition, islands are smaller than continents – many are very small – and consequently the total population size of many island species is small, and hence ‘extinction-prone’. Islands are isolated – there is no way off, no escape route; they can become a death-trap (Woinarski et al. 2011). Many islands are topographically simple and have only a limited range of habitats, so, in most cases, island species can’t escape within the island setting to refuge areas unreachable by the newly arrived threat.

Over time, many of the traits that facilitated the immigration of species to an island (such as highly dispersive propagules and high reproductive output) become counter-productive for sustainable life in a confined space, and the established island populations may lose these traits, or competitive superiority may fall to other species better adapted to island residency. So, many species long resident on islands now have relatively low reproductive output and long lifespans; their lives beat to a slow rhythm. In turn, these traits compromise their capacity to respond within sufficient time to new threats. Because they typically derive from a small population of founders, their genetic variability may be unusually limited, providing less capability to adapt to new circumstances, and lower probability of at least some individuals being immune to new diseases.

Islands with relatively benign consumer, predator or disease regimes allow many long-term resident species to lose key defensive mechanisms – island plants became thornless or lose their toxins, island birds and insects become flightless, island animals become ‘fearless’, key disease suppressants are lost (Carlquist 1974, 1980). This loss of traits relating to defence and competition may allow for – indeed, it may be needed for – stability and sustainability in isolated islands over tens or hundreds of thousands of years, but it is a card of doom when the isolation of the island is breached and new consumers, predators or diseases arrive from far more complex and crowded ecological worlds elsewhere, where robustness, vigour and short-term competitive superiority are trumps. The lot of such new arrivals is then unnaturally easy; their impact abnormally high.

Human impacts have added a profound extra dimension subverting island ecology and its equilibrium. Much island life has suffered because of the timing and circumstances of their human discovery. Many islands were first visited by nomadic humans whose interests were about resource exploitation rather than the development and maintenance of human communities living sustainably on those islands, in part a reflection of the age. For example, many Pacific Islanders initially adopted a largely slash-and-burn approach to island discoveries, consuming all available resources on an island and then moving to another (Olson and James 1982; Steadman 1995; Rolett and Diamond 2004; Steadman 2006). In the few centuries between their original human colonisation and re-discovery by European navigators, most Pacific islands lost many animal species (particularly seabirds, parrots, pigeons and flightless rails) due to direct predation pressure by man. For example, of ~135 native (and mostly endemic) bird species in the original Hawaiian bird fauna, ~80 became extinct after the arrival of Polynesians and before that of Europeans (Pimm et al. 1994). A recent estimate puts the toll as ~2000 bird species extinctions in the Pacific over the course of several centuries of the Polynesian expansion (McDaniel and Gowdy 2000). Rapid and high rates of extinctions following initial human discovery were also a dismal feature of islands in the Indian Ocean, Atlantic Ocean and the Caribbean (Morgan and Woods 1986; Cheke 1987a; Alcover et al. 1998; Triantis et al. 2010).

Hygiene wasn’t well developed, and quarantine entirely absent, among the original or subsequent discoverers of islands. Pre-European mariners spread the Pacific rat Rattus exulans, deliberately (as food) or accidentally, to many Pacific islands, at great cost to the native plants and animals of those islands (Hunt 2007). European ships of the great discovery era, the 15th to early 19th centuries, were notoriously verminous, and they too, inadvertently or carelessly, spread black (or ‘ship’) rats Rattus rattus, brown rats R. norvegicus and house mice Mus domesticus, and many novel diseases, to many islands, again with devastating consequences to island plants and animals, and, in many cases, to the islands’ previous wave of human settlers (Atkinson 1977). In an era where navigation was routinely a life-threatening venture, many sailors also adopted the ostensibly altruistic practice of leaving livestock, particularly goats and pigs, on isolated islands as insurance food for them or their shipwrecked successors. In part due to lack of native predators, these marooned animals often prospered, at the expense of the environments and native species of their new homes. Other introductions were less conspicuous – including of ants, land snails and other invertebrates, birds, fish, mongooses, reptiles, and plants – but many of these also subverted the island ecology and drove endemic species to extinction (Warner 1968; Hadfield et al. 1993; Cowie 2000; Lester 2008; Régnier et al. 2015a,b).

Where islands were colonised by European powers, there was often the need for the pioneers to rely on (and over-exploit) island resources, before regular and frequent re-supplying from the colonial centre was established. Island natural resources were invariably limited, and could rarely sustain an increasing human population, so typically those natural resources were bolstered or replaced with imported plants and animals with greater tractability and productivity.

Islands weren’t seen as the separate independent universes that their ecologies may have constructed; rather, they were replaceable parts of the great colonial engine: if a tree species was logged out on one island, the cost was seen to be small and bearable if another tree on another island could be exported back to base instead. Colonially breeding seals, penguins and other seabirds were particular casualties, with island populations especially susceptible to short-term over-harvesting. Many of these island animal colonies were sequentially wiped out within a few years or decades. For example, within 2 years of settlement of Norfolk Island, the annual harvest of the providence petrel Pterodroma solandri was more than 172 000 birds, many of them breeding females; within another 10 years, the massive breeding colony was exterminated (Bonyhardy 2000; Medway 2002). The giant and placid Steller’s sea-cow Hydrodamalis gigas on St George (Pribilof) Island in the north Pacific was exterminated within 50 years of its discovery in 1741. The dodo Raphus cucullatus, unhappily most celebrated for its extinction, lasted only about a century after its Mauritius Island home was discovered (Quammen 1996). The Enlightenment’s concept of the noble savage enjoying island life in harmony with nature was itself a myth, but also an idyll imagined and simultaneously shattered by the rapidly escalating process of colonisation, exploitation and environmental degradation of islands by European empires.

Australia is the largest of islands. In part, its ecology and biota have suffered from the typical island pattern of subversion of the pre-contact environmental equilibrium following the introduction of novel threats (Johnson 2006; Woinarski et al. 2015). But, in part, that loss has been moderated by the presence of outlying islands. Many species that disappeared from their formerly extensive ranges on the Australian mainland were saved from extinction by the fortuitous presence of populations on peripheral islands, not yet subject to the critical new threats that have caused mainland losses (Dickman 1992; Burbidge 1999). So, before European settlement, the Tasmanian native-hen Tribonyx mortierii, thylacine Thylacinus cynocephalus and Tasmanian devil Sarcophilus harrisii were lost from extensive ranges on the Australian mainland, but held on in Tasmania. Following European settlement, the mainland populations of eastern quoll Dasyurus viverrinus, ‘Tasmanian’ bettong Bettongia gaimardi and ‘Tasmanian’ pademelon Thylogale billardierii were also lost, while their populations on Tasmania have – so far – persisted (Woinarski et al. 2014c). Following European settlement, the banded hare-wallaby Lagostrophus fasciatus, greater stick-nest rat Leporillus conditor and many other mammals disappeared rapidly because of the near pervasive spread of the introduced red fox Vulpes vulpes and feral cat Felis catus across mainland Australia, but were luckily secured on a small number of (relatively small) satellite islands not yet reached by these invaders (Burbidge et al. 1997; Burbidge 1999). Over recent decades, conservation authorities have translocated species declining on mainland areas to islands, where the factor causing decline is either absent or more amenable to control (Burbidge and Morris 2002; Morris et al. 2015; Burbidge et al. 2018). These examples show the potential for the great conservation advantage of islands, should good quarantine, or geographical isolation, or unattractiveness, or luck, allow them to escape particular threats (Woinarski et al. 2014a).

One other feature of islands relevant to this story is that of their human populations. Most island human societies are challenged by logistical constraints and isolation. Many are remote from national power bases, and their scrutiny. Many have a tenuous economic base, and such economic marginality or drain may impose a severe constraint on their governance. Many island societies also have a fiercely autonomous culture, and see all the rest of the world as menacing or interfering outsiders. Some of these traits constrain the development or delivery of good conservation management, but self-reliance may also encourage good conservation practice.

3

The stage – Christmas Island

This book is as much about the place as it is the species. Christmas Island is an important character in this story. In the sections that follow, I describe in some detail the history and environment of Christmas Island. I draw this canvas because most people know little of Christmas Island, other than as caricature, as a remote holding place for refugees arriving in Australia by leaky boats, or as the site for spectacular crab migrations. But this description is not mere background: there are particular contextual features of this place and its history that contributed to the pipistrelle’s fate.

Setting

Let’s avoid the confusion from the start. Early sailors liked marking the conjunction of festive days and newly discovered islands by naming the island after the day – hence there are many New Year Islands, Easter Island, and at least two Christmas Islands. The main alternative (and slightly larger) Christmas Island (now Kiritimati), in the island republic of Kiribati in the Pacific, is the largest coral atoll in the world, unfortunately perhaps better known for ‘hosting’ nuclear bomb testing in the late 1950s and early 1960s (Schalansky 2010). The Christmas Island of this story lies in the eastern Indian Ocean (at 10°25′S and 105°43′E) and is now, administratively, a part of Australia (Fig. 3.1).

This Christmas Island is a sea-mount island, rising 4.5 km from the sea floor. It is solitary, with no fringing islets. The island has never been connected to a larger continental land mass, and, unlike most other islands in south-eastern Asia, it never fused with other islands to form larger land masses during episodes of marked sea level falls in the Pleistocene (Voris 2000). It is the sole emergent peak within a large chain of volcanoes that formed ~80 million years ago, with subsequent volcanic reactivation 40–35 million years ago (Trueman 1965), and possibly also between 5 and 3 million years ago (Borissova 1994). Over time, sea level changes, uplifts and reef formations have contributed to changing island size and relief, but it is unlikely to have ever been substantially larger (because of the steep slopes of the sea-mount and the depth of the surrounding seas), whereas it may have had periods of much smaller size, fragmentation or (perhaps) total submergence. Its basaltic core is now mostly capped by a sequence of Tertiary limestones up to 250 m thick, with fossils laid down in shallow marine waters ~26 to 10 million years ago (Ludbrook 1965). Characteristics of the limestone suggest that it has not been submerged since at least 3 million (and possibly 10 million) years ago (Humphreys and Eberhard 2001; Namiotko et al. 2004). The periodic uplifts have produced a terraced (‘wedding-cake’) profile for the island, although the terraces are also interrupted by a complex system of faults (Rivereau 1965). The lowest, most recent terrace was probably formed during the last interglacial period ~120 000 years ago (Woodroffe 1988; Hale and Butcher 2010).

All places are unique, but this place is unusually special. Writing in 1900, the pivotal figure in its history, naturalist (and geologist, oceanographer and businessman) John Murray asserted:

Fig. 3.1. General location of Christmas Island.

Down to a few years ago it was probably the only existing tropical island of any large extent that had never been inhabited by man, savage or civilized … Its interest, from a scientific point of view, is further increased by the fact that it is at least 190 miles distant from any other land, and is surrounded by an ocean in which the depths exceed three English miles (Murray 1900, p. ix).

This was indeed a lost world, where geomorphology, time, chance and evolution has, or had, choreographed a distinct environment with idiosyncratic ecology.

Christmas Island is also a place of