PHOTO: JACQUES DE SPÉVILLE
Flying foxes are hunted for food on many tropical islands and threatened by habitat loss, even though they perform crucial ecosystem functions. They are also widely perceived as vermin and as a threat to fruit harvests, leading to government-implemented culls. Pteropus niger is the last effective pollinator and disperser of large-seeded species on Mauritius, where human activities and invasive species have led to the extirpation of native birds, giant tortoises, and two other flying fox species; it is now subject to culls.
Flying foxes provide critical ecosystem services by pollinating and disseminating diverse plant species. Yet, they face intensifying threats, particularly on islands. The situation is epitomized by the Indian Ocean island of Mauritius. In December 2016, the Mauritian government implemented the second mass cull of a threatened, endemic flying fox species, Pteropus niger (see the left photo), in 2 years. Government figures suggest that at least 45% of the overall P. niger population of just over 90,000 individuals were culled during the two campaigns; illegal killing and incidental mortality of pups during the culls raise likely losses to over 50%. The dire situation of island flying foxes worldwide calls for effective, science-based conservation strategies to prevent further loss of biodiversity and function.
The flying fox species at Tomohon market on Sulawesi, Indonesia, cannot be identified.
PHOTO: XAVIER PUIG MONTSERRAT AND CARLES FLAQUER
Worldwide, there are 65 species of flying foxes (fruit bats of the genus Pteropus). The majority—53 species—are restricted to paleotropical islands and archipelagos from the Pacific to the Indian Ocean. Flying foxes feed exclusively on fruits, flowers, nectar, and leaves, and roost most commonly in colonial groups in trees. Pteropus species are highly effective pollinators and seed dispersers, because their large size and high mobility enable them to connect fragmented populations and disperse seeds of diverse sizes. The Malayan flying fox (P. vampyrus) is the largest living bat, with a wing span of up to 1.7 m and a weight of up to 1.2 kg. Many flying foxes fly distances of over 60 km each night from the roost to forage (1). Flying foxes shape the diversity and physical structure of forest communities and thereby enable the survival of dependent flora and fauna.
Worldwide, there are 65 species of flying foxes (fruit bats of the genus Pteropus). The majority—53 species—are restricted to paleotropical islands and archipelagos from the Pacific to the Indian Ocean. Flying foxes feed exclusively on fruits, flowers, nectar, and leaves, and roost most commonly in colonial groups in trees. Pteropus species are highly effective pollinators and seed dispersers, because their large size and high mobility enable them to connect fragmented populations and disperse seeds of diverse sizes. The Malayan flying fox (P. vampyrus) is the largest living bat, with a wing span of up to 1.7 m and a weight of up to 1.2 kg. Many flying foxes fly distances of over 60 km each night from the roost to forage (1). Flying foxes shape the diversity and physical structure of forest communities and thereby enable the survival of dependent flora and fauna.
The remains of a culled Blyth’s flying fox (P. melanotus) are tied to a fence on Middle Andaman Island, India.
PHOTO: ROHIT CHAKRAVARTY
On islands, evolutionary contingency and recent anthropogenic extinctions of other native dispersers mean that flying foxes are often the sole agent of pollination or dispersal (2). IslandPteropus are thus keystone species responsible for the viability of both native or endemic island plants (2) and plants consumed or sold by local communities (3). The extirpation of island flying foxes may trigger extinction cascades (4), with adverse ecological and economic consequences.
The decline of island Pteropus is substantial and widespread. Thirty-one of the world's flying fox species are threatened with extinction (that is, they are assessed as critically endangered, endangered, or vulnerable by the IUCN), and 28 of these are island species (5). All four bat species driven to extinction by human action in the past 200 years were island Pteropus; an additional three species are probably extinct (5), and further populations and subspecies of the surviving species have also been lost. Worldwide, populations of only two species—the threatened P. voeltzkowi and P. rodricensis (endemic to the islands of Pemba, Tanzania, and Rodrigues, Mauritius, respectively)—are increasing; both species were subject to intensive, sustained conservation programs that brought them back from the brink of extinction.
The main drivers of population declines are hunting and habitat loss (5). Of the 28 extant threatened island species, 25 are threatened by hunting (5). Flying foxes are hunted primarily for consumption (see the top right photo), their perceived medicinal properties, and sport (6). Unlike mainland species, island flying foxes find few refugia from exploitation pressures. The extensive loss and degradation of native forests on islands (7) threaten 21 species. Seven threatened species are affected by invasive alien species, some of which reduce food resources still further, while others exert novel predation (8). Furthermore, island Pteropus are particularly vulnerable to environmental catastrophes. Tropical storms in particular can devastate flying fox populations through fatalities and starvation-driven mortality. Climate change is likely to lead to an increase in the incidence and severity of such storms, posing further threats to 10 species (5). Most threatened species are subject to at least two threats, and small population sizes on islands exacerbate the consequences.
As natural food resources dwindle on islands, conflicts between flying foxes and fruit growers are increasing, resulting in actions ranging from ad hoc persecution by individuals to government-implemented mass culls. In some countries, persecution is legal; for instance, P. melanotus as well as P. faunulus, a threatened endemic of the Nicobar islands, are considered to be vermin and can be persecuted under the Indian Wildlife Act (see the bottom right photo). In others, laws that protect flying foxes are not enforced. For example, flying foxes are openly hunted in the Philippines, Palau, and Mauritius, and poachers do not in practice face legal actions. In Japan, local killings of P. dasymallus by farmers remain unaddressed (8).
The recent actions of the Mauritian government are of particular concern. Since the extirpation of two Pteropus species through habitat loss and hunting by 1870 and the demise of key avian dispersers (including the dodo, a giant flightless bird), the viability of much of the remaining native flora of Mauritius has rested with its remaining flying foxes (9). After weakening its biodiversity protection law, the government was able to implement mass culls of the last Pteropus species surviving on the island, even though the species has been assessed by the IUCN as threatened with extinction (10).
The low reproductive rates of flying foxes compound the numerous threats by slowing population recovery. Pteropus are long-lived, reaching 20 to 28 years in captivity and probably averaging 15 years in the wild. Females typically do not reach sexual maturity until their second or third year, and nearly all species give birth to a single young per year. Generation times are long (7 to 8 years), and per capita rates of increase extremely low.
Flying foxes were once abundant and conspicuous and play key ecological roles, yet four species have already been lost and dozens are on the path to joining them. Stemming further decline and extinction of island flying foxes is a conservation priority and an ecological necessity for maintaining biodiversity and ecosystem functions of tropical islands. Since 1989, all Pteropusspecies have been listed in Appendix I or II of CITES (Convention on International Trade in Endangered Species), restricting legal international trade in hunted bats. Nonetheless, hunting remains the biggest single threat to flying fox populations, and targeted research to identify the economic and social motivations that underpin hunting is essential to guiding intervention and effecting behavioral change (11, 12). Lasting changes will likely require multifaceted approaches that improve laws and strengthen enforcement of existing protective legislation (13), engage stakeholders in bat conservation, and provide alternatives to bats as sources of income or bushmeat.
Although attitudes are not changed by knowledge alone, it is critical that education and outreach initiatives convey to island stakeholders, from hunters to ministers, the importance of flying foxes to island ecosystems. The ecological and economic value of flying foxes must be central to policy decisions affecting hunting regulation, humanbat conflict, and development. Currently, politics rather than science guides many management decisions. Culls and forced dispersals of colonies do little to resolve fruit crop damage (14), and such measures are costly, bring countries into disrepute, and distract from economically and ecologically viable alternatives (1, 15).
As land-use change reduces native food resources and tropical fruit markets expand, human-bat conflicts over fruit crops are likely to increase. Nonlethal solutions to fruit crop damage exist (including fixed nets, deterrents, and decoy trees) (15), but research into the barriers limiting their uptake is needed. Stakeholder collaborations should explore social and economic mechanisms for overcoming barriers and promoting nonlethal mitigation measures, which might include subsidies, green-labeling of “flying-fox friendly” fruits, or compensation to farmers absorbing losses. Without such initiatives and changes, we risk losing important keystone species and function, leading to accelerated loss of ecosystem services and biodiversity on islands.
On islands, evolutionary contingency and recent anthropogenic extinctions of other native dispersers mean that flying foxes are often the sole agent of pollination or dispersal (2). IslandPteropus are thus keystone species responsible for the viability of both native or endemic island plants (2) and plants consumed or sold by local communities (3). The extirpation of island flying foxes may trigger extinction cascades (4), with adverse ecological and economic consequences.
The decline of island Pteropus is substantial and widespread. Thirty-one of the world's flying fox species are threatened with extinction (that is, they are assessed as critically endangered, endangered, or vulnerable by the IUCN), and 28 of these are island species (5). All four bat species driven to extinction by human action in the past 200 years were island Pteropus; an additional three species are probably extinct (5), and further populations and subspecies of the surviving species have also been lost. Worldwide, populations of only two species—the threatened P. voeltzkowi and P. rodricensis (endemic to the islands of Pemba, Tanzania, and Rodrigues, Mauritius, respectively)—are increasing; both species were subject to intensive, sustained conservation programs that brought them back from the brink of extinction.
The main drivers of population declines are hunting and habitat loss (5). Of the 28 extant threatened island species, 25 are threatened by hunting (5). Flying foxes are hunted primarily for consumption (see the top right photo), their perceived medicinal properties, and sport (6). Unlike mainland species, island flying foxes find few refugia from exploitation pressures. The extensive loss and degradation of native forests on islands (7) threaten 21 species. Seven threatened species are affected by invasive alien species, some of which reduce food resources still further, while others exert novel predation (8). Furthermore, island Pteropus are particularly vulnerable to environmental catastrophes. Tropical storms in particular can devastate flying fox populations through fatalities and starvation-driven mortality. Climate change is likely to lead to an increase in the incidence and severity of such storms, posing further threats to 10 species (5). Most threatened species are subject to at least two threats, and small population sizes on islands exacerbate the consequences.
As natural food resources dwindle on islands, conflicts between flying foxes and fruit growers are increasing, resulting in actions ranging from ad hoc persecution by individuals to government-implemented mass culls. In some countries, persecution is legal; for instance, P. melanotus as well as P. faunulus, a threatened endemic of the Nicobar islands, are considered to be vermin and can be persecuted under the Indian Wildlife Act (see the bottom right photo). In others, laws that protect flying foxes are not enforced. For example, flying foxes are openly hunted in the Philippines, Palau, and Mauritius, and poachers do not in practice face legal actions. In Japan, local killings of P. dasymallus by farmers remain unaddressed (8).
The recent actions of the Mauritian government are of particular concern. Since the extirpation of two Pteropus species through habitat loss and hunting by 1870 and the demise of key avian dispersers (including the dodo, a giant flightless bird), the viability of much of the remaining native flora of Mauritius has rested with its remaining flying foxes (9). After weakening its biodiversity protection law, the government was able to implement mass culls of the last Pteropus species surviving on the island, even though the species has been assessed by the IUCN as threatened with extinction (10).
The low reproductive rates of flying foxes compound the numerous threats by slowing population recovery. Pteropus are long-lived, reaching 20 to 28 years in captivity and probably averaging 15 years in the wild. Females typically do not reach sexual maturity until their second or third year, and nearly all species give birth to a single young per year. Generation times are long (7 to 8 years), and per capita rates of increase extremely low.
Flying foxes were once abundant and conspicuous and play key ecological roles, yet four species have already been lost and dozens are on the path to joining them. Stemming further decline and extinction of island flying foxes is a conservation priority and an ecological necessity for maintaining biodiversity and ecosystem functions of tropical islands. Since 1989, all Pteropusspecies have been listed in Appendix I or II of CITES (Convention on International Trade in Endangered Species), restricting legal international trade in hunted bats. Nonetheless, hunting remains the biggest single threat to flying fox populations, and targeted research to identify the economic and social motivations that underpin hunting is essential to guiding intervention and effecting behavioral change (11, 12). Lasting changes will likely require multifaceted approaches that improve laws and strengthen enforcement of existing protective legislation (13), engage stakeholders in bat conservation, and provide alternatives to bats as sources of income or bushmeat.
Although attitudes are not changed by knowledge alone, it is critical that education and outreach initiatives convey to island stakeholders, from hunters to ministers, the importance of flying foxes to island ecosystems. The ecological and economic value of flying foxes must be central to policy decisions affecting hunting regulation, humanbat conflict, and development. Currently, politics rather than science guides many management decisions. Culls and forced dispersals of colonies do little to resolve fruit crop damage (14), and such measures are costly, bring countries into disrepute, and distract from economically and ecologically viable alternatives (1, 15).
As land-use change reduces native food resources and tropical fruit markets expand, human-bat conflicts over fruit crops are likely to increase. Nonlethal solutions to fruit crop damage exist (including fixed nets, deterrents, and decoy trees) (15), but research into the barriers limiting their uptake is needed. Stakeholder collaborations should explore social and economic mechanisms for overcoming barriers and promoting nonlethal mitigation measures, which might include subsidies, green-labeling of “flying-fox friendly” fruits, or compensation to farmers absorbing losses. Without such initiatives and changes, we risk losing important keystone species and function, leading to accelerated loss of ecosystem services and biodiversity on islands.
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