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Pteropus niger 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Chiroptera Pteropodidae

Scientific Name: Pteropus niger (Kerr, 1792)
Common Name(s):
English Greater Mascarene Flying Fox, Black-Spined Fruit Bat, Mauritian Flying Fox, Mauritius Fruit Bat
French Grande roussette des Mascareignes, Roussette noire
Spanish Zorro Volador Negro de Mauricio
Synonym(s):
Vespertilio vampirus ssp. niger Kerr, 1792

Assessment Information [top]

Red List Category & Criteria: Endangered A4cde ver 3.1
Year Published: 2018
Date Assessed: 2017-11-19
Assessor(s): Kingston, T., Florens, V., Oleksy, R., Ruhomaun, K. & Tatayah, V.
Reviewer(s): Mildenstein, T. & Piraccini, R.
Contributor(s): Hutson, A.M. & Racey, P.A.
Justification:

Listed as Endangered based on estimated population decline of 50% in 2015 and 2016 and projected continued decline of >50% from January 2015 forward three generations (20 years). Observed decline is due to government-implemented mass culls in 2015 and 2016, illegal hunting and killing by the local population, and accidental mortality on powerlines. Projected declines are based on: i) continued hunting and culling pressures combined with reduced legal protection of the species; ii) continuing reduction in the extent and quality of forest, a key habitat that is relied upon for roosting and foraging); and iii) likelihood of a major cyclone occurring on Mauritius within three generations.

Previously published Red List assessments:

Geographic Range [top]

Range Description:

This species was extirpated from Réunion in the early eighteenth century, and until recently has been restricted to the western Indian Ocean island of Mauritius (Bergmans 1999, Cheke and Hume 2008). There are, however, recent records of a small subpopulation (c. 40 individuals) on Réunion from naturally recolonizing or released individuals (Probst and Sanchez 2015), so the species is no longer considered extinct on Réunion. Cheke and Hume (2008) consider it possible that bats reported by Leguat in Rodrigues in 1691-1692 (Leguat 1708) might have been this species.

Countries occurrence:
Native:
Mauritius; Réunion
Additional data:
Number of Locations:1
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:

There has been a range of population estimates (of total number of individuals on Mauritius) with the first estimate of 10,000 individuals in 1974 (Cheke and Dahl 1981). A.S. Cheke (pers. comm. 2012) admits that this was a crude estimate based on counts of a few colonies and talks with hunters and other anecdotal sources. Robin (2007) identified 54 occupied roosts, of which 36 were categorized during pre-assessment into size classes (<300, 300-600, 600-900, > 900). 24 of the 36 sites were selected in a stratified random design for evening dispersal counts (two sites for each size class from each of three geographic regions [East, West, North]). Based on the counts from the 24 sites sampled twice, she estimated that the population of the 36 sites to be about 15,700 bats. This is a partial population estimate as it did not account for bats roosting at the remaining 18 known sites. The Mauritian government has carried out counts since 2003, and data are available for 2006, 2010, 2013 and 2016. These give figures of 22-25,000 for 2006, 49-56,000 for 2010 (Sookhareea 2011), and 92,000 for 2013 (NPCS 2013) using a range of methods, but predominantly disturbance counts. These figures were questioned by the IUCN SSC Bat Specialist Group because of widespread use of disturbance counts. In disturbance counts, the colony to be counted is disturbed by a loud noise (such as a fire cracker under the roost) that causes the bats to disperse. Most animals fly out at the same time and in multiple directions, so standardized counts are challenging. Moreover, recent satellite telemetry data suggest that bats move widely across the island within and among nights (Oleksy 2015). Similarly, repeated counts of Robin (2007) over successive days, as well as separated by several weeks, exhibited high variance. Both disturbance counts and among-roost movements can lead to an over-estimation of the population. In 2016, the population was surveyed by the National Parks and Conservation Service (NPCS) using only evening dispersal counts and roost counts. To minimize error from movement of bats among roosting areas, the 2016 survey was conducted over three weeks, a shorter period than in previous years, and several roosts were counted simultaneously, although nightly movement of bats among roosts could not be accounted for. The 2016 population was estimated at 62,500 (+/- 7 % due to observer error) which gives an upper bound of 66,875, lower 58,125.

Although there is some variability in the timing and methods of counts from 2003 to 2016, they provide good evidence that the population was increasing prior to the 2015 cull, although the scale of that increase is uncertain. An increase is likely since there was no significant cyclone in that period, and major cyclones result in heavy losses, from which the population is slow to recover. The number of known roost sites has also increased from c. 14 in 2003 (Nyhagen 2004) to c. 54 (Robin 2007, Sookhareea 2011), 63 in 2013 (NPCS 2013), and 83 in 2016. In 2007 a small subpopulation (10-20 animals) was identified on Réunion (where the species formerly occurred, but has been extinct for well over 100 years). These animals are generally assumed to have blown over from Mauritius (as suggested for other stray individual records since 2000), although it is possible they were released from a captive colony following the closure of Parc Zoologique de Saint Denis in 2006-7 (V. Tatayah pers. comm.). The population was recently estimated at about 40 individuals (Probst and Sanchez 2015). However, breeding appears limited and erratic on Réunion, so this subpopulation has not been considered for the purposes of this assessment.

In October-November 2015, the government of Mauritius implemented a cull, and reported that 30,938 bats were killed (Anon. 2016). From this, and the 2016 NPCS survey of 62,500, the pre-cull 2015 population was at least 93,438 individuals (62,500 + 30,938). To this we add a conservative estimate of 5,000 individuals killed illegally in 2015 (www.mauritian-wildlife.org), either hunting for sport or food or trapped in nets, and a further 1,000 powerline fatalities (www.mauritian-wildlife.org) to calculate total estimated fatalities in 2015 as 36,938 individuals.

This suggests that the pre-cull population of 2015 was c. 99,438 individuals (2015 combined fatalities + 2016 population estimate). From this baseline of 99,438 individuals, the 2015 fatalities (36,938 individuals) represented 37.15% of the 2015 population. This does not account for off-site mortality of animals injured during the cull or mortality of orphaned young (the cull occurred in the middle of the breeding season). A second cull was implemented in December 2016, killing a further 7380 individuals (Anon. 2017). Illegal killing and powerline fatalities are conservatively estimated at 6000 in 2016, thus total population losses from October 2015 to January 2017 reached 50% ((38,318 bats culled + 10,000 illegal take 2,000 powerline fatalities)/2015 pre-cull population of 99,438).

If illegal killing and powerline fatalities remain at 6,000 per year, population growth models indicate that the species could be reduced by 64-80% within the next 12-20 years, depending on model assumptions. Life history and fecundity data are limited for Pteropus niger, so model parameters were based on those of P. poliocephalus as reported in McIlwee and Martin (2002). The most conservative assumptions were made, that is, the highest values for survival and fecundity were selected and fecundity was assumed not to decline in old age. Specifically, we assumed only 30% mortality of individuals in their first year, and 10% thereafter until year 15 when all remaining individuals died. Note these are background mortality rates, and do not include deaths from powerlines or illegal killing. We modeled that 20% of females bred in their second year, and 90% in the third year until 15 years and females gave birth to a maximum of one young per year.  This generated a generation time of 6.67 years and the maximum (or intrinsic) rate of increase per capita, rmax, of 0.122 (comparable to that of models in McIlwee and Martin 2002, as would be expected). These values were used in a simple logistic growth model to evaluate the consequence of annual offtake (mortality arising from human activities) of 6000 a year. Evidence of starvation was detected in dead bats collected in 2015, prior to the cull (V. Tatayah, pers. obs.), when the population is inferred to be less than 100,000. As 2015 was a drought year, carrying capacity was generously estimated at 150,000 individuals. With a starting population of 62,500, carrying capacity of 150,000, and offtake of 6,000 individuals per year and an additional 7,380 individuals removed by the cull of 2016, the population declines by 82% (to c. 17,703) of the pre-culls value of 2015 in 16 years (2031), or in 2.4 generations. This threshold is reached within 12 years (2027) if carrying capacity is modeled at 100,000 individuals. These models assume constant mortality (of 6,000 per year), but it is likely that bats will prove more elusive as populations decline. A constant proportion model, in which anthropogenic mortality is 10% of the population total each year with a starting population of 62,500 and including the 2016 cull of 7,380, reported a reduction by 64% (K = 150,000) and 72% (K = 100,000) of pre-cull numbers within three generations. Because of the uncertainty of the level of illegal offtake current and projected, we assess the species conservatively as Endangered. However, we highlight these are simple models that do not account for environmental stochasticity, such as the probability of extreme weather events, especially cyclones, or the implementation of additional culls. Either event will trigger reassessment as they would likely precipitate population declines approaching 80% over three generations (2015-2034), justifying an assessment of Critically Endangered.

Current Population Trend:Decreasing
Additional data:
Number of mature individuals:37700
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:

Most known roost sites are in forest, mostly in the more forested parts of mountain ranges, in secure places with restricted access, on the leeward side and generally without exposure to full sun (Sookhareea 2011), but roosts are also found in forest remnants all over the island (Oleksy 2015). Roost sites number a few hundred trees (since each roost consists of a few tall trees), with accessible canopy structures, and with terminal branches strong enough to bear the weight of a few large bats. Favoured trees genera and tree species are a mixture of native and exotic species: Eucalyptus spp., Tecoma (Tabebuia pallida), Araucaria spp., Bois noir (Albizia lebbek), and the endemic Bois de natte (Labourdonnaisia glauca). A substantial roost site was also located in the Sir Seewoosagur Ramgoolam Botanical Garden, Pamplemousses, prior to the cull of 2015. However, the roost is seasonal, with a major colony arriving around October-November which coincides with the fruiting season. During the dry season (April-September) only a few bats are present.

Roost sites represent day resting places. Many individuals collect at these roost sites, but the bats are highly vagile and move often from roost to roost, often over large distances and for a variety of reasons, such as disturbance, changes in prevailing wind, food availability, stage of the reproductive cycle. Satellite telemetry has shown that, during the night, the bats may travel up to 92 kilometres around the island to forage in different habitats, including human habitation and orchards. After foraging, they may return to their original roost or switch to new localities (Oleksy 2015).  Roosts in the north-west of the island are much more heavily used during the dry season (August–December). So, although roosts are often historic and used over many years, the number of bats using them can fluctuate markedly (and they may be deserted for part of the year), as happens with historic roosts after a major disturbance. Thus, although the roost sites are very important for conservation, and should be treated as such regarding their contribution to the maintenance of the population, they cannot be treated as individual units for a Red List assessment. In view of the nature of the major threats and the way the bats move around the island nightly and among roost sites, it is not possible to define any number of discrete locations within Mauritius: it is considered that the number of locations for this species is one, corresponding to the island of Mauritius. Moreover, mitochondrial sequence data from individuals from four roosts on the island indicate that the population is likely to be panmictic (Larsen et al. 2014).

Half the plant species that have been identified as contributing to the diet of the species are native and half exotic (Nyhagen 2004, Nyhagen et al. 2005). However, recent studies indicate that fruit bats feed on more native and endemic fruits than previously known (Florens et al. 2017a), as well as leaves and blossoms (Oleksy 2016). The breeding season starts around May and the young are born during August to December, when commercial fruits such as mango and litchi are fruiting. Because both crops are widespread in Mauritius the bats feed on them widely, foraging in plantations (orchards), small holdings and gardens. Without the mix of natural food sources and some exotic food sources it is likely that the population and breeding success of the bats will decline to some extent. During May-July (mid dry season) bats have been found dead under the roosts, probably due to food shortages (R. Oleksy, pers. obs.) as has been suggested by autopsy reports (V. Tatayah, pers. obs.). Thus, there is a strong reliance on forest, both for roosting and for foraging. 

Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):6.67

Use and Trade [top]

Use and Trade: This species is locally used for sport hunting and as a source of food.

Threats [top]

Major Threat(s):

This species is threatened by:  a) habitat destruction and decline in quality, specifically the loss of roosting and feeding trees; b) invasive alien plants that reduce flowering and fruiting of trees and animal species, namely monkeys, that destroy food resources, especially fruits; c) cyclones; d) persecution in response to conflict over fruit crops; e) illegal hunting; and f) accidental deaths e.g., electrocution on powerlines. These threats commonly interact.

a). Habitat destruction and decline in quality:
There are no data on threats to specific roost sites, although there has been a progressive net loss of larger native trees within protected forests (Florens et al. 2017b). Losses include the commonly used roost tree Labourdonnaisia glauca. Decline of large trees is probably even faster in the more invaded forest (which consist of about two thirds of the remaining ‘native’ forests). Threats to bats at roost sites in Mauritius (e.g., hunting, cyclones, human disturbance) can impact many roosts at one time and in no pattern. In the case of an intense cyclone, a very large number of roosts can be damaged at the same time, and the roosts damaged will depend on details of the movement of the cyclone and its strength.

Forest habitats suitable for roosting and important for feeding, particularly at certain times of year, have seen major decline of what is already a habitat much depleted in both area and quality. Native forests are highly fragmented (Safford 1997, Florens 2013) and dominated by invasive alien plants, particularly in the wet forests (Florens 2008, Florens et al. 2016). The total extent of forest cover in Mauritius is c. 25% of total land area, but much of this is planted forests and shrubland (14%). Only about 5% is native forest (Hammond et al. 2015), of which only one third (1.7%) is has more than 50% native canopy cover. The remaining native forest (3.3%) has less than 50% native canopy cover (Safford 1997, Ministry of Agro-Industry and Food Security 2015). In 2013, the extent of native forest with > 50% plant canopy cover, so of “reasonable quality”, was estimated at around 2,600 ha (Ministry of Agro-Industry and Food Security 2015). While the significant holdings by government have shown little decline in recent years, natural habitat on private holdings has declined, and that decline is likely to continue. Illegal habitat destruction has also been recorded in Mauritius, even in protected areas, including some prime foraging habitats like the Cabinet Nature Reserve (Florens 2013). Declining habitat quality in the remaining protected areas is also of great concern. Density of large trees (>10 cm diameter) has roughly halved in about 70 years even in lesser invaded and protected native forests (Florens et al. 2017b). This equates to a rate of loss of about 5% large tree density per generation of P. niger, with likely consequences for the island’s P. niger carrying capacity. Although potential foraging area for bats has increased following the wider introduction of fruit farms, especially for litchi and mango, these are only available for a short period of the year (October-December). Most of the year, the bats would not survive without forest foraging. Moreover, foraging on fruit crops has brought the species into conflict with people and precipitated persecution by individuals and government-implemented mass culls.

b). Invasive plant and animal species:
Invasion of native forests by alien plants is of conservation relevance to Pteropus niger subpopulations on Mauritius as it reduces production of flowers and fruits among natives (Monty et al. 2013), including those that produce fruits taken by P. niger (Nyhagen et al. 2005, Baider and Florens 2006, Krivek 2017). Introduced Crab-eating Macaques (Macaca fascicularis) further reduce the abundance of native fruits available to P. niger, taking fruits of key species before they ripen enough for bat consumption (Nyhagen 2004). For example, Baider and Florens (2006) reported losses > 95% of all the fruits of Sideroxylon grandiflorum (Sapotaceae), an endemic canopy tree reliant upon P. niger for seed dispersal. They observed similar levels of damage to unripe fruit for several ebony species, e.g., the common Black Ebony (Diospyros tessellaria) and the rarer D. nodose, and for Mimusops maxima (Sapotaceae), another important canopy tree of wet forests. These trees are important native fruit trees for P. niger, that tends to eat mostly ripe fruit (Krivek 2017). The population of macaques was reduced to an estimated 8,000 animals between 2006-2007, as wild animals were trapped for export for medical research (Sussman et al. 2011). However, macaque numbers have increased over the last decade, with censuses suggesting a wild population of 30,000–40,000 (Trask et al. 2013), and more recent estimates of 50,000.

The immediate and cumulative effects of invasive plants and monkeys combined limit the abundance of native fruits available to bats in the forest remnants. Moreover, only 500 ha or so of Mauritian native vegetation has been freed from alien plants out of the 90-km square or so (i.e., less than 4% of native vegetation is recovering from alien plant invasion – but not of monkey impacts). The vast majority of the native vegetation (96%) continues to degrade under the impact of invasive plants (Florens et al. 2017b).

c). Cyclones:
Cyclones cause direct mortality to island fruit bats, destroy roost trees, and reduce fruit and flower resources resulting in starvation and/or compromised reproduction (McConkey et al. 2004). Dramatic population declines/extirpation following cyclones have been observed in island Pteropus populations in Tonga (McConkey et al. 2004), Samoa (Craig and Syron 1992, Craig et al. 1994), Christmas Island (Richards and Hall 2012), and neighboring Rodrigues. Cheke and Dahl (1981) report previous declines of P. niger on Mauritius following cyclones Carol (1960) and Claudette (1979), based on accounts from hunters and a report by Jones (1980). Mauritius has been hit by at least 38 cyclones (winds > 120 km/hr) in the last 86 years (one cyclone every 2.26 years). This gives a mean of 8-9 such cyclones during three generations (taken as 20 years) among which an average of at least two have devastating winds exceeding 210 km/hr.  In the previous 20 years (three generations), the Mauritius Meteorological Services reported 11 cyclones/severe tropical storms, of which four were classified as intense (sustained winds > 159 km/hr) or very intense (> 210 km/hr). Although the last very intense tropical cyclone was in 2002, the risk remains high and recent trends and climate change forecasts suggest that frequency of strong cyclones is on the increase (Webster et al. 2005, Kuleshov et al. 2010, Kuleshov 2014). Maximum wind speeds are also likely to increase (Elsner et al. 2008, Deo and Ganer 2014) as is the rate at which cyclones intensify (Kishtawal et al. 2012). Climate change simulations for Mauritius further suggest a decrease in rainfall (Howells et al. 2013), which would likely negatively affect the availability of fruit and flower resources and lower the island’s carrying capacity.

d). Persecution in response to conflict over fruit crops:
Foraging on soft fruits has brought P. niger into conflict with fruit growers, both “backyard” and commercial, particularly during the litchi season in November-early January. Pressure from fruit growers resulted in a mass cull of the species by the Government from November-December 2015. The cull was carried out by Special Mobile Force using rifles of 0.22 calibre, and 26,225 cartridges 12 bore were used. Although the original target figure was 20% of the population (Anon. 2015), the total reported by the Commission of Police, as communicated by Honourable M. Seeruttun, the Minister of Agro-Industry and Food Security in Parliamentary Debate of 24 May 2016 (Anon. 2016) was 30,938. Per the Minister’s response, “the culling of bats was carried out in various regions throughout the island where bats exist, and these regions are mainly forest areas on both State and private lands. The island was split into four regions: the northern, southern, western and central eastern regions, and the culling exercise was carried out on different sites in those regions”.  The December 2016 cull killed 7,380 bats (Anon. 2017). During the 2015 cull, although bats were still protected from private action, illegal take of bats for sport or control increased from an estimated 2,000 bats per year (Hutson and Racey 2013) to about 5,000 individuals (www.mauritian-wildlife.org), and possibly as many as 6,000 (V. Tatayah, pers. comm). Collectively, losses since October 2015 – January 2017 are c. 50% ((38,318 bats culled + 10,000 illegal take + 2,000 powerline fatalities)/2015 pre-cull population of 99,438) (Vincenot et al. 2017).

Although P. niger was protected under law by the Wildlife and National Park Act of 1993, in the 20+ years of legal protection, no fines were levied on those taking bats illegally (Florens 2013).  The Wildlife and National Park Act of 1993 was repealed by the Native Terrestrial Biodiversity and National Parks Act (2015). Although the species is still protected from hunting, Clause 36 allows establishment of a Special Technical Committee specifically for “the purpose of controlling wildlife” that has attained “pest status”, and it was under this Clause that the culls of 2015 and 2016 were enacted. This erosion of protection for P. niger increases the ease and hence probability that the government will continue to implement future culls. Assessment of the species will be implemented should other culls take place.

The Sugar Protocol, which gave African, Caribbean and Pacific Group of States (ACP) countries preferential access to the EU market, expired in 2009. Consequently, there has been some conversion of land from sugar cane production to other uses, including fruit crops (Ministry of Agro-Industry and Food Security 2015).  This suggests that fruit grower-bat conflicts are likely to persist (and possibly increase) over the next three generations, unless mitigation measures are adopted (netting of trees, planting dwarf varieties, pruning). Given the weakened legal protection, and continuing conflict with fruit-growers, future government-implemented culls are considered probable, and illegal killing of bats by the public likely to remain at current levels (at least 5,000 per year) without explicit intervention.

e). Hunting:
Hutson and Racey (2013) estimated that illegal take of bats for sport or control was c. 2,000 bats per year. Since the 2015 cull, although bats were still protected from private action, illegal take of bats for sport or control increased to an estimated 5,000 individuals (www.mauritian-wildlife.org), and possibly as many as 6,000. This offtake by hunters contributes to a sizeable annual mortality rate that will influence the long-term viability of the population. Therefore, it is important to devise methods to estimate the figure with greater accuracy and to reduce the number through enforcement and management of public perceptions.

f). Accidental deaths:
It is estimated that approximately 1,000-2,000 bats land and die on power lines each year (www.mauritian-wildlife.org, V. Tatayah, pers. obs.). In addition, several hundred to a thousand bats die each year in poorly-set nets used to exclude bats from fruit crops. Bats become entangled in slack nets and die of dehydration, starvation or are actively persecuted and killed by people. 

Conservation Actions [top]

Conservation Actions:

Current conservation efforts

This species is listed on Appendix II of CITES. The Native Terrestrial Biodiversity and National Parks Act (2015) protects the species from hunting, but allows a Special Technical Committee to recommend population control measures of wildlife species that attain “pest status”.

The species occurs in protected areas, including the Black River Gorges National Park (Nyhagen 2004), nature reserves and mountain reserves, but these areas did not afford protection from the 2015 cull — bats were culled in ‘Protected Areas’, including Mountain Reserves, River Reserves, and even prime tourist sites such as the Sir Seewoosagur Ramgoolam Botanical Garden, Pamplemousses.

IUCN Motion 15 “Protection of wild bats from culling programmes” was overwhelmingly adopted by IUCN members during the IUCN World Conservation Congress 2016, with votes to accept from 94% of national and international NGO’s and 97% of governments. The resulting IUCN Resolution WCC-2016-Res-019-EN: “urges governments to seek non-lethal solutions/mitigation measures to conflicts between humans and bats, as part of a strategy that combines scientific research on bat ecology and ecosystem services, as well as on life-history characteristics that support population models; and URGES governments to not authorise or sanction culls of wild bat populations unless there is peer reviewed evidence of the significant impact of bats on food security or public health, all non-lethal solutions have been exhausted, there is clear scientific evidence and opinion that a cull will resolve the issue and not threaten species survival, and any decision to authorise a cull is underpinned by rigorous scientific evidence regarding the population structure and dynamics of the species and understanding of the impact of the proposed cull ’’.

The Mauritian Wildlife Foundation (MWF) is collaborating with Chester Zoo (UK) and NPCS to try to understand the human-fruit bat conflict and take measures to address this conflict.  These measures may range from education to practical mitigation measures.  MWF has also instigated an education program supported by a Rufford Grant. The Ecosystem Restoration Alliance (ERA), Indian Ocean, is conducting a 3-year educational program by which all the schools and community centers will be reached. Along with NPCS, ERA is testing organic repellents as well as sound systems to deter bats in orchards- non-lethal net free solution.

In June 2017, a joint initiative “The people, bats and fruit industry of Mauritius: a process towards a common solution” was launched by the IUCN SSC Task Force on Human-Wildlife Conflict, with the Ministry of Agro-Industry and Food Security, (Government of Mauritius), and the Mauritian Wildlife Foundation (MWF), in consultation with representatives of the fruit-growing industry, the IUCN SSC Bat Specialist Group, and members of the scientific community in Mauritius and overseas. The parties proposed an Action Plan that focused on a netting to manage fruit bat damage to orchards, development of a national research strategy, and mediated dialogues.

1. Net Benefits Initiative
A two-day stakeholder workshop on netting and management of fruit bat damage to orchards was held in August 2017 (Zimmerman et al. 2017). The meeting was hosted by the Ministry of Agro-Industry and Food Security via its Food and Agricultural Research Extension Institute (FAREI) and participants were drawn from small orchard owners, commercial orchard managers, netting importers and distributors extension officers and research staff from FAREI, researchers and staff of NPCS and MWF, fruit exporters, and fruit traders. In addition to the Mauritian participants, five specialists from overseas participated: lychee farmers with successful experience in netting against bats in Australia, an expert in fruit bat ecology and bat damage prevention from Thailand, and human-wildlife conflict experts from the IUCN SSC Task Force on Human Wildlife Conflict, and Chester Zoo. The workshop comprised presentations, site visits and breakout sessions wherein working groups discussed key issues and strategies for reducing damage by bats and improving lychee productivity more generally. Resulting recommendations focused on: 1. Nets and netting – provision of white, 40% UV-treated small mesh-size nets and assistance with materials/construction of net frames. 2. Pruning of fruit trees – to a maximum of 4 m (ideally 2 m). 3. Equipment and training – mechanisms for assistance with equipment hire or purchase needed. 4. Model orchards – of two types: a) existing orchards modified to improve production and ease of netting; and b) new orchards planted and managed to provide optimum production, ease of harvest and netting. 5. Development of export markets for tropical fruit – recognizing that to be competitive in overseas markets crops must be ethically sourced. 6. Backyard growers – behavior change (uptake of net use) requires peer-behavior incentive measures (social marketing, development of new social norms). 7. Continued dialogue and collaborative action.

2. Research Strategy
A workshop is planned to identify the knowledge and research needs for managing the Mauritius fruit-bat conflict in the long-term. Participants will produce a jointly-designed research needs strategy, determine a plan of action and sequence of priorities, and build collaborations to tackle each action in turn going forward.

3. Mediated dialogues
To resolve additional conflicts and build lasting working relationships.

Conservation needs/priorities

There is a clear need to maintain monitoring of the population size, population dynamics, and response to cyclones. The basic biology of Pteropus niger remains quite poorly known, and data are urgently needed to parameterize population growth and viability models. Specifically, studies that detail life history and demographic information, especially age-specific fecundity and mortality rates, and that quantify illegal offtake (hunting/killing) and mortality due to powerlines and net entanglement, are critical for modeling population viability. Regular surveys provide insights into population dynamics and a means by which conservation interventions could be assessed.

Similarly, the intensity of other threats need to be quantified and ultimately reduced. Notably, competition with non-native frugivores and the effect of degradation and invasive plants on food availability in native forests, as these factors affect carrying capacity. Hunting and persecution need to be reduced through enforcement of the existing law that protect bats from public action (Native Terrestrial Biodiversity and National Parks Act 2015), and campaigns to change the public perceptions of bats. Public perceptions are entrenched and polarized, so research into campaign strategies that might prove effective is needed before widespread implementation.  Ecological studies that can feed in to such campaigns include research into dietary phenology and movement ecology to provide further insights into the importance of P. niger as an agent of dispersal and pollination of the island’s native flora, as well as the extent, distribution and timing of P. niger’s exploitation of fruit crops.

The culls of 2015 and 2016 were precipitated by conflicts with fruit-growers, particularly litchi growers. Although there have been both government (FAREI 2015) and independent (Oleksy 2016) evaluations of fruit loss to bats, continued long-term multi-site studies of the intensity of fruit crop-offtake by bats relative to other sources of loss (birds, fungi, wind) are needed. Bats will take some proportion of fruit crops, but use of dwarf varieties and pruning, and protection of crops with nets can reduce losses to marginal economic relevance. Sustainable resolution of this conflict is a conservation priority, and it is critical that the recent initiative “The people, bats and fruit industry of Mauritius: a process towards a common solution” (see Conservation Actions) continue and that there is follow-up and implementation of recommendations arising (e.g., Zimmerman et al. 2017).


Citation: Kingston, T., Florens, V., Oleksy, R., Ruhomaun, K. & Tatayah, V. 2018. Pteropus niger. The IUCN Red List of Threatened Species 2018: e.T18743A86475525. . Downloaded on 15 August 2018.
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