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. 

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.

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).