Capture success of Fijian bats (Pteropodidae) and their evaluation as umbrella species for conservation

Easily captured species provide powerful opportunities to motivate research and conservation action. Conversely, rare and cryptic species with low capture probability can be difficult to study. We examined the capture success of Fiji’s Pteropodidae (Pteropus tonganus, P. samoensis, Notopteris macdonaldi, and Mirimiri acrodonta) and incorporated capture success and associated observations into an assessment of their suitability as umbrella species for conservation. We caught 252 bats from 2493 mist-net-hours in lowland rainforest near Waisali on Vanua Levu, and 38 bats from 1915 mist-net-hours in cloud forest on Taveuni. Of these captures, 67% were N. macdonaldi, 16% P. tonganus, 18% P. samoensis, and <1% M. acrodonta. All species were difficult to net in cloud forest, where we recorded a female sex bias. Capture success was affected by site, season, and net height; peak capture times varied among species and between sites. N. macdonaldi was recaptured most frequently (8.8%), revealing habitual nightly movements. It has strong potential as an umbrella species for rainforest and cave-dwelling organisms of Fiji, and was readily netted. P. tonganus is an unsuitable umbrella species, P. samoensis has potential as an umbrella species, and M. acrodonta has many attributes of a flagship species. Capture efficiency of N. macdonaldi provides opportunities for monitoring and conservation management activities in Fiji. However, variability in capture success among species means that different approaches should be explored for conserving bats effectively with limited resources.

The conservation status of bats in Fiji

Bats provide important ecosystem services throughout the South Pacific but many species are threatened. The Fiji archipelago has a rich bat fauna yet few arrangements exist to promote the conservation of this group. From July 2008 to March 2011 we visited important sites identified in previous surveys for bats on Vanua Levu, Taveuni, Viti Levu and the Yasawa Islands. We netted and recorded five of Fiji's six bat species (Pteropus tonganus, Pteropus samoensis nawaiensis, Notopteris macdonaldi, Chaerephon bregullae and the Critically Endangered Mirimiri acrodonta). This was only the sixth recorded capture of M. acrodonta. P. tonganus is widespread in Fiji and exploits many different environments. P. samoensis nawaiensis mostly uses forested areas, and large tracts of forest are required for its long-term protection. Cave protection is vital for the two insectivorous species (C. bregullae and Emballonura semicaudata) and N. macdonaldi. In particular, the Nakanacagi maternity site remains globally significant for C. bregullae. E. semicaudata was not caught or detected during our surveys. It appears to be extinct from most large islands in Fiji and has abandoned the only large cave roost (Yaqeta) observed 10 years ago. This species has disappeared from or declined dramatically on Vanuatu, Samoa, Tonga and Fiji. We recommend that the category of E. semicaudata semicaudata on the IUCN Red List be changed to Critically Endangered. Management priorities should focus on community engagement and education, and improved cave and forest management and protection.

Distribution, status and conservation of the bats of the Fiji Islands

The poorly studied bat fauna of the Fiji Islands is of notable conservation importance because it includes one endemic species, several near endemics, and the best global populations of several threatened species. In addition, some of the species play a keystone role as pollinators and seed dispersers in valuable forest ecosystems. We visited 30 islands of the archipelago to survey bats and assess their conservation status and the potential threats to their continued existence. The Vulnerable Notopteris macdonaldi occurs on the three main islands but may only have nurseries on one of them. The Critically Endangered, endemic Mirimiri acrodonta appears to be restricted to a small montane area on a single island. Pteropus tonganus is consumed throughout rural Fiji but remains common and is not currently threatened by the harvest. The Near Threatened Pteropus samoensis is locally common on the largest islands but threatened on some smaller islands. The Endangered Chaerephon bregullae exists only on two islands and appears to concentrate in a single large colony to nurse young. The Endangered Emballonura semicaudata has declined dramatically in Fiji, as across most of its range, although a few substantial populations remain on some small islands. Factors threatening these species are variable but include small ranges, concentration in a reduced number of colonies, deforestation, over-harvesting, and introduced predators. We propose conservation measures and indicate a number of priority sites.

The Tongan flying fox Pteropus tonganus: status, public attitudes and conservation in the Cook Islands

In the Cook Islands the population of Pteropus tonganus tonganus is thought to be declining, but a lack of knowledge of its status, feeding and roosting requirements has precluded effective conservation plans. We surveyed P. t. tonganus on the Cook Islands through observations, counts and interviews with local residents. We estimated the population to be c. 1,730 on Rarotonga and 78 on Mangaia. A lack of suitable habitat on Mangaia was the most important factor affecting abundance. Overhunting appears to have reduced the populations on both islands. All roost sites were found in undisturbed forest on steep slopes and ridges in the inner and most inaccessible parts of the islands, with roost preference determined by the relative safety from humans rather than food availability. The residents of the Cook Islands seem generally unaware of the serious threat the bats face, with little thought for sustainable hunting. For successful conservation it will be important to alter people's negative perception of these mammals, promoting the value of the bats both ecologically and as a potential source of income from tourists. Habitat protection and enhancement, particularly on Mangaia, will be essential.

Effects of Cyclone Waka on flying foxes (Pteropus tonganus) in the Vava'u Islands of Tonga

Severe tropical cyclones are a major cause of episodic mortality for Pacific Island flying foxes (large fruit bats). Many flying foxes starve after forests are stripped of food sources, and hunting by humans may also increase in the post-cyclone period. In December 2001, Cyclone Waka passed directly over the Vava'u Islands in the Kingdom of Tonga, western Polynesia. We visited the islands 6 mo later to survey the flying fox (Pteropus tonganus) population and assess availability of potential food items (fruit and flower) in primary, secondary and plantation forests. Less than 20% of the pre-cyclone bat population (surveyed in 1999–2001) remained 6 mo after the storm. The density of potential food trees in flower or fruit at this time was only 15% of pre-cyclone density, and the main species available were different in the two time periods. The highest density of potential food trees occurred in secondary forest (26 flowering or fruiting trees ha−1) and plantations (23 ha−1); primary forest offered the least food (18 ha−1). Since 65–70% of the land area has been converted to agricultural plantations, this vegetation type had the highest absolute number of food-bearing trees – almost seven times that of primary forest. Flowering coconuts (Cocos nucifera) were the most abundant food source overall and we suggest that this species may be important in sustaining flying foxes following severe storms.

Electrophoretic studies of the systematic and biogeographic relationships of the Fijian bat genera Pteropus, Pteralopex, Chaerephon and Notopteris.

Allozyme variation at 24 - 29 presumptive loci was used to examine the systematic relationships between Fijian bats and those from neighbouring areas such as Vanuatu, Solomon Islands, New Caledonia, New Guinea and Australia. Genetic data indicate that the Fijian bat fauna contains highly divergent taxa as well as some populations that are virtually indistinguishable electrophoretically from conspecifics in neighbouring islands groups, particularly species shared with Vanuatu. The endemic Fijian monkey-faced bat Pteralopex acrodonta, had a level of distinctiveness from two of its congeners in the Solomon Islands comparable to that between different genera. There was also considerable electrophoretic variation within what is generally considered a single species, the northern freetail-bat Chaerephon jobensis. The Australian form, C. j. colonicus, shows levels of divergence from the Fiji/Vanuatu subspecies, C. j. bregullae, consistent with that of a distinct species. C. j. solomonis from the Solomon Islands appears to represent a third species within this group. Moderate levels of divergence were found within the one subspecies of long-tailed flying-fox Notopteris macdonaldii sampled from Fiji and Vanuatu. In contrast to Pteralopex and Chaerephon, close affinities were found between and within several other southwest Pacific bat species, in particular, the two different subspecies of insular flying-fox Pteropus tonganus from Fiji, Vanuatu and the Solomon Islands. Low levels of genetic divergence were also found between P. tonganus and the morphologially similar spectacled flying-fox P. conspicillatus from Australia and New Guinea. The Samoan flying-fox Pteropus samoensis appeared to be most closely allied to the Temotu flying-fox Pteropus nitendiensis, from the Solomon Islands.