Lyle's Flying Fox (Pteropus lylei)
HB: 200-250; T: None; FA: 145-160; E: 35-39; HF: 40-45; W:
Lyle’s flying fox (Pteropus lylei) is a medium-sized flying fox which forms large colonies high up in trees. Lyle’s flying fox has a long dark muzzle, large eyes and a ring of orange fur around the neck, and bears some resemblance to a fox, hence the common name ‘flying fox’. Lyle's flying fox (Pteropus lylei) is medium-sized bat species, weighting between 390-480 g. It distributes in Cambodia, Thailand and Vietnam.9 It has the nocturnal lifestyle like other bat species, forages at night and returns to the colony before sunrise. Via satellite, Hondo et al. (2010) showed high mobility of Lyle's flying fox, speeding up to 49.83 km/h for foraging on fruit, nectar and pollen.8 Along the way, it usually distributes seeds in its droppings.5 This has secured its position as keystone species-animal that is disproportionately important in determining the ecological diversity, distribution and abundance of plants and other animals.12 However, Lyle's flying fox is considered as a pest by fruit growers in agricultural areas of Thailand. Owing to this attitude, it is threatened by humans.2 Consequently, it was classified as vulnerable species in IUCN red list. Killing is not only a factor resulted in the population size declining, reduction in roosting area due to habitat change by humans and effects of continual use by bats may have an impact on population size of these bats in future. The effective management and conservation for this bat species are essential. The wings and back of Lyle's flying fox are dark brown or black, which strongly contrast against the bright fur around the head and neck. Its lower body varies from a deep dark-brown to a brighter yellow-brown. Its breast and belly are black-brown, which is similar to the large flying fox (Pteropus vampyrus).
Lyle’s flying fox is native to Southeast Asia and is found in Thailand, Vietnam, Cambodia, Malaysia, and Yunnan in China. This species has been mostly documented in Thailand, where at least 11 colonies have been identified, the largest containing around 3,000 individuals .
Lyles’s flying fox can be found in some of Southeast Asia’s most secluded jungles, as well as in the middle of villages or even large urban metropolises such as Bangkok. The species usually roosts in temples in the middle of urban areas. Colonies inhabiting the forest roost in the tops of tall canopy trees, which they revisit year after year. Lyle's flying fox is a vulnerable species of Thailand. Large colonies are established in the central Plain of Thailand, but the ecology and behaviour of this bat remain largely unknown.
The diet of Lyle’s flying fox consists mainly of ripe fruit. However, this species will also feed on nectar, pollen and blossoms to ensure it gets enough energy. Fruit is very low in protein and sodium, so the salivary gland of Lyle’s flying fox has become specially adapted to ensure this species can extract the required nutrients .
Lyle’s flying fox’s primary sense when foraging is vision, as it lacks the echolocation abilities of insectivorous bats. It has well developed teeth which are used to chew fruit while spitting out most of the seeds and pulp. Some seeds are ingested, which is important for the local ecosystem as it allows for the dispersal of seeds into other areas.
Although it is a nocturnal species, Lyle’s flying fox is very sociable and noisy during the day, as this is when females suckle their young . Large noisy colonies are very conspicuous, but they have few natural predators and so can hang safely up in the trees all day .
Unlike other bat families, fruit bats do not hibernate. Instead, Lyle’s flying fox produces heat by shivering, which keeps its body temperature between 33 and 37 degrees Celsius.
Lyle’s flying fox, and other species of bat, have been found to harbour large reservoirs of the Nipah virus. Although the virus does not harm the bat, it can be deadly to humans, and there is substantial data suggesting that recent outbreaks were caused by bat to person transmission of the virus .Nothing is known from China about the ecology of this species (Smith et al. 2008). In other areas, it is known to form large colonies in trees that can become stripped of leaves by the bats? activity. It feeds in orchards and is regarded as a serious pest in Thailand (S. Bumrungsri pers. comm.). It occurs in mangrove forest in Vietnam (Son Nguyen Truong pers. comm.). This species travels up to 50 km between colonies (S. Bumrugsri pers. comm.).
The most common behaviours performing by bats were sleeping, grooming and wing flapping. Sleeping, grooming, wing spreading, movement, wing flapping, aggression and mating/courtship were varied significantly throughout the day, while nursing/maternal was the only behaviour that did not change between times of day. Sleeping, grooming and mating/courtship occurred mostly in morning and late afternoon, while aggression and wing flapping occurred mostly in morning and noon respectively. Seasonal variation was mostly found in grooming, wing spreading, movement and wing flapping. Grooming, wing spreading and movement were more frequency found in wet season than in dry season, while wing flapping was less frequent in wet season than dry season. This study can conclude that the season and the times of day have influenced on daytime behaviours of Lyle's flying foxes.
Mating and Courtship:
There were significant differences in number of bats performing this behaviour between wet and dry seasons in some durations of the day (p<0.05. The percentages of bat mating and courtship in dry season were significantly higher than in wet season between 0600 to 0800 hours, and between 1600 to 1800 hours. There were also significant differences in the percentage of bats mating and courtship during the day both in wet and dry seasons (p<0.05). The highest percentage of mating and courtship was recorded in morning (0600 to 0900 hours) and in evening (1700 to 1800 hours). Increasing in mating and courtship activity levels was suggested to be the result from the elevations of testosterone. Testosterone secretion has a circadian rhythm, highest in the morning and lower in the afternoon.
There were differences in number of bats performing this behaviour between wet and dry season between 0700 to 1100 hours, but there was no significant difference in the percentage of bats performing this behaviour among time of day both in wet and dry seasons (p>0.05, figure. 8). This result can be explained by the number of lactating females with juvenile attached. Similar numbers of lactating females with juvenile attached were observed in two sampled periods (wet season and dry season). Lactating females usually take care their pups throughout the day, so the time of day has no influence on this behaviour. However, Boonneung (1977) found the negative relationship between precipitation and juvenile number. In the middle of wet season, number of juveniles was low because rainfall has negative impact on giving birth and maternal care.1 During field observations, maternal care was exhibited by females only. Environmental factors such as temperature and precipitation would be the cause of seasonal variation in daytime behaviour of Lyle's flying foxes because they are exposed to open environment while roosting on tree. Internal factors such as hormones can also affect on Lyle's flying foxes behaviour. Owing to the short observation periods, we are not able to explain all behaviours that we observed in Lyle’s flying foxes. We need further study for intensive knowledge on Lyle’s flying foxes behaviour.
In Thailand the species is threatened through
loss of roosting habitat, as existing trees die and are not replaced, it is also
subject to hunting (S. Bumrungsri pers. comm.). It is also threatened in
Cambodia by hunting (P. Bates pers. comm.).
This species is listed on Appendix II of CITES. There are no known populations within protected areas in Vietnam (Son Nguyen Truong pers. comm.) or Cambodia. The species is protected by monks in Thailand (S. Bumrungsri pers. comm.).