Australian Flying-foxes Research Articles

Mass mortalities of grey-headed flying-foxes (Pteropus poliocephalus) from tree collapses

Mortality factors are an important subject of research, especially when mortalities concern threatened taxa. The grey-headed flying-fox (Pteropus poliocephalus) is a vulnerable species endemic to eastern and south-eastern Australia that is known to be susceptible to a spectrum of compounding threats including factors producing simultaneous deaths. We describe two incidents of trees within a flying-fox roost collapsing and causing mass mortalities in individuals roosting in those trees. Each incident resulted in 335 and 57 deaths, as well as 74 and 45 individuals that would have died if not taken into ex-situ care. Total mortality for each incident equated to approximately 15% and 2% of the colony at the time of those incidents. Although flying-foxes are capable of flight, take-off from a roosting position requires an initial freefall, which makes escape from a collapsing tree difficult. Our accounts potentially represent the first reports of tree collapses causing mortality in Australian flying-foxes, which highlight the relevance of tree health in roosts to flying-fox welfare and conservation. This information also builds upon our growing knowledge of factors producing mass mortalities in flying-foxes.

Going it alone: observations of solitary roosting in two Australian flying-foxes (Pteropus alecto and P. poliocephalus)

Unlike some flying-fox species that exhibit solitary roosting, all flying-fox species of the Australian mainland are strongly colonial, though some extent of solitary roosting in these species is anecdotally known. This note reports on five accounts of solitary roosting in black flying-foxes (Pteropus alecto) and grey-headed flying-foxes (Pteropus poliocephalus), herein referred to as 'singletons'. These accounts are potentially the first published detailed observations of singletons in Australian flying-foxes outside of visible periods of food shortages. In particular, one account involved solitary roosting recorded over multiple days. The frequency and extent of singletons in Australian flying-foxes remain completely unknown. In terms of deriving population sizes in these species from counts at communal roosts, these individuals represent an addition to those estimates.

Estimating flying-fox mortality associated with abandonments of pups and extreme heat events during the austral summer of 2019–20

Mass mortalities in flying-foxes occur in summers that reach extremely hot temperatures. In this study, we examine the spatiotemporal distributions of mortality from pup abandonments and extreme heat events in Australian flying-fox camps during the 2019–20 summer. We recorded data on flying-fox mortality in known affected camps and applied a standard method to estimate the number of deaths. Pup mortalities from abandonments were recorded in 10 camps in New South Wales. A minimum estimate of 2612 flying-foxes died in pup abandonments, the majority of which occurred in one camp in Bomaderry. Die-offs from extreme heat events were recorded in 40 camps associated with eight separate heat events in south-eastern Australia. A minimum estimate of 72 175 flying-foxes died during these heat events, which all occurred within the range of the threatened grey-headed flying-fox (Pteropus poliocephalus). Further, 409 and 2251 live flying-foxes were taken into care from pup abandonments and heat events respectively. The minimum mortality estimated represents the highest recorded mortality of Australian flying-foxes within a single summer. This highlights a need to restore vegetation in flying-fox foraging areas and camps, address anthropogenic climate change and gather more empirical data to inform heat stress interventions to minimise flying-fox mortalities.

Evidence of chronic cadmium exposure identified in the critically endangered Christmas Island flying-fox (Pteropus natalis)

The Christmas Island flying-fox (Pteropus natalis) is the last native mammal on Christmas Island and its population is in decline. Phosphate mining occurs across much of the eastern side of Christmas Island. The phosphate deposits are naturally rich in cadmium, and potentially other metals, which may be threatening the Christmas Island flying-fox population. To test this, concentrations of metals (cadmium, copper, iron, mercury, lead, and zinc) were measured in fur and urine collected from Christmas Island flying-foxes and interpreted concurrently with urinalysis and serum biochemistry data. In addition, metal concentrations in liver and kidney samples from two Christmas Island flying-foxes and associated histological findings from one of these individuals are reported. Fur cadmium concentrations were significantly higher in the Christmas Island flying-fox compared to concentrations found in flying-foxes in mainland Australia. Additionally, 30% of Christmas Island flying-foxes had urine cadmium concentrations exceeding maximum concentrations previously reported in flying-foxes in mainland Australia. Glucosuria and proteinuria were identified in two Christmas Island flying-foxes, suggestive of renal dysfunction. In one aged flying-fox, kidney cadmium concentrations were four-fold higher than toxic thresholds reported for domestic mammals. Microscopic evaluation of this individual identified bone lesions consistent with those described in laboratory animals with chronic cadmium poisoning. These results suggest that Christmas Island flying-foxes are being exposed to cadmium and identification of these sources is recommended as a focus of future research. Unexpectedly, urine iron concentrations in Christmas Island flying-foxes were higher compared to previous studies of Australian mainland flying-foxes, which suggests that urinary excretion of iron may be an important aspect of iron homeostasis in this species whose diet is iron rich.

Predation on cicadas by an Australian Flying-fox Pteropus poliocephalus based on DNA evidence

ABSTRACT Historically, reports of insectivory in family Pteropodidae have largely been anecdotal and thought to be an incidental corollary of flying-foxes feeding on plant products. More recent direct observations of flying-foxes catching and consuming insects, as well as advances in techniques that increase our ability to detect dietary items, suggest that this behaviour may be deliberate and more common than previously thought. Usually, multiple insects are consumed, but it appears that flying-foxes hunt and eat them one at a time. However, we have collected and photographed oral ejecta pellets under trees with high flying-fox activity, some containing evidence of multiple masticated insects. Further genetic analysis proved that these pellets came from Grey-headed Flying-foxes Pteropus poliocephalus. We propose that flying-foxes use an array of insect feeding strategies, most likely in response to variation in insect abundance and activity, as well as abiotic factors such as light and temperature.

Variation in fur properties may explain differences in heat-related mortality among Australian flying-foxes

Fur properties play a critical role in the thermoregulation of mammals and are becoming of particular interest as the frequency, intensity, and duration of extreme heat events are increasing under climate change. Australian flying-foxes are known to experience mass die-offs during extreme heat events, yet little is known about how different fur properties affect their thermoregulatory needs. In this study, we examined the differences and patterns in fur properties among and within the four mainland Australian flying-fox species: Pteropus poliocephalus, P. alecto, P. conspicillatus, and P. scapulatus. Using museum specimens, we collected data on fur solar reflectance, fur length and fur depth from the four species across their distribution. We found that P. poliocephalus had significantly longer and deeper fur, and P. alecto had significantly lower fur solar reflectivity, compared with the other species. Across all species, juveniles had deeper fur than adults, and females of P. alecto and P. conspicillatus had deeper fur than males. The biophysical effects of these fur properties are complex and contingent on the degree of exposure to solar radiation, but they may help to explain the relatively higher mortality of P. alecto and of juveniles and females that is commonly observed during extreme heat events.

Insights into the ancestral organisation of the mammalian MHC class II region from the genome of the pteropid bat, Pteropus alecto

BackgroundBats are an extremely successful group of mammals and possess a variety of unique characteristics, including their ability to co-exist with a diverse range of pathogens. The major histocompatibility complex (MHC) is the most gene dense and polymorphic region of the genome and MHC class II (MHC-II) molecules play a vital role in the presentation of antigens derived from extracellular pathogens and activation of the adaptive immune response. Characterisation of the MHC-II region of bats is crucial for understanding the evolution of the MHC and of the role of pathogens in shaping the immune system.ResultsHere we describe the relatively contracted MHC-II region of the Australian black flying-fox (Pteropus alecto), providing the first detailed insight into the MHC-II region of any species of bat. Twelve MHC-II genes, including one locus (DRB2) located outside the class II region, were identified on a single scaffold in the bat genome. The presence of a class II locus outside the MHC-II region is atypical and provides evidence for an ancient class II duplication block. Two non-classical loci, DO and DM and two classical, DQ and DR loci, were identified in P. alecto. A putative classical, DPB pseudogene was also identified. The bat’s antigen processing cluster, though contracted, remains highly conserved, thus supporting its importance in antigen presentation and disease resistance.ConclusionsThis detailed characterisation of the bat MHC-II region helps to fill a phylogenetic gap in the evolution of the mammalian class II region and is a stepping stone towards better understanding of the immune responses in bats to viral, bacterial, fungal and parasitic infections.

No Evidence of Hendra Virus Infection in the Australian Flying-fox Ectoparasite Genus Cyclopodia.

Hendra virus (HeV) causes potentially fatal respiratory and/or neurological disease in both horses and humans. Although Australian flying-foxes of the genus Pteropus have been identified as reservoir hosts, the precise mechanism of HeV transmission has yet to be elucidated. To date, there has been limited investigation into the role of haematophagous insects as vectors of HeV. This mode of transmission is particularly relevant because Australian flying-foxes host the bat-specific blood-feeding ectoparasites of the genus Cyclopodia (Diptera: Nycteribiidae), also known as bat flies. Using molecular detection methods, we screened for HeV RNA in 183 bat flies collected from flying-foxes inhabiting a roost in Boonah, Queensland, Australia. It was subsequently demonstrated that during the study period, Pteropus alecto in this roost had a HeV RNA prevalence between 2 and 15% (95% CI [1, 6] to [8, 26], respectively). We found no evidence of HeV in any bat flies tested, including 10 bat flies collected from P.alecto in which we detected HeV RNA. Our negative findings are consistent with previous findings and provide additional evidence that bat flies do not play a primary role in HeV transmission.

Assessing the risk of Nipah virus establishment in Australian flying-foxes.

Nipah virus (NiV) is a recently emerged zoonotic virus that causes severe disease in humans. The reservoir hosts for NiV, bats of the genus Pteropus (known as flying-foxes) are found across the Asia-Pacific including Australia. While NiV has not been detected in Australia, evidence for NiV infection has been found in flying-foxes in some of Australia's closest neighbours. A qualitative risk assessment was undertaken to assess the risk of NiV establishing in Australian flying-foxes through flying-fox movements from nearby regions. Events surrounding the emergence of new diseases are typically uncertain and in this study an expert opinion workshop was used to address gaps in knowledge. Given the difficulties in combining expert opinion, five different combination methods were analysed to assess their influence on the risk outcome. Under the baseline scenario where the median was used to combine opinions, the risk was estimated to be very low. However, this risk increased when the mean and linear opinion pooling combination methods were used. This assessment highlights the effects that different methods for combining expert opinion have on final risk estimates and the caution needed when interpreting these outcomes given the high degree of uncertainty in expert opinion. This work has provided a flexible model framework for assessing the risk of NiV establishment in Australian flying-foxes through bat movements which can be updated when new data become available.

Recrudescent Infection Supports Hendra Virus Persistence in Australian Flying-Fox Populations

Zoonoses from wildlife threaten global public health. Hendra virus is one of several zoonotic viral diseases that have recently emerged from Pteropus species fruit-bats (flying-foxes). Most hypotheses regarding persistence of Hendra virus within flying-fox populations emphasize horizontal transmission within local populations (colonies) via urine and other secretions, and transmission among colonies via migration. As an alternative hypothesis, we explore the role of recrudescence in persistence of Hendra virus in flying-fox populations via computer simulation using a model that integrates published information on the ecology of flying-foxes, and the ecology and epidemiology of Hendra virus. Simulated infection patterns agree with infection patterns observed in the field and suggest that Hendra virus could be maintained in an isolated flying-fox population indefinitely via periodic recrudescence in a manner indistinguishable from maintenance via periodic immigration of infected individuals. Further, post-recrudescence pulses of infectious flying-foxes provide a plausible basis for the observed seasonal clustering of equine cases. Correct understanding of the infection dynamics of Hendra virus in flying-foxes is fundamental to effectively managing risk of infection in horses and humans. Given the lack of clear empirical evidence on how the virus is maintained within populations, the role of recrudescence merits increased attention.

Latitudinal range shifts in Australian flying‐foxes: A re‐evaluation

AbstractRecent range shifts towards higher latitudes have been reported for many animals and plants in the northern hemisphere, and are commonly attributed to changes in climate. Relatively little is known about such changes in the southern hemisphere, although it has been suggested that latitudinal distributions of the fruit‐batsPteropus alectoandPteropus poliocephaluschanged during the 20th century in response to climate change in eastern Australia. However, historical changes in these species distributions have not been examined systematically. In this study we obtained historical locality records from a wide range of sources (including banding and museum records, government wildlife databases and unpublished records), and filtered them for reliability and spatial accuracy. The latitudinal distribution of each species was compared between eight time‐periods (1843–1920, 1921–1950, five 10‐year intervals between 1950 and 2000, and 2001–2007), using analyses of both the filtered point data (P. alecto870 records,P. poliocephalus2506) and presence/absence data within 50 × 50 km grid cells. The results do not support the hypothesis that either species range is shifting in a manner driven by climate change. First, neither the northern or southern range limits ofP. poliocephalus(Mackay, Queensland and Melbourne, Victoria respectively) changed over time. Second,P. alecto's range limit extended southward by 1168 km (approximately 10.5 degrees latitude) during the twentieth century (from approximately Rockhampton, Queensland to Sydney, New South Wales). Within this zone of southward expansion (25–29°S), the percentage of total records that wereP. alectoincreased from 8% prior to 1950 to 49% in the early 2000s, and local count data showed that its abundance increased from several hundred to more than 10 000 individuals at specific roost sites, as range expansion progressed.Pteropus alectoexpanded southward at about 100 km/decade, compared with the 10–26 km/decade rate of isotherm change, and analyses of historical weather data show that the species consequently moved into recently‐colder regions than it had previously occupied. Neither climate change nor habitat change could provide simple explanations to explainP. alecto's observed rapid range shift. More generally, climate change should not be uncritically inferred as a primary driver of species range shifts without careful quantitative analyses.

Pituitary content of luteinizing hormone reveals species differences in the reproductive synchrony between males and females in Australian flying-foxes (genus Pteropus).

Flying-foxes (genus suborder, Pteropus Megachiroptera) are long-lived tropical mammals. Their seasonal reproduction appears to be regulated by an endogenous, circannual rhythm modified by multiple environmental cues. Luteinizing hormone (LH) content in pituitary extracts was examined to establish the broad time-frame of pituitary stages in the reproductive seasonality of the flying-foxes. A comparison was made between the grey-headed flying-fox P. poliocephalus, which mates and conceives in autumn, and the little red flying-fox P. scapulatus, which mates and conceives in spring. In P. scapulatus, LH was maximum during the spring mating season at 1494 ng mg(-1) in males and 896 ng mg(-1) in females. In P. poliocephalus males, LH increased to 1082 ng mg(-1) in early summer, 4 months before the mating season; LH concentrations in male P. poliocephalus returned to a low of 222 ng mg(-1) by the time of the autumn mating, by which time the female P. poliocephalus expressed elevated LH concentrations (624 ng mg(-1)). Apparently in P. poliocephalus, the peak LH concentrations in females are delayed by 4 months relative to LH concentrations in males. This is associated with 4 months of energetic courtship on the part of male P. poliocephalus, which is not observed in P. scapulatus, the fertility of which is synchronized between the sexes. The heterologous radioimmunoassay developed using monoclonal antibody 518B7 confirmed classic suppression of LH during pregnancy and lactation in flying-foxes and LH elevation in response to gonadectomy. Juveniles generally had pituitary levels similar to non-breeding levels in adults.

Mobility of Australian flying-foxes, Pteropus spp. (Megachiroptera): evidence from genetic variation.

Black (Pteropus alecto) and grey-headed (Pteropus poliocephalus) flying-foxes inhabit large ranges in coastal north and eastern Australia. P. poliocephalus is endemic to region and is classified as vulnerable. The bats are known to migrate in response to flowering and fruiting of their food plants, but direct observation of movement patterns is difficult. Protein electrophoresis was used to investigate genetic subdivision among populations. High gene flow was inferred for both species with an estimated exchange of 15 (P. alecto) and 28 (P. poliocephalus) individuals between populations per generation. Wright's FST, an index of among population genetic variation, was low, 0.023 (P. alecto), 0.014 (P. poliocephalus), reflecting the homogenising action of movements across the species' ranges. An FST value of 0.028 has been reported for a third Australian species, the little red flying-fox, P. scapulatus. The FST values for Australian flying-foxes are closer to those found for birds than the typically higher values for mammals and we conclude that these flying-foxes are essentially panmictic and for management purposes should be treated as migratory species.

Ovarian and uterine lymphatic drainage in Australian flying-foxes (genus Pteropus, suborder Megachiroptera).

Ovarian lymphatics of flying-foxes were traced to determine if they could transport hormones directly from ovary to ipsilateral uterine horn, thereby stimulating the localised endometrial growth which is characteristic of these animals. Intra-ovarian injections of ink and serial histological sections did not reveal any such connection. All major ovarian lymphatics and those from the cranial tip of each uterine horn drain cranially, terminating in 1 or 2 lymph nodes lying caudal to the ipsilateral kidney. For much of their course, the major ovarian lymphatics run in the adventitia of the ovarian venous sinus. This sinus encloses the coiled ovarian artery, which provides the major blood supply to the cranial end of the ipsilateral uterine horn. Some fine ovarian lymphatics run in the adventitia of the coiled ovarian artery. The enclosure of the coiled ovarian artery by the ovarian venous drainage is thought to provide the main route for transfer of steroids from ovarian vein to ovarian artery and thence to ipsilateral uterine horn. The ovarian lymphatics described here do not bypass the vascular pathway but provide an additional route for counter- or cross-current transfer of ovarian steroids to the ovarian arterial supply to the uterus.

Ovarian and uterine lymphatic drainage in Australian flying-foxes (genus Pteropus , suborder Megachiroptera)

Ovarian and uterine lymphatic drainage in Australian flying-foxes (genus Pteropus , suborder Megachiroptera)

Identification, distribution and taxonomy of Australian flying-foxes (Chiroptera: Pteropodidae)

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Observations on the transmission and development of Toxocara pteropodis (Ascaridoidea: Nematoda) in the Australian grey-headed flying-fox, Pteropus poliocephalus (Pteropodidae: Megachiroptera).

Findings in the Australian Grey-Headed Flying-Fox, Pteropus poliocephalus, have elucidated the life-cycle of Toxocara pteropodis. In adult bats, other than parturient females, larvae were found only in the livers. Following parturition, larvae were recovered only from mammary glands up to 2 weeks post-partum. Developing larvae were found only in the intestine of young bats from the age of two days onwards; there was no evidence of pulmonary migration. The evidence indicates that juvenile bats commence passing Toxocara eggs in their faeces at about 2 months of age and expel the worms spontaneously following weaning at about 5 months. The eggs passed in the faeces of the young bat and its mother are disseminated throughout their environment and embryonate rapidly, being infective to mice after 10 days. Under natural conditions the eggs remain viable for 6 weeks or less and are infective to bats by the oral route.