Baseline and stress-induced glucocorticoids during reproduction in the variable flying fox, Pteropus hypomelanus (Chiroptera: Pteropodidae)

Baseline and stress-responsive glucocorticoid (GC) levels were assessed during early pregnancy, late pregnancy, and lactation in female variable flying foxes (Pteropus hypomelanus) and in males over the same time period. Animals were maintained in a breeding colony in captivity. High levels of both cortisol and corticosterone were detected, with total plasma GC levels being among the highest documented in vertebrates (up to 3000 ng/ml in individual animals, with cortisol being the primary GC, accounting for approximately 78% of total GCs), and significantly greater in males than in females. Plasma levels of cortisol and corticosterone showed nearly identical profiles within each sex, with the exception of females in late pregnancy, in which corticosterone, but not cortisol, increased significantly. Baseline levels of plasma cortisol were highest in September (when pups were between 1 and 2 months of age) in both sexes, which may be related to the approaching onset of the mating period. There was a continuum in the magnitude of the response to stress (handling and sampling) over time in females, with the greatest stress response in early pregnancy, a dampened response during late pregnancy, and no significant stress response during lactation. Surprisingly, males failed to exhibit elevated GCs after this stress, but did have significant stress-induced hyperglycemia and suppression of plasma testosterone levels. This may be due to their high (perhaps maximal) baseline levels, which suggests that being in a breeding group was chronically stressful for males.     

Mating-associated peak in plasma testosterone concentration in wild male grey-headed flying foxes (Pteropus poliocephalus)

Plasma testosterone (T) concentrations, measured in wild bats of P. poliocephalus in Queensland in 1983-87, showed a peak during the mating season in March. Plasma androstenedione (A) concentrations changed less dramatically with season. Mean testicular concentration and total content of T and A was substantially greater in March than in regressed testes in July-October. Paired adrenal glands were heavier during February to April than during September to November. In the same wild population, throughout a single breeding season (1987), plasma T concentrations were significantly higher in mid-March than 3 weeks previously or 3 weeks later. Testicular T content rose as the breeding season progressed, being greatest during March, coinciding with the large rise in plasma T concentrations. Testicular T concentration and content were correlated significantly with plasma T concentrations. Adrenal glands contained T, but the absolute concentrations were much lower than in the testis. No significant changes in plasma, testicular or adrenal A concentrations were found as the breeding season progressed. The large increase in plasma T during the mating season appears to be due to increased testicular production.     

Structural modifications involved in the fore- and hind limb grip of some flying foxes (Chiroptera: Pteropodidae)

A mechanism which enables flying foxes to lock their hind limb digits and thumbs in flexion is described. The deep digital tendons of the hind limbs have roughened fibrocartilage surfaces. The adjacent flexor tendon sheath supports ridges which interact with the rough tendon surface, temporarily 'locking' the two structures together. This tendon locking mechanism is of importance as it enables bats to reduce the energetic cost of hanging from branches. It does this by reducing, or eliminating, the need for digital flexor muscle activity.     

Allomaternal care: helper-assisted birth in the Rodrigues fruit bat, Pteropus rodricensis (Chiroptera: Pteropodidae)

We report observations of allomaternal care, or epimeletic (care-giving) behaviour, exhibited by one female toward another, before, during, and after giving birth, in the Rodrigues fruit bat, Pteropus rodricensis (Chiroptera: Pteropodidae). Interactions between the expectant mother and other roost mates, from the onset to completion of birth, were observed continuously over a period of approximately three hours. The attending female assisted the mother when she: (I) intermittently groomed her anovaginal region; (2) grasped her with partially outstretched wings; (3) 'tutored' her in a feet-down birthing posture; (4) groomed the emerging pup; and (5) physically assisted the mother by manoeuvring the pup into a suckling position. This is the first report of extensive assistance given by a female bat to another during parturition. We suggest that epimeletic behaviour may be common in the highly social Chiroptera, especially among primiparous or inexperienced females and/or when an expectant mother experiences difficulty during labour and parturition. Our observations support the hypothesis that roosting associations in bats may be as important as relatedness in explaining the occurrence of apparently altruistic acts.     

Evolutionary relationships of flying foxes (genus Pteropus) in the Philippines inferred from DNA sequences of cytochrome b gene

Six flying fox species, genus Pteropus (four from the Philippines) were investigated using complete cytochrome b gene sequences (1140 bp) to infer their evolutionary relationships. The DNA sequences generated via polymerase chain reaction were analyzed using the neighbor-joining, parsimony, and maximum likelihood methods. We estimated that the first evolutionary event among these Pteropus species occurred approximately 13.90 ± 1.49 MYA. Within this short period of evolutionary time we further hypothesized that the ancestors of the flying foxes found in the Philippines experienced a subsequent diversification forming two clusters in the topology. The first cluster is composed of P. pumilus (Philippine endemic), P. speciosus (restricted in western Mindanao) with P. scapulatus, while the second one comprised P. vampyrus and P. dasymallus species based on the analysis from first and second codon positions. Consistently, all phylogenetic analyses divulged close association of P. dasymallus with P. vampyrus contradicting the previous report categorizing P. dasymallus under subniger species group with P. pumilus, P. speciosus, and P. hypomelanus. The Philippine endemic species (P. pumilus) is closely linked with P. speciosus. The representative samples of P. vampyrus showed a large genetic distance of 1.87%. The large genetic distance between P. dasymallus and P. hypomelanus, P. pumilus and P. speciosus denotes a distinct species group.     

Detection of Hepatocystis sp. in southeast Asian flying foxes (Pteropodidae) using microscopic and molecular methods

Three species of flying fox (Pteropus hypomelanus, P. vampyrus, and P. lylei) from Malaysia and Vietnam were screened for apicomplexan parasites by thin blood smears and polymerase chain reaction. Only 1 of 16 bats sampled from 3 localities in southeast Asia was found to be infected (P. hypomelanus from Pulau Pangkor, Malaysia). We observed micro- and macrogametocytes, with morphology consistent with Hepatocystis sp. parasites, using light microscopy. Phylogenetic analysis of the cytochrome b gene showed that the parasite from P. hypomelanus groups with 2 published sequences from Hepatocystis spp., including one from Cynopterus brachyotis, another fruit bat in the Pteropodidae.     

Evaluation of medetomidine/ketamine for short-term immobilization of variable flying foxes (Pteropus hypomelanus)

Four medetomidine/ketamine (M/K) doses (30 microg/kg/3 mg/kg; 40/4; 50/5; 60/6), administered by intramuscular injection, were evaluated for short-term immobilization of adult male variable flying foxes (Pteropus hypomelanus). The highest dose (60 microg/kg/6 mg/kg) produced a significantly faster induction (31 +/- 46 sec) than the lowest dose (30/3) (125 +/- 62 sec). The highest dose levels (50/5, 60/6) produced significantly longer immobilization times (52.5 +/- 25.7 min and 60.6 +/- 20.8 min, respectively) than did the lower doses (30/3, 40/4) (18.8 +/- 8.7 min and 31.0 +/- 14.3 min, respectively). The dose at which 50% of the bats were immobilized for > or = 30 min (ED(50)) was approximately 40 microg/kg/4 mg/kg. This dose produced a mean immobilization time of 31 +/- 14 min, bradypnea and bradycardia. In conclusion, a M/K dose of 50 microg/kg/5 mg/kg is recommended for greater than 30 min of relaxed immobilization in free-living variable flying foxes and is sufficient for safe collection of samples.     

Comparison of intravenous medetomidine and medetomidine/ketamine for immobilization of free-ranging variable flying foxes (Pteropus hypomelanus)

Medetomidine (0.03 mg/kg) and medetomidine/ketamine (0.05/5.0 and 0.025/2.5 mg/kg), administered by intravenous injection, were evaluated for short-term immobilization of wild-caught variable flying foxes (Pteropus hypomelanus). Medetomidine alone produced incomplete chemical restraint and a stressful, prolonged induction. Both ketamine/medetomidine doses produced a smooth induction and complete immobilization. The combined medetomidine/ketamine dose of 0.025/2.5 mg/kg produced a rapid induction (232±224 sec) with minimal struggling and vocalization, a complete and effective immobilization period, and tended to lead to a faster and better quality recovery than medetomidine alone or a higher dose of medetomidine and ketamine (0.05/5.0 mg/kg), thus reducing holding time and permitting an earlier release of the bat back into the wild.     

Reproduction and nutritional stress are risk factors for Hendra virus infection in little red flying foxes (Pteropus scapulatus)

Hendra virus (HeV) is a lethal paramyxovirus which emerged in humans in 1994. Poor understanding of HeV dynamics in Pteropus spp. (flying fox or fruit bat) reservoir hosts has limited our ability to determine factors driving its emergence. We initiated a longitudinal field study of HeV in little red flying foxes (LRFF; Pteropus scapulatus) and examined individual and population risk factors for infection, to determine probable modes of intraspecific transmission. We also investigated whether seasonal changes in host behaviour, physiology and demography affect host-pathogen dynamics. Data showed that pregnant and lactating females had significantly higher risk of infection, which may explain previously observed temporal associations between HeV outbreaks and flying fox birthing periods. Age-specific seroprevalence curves generated from field data imply that HeV is transmitted horizontally via faeces, urine or saliva. Rapidly declining seroprevalence between two field seasons suggests that immunity wanes faster in LRFF than in other flying fox species, and highlights the potentially critical role of this species in interspecific viral persistence. The highest seroprevalence was observed when animals showed evidence of nutritional stress, suggesting that environmental processes that alter flying fox food sources, such as habitat loss and climate change, may increase HeV infection and transmission. These insights into the ecology of HeV in flying fox populations suggest causal links between anthropogenic environmental change and HeV emergence.     

Seasonal changes in testicular size, plasma testosterone concentration and body weight in captive flying foxes (Pteropus poliocephalus and P. scapulatus)

Adult male flying foxes Pteropus poliocephalus and P. scapulatus were captured in south-east Queensland and kept in outdoor enclosures. Testicular size (TS), plasma testosterone concentrations (PTC) and body weight (BW) were measured over 1-year periods. Testicular recrudescence in P. poliocephalus began before the summer solstice and TS was greatest during mid-March (autumn) and lowest from July to September. Large increases in PTC were observed in all individuals approximately 1 month after the peak in TS. BW also increased around the time of the mating season, changes being correlated significantly with changes in TS. Mating occurred between April and June, and births from late October to late November. In P. scapulatus, TS was greatest in the spring (October) and least in the autumn (February to May); PTC fluctuated throughout the year in this species but, unlike P. poliocephalus, did not show a single large increase in the mating season. BW showed a similar seasonal pattern to that seen in P. poliocephalus, being greatest at the time of greatest TS. Mating occurred in October to November, and births in autumn. In captivity, in outdoor enclosures, these species maintained the seasonal reproductive patterns observed in the wild. The 2 species respond differently to the same environmental cues in terms of regulation of the timing of their breeding seasons.     

The hormonal and behavioral response to group formation, seasonal changes, and restraint stress in the highly social Malayan Flying Fox (Pteropus vampyrus) and the less social Little Golden-mantled Flying Fox (Pteropus pumilus) (Chiroptera: Pteropodidae)

This study examined behavioral and physiological responses (changes in inter-animal spacing, total glucocorticoids, testosterone, and body mass) to the formation of breeding and same-sex groups in two bat species, the socially gregarious Malayan Flying Fox (Pteropus vampyrus) and the less social Little Golden-mantled Flying Fox (Pteropus pumilus). We hypothesized that social instability, especially in the breeding groups and especially in P. vampyrus, would result in elevated glucocorticoids and that social facilitation of breeding and/or male-male competition would result in persistently higher levels of testosterone in breeding males. Seasonal rhythms in all measures were also predicted, and the glucocorticoid stress response was expected to vary by sex, season, and group type. Nearly all animals responded to group formation with elevated glucocorticoids, but, for breeding animals (especially aggressive male P. vampyrus), these responses persisted over time. In both species, breeding group formation resulted in elevated testosterone in males. Glucocorticoids, testosterone, testes volume, and body mass generally peaked in the breeding season in males (late summer and early autumn), but the seasonal glucocorticoid peak in females occurred in late winter and early spring. All animals responded to restraint stress with elevations in glucocorticoids that largely did not differ by sex, time of year, reproductive condition, group type, or, in lactating females, the presence of her pup. Changes in both behavior and physiology were more evident in P. vampyrus than in P. pumilus, and we believe that their underlying social differences influenced their responses to group formation and to the changing seasonal environment.     

Catecholamine innervation of the intestine of flying foxes (Pteropus spp.): a substantial supply from enteric neurons

The distribution of catecholamines in the small and large intestine of flying foxes (Pteropus spp.) was investigated using glyoxylic-acid-induced fluorescence and immunohistochemical staining of tyrosine hydroxylase and dopamine--hydroxylase. Dense networks of varicose axons stained by each of these methods supplied blood vessels, the mucosa and both submucous and myenteric ganglia, but were scarce in the circular and longitudinal muscle. The majority (>90%) of submucous neuronal perikarya contained both enzymes and most of these also exhibited catecholamine fluorescence. Somata of similar staining characteristics were less common in the myenteric plexus, where single cells were found in only the minority of ganglia. All of the stained submucosal somata and mucosal axons contained vasoactive intestinal peptide, whereas catecholamine-containing axons that supplied the ganglia, external muscle and blood vessels did not. It is concluded that (1) there is dense catecholamine innervation of most tissues in the flyingfox intestine, similar to many other mammals, (2) mucosal axons originate from enteric catecholamine neurons, not found in other mammals, and (3) axons supplying the blood vessels and enteric ganglia are probably of sympathetic origin and can be distinguished from the intrinsic catecholamine-containing axons by their lack of vasoactive intestinal peptide. The roles and interactions of these two types of catecholamine innervation in the control of secretion and motility remain to be identified.     

Urban habituation, ecological connectivity and epidemic dampening: the emergence of Hendra virus from flying foxes (Pteropus spp.)

Anthropogenic environmental change is often implicated in the emergence of new zoonoses from wildlife; however, there is little mechanistic understanding of these causal links. Here, we examine the transmission dynamics of an emerging zoonotic paramyxovirus, Hendra virus (HeV), in its endemic host, Australian Pteropus bats (fruit bats or flying foxes). HeV is a biosecurity level 4 (BSL-4) pathogen, with a high case-fatality rate in humans and horses. With models parametrized from field and laboratory data, we explore a set of probable contributory mechanisms that explain the spatial and temporal pattern of HeV emergence; including urban habituation and decreased migration-two widely observed changes in flying fox ecology that result from anthropogenic transformation of bat habitat in Australia. Urban habituation increases the number of flying foxes in contact with human and domestic animal populations, and our models suggest that, in addition, decreased bat migratory behaviour could lead to a decline in population immunity, giving rise to more intense outbreaks after local viral reintroduction. Ten of the 14 known HeV outbreaks occurred near urbanized or sedentary flying fox populations, supporting these predictions. We also demonstrate that by incorporating waning maternal immunity into our models, the peak modelled prevalence coincides with the peak annual spill-over hazard for HeV. These results provide the first detailed mechanistic framework for understanding the sporadic temporal pattern of HeV emergence, and of the urban/peri-urban distribution of HeV outbreaks in horses and people.     

Insectivory in captive Livingstone's and Rodrigues fruit bats Pteropus livingstonii and P. rodricensis (Chiroptera: Pteropodidae): a behavioural adaptation for obtaining protein

Captive Pteropus livingstonii and P. rodricensis were observed actively to catch and eat insects. Both species adopt the same technique to trap flying insects, using their wings to envelop them. The spontaneity of the response indicates that it is not an artefact of captivity. The behaviour was observed in captive-bred P. rodricensis which had no prior access to insects, suggesting that it is also innate. A higher rate of successful captures was recorded for an older, wild caught P. livingstonii female, indicating that the effectiveness of the technique used may improve with age. Significant differences in the amount of time spent catching insects by males and females were evident in this species. This study supports suggestions that insects are eaten by some megachiopterans in order to supplement their protein intake.     

亚洲南部球果蝠Sphaerias blanfordi(Thomas,1891)的亚种分化

球果蝠Sphaerias blanfordi(Thomas,1891)是亚洲南部喜马拉雅-印度支那地区的特有种,甚为罕见而少有报道.曾被认为是单型种,几乎无雄性特征的描述.蔡桂全和张遁治(1980)根据采自西藏东南部墨脱的2只雄性标本订了一亚种一墨脱亚种Sphaerias blanfordi motuoensis,其主要特征是颈下侧有一对灰黄色的圆形毛斑.中国科学院昆明动物研究所先后在云南西北部高黎贡山地区采获25号标本(9♂♂,16♀♀),发现球果蝠两性在外形上有明显的性别差异,雄性的颈下侧有一对圆形、灰黄色的刷状毛斑,但雌性均无;对比墨脱标本,认为墨脱亚种的鉴别特征不可靠,亚种不能成立.Lunde(2003)曾报道采自越南北部Mt.Tay Con Linh Ⅱ地区的43号标本,其前臂长和上犬齿外宽明显与印度、缅甸和云南西北部高黎贡山地区的标本不同,可能是真正的地理亚种.     

Chemical compounds from femoral gland secretions of male Iberian rock lizards, Lacerta monticola cyreni

In spite of the importance of chemoreception and chemical signals in the social organization of lizards, there are only a few studies examining the chemical composition of secretions of lizards used for scent marking. The secretion of the femoral glands of male Iberian rock lizards (Lacerta monticola cyreni) contains 44 lipophilic compounds, including several steroids (mainly cholesterol), and n-C6 to n-C22 carboxylic acids, and minor components such as esters of carboxylic acids, alcohols, squalene, and one lactone. These compounds were identified on the basis of mass spectra, obtained by GC-MS. Most lipids were detected in all individuals, although relative proportions of each chemical show a high interindividual variability. This variability might be related to the characteristics or physical and health condition of males and might be the basis of female choice based on chemical cues observed in this lizard species.