Syconycteris Australis Research Articles

Pronounced differences in heart rate and metabolism distinguish daily torpor and short-term hibernation in two bat species

Torpor, and its differential expression, is essential to the survival of many mammals and birds. Physiological characteristics of torpor appear to vary between those species that express strict daily heterothermy and those capable of multiday hibernation, but comparisons are complicated by the temperature-dependence of variables. Previous reviews have compared these different torpor strategies by measuring the depth and duration of torpor in multiple species. However, direct comparison of multiple physiological parameters under similar thermal conditions are lacking. Here, we quantified three physiological variables; body temperature, metabolic rate (MR) and heart rate (HR) of two small heterothermic bats (daily heterotherm Syconycteris australis, and hibernator Nyctophilus gouldi) under comparable thermal conditions and torpor bout durations. When normothermic and resting both MR and HR were similar for the two species. However, during torpor the minimum HR was more than fivefold higher, and minimum MR was 6.5-fold higher for the daily heterotherm than for the hibernator at the same subcutaneous Tb (16 ± 0.5 °C). The data show that the degree of heterothermy defined using Tb is not necessarily a precise proxy for physiological capacity during torpor in these bats and is unlikely to reveal accurate energy budgets. Our study provides evidence supporting a distinction between daily torpor in a daily heterotherm and short term torpor in a hibernator, at least within the Chiroptera with regard to these physiological variables. This exists even when individuals display the same degree of Tb reduction, which has clear implications for the modelling of their energy expenditure.

Diet of an Eastern Grass Owl Tyto longimembris in northern New South Wales

A single Eastern Grass Owl Tyto longimembris was observed in Bundjalung National Park, New South Wales, in September 2019. Pellets (n = 17) collected from its roost contained the remains of House Mouse Mus musculus, Grassland Melomys Melomys burtoni, Black Rat Rattus rattus, Swamp Rat R. lutreolus, Fawn-footed Melomys Melomys cervinipes, Common Planigale Planigale maculata, Eastern Blossom Bat Syconycteris australis and honeyeater Phylidonyris sp. The most interesting findings were the Eastern Blossom Bat (the first published record of a bat in the diet of an Eastern Grass Owl in Australia) and that one of the Grassland Melomys specimens had pink bones.

Measuring subcutaneous temperature and differential rates of rewarming from hibernation and daily torpor in two species of bats

Prolonged and remote measurement of body temperature (Tb) in undisturbed small hibernators was not possible in the past because of technological limitations. Although passive integrated transponders (PITs) have been used previously to measure subcutaneous temperature (Tsub) during daily torpor in a small marsupial, no study has attempted to use these devices at Tbs below 10°C. Therefore, we investigated whether subcutaneous interscapular PITs can be used as a viable tool for measuring Tb in a small hibernating bat (Nyctophilus gouldi; Ng) and compared it with measurements of Tb during daily torpor in a heterothermic bat (Syconycteris australis; Sa). The precision of transponders was investigated as a function of ambient temperature (Ta) and remote Tsub readings enabled us to quantify Tsub–Tb differentials during steady-state torpor and arousal. Transponders functioned well outside the manufacturer's recommended range, down to ~5°C. At rest, Tsub and rectal Tb (Trec) were strongly correlated for both bat species (Ng r2=0.88; Sa r2=0.95) and this was also true for N. gouldi in steady-state torpor (r2=0.93). During induced rewarming Tsub increased faster than Trec in both species. Our results demonstrate that transponders can be used to provide accurate remote measurement of Tb in two species of bats during different physiological states, both during steady-state conditions and throughout dynamic phases such as rewarming from torpor. We show that, at least during rewarming, regional heterothermy common to larger hibernators and other hibernating bats is also present in bats capable of daily torpor.

Activity patterns and roosting of the eastern blossom-bat (Syconycteris australis)

We quantified activity patterns, foraging times and roost selection in the eastern blossom-bat (Syconycteris australis) (body mass 17.6 g) in coastal northern New South Wales in winter using radio-telemetry. Bats roosted either in rainforest near their foraging site of flowering coast banksia (Banksia integrifolia) and commuted only 0.3 ± 0.1 km (n = 8), whereas others roosted 2.0 ± 0.2 km (n = 4) away in wet sclerophyll forest. Most bats roosted in rainforest foliage, but in the wet sclerophyll forest cabbage palm leaves (Livistonia australis) were preferred roosts, which likely reflects behavioural thermoregulation by bats. Foraging commenced 44 ± 22 min after sunset in rainforest-roosting bats, whereas bats that roosted further away and likely flew over canopies/open ground to reach their foraging site left later, especially a female roosting with her likely young (~4 h after sunset). Bats returned to their roosts 64 ± 12 min before sunrise. Our study shows that S. australis is capable of commuting considerable distances between appropriate roost and foraging sites when nectar is abundant. Bats appear to vary foraging times appropriately to minimise exposure to predators and to undertake parental care.

The bats (Mammalia:Chiroptera) of the lower Waria Valley, Morobe Province, Papua New Guinea: a survey and comparison across habitat types using mist nets

From June 2007 to February 2009 the Waria Valley Community Conservation and Sustainable Livelihoods Project completed a mist net survey of bats in the lower Waria Valley, Morobe Province, Papua New Guinea. The Waria Valley is located on the north coast of the Morobe Province ~190 km south-east of Lae, and still has large tracts of intact lowland hill and plain rainforest. Four broad habitats (agricultural, secondary forest edge, primary forest edge and primary forest) were surveyed using mist nets. A total of 596 individuals representing 11 species were caught, measured and identified over 8824 net-m h–1 across 99 nights. Within the limitations of this method, primary forest edge sites in general showed the highest degree of species richness and diversity and along with secondary forest edge sites were more even in species composition. Primary forest and agricultural sites were each dominated by a single species, Syconycteris australis and Macroglossus minimus respectively. Most captures were megachiropterans and microchiropterans were underrepresented, presumably in part because of the survey method employed.

Daily torpor in relation to photoperiod in a subtropical blossom-bat, Syconycteris australis (Megachiroptera)

Daily torpor in many temperate-zone mammals is affected by photoperiod. As little is known about the effects of photoperiod on torpor in subtropical species, we investigated whether, and if so how, torpor use, duration, and depth are affected by acclimation to three photoperiods (short, intermediate, long) in the blossom-bat Syconycteris australis. In contrast to many other studies, torpor occurrence, duration, and depth did not significantly respond to photoperiod acclimation in S. australis. Interestingly, the trend of a decline in torpor use under long photoperiod was the opposite of that observed previously in S. australis, which had been captured from the wild in summer and winter. Our study suggests that some species living in low latitude areas with unpredictable weather like S. australis may not use photoperiod for seasonal adjustments in physiology because it is not a reliable cue for food availability.

Food Hardness and Feeding Behavior in Old World Fruit Bats (Pteropodidae)

Old World fruit bats (family Pteropodidae) are common throughout the Paleotropics, where they play an important ecological role as seed dispersers and pollinators. Although many regions host diverse assemblages of fruit bats, mechanisms of resource partitioning are only beginning to be documented. This study investigates the potential role of feeding behavior in patterns of resource use within a sympatric assemblage of pteropodids from Papua New Guinea. Individuals of Syconycteris australis, Dobsonia minor, Pteropus conspicillatus, Nyctimene albiventer, and Paranyctimene raptor were videotaped during feeding experiments designed to elicit shifts in feeding (biting) behavior by varying fruit hardness. Although significant variation exists among species in biting behavior, the clear association between trophic ecology and feeding behavior seen in New World fruit bats does not exist in this assemblage of Old World species. Rather, the combinations of behavior and morphology exhibited by these bats appear to represent 2 different solutions to the ecological challenge of feeding on relatively hard fruits.

The diet of the common blossom bat (Syconycteris australis) in upland tropical rainforest and the importance of riparian areas

The diet of the common blossom bat (Syconycteris australis) was investigated in upland rainforest on the Atherton Tablelands. Faeces or fur pollen samples from 62 S. australis and feeding observations on 5 captive and 10 radio-tagged bats were collected. Syconycteris australis fed on blossoms from at least 18 plant species found in rainforests (plus unidentified species of Loranthaceae), 2 species from non-rainforest communities and from flowers of the cultivated banana (Musa sp.) grown on farms. Rainforest plants included 13 species of trees, 1 shrub and 4 climbers. Myrtaceae was the most important family contributing to the diet of S. australis, particularly the genus Syzygium. The chiropterophilus flower syndrome was only partly useful as a predictor of the diet of S. australis in these forests. Fruit was also eaten, being most common in the diet from late summer to autumn (wet season). Twelve months of mist-netting in riparian and non-riparian rainforest found higher capture rates in riparian rainforest in spring and summer, but not during autumn or winter. It is suggested that the availability of food species (both blossom and fruit) is high in riparian rainforest during spring and summer when S. australis is most frequently caught in this habitat. Efforts to rehabilitate rainforest along degraded creeks should offer a significant conservation benefit to this small pollinator.

An Observation Of Cat Predation Upon An Eastern Blossom Bat Syconycteris Australis

WITH a body weight of 15 - 19 g and a mean headbody length of just over 60 mm (Churchill 1998), the eastern blossom bat Syconycteris australis is one of the smallest members of the sub-order Megachiroptera. Within Australia S. australis is restricted in distribution to the east coast from Cape York in Queensland to near Forster on the mid-north coast of New South Wales (NSW) (Law 1994a). Habitat requirements include both rainforest and/or wet sclerophyll forest for roosting purposes and proximal areas of heathland for foraging (Law 1993). The species survives on a diet of nectar and pollen and is heavily dependent upon Banksia integrifolia inflorescences during the winter months (Law 1994b, 1996; Coburn 1995). Blossom bats are generally regarded as solitary and exhibit strong fidelity to their feeding areas (Law 1993), although movements of up to 30 km have been reported (Law 1996).

HOME RANGE OF THE SOUTHERN BLOSSOM BAT,SYCONYCTERIS AUSTRALIS,IN PAPUA NEW GUINEA

Southern blossom bats, Syconycteris australis (Pteropodidae), were followed by radiotelemetry in lowland rainforest in Kau Wildlife Area, Madang Province, Papua New Guinea. Eleven individuals were monitored ≤31 days. Based on 706 radiotelemetry positions, home ranges of 11 bats were 2.7–13.6 ha. There were no significant differences in home-range sizes between sex or age classes, but there was individual overlap of the home ranges of these bats. Long axes of home ranges were 263–725 m. During each night, bats visited most parts of their home ranges; however, activity was concentrated in core-use areas representing 19–33% of the home range and containing ≥1 food patches. During the day, S. australis roosted in the foliage of trees. Bats showed fidelity to a day-roost area (0.4–10.8% of home range) but not to a single roost tree. Day-roost areas monitored within a given year showed virtually no overlap.

Common blossom bats ( Syconycteris australis) as pollinators in fragmented Australian tropical rainforest

The effectiveness of the common blossom bat ( Syconycteris australis) as a pollinator of the rainforest tree Syzygium cormiflorum was assessed by comparing movements, pollen loads, and visitation frequency, with those of birds. The study was carried out in a fragmented rainforest landscape in north Queensland and movements were determined by radio-telemetry. Bats carried 6 times more pollen than birds, but were less frequent visitors to S. cormiflorum, suggesting that the quantity of pollen distributed by the two groups may not differ greatly. However, pollen quality (the geographic/genetic distance moved) may be a more important factor in determining pollinator effectiveness. Bats were very mobile in the fragmented landscape, with home ranges varying from 12 to 1796 ha and often encompassing more than one forest fragment. Bats usually moved along strips of vegetation, but were found to fly up to 5.8 km (mean=1 km) across cleared land. This mobility led to similar numbers of S. australis being caught in small (<50 ha) forest fragments and continuous forest. At the scale of individual trees, bats fed for an average of 1.2 min per tree, compared to 5.0 min for birds. Short foraging times per tree and frequent movements of >200 m should increase the opportunity for movement of pollen between individual trees. Collectively, these observations suggest that S. australis carry pollen of high quality. Although they fly across cleared land, fragmentation may impact bat populations by allowing increased owl predation in open country and by increasing the reliance of bats on flower resources in the agricultural matrix. On the Atherton Tablelands, the latter is provided mostly by cultivated bananas ( Musa sp.), which produce nectar but not pollen.

Field metabolic rates and water uptake in the blossom-bat Syconycteris australis (Megachiroptera).

Blossom-bats, Syconycteris australis (18 g) are known to be highly active throughout the night. Since this species frequently enters torpor, we postulated that their use of heterothermy may be related to a high energy expenditure in the field. To test this hypothesis we measured field metabolic rates (FMR) of S. australis at a subtropical site using the doubly labelled water (DLW) method. We also measured DLW turnover in captive animals held at constant ambient temperature (Ta) with ad libitum food to estimate whether Ta and food availability affect energy expenditure under natural conditions. The FMR of S. australis was 8.55 ml CO2 g-1 h-1 or 76.87 kJ day-1 which is 7.04 times the basal metabolic rate (BMR) and one of the highest values reported for endotherms to date. Mass-specific energy expenditure by bats in the laboratory was about two-thirds of that of bats in the field, but some of this difference was explained by the greater body mass in captive bats. This suggests that foraging times in the field and laboratory were similar, and daily energy expenditure was not strongly affected by Ta or ad libitum food. Water uptake in the field was significantly higher than in the laboratory, most likely because nectar contained more water than the laboratory diet. Our study shows that S. australis has a FMR that is about double that predicted for its size although its BMR is lower than predicted. This supports the view that caution must be used in making assumptions from measurements of BMR in the laboratory about energy and other biological requirements in free-ranging animals.

Daily torpor and energetics in a tropical mammal, the northern blossom-bat Macroglossus minimus (Megachiroptera).

Little is known about torpor in the tropics or torpor in megachiropteran species. We investigated thermoregulation, energetics and patterns of torpor in the northern blossom-bat Macroglossus minimus (16 g) to test whether physiological variables may explain why its range is limited to tropical regions. Normothermic bats showed a large variation in body temperature (Tb) (33 to 37 degrees C) over a wide range of ambient temperatures (Tas) and a relatively low basal metabolic rate (1.29 ml O2 g-1 h-1). Bats entered torpor frequently in the laboratory at Tas between 14 and 25 degrees C. Entry into torpor always occurred when lights were switched on in the morning, independent of Ta. MRs during torpor were reduced to about 20-40% of normothermic bats and Tbs were regulated at a minimum of 23.1 +/- 1.4 degrees C. The duration of torpor bouts increased with decreasing Ta in non-thermoregulating bats, but generally terminated after 8 h in thermoregulating torpid bats. Both the mean minimum Tb and MR of torpid M. minimus were higher than that predicted for a 16-g daily heterotherm and the Tb was also about 5 degrees C higher than that of the common blossom-bat Syconycteris australis, which has a more subtropical distribution. These observations suggest that variables associated with torpor are affected by Ta and that the restriction to tropical areas in M. minimus to some extent may be due to their ability to enter only very shallow daily torpor.

Seasonal changes in energetics and torpor patterns in the subtropical blossom-bat Syconycteris australis (Megachiroptera).

Little is known about how animals from tropical and subtropical climates adjust their energy expenditure to cope with seasonal changes of climate and food availability. To provide such information, we studied the thermal physiology, torpor patterns and energetics of the nocturnal blossom-bat (Syconycteris australis 18 g) from a subtropical habitat in both summer and winter. In both seasons, S. australis frequently entered daily torpor at ambient temperatures between 12 and 25°C when food and water were withheld. Unlike patterns observed in temperate animals, mean minimum metabolic rates during torpor were lower in summer (0.47 ± 0.07 ml O2 g-1 h-1) than in winter (0.75 ± 0.11 ml O2 g-1 h-1). Body temperatures during torpor were regulated at 19.3 ± 1.0°C in summer and at 23.4 ± 2.0°C in winter. Torpor bout duration was significantly longer in summer (7.3 ± 0.6 h) than in winter (5.5 ± 0.3 h), but in both seasons, bout duration was not affected by ambient temperature. Consequently, average daily metabolic rates were also significantly lower in summer than in winter. Body temperatures and metabolic rates in normothermic bats did not change with season. Our findings on seasonal changes of torpor in this bat from the subtropics are opposite to those made for many species from cold climates which generally show deeper and longer torpor in winter and are often entirely homeothermic in summer. More pronounced torpor in subtropical S. australis in summer may be due to low or unpredictable nectar availability, short nights which limit the time available for foraging, and long days without access to food. Thus, the reversed seasonal response of this subtropical bat in comparison to temperate species may be an appropriate response to ecological constraints.

The Lunar Cycle Influences Time of Roost Departure in The Common Blossom Bat, Syconycteris australis.

Observations of radio-tagged Common Blossom Bats Syconycteris australis on the Atherton Tablelands, Queensland indicate that the time of departure from roost areas is related to the lunar cycle. During the dark phase of the moon, bats leave their roost between 5-20 mins after dark. Departure times are delayed up to 4 hrs between the period of the first quarter and full moon when the moon is bright after dusk. The predatory role of owls at night is suggested as the probable cause of this behavioural change.

Plasticity of Energetics in Blossom Bats (Pteropodidae): Impact on Distribution

Blossom bats, Macroglossus minimus and Syconycteris australis , from New Guinean lowland rainforests usually enter torpor at low ambient temperatures (11–29°C). Torpid individuals maintain a 2–5°C differential of body temperature above ambient temperature. Individuals from highlands, however, regulate body temperature at 36–37°C at ambient temperatures as low as 13°C. A third species, Melonycteris melanops , exhibits imprecise temperature regulation, but rarely enters torpor. Basal rates of metabolism for lowland populations of the three species are low compared to the mammalian standard, whereas highland and subtropical S. australis and highland M. minimus have basal rates near expected values. Thermal conductances of blossom bats are lower than the mammalian standard, except in subtropical S. australis . The variation in basal rates of metabolism in nec-tarivorous bats correlates with body size and effectiveness of thermoregulation. M. minimus and S. australis have large geographic distributions, ability to cross narrow oceanic water gaps, and sufficient plasticity in energetics to meet demands imposed by environments including small oceanic islands, disturbed successional forests, and primary lowland and montane rain forests.

Ecomorphology of the Tongues of Australian Megachiroptera (Chiroptera: Pteropodidae)

The tongues of six species of Australian megachiropterans were studied macroscopically and microscopically to observe whether there were any morphological characteristics correlating with their foraging and feeding behaviour. Tongues varied from being extensible and brush-like (with long hair-like papillae) in Syconycteris australis, to club-like (with very few types of papillae) in Nyctimene robinsoni, to long-pointed (possessing several types of surface papillae) in the Pteropus species. The morphology of the tongue of S. australis and the Pteropus species was similar to that of nectar-feeding birds, marsupials and other mammals. N. robinsoni possessed a tongue highly structured for processing the fruit on which it feeds, whilst the tongue of the S. australis and P. scapulatus was highly structured for a diet predominantly made up of nectar. Although the surface papillae were similar among P. poliocephalus, P. alecto and P. conspicillatus, the shape of the tongue varied considerably, suggesting that there may be subtle differences between individual feeding strategies. The morphology of the tongues in this study, combined with field observations, suggest that many megachiropterans are able to consume different food types when their preferred food source is unavailable. In addition, the structure of tongue and its papillae support the role of megachiropterans in both pollination and seed dispersal.

Residency and Site Fidelity of Marked Populations of the Common Blossom Bat Syconycteris australis in Relation to the Availability of Banksia Inflorescences in New South Wales, Australia

Residency and site fidelity of marked populations of the nectar-feeding common blossom bat Syconycteris australis were monitored for three years in three areas of high food availability (density of Banksia integrifolia inflorescences) and three of low food availability on the north coast of New South Wales, Australia. Resident bats were present in all sites; however, populations in areas with low food abundance were more likely to be resident (63% recaptured) over a six-month flowering season than populations in areas with high food abundance (20% recaptured). Residents were more likely to be adult males, than females or juveniles. Intruder pressure fluctuated throughout the year with food abundance as the number of transients was correlated with the density of inflorescences. This had a marked effect on bats in autumn, when a lower percentage of residents than transients was reproductive in sites with high intruder pressure. Also, residents at sites with high intruder pressure were less likely to be reproductive and their body condition was lower than residents experiencing low intruder pressure. Thus intruder pressure was probably the most important factor reducing residency. Nectar and pollen was locally scarce after B. integrifolia finished flowering; however, many bats returned to the same site in the following year. Site fidelity between consecutive B. integrifolia flowering seasons (years), was greater in low-food sites (28%) than areas of high food (12%). The proximity of non B. integrifolia food sources may contribute to the degree of site fidelity, but this is yet to be tested. One site was monitored for five consecutive years and at least 4% of those marked in the first year were site faithful after five years. Strong site attachment would increase the vulnerability of this species to the effects of disturbance. These observations indicate that the abundance and dispersion of food has an important influence on behaviour and population dynamics of S. australis over long periods.

Thermoregulation, energy metabolism, and torpor in blossom‐bats, Syconycteris australis (Megachiroptera)

Since little information is available on torpor in bats of the suborder Megachiroptera, we investigated whether the small (18 g) blossom‐bat Syconycteris australis displays torpor in the laboratory. Bats entered daily torpor when food and water were withheld for one night and the air temperature (Ta) was below about 26°. Torpor began shortly after lights went on in the morning and lasted for a maximum of 12 hours. During torpor at Ta18°, metabolic rates fell to a minimum of about 15% of that in resting individuals at the same Ta, and to about 40% of the basal metabolic rate. The body temperature (Tb) during torpor was metabolically defended at or above about Tb 18°. Individuals that did not enter torpor in the morning reduced their Tb from about 34.5°, observed in resting individuals that had been fed during the previous night, to values between 30.2 and 32.8°, and the resting metabolic rate fell by about 25%. The ability to undergo short periods of torpor may explain why the distribution range of S. australis extends much further south than that of other small Australian megachiropteran bats.

The Effect of Energy Supplementation on the Local Abundance of the Common Blossom Bat, Syconycteris australis, in South-Eastern Australia

This study investigates the effects of providing supplementary energy to populations of blossom bats Syconycteris australis in south-eastern Australia. This bat specializes on a diet of nectar (energy) and pollen (nitrogen), allowing the effects of energy addition to be investigated in isolation from nitrogen. Bats were marked in six independent study areas, before the addition of concentrated sugar solutions to three of the six areas. The numbers of unmarked immigrant bats in supplementary-fed areas increased compared to control areas after one and two weeks of feeding. Adult immigration was greater in supplemented areas than in control areas; however, no clear effect on juvenile immigration was detected. Juveniles may have been prevented from moving into areas of abundant food by aggressive responses of adults. The number of resident bats decreased in supplemented sites relative to control sites, again possibly due to greater intruder pressure. The suggestion of territorial behaviour in this species requires further investigation to determine the extent of any spacing behaviour. These results provide the first experimental evidence that a species of bat is limited by the availability of energy, and contrast with previous observational studies of megachiroptera that have implicated nitrogen as a limiting factor