Search

We explore the effects of biotic and abiotic factors on the population demography of frillneck lizards ( C hlamydosaurus kingii) in the Australian wet-dry tropics. Annual growth rates of males were significantly higher across all body sizes compared to females, resulting in a significant larger maximum body size in males. Both male and female lizards were highly philopatric and 81% of the among-year recapture distances were less than 200 m. Juvenile and adult frillnecks were subjected to low but highly variable annual survival rates. Both proportion of juveniles and relative proportion of reproductive females showed extensive among-year variations. No relationship was, however, observed between proportion of gravid females and that of juveniles captured during the subsequent year. High rainfall in January was negatively correlated with recruitment most likely caused by increased egg/embryo mortality due to flooding of nest sites. We therefore suggest that the lack of association between female reproduction and juvenile recruitment was due to the effects of stochastic variation in January rainfall. Lizard numbers increased during the first five years of the study followed by a decline during the subsequent four years. Our analyses show that annual variation in survival constituted the main determinant in driving the annual change in frillneck numbers. Surprisingly, no relationship was observed between fillneck population dynamics and annual variation in juvenile recruitment. We suggest that the 7-years over which these analyses were conducted were insufficient to detect any significant effects of recruitment on lizard numbers, demonstrating the need for long-term studies to accurately document vertebrate population demographic processes in areas experiencing stochastic variations rainfall such as the Australian wet-dry tropics. [ABSTRACT FROM AUTHOR]

There is growing interest in associations between non-native species and native foundation species. Along the southeast coast of Australia, the European shore crab, Carcinus maenas , overlaps with the distribution of the grey mangrove, that provides refuge to many native invertebrates from predators and physiological stress. We tested the hypothesis that C. maenas would be more abundant under the canopy of mangrove forests than in adjacent unvegetated intertidal habitat. Trapping surveys within three estuaries found greater abundances of C. maenas in mangrove forests than in adjacent unvegetated habitat and, within mangrove forests, under the canopy than in the pneumatophores zone. Average temperatures under the mangrove canopy were up to 2 °C lower than in unshaded habitats and maximum temperatures up to 5.7 °C less. The results of tethering studies did not support the hypothesis that predatory mortality of C. maenas was reduced in mangroves. To the contrary, survivorship of tethered crabs was much lower under the mangrove canopy than in adjacent unvegetated habitat. Habitat choice experiments, however, indicated that crabs chose shaded and protected over unshaded and exposed habitat. Hence, along this coastline where summertime maximum air temperatures may approach the known LD 50 of C. maenas (40 min at 40 °C), mangroves may help to facilitate persistence in intertidal habitats. Our study adds to a growing number indicating that foundation species may not only facilitate native species, but non-native species too. Additional studies are now needed to confirm the mechanism of the association between C. maenas and mangroves in eastern Australia. [ABSTRACT FROM AUTHOR]

The article discusses a study about the predation of freshwater sawfish by bull sharks, estuarine crocodile and Australian freshwater crocodile at Fitzroy River in Australia. The healed bite marks observed in several sawfishes were cited to be proof of regular attacks of crocodiles which were unsuccessful due to the size and defense capabilities of preys. Freshwater sawfish pups were also found to migrate from estuaries into freshwater nursery pools to avoid larger predators.

The Australian desert ant Melophorus bagoti ( Formicidae) is a thermophilic, solitary foraging ant that inhabits the semi-arid regions of Australia. In recent years, it has become a model species for the study of navigation. However, its ecological traits are not well understood, especially on the level of the entire colony. Here, we investigated this species daily activity schedule and diet composition, and examined its foraging behaviour. Foraging activity is confined to a window of roughly 50-70°C soil surface temperature, and foragers reacted quickly to temperature changes. Consequently, the pattern of daily outbound traffic during summer is unimodal on warm days and bimodal on very hot days. Foragers are opportunistic scavengers; dead insects make up a large proportion of food items, but grass seeds are also occasionally brought back to the nest in large amounts. Diet composition changes with the seasonal availability of certain food groups. Melophorus bagoti foragers have the ability to recruit nestmates to profitable food sources. Recruitment seems to function without the use of pheromone trails, but the exact mechanism requires further investigation. [ABSTRACT FROM AUTHOR]

Abstract: To promote close encounters with wildlife, humans sometimes provision wild animals with food. However such practices can be harmful, and the impacts of human provisioning on wild animals can be difficult to determine, especially indirect effects such as those on the offspring of provisioned animals. In Shark Bay, Australia, a small subset of the resident population of bottlenose dolphins is regularly provisioned with fish handouts under the supervision of the West Australian Department of Environment and Conservation (DEC). Previous studies have shown that calves born to provisioned females experienced reduced care and higher mortality relative to calves of non-provisioned mothers. These results led to changes in the management practices in 1994, which we assessed the efficacy of by comparing (1) calf mortality before and after the intervention and (2) behavior of provisioned with non-provisioned dolphins in the population. Although calves born to provisioned females exhibited higher survivorship (86.7%) than before the intervention (23.1%, χ 2 =9.05, df =1, p =0.003, N =28), group differences in maternal and calf activity budgets were still observed over the course of calf development. Provisioned mothers provided less care to their calves and their calves appeared to compensate by foraging more and separating more from their mothers compared to their non-provisioned counterparts (N =114 calves). Our study shows that careful regulation and reduced wildlife provisioning can increase calf survivorship, but behavioral development continues to be affected. [Copyright &y& Elsevier]

The abundance and distribution of Rainbow (Trichoglossus haematodus) and Musk (Glossopsitta concinna) Lorikeets in Melbourne have increased markedly in recent years. We studied the feeding ecology of the two species, and their interspecific aggressive interactions, in some parks in Melbourne in spring and summer to determine how availability of food might affect the success of this urban proliferation. The diets of both species were dominated by nectar or pollen (the two were not distinguished in this study) from 5?6 species of eucalypts. Feeding on native plants not indigenous to the Melbourne region accounted for 61% and 74% of feeding records of Rainbow and Musk Lorikeets respectively. Both lorikeets foraged mainly in the tree canopy (99% of records), mostly perching upright or hanging to reach their food. Nectar and pollen were readily available through spring and summer because five important eucalypt food-plant species flowered constantly and several other food-plant species flowered for a substantial proportion of the time. There was little use of lorikeet food resources by other species of bird, and lorikeets were only involved in 3.5 interspecific aggressive encounters at feeding sites per observation week. The feeding ecology of the lorikeets in spring?summer was broadly similar to that reported for Melbourne in winter and for non-urban habitats in northern and eastern Australia. Abundant nectar and pollen from ornamental eucalypts planted in the twentieth century and the apparently low level of competitive interactions with other bird species for these resources have probably been important in facilitating the recent increase in abundance and distribution of both lorikeets in Melbourne. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that providing high-quality food and water would increase reproduction, survival and population size in house mice living in a semi-arid cropping environment in the mallee region of western Victoria, Australia, where outbreaks of house mice ( Mus domesticus) occur irregularly. We employed a factorial design and applied treatments along internal fencelines (16 sites), adjacent to cropping areas, from November 2003 to July 2004. Population abundance was low during the experiment (0–26 mice per site), and the summer rainfall was below average. We confirmed that mice used the supplementary food and water through a reduction in weight of food containers over time and for water through the presence of Rhodamine B in blood samples and positive bands in whiskers. Abundant food was also available through grain spilt on the ground after harvest of the wheat and barley crops. There was some evidence of increased breeding on sites where water was added, but no effect of food or food and water in combination. Sites where free water was available had marginally higher populations over summer (∼2 more mice on average; P = 0.07). This difference was well below any biologically meaningful effect. Mice were 0.9 g heavier on sites where water was added ( P = 0.04), and were in better condition ( P = 0.03). The addition of high-quality food did not affect mouse population dynamics, and the addition of water resulted in only marginal responses for some demographic characteristics. We conclude that other factors appear to be important for limiting mouse population growth in summer and autumn. [ABSTRACT FROM AUTHOR]

1. For air-breathing animals in aquatic environments, foraging behaviours are often constrained by physiological capability. The development of oxygen stores and the rate at which these stores are used determine juvenile diving and foraging potential. 2. We examined the ontogeny of dive physiology in the threatened Australian sea lion Neophoca cinerea. Australian sea lions exploit benthic habitats; adult females demonstrate high field metabolic rates (FMR), maximize time spent near the benthos, and regularly exceed their calculated aerobic dive limit (cADL). Given larger animals have disproportionately greater diving capabilities; we wanted to determine the extent physiological development constrained diving and foraging in young sea lions. 3. Ten different mother/pup pairs were measured at three developmental stages (6, 15 and 23 months) at Seal Bay Conservation Park, Kangaroo Island, South Australia. Hematocrit (Hct), haemoglobin (Hb) and plasma volume were analyzed to calculate blood O2 stores and myoglobin was measured to determine muscle O2. Additionally, FMR's for nine of the juveniles were derived from doubly-labelled water measurements. 4. Australian sea lions have the slowest documented O2 store development among diving mammals. Although weaning typically occurs by 17·6 months, 23-month juveniles had only developed 68% of adult blood O2. Muscle O2 was the slowest to develop and was 60% of adult values at 23 months. 5. We divided available O2 stores (37·11 ± 1·49 mL O2 kg−1) by at-sea FMR (15·78 ± 1·29 mL O2 min−1 kg−1) to determine a cADL of 2·33 ± 0·24 min for juvenile Australian sea lions. Like adults, young sea lions regularly exceeded cADL's with 67·8 ± 2·8% of dives over theoretical limits and a mean dive duration to cADL ratio of 1·23 ± 0·10. 6. Both dive depth and duration appear impacted by the slow development of oxygen stores. For species that operate close to, or indeed above their estimated physiological maximum, the capacity to increase dive depth, duration or foraging effort would be limited. Due to reduced access to benthic habitat and restricted behavioural options, young benthic foragers, such as Australian sea lions, would be particularly vulnerable to resource limitation. [ABSTRACT FROM AUTHOR]

Growth characteristics of native and invasive Caulerpa taxifolia from coastal eastern Australia were compared in warm (22–25°C) and cool (15–18°C) water in two laboratory experiments. Measurements of biomass, stolon length, mean frond length and numbers of fronds and stolon meristems, demonstrated that the growth of native and invasive C. taxifolia in warm water was up to ten times greater than in cool water. Growth rates differed substantially among locations over 9 weeks, but for most variables, the growth of native C. taxifolia was greater than the growth of invasive C. taxifolia in warm water. In cool water, there was little difference in growth of invasive versus native C. taxifolia. The morphology of C. taxifolia changed considerably in response to temperature, such that native and invasive samples that were morphologically distinct at the start of the experiment became indistinguishable after 69 days in warm water. We concluded there was little evidence that the C. taxifolia which recently invaded temperate estuaries in New South Wales could spread faster in cool water than could native C. taxifolia from Queensland. Native tropical C. taxifolia appears tolerant of a wide range of environmental conditions and seems capable of surviving and becoming invasive in temperate estuaries. [ABSTRACT FROM AUTHOR]

Examines the nestling growth and survival in asynchronously hatching crimson rosellas in Australia. Observations on the growth rate of chicks; Suggestions on the cost of hatching asynchrony; Relation of asynchronous hatching to reduce growth and survival of later hatched chicks.

Studies gum tree thrips Isoneurothrips australis Bagnal by researchers from Australia. Role of its ability to survive periods of fasting on the continuity of the species; Measurement of the thrips' survival at various temperatures and humidities; Correlation between survival and saturation deficit.

The article presents two cases of commensal foraging associations of Common Blackbirds Turdus merula, with Masked Lapwings Vanellus miles and with a Brown Thornbill Acanthiza pussila in Australia. It notes that the juvenile Lapwings were regarded in Blackbird-assisted foraging, and that the adult birds continued being impassive. It mentions that the manner of foraging came out to be similar to the feeding association registered between the Pilotbird Pycnoptilus floccosus and Superb Lyrebird Menura novaehollandiae. It concludes that the species' foraging behaviour was not shared by the adults to the young birds, but was discovered through other means.