Resource partitioning among five sympatric species of freshwater turtles from the wet–dry tropics of northern Australia

2017 ◽  
Vol 44 (3) ◽  
pp. 219 ◽  
Author(s):  
Michael A. Welsh ◽  
J. Sean Doody ◽  
Arthur Georges
Keyword(s):  
Resource Partitioning ◽  
Niche Overlap ◽  
Sympatric Species ◽  
Dry Season ◽  
Gut Contents ◽  
Microhabitat Use ◽  
Freshwater Turtles ◽  
Northern Australia ◽  
Dietary Shift ◽  
Dry Tropics

Context Resource partitioning of diet and microhabitat was examined for five sympatric species of freshwater turtles in the Daly River in the northern end of Northern Territory (Top End) in Australia. The Daly River supports a high diversity of freshwater turtles, making it the ideal place to study a freshwater turtle community. Aims To determine the dry-season diet and microhabitat use of Carettochelys insculpta, Elseya dentata, Chelodina oblonga, Emydura victoriae and Emydura subglobosa worrelli and examine intraspecific and interspecific niche overlap and ontogenetic dietary shift. Methods Gut contents were collected by stomach flushing, and microhabitat use was determined by recording where each turtle was first seen before capture. Diet and microhabitat use were compared using an index of relative importance. Niche overlap was measured with Horn’s overlap index. Key results Carettochelys insculpta is an opportunistic omnivore that feeds mostly on ribbonweed (Vallisneria spiralis) and aquatic snails. Elseya dentata is herbivorous, feeding primarily on aquatic algae. The diets of C. insculpta and E. dentata overlapped moderately, but the overall niche overlap was low because they occupied different microhabitats within the river. Chelodina oblonga fed very little, and may use the Daly River as a dry-season refuge. Emydura victoriae is molluscivorous, consuming more molluscs as it grows. This ontogenetic dietary shift was associated with megacephaly (extreme broadly expanded head that is too large to fit into the carapace) and expanded triturating surfaces. This specialisation allows adult E. victoriae to feed exclusively on molluscs and so their diet overlapped little with other species. Emydura subglobosa worrelli was omnivorous, consuming mostly freshwater sponge and apparently preferring more lentic water. Conclusions The freshwater turtles of the wet–dry tropics are usually reported as being heavily reliant on the seeds, fruits and leaves of riparian vegetation; however, the present study showed that the dry-season diet in perennial rivers is primarily of aquatic origin. Implications The study suggested that populations of C. insculpta, E. dentata and E. victoriae could be threatened by broad-scale development in northern Australia if there were substantive impacts on aquatic macrophytes and molluscs in the Daly River system.

The influence of weather on the quality of tropical legume pasture during the dry season in northern Australia. III. Effects of digestibility and chemical composition

1989 ◽  
Vol 40 (3) ◽  
pp. 573 ◽  
Author(s):  
RL McCown ◽  
BH Wall
Keyword(s):  
Dry Matter ◽  
Mediterranean Climate ◽  
Dry Season ◽  
In Vitro Digestibility ◽  
Northern Australia ◽  
Pasture Legumes ◽  
Dry Matter Digestibility ◽  
Dry Tropics

In the semi-arid tropics, accumulated shed leaf of certain pasture legumes can provide highly nutritious feed for cattle in the dry season. Previous papers in this series have dealt with the fungal spoilage of leaf of Caribbean stylo in response to dew and unseasonal rainfall and the threat to acceptability by cattle. This paper focuses on the effects of varying degrees of moulding and leaching on dry matter digestibility of leaf of this legume. Uniform leaf material of high digestibility was exposed at six locations during the dry season and samples retrieved at 4-weekly intervals. From initial values of 75%. in vitro digestibility dropped to as low as 50%. Degree of moulding, as indicated by a quantitative index of discoloration, accounted for about 80�/o of loss. Moulding was much more important than leaching. This latter finding in the winter-dry tropics contrasts with previous findings in the summer-dry Mediterranean climate.

The influence of weather on the quality of tropical legume pasture during the dry season in Northern Australia. II. Moulding of standing hay in relation to rain and dew

1981 ◽  
Vol 32 (4) ◽  
pp. 589 ◽  
Author(s):  
RL McCown ◽  
BH Wall
Keyword(s):  
Relative Humidity ◽  
Leaf Litter ◽  
Bulk Sample ◽  
Dry Season ◽  
Northern Australia ◽  
Mould Growth ◽  
Tropical Legume ◽  
Dry Tropics

Naturally desiccated legume pasture is valuable forage in the dry season but is very vulnerable to moulding, which drastically reduces its acceptability to cattle. At a network of sites in the wet-dry tropics of Australia, trends in mouldiness of standard leaf 'litter' samples were monitored in relation to rain, dew, and rates of drying. Although heavy dews occurred frequently at some sites, only the immediate top layer of fallen leaf moulded. This had a very small effect on the mouldiness of the bulk sample. Appreciable moulding occurred only after at least 2 mm rain, but in some cases there was no mould growth after over 10 mm rain; the amount of rain accounted for only 23 % of the variation in mouldiness. The duration of wetness of the leaf litter, as indicated by the duration of 95 % relative humidity 10 cm above the ground after rain, accounted for 91 % of the variation in mouldiness. At the more humid sites, material which was exposed for several weeks before rain moulded more rapidly after rain than did recently exposed material, even though at the time of rain there were no visible differences. Differences in causation of moulding of conventional hay and of 'standing hay' are discussed.

Niche overlap and sett-site resource partitioning for two sympatric species of badger

2009 ◽  
Vol 21 (2) ◽  
pp. 89-100 ◽  
Author(s):  
L. Zhang ◽  
Y.-B. Zhou ◽  
C. Newman ◽  
Y. Kaneko ◽  
D.W. Macdonald ◽  
...  
Keyword(s):  
Resource Partitioning ◽  
Niche Overlap ◽  
Sympatric Species

Growth patterns of two widely distributed freshwater turtles and a comparison of common methods used to estimate age

2002 ◽  
Vol 50 (5) ◽  
pp. 477 ◽  
Author(s):  
Ricky-John Spencer
Keyword(s):  
Growth Models ◽  
Sympatric Species ◽  
Growth Patterns ◽  
Juvenile Stage ◽  
Age And Growth ◽  
Logistic Growth ◽  
Freshwater Turtles ◽  
Dietary Shift ◽  
Demographic Models ◽  
Murray River

Turtles are long lived and demographic models requiring estimates of age, growth, fecundity and survival are central for management. Most studies that estimate age and growth of freshwater turtles use annuli as an index of age without estimating its error and very few studies that use growth models include many juveniles, where growth is often large and variable. In this paper, I compare the reliability of growth annuli and common models in determining age and growth of two widely distributed turtles in Australia. Most turtles are carnivorous during the juvenile stage but many species shift to a lower-quality omnivorous diet prior to maturing. Patterns of growth are often characterised by this dietary shift and I compared the growth of a common omnivorous turtle (Emydura macquarii) and a vulnerable sympatric species that is an obligate carnivore (Chelodina expansa). Mark–recapture programs were established in three lagoons on the Murray River. In total, 1218 hatchling E. macquarii were released into two of the lagoons and growth annuli were found to be unreliable in estimating their age by Year 2. The von Bertalanffy and logistic growth models can reliably estimate age of both male and female E. macquarii and C. expansa respectively. Growth is extremely rapid during the juvenile stage of E. macquarii, but is highly variable in C. expansa, with rapid growth occurring only beyond three years of age. Hence growth models fail to predict age when juveniles are excluded from the analyses. Female E. macquarii delay maturity until 9–12 years of age because clutch size is positively related to body size and they can produce only one large clutch per year. Female C.�expansa mature later (at ~14 years) than female E. macquarii and both species are sexually dimorphic, as males mature earlier at smaller sizes than females. Common growth models describe the growth of two widely distributed freshwater turtles, but different patterns of growth and age at maturity relate to quality of diet and reproduction.

Food habits of Brazilian boid snakes: overview and new data, with special reference to Corallus hortulanus

2009 ◽  
Vol 30 (4) ◽  
pp. 533-544 ◽  
Author(s):  
Lígia Pizzatto ◽  
Otavio Marques ◽  
Kátia Facure
Keyword(s):  
Literature Review ◽  
Food Habits ◽  
Prey Size ◽  
Niche Overlap ◽  
Sympatric Species ◽  
Geographic Range ◽  
Gut Contents ◽  
Museum Specimens ◽  
Important Prey ◽  
Prey Items

AbstractThis study examines the diet of eight boid snakes: Boa c. constrictor, Boa c. amarali, Corallus caninus, C. hortulanus, Epicrates cenchria, E. crassus, E. assisi and Eunectes murinus mainly by analyzing the gut contents of preserved museum specimens, and includes a literature review to present an overview of the diet of Brazilian boids. Mammals constitute the primary prey consumed by the majority of the species. Birds are also frequently consumed by C. hortulanus and Boa contrictor, and are the most important prey for B. c. amarali. Ectotherms (mostly lizards) were only consumed by immature snakes. Such prey is rarely consumed by B. c. amarali and not recorded for Epicrates and Eunectes species in our dissections. C. caninus is likely a mammal specialist and Epicrates prey on birds more opportunistically. The niche overlap index varied from 0.27-0.52 for species occurring in the same bioma and geographic range but it is possible this overlap is lower as most sympatric species explore different macrohabitat. C. hortulanus exhibited a significant relationship between prey size and predator head size; this relationship did not differ among mature and immature snakes. In comparison to immature individuals heavier adult snakes fed on heavier prey items however, the ratio between prey/predator mass decreased with increase in predator mass (or size). Most boids exploit diurnal and nocturnal preys, probably using both sit-and-wait and active tactics. They feed on the ground but boas and C. hortulanus and possibly E. cenchria also exploit arboreal prey.

Reproductive seasonality in the tropical butterfly Hypolimnas bolina (Lepidoptera: Nymphalidae) in northern Australia

2001 ◽  
Vol 17 (4) ◽  
pp. 483-494 ◽  
Author(s):  
DARRELL J. KEMP
Keyword(s):  
Reproductive Activity ◽  
Dry Season ◽  
Northern Australia ◽  
Breeding Phenology ◽  
Reproductive Seasonality ◽  
Leaf Quality ◽  
Tropical Environments ◽  
Dry Tropics ◽  
Nymphalid Butterfly ◽  
The Tropics

Because seasonality in tropical environments is driven by variation in rainfall, phytophagous tropical organisms are expected to exhibit mechanisms of escape in space and time that allow them to synchronize their breeding efforts with suitably wet periods of the year. This hypothesis was addressed by studying the breeding phenology of the nymphalid butterfly Hypolimnas bolina (L.) in the Australian wet-dry tropics. This species favours small, herbaceous larval foodplants that either die off annually or exhibit marked declines in leaf quality during the dry season. As expected, reproductive activity in H. bolina was broadly correlated with both rainfall and humidity, with individuals spending part of the dry season (early April to late August) sheltering in overwintering sites in a state of reproductive diapause. The timing of the overwintering period was similar between the 2 years, which suggests that individuals respond to seasonally predictable cues such as photoperiod. At least in 1998, the exit of butterflies from overwintering sites was relatively sudden and coincided with the first spring rainfall event. These findings suggest that H. bolina copes with seasonal adversity in the tropics by means of a regularly timed diapause.

An analysis of cattle live-weight changes on tropical grass pasture during the dry and early wet seasons in northern Australia: 2. Relations to trends in the pasture, diet and grazing behaviour

1983 ◽  
Vol 101 (1) ◽  
pp. 25-31 ◽  
Author(s):  
R. L. McCown ◽  
R. W. McLean
Keyword(s):  
Nitrogen Concentration ◽  
Live Weight ◽  
Dry Season ◽  
Green Leaf ◽  
Gut Contents ◽  
Northern Australia ◽  
Weight Changes ◽  
High Quality ◽  
Short Period ◽  
Grazing Behaviour

SUMMARYCattle grazing buffel grass pastures during the dry season at Katherine lose large amounts of live weight during a short period following first rain. In Part 1 we showed that these losses were due mainly to reduction in gut contents. Part 2 examines the changes in pasture, diet and grazing behaviour to assess the probable change in nutritional status of cattle following rain.During the dry season the most valuable pasture component, green leaf, was very scarce and had a nitrogen concentration of about 1%. Diets of oesophageally-fistulated cattle contained less than 0·5% N. Shortly after first rain diet N doubled owing both to rapidly increasing amounts of green leaf and to the increase in N concentration in young leaf to over 3%. Although intake was not measured, literature is cited to show that this increase in dietary N would be expected to increase rumen digestion rates with a resultant marked increase in D.M. intake and a reduction in gut contents.Although availability of high quality herbage increased very rapidly following first rain, a period of increased nutritional stress immediately following rain could not be ruled out. However, any such decline in nutrition appears to be short-lived.

An analysis of cattle live-weight changes on tropical grass pasture during the dry and early wet seasons in northern australia: 1. The nature of weight changes

1983 ◽  
Vol 101 (1) ◽  
pp. 17-24 ◽  
Author(s):  
R. W. McLean ◽  
R. L. McCown ◽  
D. A. Little ◽  
W. H. Winter ◽  
R. A. Dance
Keyword(s):  
Live Weight ◽  
Dry Season ◽  
Gut Contents ◽  
Northern Australia ◽  
Weight Changes ◽  
Wet Season ◽  
Tissue Water ◽  
Weight Losses ◽  
Gut Fill ◽  
Total Body

SUMMARYStudies were conducted to elucidate the nature and cause of the drastic losses of live weight of cattle grazing buffel grass pastures after first rains at the end of the dry season in northern Australia. This paper examines trends in weight and body composition during the dry and early wet seasons; it shows that although most of the loss in fasted live weight occurred just after first rain, most of the loss of body solids, mainly fat, had already occurred by this time. Losses of body solids in the dry season were not fully reflected in live-weight losses because of increases in total body water and in gut ‘fill’. The greatly accelerated weight loss in the period following first rain appears to have been due mainly to a large reduction in gut contents. Empty-body weight actually increased during this period owing to increases in tissue water. Continuation of this trend in tissue water into the early wet season resulted in the rate of live-weight gain greatly exceeding that of body solids.

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