摘要:

AbstractFunctional response curves were constructed for adultRanatra disparfeeding on four different densities of notonectid prey at 15, 20, 25 and 30°C. Values for the attack‐rate and handling time were estimated from Roger's random predator equation. The most generally applicable response was the type II, with the mean number of prey eaten increasing with increase in temperature. The attack‐rate was linearly related to temperature while handling time decreased exponentially with increase in temperature, although values changed very little between 20 and 30°C. It is suggested that changes in metabolic activity and related ‘hunger’ effects on various components of predatory behaviour account for the observed number of prey eaten up to 25°C, however, an increase in the level of prey activity at 30°C may influence the observed number of prey caught (and eaten) at this higher

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01448.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThis study investigates the effects of supplementary feeding on populations of Antechinus stuartii, an insectivorous, semi‐arboreal species of dasyurid marsupial. Animals were live‐trapped, marked and released in three study areas in forest near Canberra, from September 1980 to November 1981. Supplementary food was supplied above ground in trees in one study area from January to November 1981, and in the second study area from January to May 1981, while the third study area was left unmanipulated as a control. The supplemented populations increased in numbers, mean body weights and survival, and showed decreased movements between traps and smaller overlaps in home ranges. Discontinuation of food in the second study area in May 1981 produced reciprocal shifts in these parameters. Reproduction, home‐range area, mean head‐body length, use of the terrestrial and arboreal parts of the habitat were largely unaffected by provision of supplementary food. In contrast to rodents, where fed populations usually increase rapidly due to immigration or increased reproduction, the supplemented populations of A. stuartii responded relatively slowly via increased survival of young. Population responses were probably retarded at the beginning of the experiments in summer due to the abundance of natural invertebrate prey, but became more obvious in winter when natural food was scarce. The added food probably contributed directly to increased numbers, survival and body weights, but may also have enhanced these parameters indirectly by allowing foraging animals to space out and avoid intraspecific intolerant contacts. These responses in A. stuartii suggest strongly that populations are limited by the food

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01449.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractLeaf‐fall, leaf‐flush (newly expanded leaves), flowering and fruiting were recorded monthly between April 1982 and May 1985 in 703 individuals of 99 species of trees, shrubs and herbs in a logged lowland, complex rainforest. Weekly water availability and demand were modelled using pan evaporation, rainfall, and a range of estimated maximum soil water storage. The water balance model indicated that rainfall distribution was an inadequate measure of the seasonal availability of water for growth and reproduction. Intermittent shortages in available water were predicted between October and February, well into what is the wettest season of the year in terms of long‐term rainfall averages. Adequate water was available in soil water stores through most of the August–October ‘dry season’.Leaf‐fall, flowering, and fruiting all followed distinct seasonal patterns although appreciable levels of activity occurred in all months. Community leaf‐fall increased rapidly following an annual low in the very wet, February–May period, to a peak in August. The rapid increase in leaf‐fall activity was accompanied by pronounced depressions in flowering and leaf‐flushing and coincided with the period of minimum temperatures and insolation. There was no evidence to suggest that this leaf‐fall peak was accompanied or induced by drought. This ‘winter’ was followed by rising temperatures and insolation at a time when adequate soil water was usually available, and flowering activity (number of species, number of individuals, and total abundance) increased rapidly in August and peaked from September to October. The flowering peak was accompanied by a major leaf‐flush. Leaf‐flushing continued intermittently from October to February, a period characterized by maximum temperature, maximum insolation, and periods of predicted water stress when soil water stores were depleted during short, rainless periods. A second peak in leaf‐flushing coincided with the wet in March‐April. This was accompanied by a relatively small increase in leaf‐fall activity. Fruiting showed a bimodal peak from October to April each year. Prediction of functional relationships between climate and species and individual behaviour from community phenological patter

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01450.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractRemoval of almost all honeyeater nectar sources from a 5.6 ha area during February to July had no apparent effect on honeyeater nesting or total abundance. Behaviour in the experimental area was also generally unaffected except for the extent of nectar‐feeding which was significantly reduced for the most commonly observed species. The honeyeaters must have compensated for the nectar removal by flying to nearby productive areas to feed on nectar.Nectar‐removal had no significant effect on the species composition of resident honeyeaters but did affect the species composition of all observed honeyeaters. Nectar removal resulted in a decrease in the abundance of the large and dominant Little Wattlebirds(Anthochaera chrysoptera)and an increase in the abundance of the other, smaller spec

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01451.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractLittle is known of the extent to which differences in methodology contribute to differences in reported levels of tree defoliation. In this study several common methods of assessing defoliation were compared onEucalyptus blakelyiMaiden trees growing in a stand known to sustain a range of defoliation levels. Assessments were made of whole trees and of individual leaves collected at discrete intervals as well as of tagged samples of leaves that were monitored over a year. Despite fortnightly monitoring intervals, I was not able to identify with certainty any specific cause of loss of whole leaves other than senescence. Annual defoliation assessed on discrete samples of leaves was higher than annual defoliation assessed on monitored samples, presumably because the age of leaves in the discrete samples was sometimes underestimated. Leaf‐level defoliation assessed from visual estimates was consistently higher than digitizer measurements of leaf areas, but calibration of estimates resulted in similar values. Values derived for tree‐level defoliation from leaf‐level measurements differed widely. depending on the method of calculation. For the samples collected from trees in this study, mean percentage defoliation per leaf was not an adequate descriptor of defoliation for the samples, since the frequency distributions of defoliation per leaf were markedly non‐normal. This problem was avoided by using the samples, rather than the individual leaves, as the basic unit of expression of defoliation, with the total percentage defoliation per sample calculated from the ratio of total area of damage to total potential area, summed for all the leaves in the sample. For expanding leaves, the percentage of area damaged was not equivalent to the percentage of area missing from the expanded leaves, because of differences in the relative rates of growth of holes and

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01452.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractChanges in small mammal succession along a forested coastal dune system in the Myall Lakes‐National Park, New South Wales, during 15 years of regeneration after sand mining, were determined by surveys in 1982 and 1987. The results clearly demonstrate a wave of succession moving along the mining path, and confirm that over the intervening 5 year period to 1987, small mammal succession has followed a path indicated by that of the 1982 chronosequence. The house mouse, Mus musculus quickly recolonizes disturbed areas, and peak abundance occurred on plots with a regeneration age of 3.7 years in 1982 and 3.4 years in 1987 (i.e. the 3.0–4.5 age class). Colonization by the New Holland mouse. Pseudomys novaehollandiae was first recorded on plots with 4.6 years regeneration in 1982 and 5.4 years in 1987. Peak Pseudomys numbers occurred on plots in the 7.5–9.0 age class in both 1982 and 1987. The common dunnart, Sminthopsis murina appears to be the third species to enter the succession. This modified primary succession closely resembles the mammalian secondary succession following fire where additional evidence suggests that the use of chronosequence analysis may also be approp

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01453.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA peat deposit within the valley of Louisa Creek in the central highlands of Queensland formed because the valley is incised below the water table in the Precipice Sandstone, an important Jurassic aquifer in the Great Artesian Basin. Peat growth appears to have been rapid, reaching a maximum depth of some 4 m in 1000 years. The pollen record preserved in the peat indicates that the vegetation communities have not altered over this period except for recent modifications perhaps attributable to increased salinity and the influence of cattle grazing. Both the Louisa Creek peat and the floodplain sediments on the Nogoa River downstream testify to a dynamic geomorphic environment. The geomorphic setting and the location of this site on the dry‐subhumid/semi‐arid boundary in Queensland, suggest that minor climatic shifts have had a substantial environmental impact leading to alternating conditions of scour and fill of valley sedime

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01454.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractSeasonal foraging activity and microhabitat selection by echidnas on the New England Tablelands was determined by monitoring the number and relative predominance of different types of digging activity on a 2 km × 50 m transect over a 12 month period. Digging was classified into four basic types: those into the soil surface (SOILDIGS); those at the base of logs, stumps or trees (LOGDIGS); those at the base of termite mounds; and those in the litter. SOILDIGS were most prevalent, accounting for 490 (74%) of the total 666 digging records. The number of SOILDIGS correlated with season and temperature, reaching a maximum of 11 ha−1per month in late spring and a minimum of zero in winter. SOILDIGS were attributed to searches for ants and scarab beetle larvae. Approximately half of the SOILDIGS exposed ant nests or galleries, while the remainder were presumed to result from searches for the larvae of pasture dwelling scarab beetles, particularly Sericesthis spp. Scarab beetle larvae were absent from echidna scats collected during winter but occurred in 20% of scats collected during summer, LOGDIGS accounted for 157 digging records (24%) and were attributed to searches for ants and termites, LOGDIGS did not vary with season or climate, but the proportion of LOGDIGS that exposed ant or termite nests or galleries changed from 48% in winter to 5% in summer. The distribution and density of SOILDIGS and LOGDIGS along the transect correlated significantly with the availability of echidna shelter (or refuge) sites, in all seasons Some residual variation in digging activity was explained by the number and biomass of ants active on the soil surface, but not with any other direct or indirect measures of food availability. Seasonal changes in foraging activity by echidnas, and their apparent dependence on shelters, are interpreted in an energetic context as strategies for reducing predation and overcoming a period of increased energy demand and decreased food availability experienced during wint

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01455.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe environmental conditions that allow the growth of Barley Mitchell grass,Astrebla pectinata, and the development of the Australian plague locust,Chortoicetes terminifera, are similar. A single fall of more than 20 mm rain and a mean monthly maximum temperature above 23°C ensures sustained growth of Barley Mitchell grass and hatching of eggs of the Australian plague locust. Curly Mitchell grass,Astrebla lappacea, is found in heavier clay soils and requires about 40 mm to respond. Both Mitchell grasses normally remain green for about 2 months after rain which is slightly longer than the duration of locust development to the adult stage. As a result, locusts in Mitchell grass areas can complete their development to migration and laying on a single substantial fall of rain: an adaptation of critical importance in the arid zone where follow‐up rain is unlikely.Under similar circumstances, ephemerals like Button grass,Dactyloctenium radulans, are dry in approximately 6 weeks. The locusts are usually at the late nymphal stage by this time and even though Mitchell grass is still quite green, nymphal growth is retarded, resulting in adults which are smaller than normal. These adults are able to accumulate the fat needed for migration by feeding on the dry green Mitchell grasses. In the absence of dry green or green Mitchell grass, the locusts persist locally and die without laying unless there is further ra

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01456.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe bills and tongues of nectar‐feeding birds differ from continent to continent. The major differences are that: (i) the tongues of A Australian honeyeaters are broader any more fimbricated at the tip than the bifurcated tongues of sunbirds and hummingbirds; (ii) the bills of hummingbirds are more uniformly narrow and taper less markedly towards their tips than those of sun‐birds and honeyeaters; and (iii) bill curvatures are generally greater for sunbirds and honey‐creepers than for hummingbirds. A variety of hummingbirds has straight or even slightly upturned bills, while bills for all sunbirds, honeycreepers and honeyeaters are decurved to some extent. Despite differences in tongue morphology, hummingbirds, sunbirds and honeyeaters extract nectar at a similar range of rates, averaging approximately 40 γL s−1from adlibitumfeeders, and 1–15 γL−1from flowers. All tongues collect nectar by capillarity, with licking rates of 6–17 s−1. Licking behaviour has been little studied, although speeds of licking respond to changes in sugar concentration and corolla length. The tongues of honeyeaters are broad, and may need to be brush‐tipped in order to allow capillary collection of nectar. Brush‐tipped tongues can cover large surface areas on each lick, and may allow honeyeaters to exploit nectar and honeydew that is thinly spread over large surface areas. Bill lengths of nectarivorous birds are similar in all regions, though species of hummingbird have the shortest and longest bills. Bill lengths largely determine the range of floral lengths that can be legitimately probed. Maximum floral lengths exceed bill lengths, since hummingbirds, sunbirds and honeyeaters protrude their tongues beyond the tips of their bills. Rates of nectar extraction, however, decline rapidly once the floral length exceeds bill length. Decurved bills may have evolved in honeyeaters and sunbirds to enable perching birds to reach flowers at the ends of branches more easily. Consistent differences in bill length between the sexes suggest that males and females may exploit different floral resources or different proportions of the same resources. For honeyeaters and sunbirds, males have longer bills than females, but the reverse is true

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1989.tb01457.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY