M.C. Calver

The impact of cats and foxes on the small vertebrate fauna of Heirisson Prong, Western Australia. II. A field experiment

The hypothesis that predation by feral cats and introduced foxes reduces population sizes of small, native vertebrates was supported by results of a predator-removal experiment at Heirisson Prong, a semi-arid site in Western Australia. The methods of control used against cats and foxes to protect native mammals reintroduced to Heirisson Prong produced three broad ‘predator zones’: a low-cat and low-fox zone, where foxes were eradicated and spotlight counts of cats declined after intensive cat control; a high-cat and low-fox zone where spotlight counts of cats increased three-fold after foxes were controlled; and a zone where numbers of cats and foxes were not manipulated. Small mammals and reptiles were monitored for one year before and three years after predator control began. Captures of small mammals increased in the low-cat and low-fox zone, but where only foxes were controlled captures of small mammals declined by 80%. In the absence of cat and fox control, captures of small mammals were variable over the sampling period, lower than where both cats and foxes were controlled, yet higher than where only foxes were controlled. The capture success of reptiles did not appear to be related to changes in predator counts. This study presents the first experimental evidence from mainland Australia that feral cats can have a negative impact on populations of small mammals.

Control of feral cats for nature conservation. I. Field tests of four baiting methods

Four methods of baiting were evaluated on a radio-collared population of feral cats on Heirisson Prong, Shark Bay, Western Australia. Dried-meat baits, baiting rabbits to kill cats through secondary poisoning, a fishmeal-based bait and a bait coated in the flavour enhancer Digest were tested. All proved to be ineffective for controlling feral cats. Future research should explore baits more ‘natural’ in appearance and the effect of visual lures, and possibly bait over a larger area to increase the number of cats exposed to baits.

The index of relative importance: An alternative approach to reducing bias in descriptive studies of animal diets

The Index of Relative Importance (IRI) is a composite measure that reduces bias in descriptions of animal dietary data. The two papers introducing the IRI in 1971 had been cited a total of 214 times by the end of 2001 and proposed as a standard methodology. However, 180 of these citations concerned the description of the diets of fish, indicating that the IRI is not well known outside fisheries biology. This illustrates how the interests of researchers in a narrow range of taxa may restrict the application of a useful technique to particular groups of animals. Here we apply the IRI to dietary data from one mammal species, two bird species and two species of geckoes to illustrate its applicability to a wide range of taxa. We believe the approach should be considered seriously by terrestrial ecologists concerned about the biases inherent in single-index approaches to describing animal diets.

Phenotypic variation in a clonal lineage of two Phytophthora cinnamomi populations from Western Australia

Seventy-three isolates of Phytophthora cinnamomi were collected from diseased Eucalyptus marginata (jarrah) and Corymbia calophylla (marri) trees in two forest communities in the southwest of Western Australia. Both populations of P. cinnamomi were examined for phenotypic and genotypic variation. Microsatellite DNA analysis showed that all isolates were of the same clonal lineage. We show, for the first time for P. cinnamomi, that morphological and pathogenic variation between populations of the clonal lineage are very broad and continuous. The phenotypes examined included growth rates and colony morphology on potato dextrose agar at different temperatures, sporangial and gametangial morphology, ability to form lesions in detached jarrah and marri stems, and ability to cause deaths of clonal jarrah plants in a glasshouse trial. Phenotype variation was derived asexually. All phenotypes investigated varied independently from one another. Cluster analysis of 24 morphological and pathogenicity phenotypes identified two main clusters of isolates corresponding to each population. The ability to cause deaths in both populations ranged from killing all plants within 59 d to plants being symptomless 182 d after inoculation.

Why does experimentation matter in teaching ecology

The inquiry-based approach is an important component of secondary school biology curricula. However, we found that common Australian texts included little coverage of controlled experimentation in ecological practical work. The logistical and ethical difficulties in designing suitable ecological practicals may be a factor in these observations, as well as a perception that investigations of the complex interrelationships in ecology require scientific approaches other than experimentation. We argue that because controlled experiments are used extensively by professional ecologists to solve both theoretical and applied problems, experimentation should be a key component of secondary school ecology curricula. We suggest five teaching principles to guide secondary school biology teachers in providing a more realistic view of the possibilities and limitations of ecological experimentation. We also review ways in which computer simulations and microcosm experiments can be used to overcome logistical and ethical problems and allow students to design and implement ecological experiments. Whether based in the classroom or the field, the use of experimental approaches in secondary school ecology curricula illustrates ecological concepts, reinforces principles of experimental design and highlights the value of the inquiry-based approach in biological education.

What makes a journal international? A case study using conservation biology journals

The qualitative label ‘international journal’ is used widely, including in national research quality assessments. We determined the practicability of analysing internationality quantitatively using 39 conservation biology journals, providing a single numeric index (IIJ) based on 10 variables covering the countries represented in the journals’ editorial boards, authors and authors citing the journals’ papers. A numerical taxonomic analysis refined the interpretation, revealing six categories of journals reflecting distinct international emphases not apparent from simple inspection of the IIJs alone. Categories correlated significantly with journals’ citation impact (measured by the Hirsch index), with their rankings under the Australian Commonwealth’s ‘Excellence in Research for Australia’ and with some countries of publication, but not with listing by ISI Web of Science. The assessments do not reflect on quality, but may aid editors planning distinctive journal profiles, or authors seeking appropriate outlets.

Should we use the mean citations per paper to summarise a journal’s impact or to rank journals in the same field?

The mean citations per paper is used increasingly as a simple metric for indicating the impact of a journal or comparing journal rankings. While convenient, we suggest that it has limitations given the highly skewed distributions of citations per paper in a wide range of journals.

Comparisons of the food niches of three native and two introduced fish species in an Australian river

SynopsisThe breadth, correspondence and overlap of the diets of the small and large size classes of the three native species (Galaxias occidentalis, Bostockia porosa and Edelia vittata) and two introduced species (Gambusia holbrooki and Perca fluviatilis) of fishes found in the shallows of the main channel and in the tributary creeks of a south-western Australian river have been compared in each season. Classification and ordination were used to examine the overall interrelationships of the diets across species, size groups, seasons and the location where the fish were caught (channel or creek). The smaller fish had a narrower dietary breadth than larger fish in the spring and summer, presumably reflecting the size limit imposed on prey size by their possession of a relatively small mouth in these seasons. Intraspecific dietary overlap between large and small size classes was usually high in G. occidentalis, but generally low in G. holbrooki and P. fluviatilis, and also in B. porosa and E. vittata when the difference between the lengths of the two size groups was greatest. Dietary overlap was least in autumn when the main prey taxa were most abundant. During winter, the diets of the three native species in the tributaries converged, probably reflecting a relatively low faunal diversity in these highly seasonal water bodies. The only relatively consistent interspecific overlap in diet was between B. porosa and E. vittata. Classification and ordination of the dietary samples separated G. occidentalis (which fed extensively on terrestrial organisms from the water surface) from the smaller P. fluviatilis (that concentrated on copepods in the plankton) and from B. porosa and E. vittata (which ingested primarily benthic organisms). Furthermore, B. porosa tended to ingest larger prey taxa than E. vittata. The diet of Gambusia holbrooki is sometimes dominated by terrestrial insects and at other times by benthic organisms, demonstrating that this species is an opportunistic carnivore. It is concluded that food partitioning by the three native and two introduced fish species in the Collie River is likely to be one of the principal factors facilitating the coexistence of substantial populations of these species in this system.

Towards resolving conflict between forestry and conservation in Western Australia

SUMMARY There is widespread agreement that the indigenous forests of south-western Australia are an important refuge for wildlife in an otherwise extensively cleared landscape and that sustainable use of these forests is possible. Nevertheless, principles-based theses that have been proposed for assessing sustainability of forest use are of limited value unless they include assessable criteria for application. We argue that it is important to recognise that ecological science, like other disciplines is value-laden and that a statement of values is an important part of the scientific process. Furthermore, we believe that there is presently inadequate evidence to judge whether or not the current forest use is sustainable. Several areas of empirical work are suggested to resolve the outstanding issues. ‘The value of criticism and dissenting views is that they force a clearer articulation of the questions and the range of possible answers. This is the process that will hasten the resolution of fundamental iss...

Does intraspecific variation in the energy value of a prey species to its predators matter in studies of ecological energetics? A case study using insectivorous vertebrates

This study tested the assumption that variation in the energy value of different instars of a hemimetabolous insect makes no ecologically significant difference to rates of energy gain by its vertebrate predators and found it to be supported. Three mammal species, four bird species and a lizard species were used as predators and one grasshopper species as prey. Although instars of both male and female grasshoppers differed significantly in energy values, the energy returns to their predators based on these exact values were qualitatively similar to those produced when a commonly-used constant energy value of 23 J/mg dry weight was substituted. Regressions of specific energy returns on those based on the 23 J/mg constant were highly significant, so energy returns based on the constant were good predictors of those based on specific energy values. Although significant intraspecific variations in energy values occur in Acrida conica and probably in other hemimetabolous insects as well, the 23 J/mg dry weight constant appears adequate for most predation studies.