Terrestrial apnoeas and the development of cardiac control in Australian fur seal (Arctocephalus pusillus doriferus) pups

The development of cardiac control in association with terrestrial respiration patterns was examined throughout the period of maternal dependence in Australian fur seal pups. Resting eupnoic heart rate and respiration rate were significantly correlated (r² = 0.49) and both decreased with age (P < 0.05 in both cases). From an early age (1 month), pups displayed terrestrial apnoeas (18.1 ± 0.5 s) accompanied by substantial bradycardia (127 beats min^-1, a 13% decrease from eupnoic HR). Terrestrial apnoea duration increased significantly with age reaching a mean of 41 s just prior to weaning, slightly lower than the mean dive duration (52 s) previously recorded for pups of the same age. Correspondingly, mean apnoic heart rate decreased with age to 74 beats min^-1 just prior to weaning, representing a 25% decrease on eupnoic heart rate. Importantly, concomitant with the decrease in mean apnoic heart rate with age, an increase in the control
of bradycardia was evident with the variability in instantaneous apnoic heart decreasing such that older pups were able to maintain a low steady heart rate for the duration of the apnoea. The changes seen in these parameters are similar to those reported during postnatal development in elephant seals (Mirounga spp.) and harbour seals (Phoca vitulina), and are considered indicative of the development of cardiac control. These findings suggest a common strategy for the development of bradycardia control in both otariid and phocid seals.

A comparison of the effectiveness of camera trapping and live trapping for sampling terrestrial small-mammal communities

Context. There is an increasing reliance on the use of camera-trap technologies for surveys of medium to large terrestrial mammals. Camera trapping may, however, also have significant applications for broad-scale surveys of small mammals.
Aims. The present study aims to compare results from camera-trapping surveys to those of the more traditional live trapping techniques. Specifically, it aims to test the effectiveness of the techniques for detecting species, and the cost effectiveness of both approaches.
Methods. Surveys were conducted across 36 sites in the Grampians National Park, Victoria, Australia, between April and July 2009. At each site, independent surveys were conducted for small mammals by using a combination of Elliot and cage trapping, then camera trapping. Results for the two different approaches were compared for both their ability to generate small-mammal presence data and their cost effectiveness.
Key results. Camera-trapping surveys of 36 sites in the Grampians National Park compared favourably with those of live trapping surveys. Similar species were detected across the sites, and camera trapping was a considerably more cost effective than live trapping.
Conclusions. Camera-trapping surveys of small terrestrial mammals may provide a new and cost-effective technique for surveying terrestrial small mammals. This is particularly the case when presence data are the main requirement of the survey, with no requirement to capture and tag animals.
Implications. Given the cost-effective nature of camera trapping, there is potential to use this approach to increase the level of replication and spatial coverage of small-mammal surveys. Improving the replication and spatial coverage of studies has the potential to significantly increase the scope of research questions that can be asked, thus providing the potential to improve wildlife management.

Ageing mallee eucalypt vegetation after fire : insights for successional trajectories in semi-arid mallee ecosystems

A critical requirement in the ecological management of fire is knowledge of the age-class distribution of the vegetation. Such knowledge is important because it underpins the distribution of ecological features important to plants and animals including retreat sites, food sources and foraging microhabitats. However, in many regions, knowledge of the age-class distribution of vegetation is severely constrained by the limited data available on fire history. Much fire-history mapping is restricted to post-1972 fires, following satellite imagery becoming widely available. To investigate fire history in the semi-arid Murray Mallee region in southern Australia, we developed regression models for six species of mallee eucalypt (Eucalyptus oleosa F.Muell. ex. Miq. subsp. oleosa, E. leptophylla F.Muell. ex. Miq., E. dumosa J. Oxley, E. costata subsp. murrayana L. A. S. Johnson & K. D. Hill, E. gracilis F.Muell. and E. socialis F.Muell. ex. Miq.) to quantify the relationship between mean stem diameter and stem age (indicated by fire-year) at sites of known time since fire. We then used these models to predict mean stem age, and thus infer fire-year, for sites where the time since fire was not known. Validation of the models with independent data revealed a highly significant correlation between the actual and predicted time since fire (r = 0.71, P < 0.001, n = 88), confirming the utility of this method for ageing stands of mallee eucalypt vegetation. Validation data suggest the models provide a conservative estimate of the age of a site (i.e. they may under-estimate the minimum age of sites >35 years since fire). Nevertheless, this approach enables examination of post-fire chronosequences in semi-arid mallee ecosystems to be extended from 35 years post-fire to over 100 years. The predicted ages identified for mallee stands imply a need for redefining what is meant by ‘old-growth’ mallee, and challenges current perceptions of an over-abundance of ‘long-unburnt’ mallee vegetation. Given the strong influence of fire on semi-arid mallee vegetation, this approach offers the potential for a better understanding of long-term successional dynamics and the status of biota in an ecosystem that encompasses more than 250 000 km² of southern Australia.

Impact of secondary salinisation on freshwater ecosystems : effect of experimentally increased salinity on an intermittent floodplain wetland

Intermittent wetlands are particularly at risk from secondary salinisation because salts are concentrated during drawdown. We conducted a field experiment to examine the effect of adding salt at two different concentrations (to achieve nominal conductivities of 1000 μS cm–1 (low salt) and 3000 μS cm–1 (high salt)) on water quality, freshwater plants and epiphytic diatoms in an intermittent wetland during a 3.3-month drawdown. Conductivity increased to 3000 and 8500 μS cm–1 in low-salt and high-salt treatments respectively. Salt was apparently lost to the sediments, causing protons to be released from the sediments and reducing water column pH from 6.9 to 5.5 in the low-salt treatment and to 4.0 in the high-salt treatments. Forty days after adding the salt, biomass, %cover and flower production in Potamogeton cheesmanii were significantly reduced, whereas Amphibromus fluitans was not significantly affected. The salt effect on Triglochin procera was intermediate between the other two macrophytes. Significant reductions in the density, species richness and diversity of epiphytic diatoms occurred in the high-salt, but not in the low-salt, treatments. Our work shows that increases in salinity, and thus conductivity (up to 8500 μS cm–1), in low-alkalinity intermittent wetlands can change water quality, with significant adverse effects on some macrophyte and diatom communities.

Cellulose and hemicellulose digestion by herbivorous terrestrial crustaceans

Cellulose, the main component of plant cell walls, is insoluble and difficult to digest enzymatically. This research discovered that herbivorous land crabs have an efficient gastric mill in the stomach which disrupts this insoluble material, and a range of highly specialised enzymes that can then break down the cellulose.

Fire and the conservation of the avifauna of mallee ecosystems

This research demonstrates that in mallee ecosystems the bird community changes with time-since-fire and is influenced by the spatial arrangement of landscape mosaics comprised of different post-fire-age vegetation. Fire alters vegetation structure and food availability for birds. The management of fire is critical for the conservation of mallee birds.

Droughts, floods and freshwater ecosystems : evaluating climate change impacts and developing adaptation strategies

Climate change is expected to have significant impacts on hydrologic regimes and freshwater ecosystems, and yet few basins have adequate numerical models to guide the development of freshwater climate adaptation strategies. Such strategies can build on existing freshwater conservation activities, and incorporate predicted climate change impacts. We illustrate this concept with three case studies. In the Upper Klamath Basin of the western USA, a shift in land management practices would buffer this landscape from a declining snowpack. In the Murray–Darling Basin of south-eastern Australia, identifying the requirements of flood-dependent natural values would better inform the delivery of environmental water in response to reduced runoff and less water. In the Savannah Basin of the south-eastern USA, dam managers are considering technological and engineering upgrades in response to more severe floods and droughts, which would also improve the implementation of recommended environmental flows. Even though the three case studies are in different landscapes, they all contain significant freshwater biodiversity values. These values are threatened by water allocation problems that will be exacerbated by climate change, and yet all provide opportunities for the development of effective climate adaptation strategies.

Building nature’s safety net 2011 : the state of protected areas for Australia’s ecosystems and wildlife.

This report is the third in a series with the two previous reports published in 2006 and 2008. This report details major conservation initiatives that have occurred in Australia since the last report, in which data was current to 2006, and highlights emerging issues. A major enhancement on previous reports is the inclusion of ecosystem and threatened species gap analyses, and the reporting on Australia's protected area systems on both land and sea. We define a minimum standard for an adequate, representative, and comprehensive reserve system by sampling ecosystem and species level diversity. Using the latest protected area and national species and ecosystem spatial data, we quantify the gaps: those areas needing to move from the current reserve system to one which meets the minimum standard. We also use data provided by various parks agencies, from responses to a questionnaire or as published by the agencies, to detail financial investments in protected areas, and estimate the investment levels needed to fill the documented gaps. We also identify critical policy changes needed to more effectively fill the identified gaps.

Space-for-time substitution to assess likely response of aquatic ecosystems to future climate-related change

Predicting and managing ecological response to a changing climate is often limited by an incomplete understanding of response thresholds and biogeographic differences. For example, step changes in rainfall and runoff, and threshold dynamics and hysteresis in ecological response make projection of future conditions difficult. To combat these constraints we propose that biophysical data across exiting climatic gradients can be used in a space-for-time substitution to predict climate-related ecological response elsewhere. This method builds on previous attempts at space-for-time substitution by using patterns in physical and physicochemical data to explain biological differences across the spatial gradient, then using those patterns to formulate hypotheses of temporal ecological response and finally testing those hypotheses on temporal data available in a second, similar region of interest. 

Fire mosaics and reptile conservation in a fire-prone region

Fire influences the distribution of fauna in terrestrial biomes throughout the world. Use of fire to achieve a mosaic of vegetation in different stages of succession after burning (i.e., patch-mosaic burning) is a dominant conservation practice in many regions. Despite this, knowledge of how the spatial attributes of vegetation mosaics created by fire affect fauna is extremely scarce, and it is unclear what kind of mosaic land managers should aim to achieve. We selected 28 landscapes (each 12.6 km2) that varied in the spatial extent and diversity of vegetation succession after fire in a 104,000 km2 area in the semiarid region of southeastern Australia. We surveyed for reptiles at 280 sites nested within the 28 landscapes. The landscape-level occurrence of 9 of the 22 species modeled was associated with the spatial extent of vegetation age classes created by fire. Biogeographic context and the extent of a vegetation type influenced 7 and 4 species, respectively. No species were associated with the diversity of vegetation ages within a landscape. Negative relations between reptile occurrence and both extent of recently burned vegetation (≤10 years postfire, n = 6) and long unburned vegetation (>35 years postfire, n = 4) suggested that a coarse-grained mosaic of areas (e.g. >1000 ha) of midsuccessional vegetation (11–35 years postfire) may support the fire-sensitive reptile species we modeled. This age class coincides with a peak in spinifex cover, a keystone structure for reptiles in semiarid and arid Australia. Maintaining over the long term a coarse-grained mosaic of large areas of midsuccessional vegetation in mallee ecosystems will need to be balanced against the short-term negative effects of large fires on many reptile species and a documented preference by species from other taxonomic groups, particularly birds, for older vegetation.