Estimating animal populations and body sizes from burrows: marine ecologists have their heads buried in the sand

Most ecological studies require knowledge of animal abundance, but it can be challenging and destructive of habitat to obtain accurate density estimates for cryptic species, such as crustaceans that tunnel deeply into the seafloor, beaches, or mudflats. Such fossorial species are, however, widely used in environmental impact assessments, requiring sampling techniques that are reliable, efficient, and environmentally benign for these species and environments.2.Counting and measuring the entrances of burrows made by cryptic species is commonly employed to index population and body sizes of individuals. The fundamental premise is that burrow metrics consistently predict density and size. Here we review the evidence for this premise. We also review criteria for selecting among sampling methods: burrow counts, visual censuses, and physical collections.3.A simple 1:1 correspondence between the number of holes and population size cannot be assumed. Occupancy rates, indexed by the slope of regression models, vary widely between species and among sites for the same species. Thus, 'average' or 'typical' occupancy rates should not be extrapolated from site- or species specific field validations and then be used as conversion factors in other situations.4.Predictions of organism density made from burrow counts often have large uncertainty, being double to half of the predicted mean value. Whether such prediction uncertainty is 'acceptable' depends on investigators' judgements regarding the desired detectable effect sizes.5.Regression models predicting body size from burrow entrance dimensions are more precise, but parameter estimates of most models are specific to species and subject to site-to-site variation within species.6.These results emphasise the need to undertake thorough field validations of indirect census techniques that include tests of how sensitive predictive models are to changes in habitat conditions or human impacts. In addition, new technologies (e.g. drones, thermal-, acoustic- or chemical sensors) should be used to enhance visual census techniques of burrows and surface-active animals.

Little penguin Eudyptula minor at Middle Island, Western Victoria : current status

We examined the status of the Little Penguin Eudyptula minor at Middle Island on the west coast of Victoria during the species' 1999/2000 breeding season. The vegetated upper surface of the island had 292 occupied burrows at a density of 0.02/m². Peak dusk arrival occurred in January with 502 penguins coming ashore during a one-hour period. Little Penguins at Middle Island displayed important differences in breeding ecology from penguins in other Australian colonies. Early breeding combined with heavier adult and chick weights resulted in high breeding success. However, as Middle Island is a popular destination for day visitors, during the 1999/2000 Little Penguin breeding season, tourism ·was found to cause detrimental effects, including deaths of some eggs and chicks. There are also concerns for the conservation of the Little Penguin colony as faxes or dogs may readily access the island.

Hypnosis in childbirth

The client in this case report self referred for the use of hypnosis during childbirth. The current pregnancy had been uneventful except for intermittent problems with elevated blood pressure. The client was seen for four sessions prior to a successful delivery using hypnosis. This paper describes in detail the preparation for childbirth using hypnotic techniques, an abreaction that occurred during this time and the use of hypnosis to control blood pressure.

Commensalism used by freshwater crayfish species to survive drying in seasonal habitats

Gramastacus insolitus is a very small non-burrowing Australian freshwater crayfish with a restricted distribution, occurring almost exclusively in seasonal habitats throughout its range. It is listed as a threatened species but its strategy for surviving dry periods was unknown. Eight seasonal surveys of crayfish distribution showed that members of G. insolitus were never found at sites that were outside the distribution of two larger burrowing freshwater crayfish species, Geocharax falcata and Cherax destructor. Excavation of 80 burrows of members of G. falcata and C. destructor in three different seasonal habitats in the Grampians National Park, Victoria, Australia, revealed that individuals of G. insolitus found refuge from drying by estivating in cracks and shallow depressions at the side of the main burrow tunnels constructed by larger species. Members of G. insolitus were not found estivating at the surface, such as under fallen wood, nor was it usually found in crayfish burrows unoccupied by the host crayfish. This study indicates that members of G. insolitus are commensal upon larger crayfish species, using their burrows to survive the seasonal drying of their habitat. Conservation strategies for populations of G. insolitus will need to consider co-existing species of burrowing crayfish.