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A line transect on a rocky intertidal habitat at Heron Island Research Station.

The study of any species requires an estimate of their density in different habitats. Scientists use many different methods of measuring density, depending on the size, abundance, behaviour and habitat of the species. Our class used a line transect and quadrats to measure the abundance and cover of different floral species in a grassland reserve. Other methods to measure relative density include:

1. Aerial photographs (eg. herds of moose or other hoofed mammals during migration, flamingos)
2. Capture-recapture (or mark and release)
3. Traps (eg. Elliot traps for small mammals, pit-fall traps for reptiles, light traps for insects, harp traps for bats)
4. Number of fecal pellets
5. Vocalisation frequency
6. Pelt records
7. Catch per unit fishing effort
8. Number of artifacts (nests, pupal cases, burrows etc.)
9. Questionnaires (of hunters and trappers for example)
10. Cover (of plants)
11. Feeding capacity (amount of bait taken)
12. Roadside counts

Each method has it’s advantages and disadvantages and is most valubale when used as an adjunct to more direct methods.

Reference: Charles J. Krebs (1985) “Ecology – The Experimental Analysis of Distribution and Abundance” Harper International, New York.

You might think that providing water in arid areas would allow native species to flourish, as well as the stock it is intended to supply. However, sinking bores and providing tanks or troughs allows larger predators of native species access to areas that previously they found too dry to survive in. Small, native marsupials have become increasingly rare in the arid zones of Australia due to increased predation from both indigenous predators (wedge-tailed eagles, dingoes, dasyrids) and feral pests (foxes, feral cats, wild dogs). These predators have wide home ranges in desert areas and need to have access to water to survive. Smaller marsupials manage to survive in very dry areas due to a number of structural, functional and behavioural adaptations. These may include low SA:V ratio that reduces evaporation, nocturnal or crepuscular feeding habits, concentrated urine and dry faeces and the ability to obtain their water needs from the food they eat, without drinking.

Martin Westbrook is an environmental scientist working with the University of Ballarat at Nanya station, 140 km north of Mildura. He has been able to perform experiments at the 40,000 hectare former pastoral property, to determine the impact on biodiversity when removing water points. The Age has produced an article about his research here.

Here you can see just a few of the marine invertebrates we met in the touch tank at Heron Island Research Station, 65km east of Gladstone, on the southern end of the Great Barrier Reef. We learnt about molluscs (such as the blue-lipped clam, sea hare and cone shells), echinoderms (sea stars and sea cucumbers), corals and cnidarians (jellyfish). A coral cay is a great example of succession – how a landscape changes over time as new plants and animals colonize an area.