Sampling Considerations

Three considerations are also necessary when planning to survey fauna:

population size
identification
voucher specimens

Explore each of these.

Population size

A common misconception in fauna surveys is that by catching lots of animals and letting them go again, you are estimating the population size of each species. Wrong!! This is simply measuring the relative abundance of the captured animals. Estimating the population size (absolute abundance) requires more planning, effort and analysis compared with simple measurements of relative abundance of a species. Hence it is important to determine whether it is necessary to determine the absolute size of populations of each species.

Absolute population estimates are required to manage pest species, employ sustainable harvest techniques, estimate energy flows or to examine the relationship between population density and reproductive rate or any other vital statistic.

There are a number of different techniques used for estimating abundance: enough to fill a whole unit. A simple list will be sufficient in this unit, but many excellent books have been published to assist researchers with this common area (See Caughley 1977, Krebs 1989).

Mark-recapture techniques
One way to estimate the size of a population is to capture and mark individuals from a population. Here are some of the more common mark-recapture techniques. Each technique is based on a number of assumptions that should be considered prior to sampling.

• Petersen method - single episode of marking (closed populations)
  
• Schnabel method - series of sampling episodes (closed populations)
  
• Jolly-Seber method - series of sampling episodes (open populations)
  
• Tests of Equal Catchability - test of assumptions.

Please Read For further explanation of these mark-recapture methods, please refer to pages 17-46 of your textbook.

Line transects
Based on the probability of sighting an individual in relation to the distance and angle from the observer.

• ground based surveys: may be traversed on foot or vehicle
  
• aerial surveys - a common technique for estimating the population size of larger animals or large flocks of birds, and is widely used in Australia.

Please Read For further explanation of line transect methods, please refer to pages 54-59 of your textbook.

	For more information Additional reading: Krebs, C. J. (1989). Ecological Methodology. Harper and Collins, New York. Caughley, G. (1977). Analysis of Vertebrate Populations. Wiley, London. Burnham, K.P., Anderson, D.R., & Lake, J.L. (1980). Estimation of density from line transect sampling of biological populations. Wildlife Monograph 72:1-202.

Identification

The importance of accurately identifying species is paramount in surveys, as this is the primary unit of measurement.

Very distinct species such as the echidna (Tachyglossus aculeatus) are unmistakable. However, many species are much harder to accurately identify. For example, small skinks offer few obvious features that allow a simple identification.

The use of field guides and taxonomic keys are important components of surveying fauna. Many local field guides and keys are available. Along with information on how to identify the animals, field guides and reference books provide valuable information on the habitat, diet, breeding and distribution of different species.

Listed below are the major references, along with some local field guides.

Mammals
Cole, J.R. & Woinarski, J.C.Z. (in press). Field Guide to Small Mammals of the Northern Territory. Reed Books, Sydney.

Strahan, R. (1995). Mammals of Australia. Australian Museum/Reed Books, Sydney.

Thompson, B.G. (1992). A Field Guide to Bats of the Northern Territory. Conservation Commission of the Northern Territory, Darwin.

Triggs, B. (1996). Tracks, Scats and Other Traces. Oxford University Press, Melbourne.

Birds
Lane, B.A. (1987). Shorebirds of Australia. Nelson Publishers, Australia.

Christidis, L. & Bowles, W.E. (1994). The taxonomy and species of birds of Australia and its Territories. Monograph 2. Royal Australasian Ornithologist Union, Melbourne.

Pizzey G.E. & Knith F. (1997). The Graham Pizzey & Frank Knight Field Guide to the Birds of Australia. Angus & Robertson, Pymble.

Slater, P., Slater, P. & Slater, R. (1989). The Slater Field Guide to Australian Birds. Weldon Publishing, Sydney.

Simpson, K. & Day, N. (1996). Field Guide to the Birds of Australia. Penguin Books, Melbourne.

Reptiles and Frogs
Cogger, H.G. (1992). Reptiles and Amphibians of Australia. Reed Books, Sydney.

Tyler, M.J.& Davies, M. (1986). Frogs of the Northern Territory. Conservation Commission of the Northern Territory, Darwin.

Wilson, S.K. & Knowles, D.G. (1988). Australia's Reptiles: A Photographic Reference to the Terrestrial Reptiles of Australia. Collins Australia, Sydney.

Horner, P. (1992). Skinks of the Northern Territory. Museum and Art Gallery of the Northern Territory, Darwin.

Fish
Larson, H.K. & Martin, K.C. (1989). Freshwater Fishes of the Northern Territory. Northern Territory Museum of Arts and Sciences, Darwin.

Australian Biological Resources Study (1994). Census of Australian Vertebrates (CAVS) Version 8.

Invertebrates
Andersen, A.N. & Jacklyn, P.J. (2001). The Ants of Northern Australia: A guide to the
monsoonal fauna. CSIRO Publishers.

Andersen, A.N. & Jacklyn, P.J. (1993). Termites of the Top End. CSIRO Publishers, Melbourne.

Naumann, I.D. (1991). Insects of Australia. CSIRO Publishers, Melbourne.

Zborowski, P & Storey, R (1997). Field Guide to Insects in Australia. CSIRO Publishers, Melbourne.

Voucher Specimens

Voucher specimens are representative specimens collected during fauna and flora surveys and lodged in a permanent records collection (e.g. museum or herbarium).

The species are usually collected due to taxonomic uncertainty or because they are of high conservation value and proof of their existence is required.

In the Northern Territory all voucher specimens must be lodged with the Museum and Art Gallery of the Northern Territory (MAGNT).

Preservation of voucher specimens - procedure
1. euthanasia of the individual
2. tag with a unique number, date, location and collectors name
3. inject body cavity with 10% Formalin and leave in Formalin for 2 days
4. rinse in cold water
5. place in 70% alcohol.

Numerous restrictions apply to the collection of voucher specimens
1. authorisation to possess a Schedule 4 poison (for euthanasia) is required from the Department of Health (DOH);
2. authorisation to possess spirit alcohol is required from the DOH
3. authorisation is required from the Animal Experimentation Ethics Committee
4. authorisation is required from Parks and Wildlife Commission to collect voucher specimens.

For more information weblink http://www.agric.nsw.gov.au/reader/2568 Animal Welfare Unit NSW Agriculture: "Guidelines for collection of voucher specimens"