Methods Manual for Salt Lake Studies/Vertebrates

Authors: PSJ Coleman,

Overview

Vertebrates that use salt lakes include birds, fish, reptiles and bats and other mammals. To develop an understanding of the food web interdependencies of your lake, it is necessary to know what species use the lake and the use they make of it - be it for feeding, breeding or resting.

Observational surveys

The simplest and least invasive method of collecting vertebrate fauna information is the observational survey. Observational methods of survey include the following activities:

1. dawn and dusk bird point counts,
2. dusk bat walks (with or without bat detectors),
3. "scats, tracks and traces" observations for terrestrial vertebrates,
4. "active search" (sometimes called "checklist") or "pollard walk" for reptiles,
5. audio recording of bat and nocturnal bird calls,
6. hair tubes for mammals,
7. the recording of opportunistic sightings,
8. photography, and
9. evening spotlighting.

It may be difficult to decide whether you have conducted sufficient observations and the following advice may assist:

1. For point counts, active search, recordings etc, make a note of the time you spend observing and the new species recorded, to construct a species accumulation curve (Smith, 1996).
2. Where a 'pollard walk' is set up, ensure that it passes through all the habitat patches on the site and traverses the landscape perpendicular to the slope at least once. For organisms that are sedentary, one walk may be sufficient. For mobile organisms, determine whether new species are detected on a second walk. If they are, consider further walks.

Resources for observational surveys

[1] - the collection and identification of hair samples

[2] Wyoming bat call library

[3] British bat call library

[4] Bat call library, University of New Mexico

[5] Bat call library for south-eastern Australia

[6] Pacific North-West bat call library

Comprehensive (trapping) fauna surveys

Trapping methods include:

1. cage and elliott traps for medium and small mammals,
2. dry pitfalls with drift fencing for small mammals and reptiles,
3. small traps for fish (minnow traps, opera traps, small nets.

Invasive survey methods such as vertebrate trapping usually require a permit from regional authorities. Always ensure that you have the correct permit and that you are aware of all the licence and reporting conditions that apply to the permit. Given the invasive nature of trapping, it is important that you do not impact on the population more than you need to (overtrapping). It is equally important that you do not subject the population to this stress only to produce data that is too scant to be statistically useful (undertrapping). In South Australia, the Biological Survey of SA has published "Guidelines for Vertebrate Surveys in South Australia", which may be downloaded from [7] The manual provides information on the layout of traplines, numbers of specific types of traps per trapline, appropriate numbers of trap nights, OH&S requirements, equipment lists, animal handling and ethics considerations.

Specimen records

Some records must be made in the field. Other determinations may wait until a laboratory is available (audio record analysis, hair samples, scats and remains). Record field determinations on field data sheets or in filed books, using a soft pencil (ink runs when wet). Sometimes a secondary record (eg a photograph or an audio tape) can be made to be returned to base for further consideration. The records most usefully made in the field include:

1. Locational details (remember to record the datum you are using)
2. Birds - names, photographs of indeterminate species, audio recordings
3. Mammals and reptiles - names, body weights, body length, tail length, sex (if easily determined), photographs of indeterminate species (as appropriate: overall view, face side on and full face, front and rear feet, head scale pattern, ventral and dorsal views of scales or patterns), audio recordings
4. Fish - names, photographs of indeterminate species (ensure a scale is present in all photographs)

Vouchering

Vertebrate species should only be vouchered if strictly necessary. The authority that issues you with any necessary permit will specify whether there are species that they wish you to voucher. Unknown (new to science) species should be vouchered for provision to the appropriate taxonomic authority.

Vouchering vertebrates requires the use of a prescription drug to euthanise the animal, and you may require a veterinary licence to use this. If you trap a vertebrate that should be vouchered (a new species, or a species where a voucher has been requested by the authorities and you do not have the appropriate drug to euthanise the animal you will need to return the animal alive, to the permitting authority, where appropriately licenced staff will euthanise it.