Practical Field Ecology. C. Philip Wheater
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of the tree, and acts like a funnel trap to prevent bats escaping from the inside of the collection bag.
Once the net has been set up, a thermal imaging camera can be used to monitor the contents of the collection bag. To minimise disturbance, Henry Andrews recommends that two to three bats are sampled from each roost, as in most cases this will provide sufficient information about the composition of the roost.
Advice for students wanting to work with bats
Bats and their roosts receive full legal protection throughout Europe and should never be disturbed without a license to do so. If you are interested in getting involved in bat research, you could volunteer with your local Bat Conservation Trust group (www.bats.org.uk) who will almost certainly provide opportunities for you get involved in bat surveys. You could also contact academics or ecological consultants that study bats to find out whether you could assist them with any of their work.
Creating aims, objectives, and hypotheses
Once a topic for research has been chosen, you can work out the aims of the study. These are important, since tightly defining the aims helps to focus more clearly on the work in hand and can avoid problems in implementation. ‘Woolly’ aims, such as ‘to investigate invertebrates under logs’, may be a starting point for a more focused aim, such as ‘to determine whether the number of invertebrates found under logs is related to the size of the log’. This then leads to further questions, including:
Which invertebrates are to be examined, i.e. should they be identified to species, or merely counted en masse, or allocated to ecological functional groups (e.g. predators, herbivores, etc.)?
What is a log (i.e. when is a fallen piece of wood a log rather than a twig?) and how many logs should be investigated?
How should we standardise or otherwise account for the condition and type of the logs (degree of decomposition, species of tree, etc.)?
Which measurements of size should be incorporated (e.g. length, width, surface area touching the ground, volume, depth of log in the soil, presence of other organisms such as fungi, etc.)?
Where should we sample the logs?
Which statistical method(s) should we use to analyse the data?
Once these questions have been answered, they become objectives that can be used to determine your methods. The aims and objectives lead us to the setting up of working hypotheses. For example, in our study of possible relationships between log size and the numbers of invertebrates found beneath them, we would set up a statistical hypothesis to be tested. It is common practice that the statistical hypothesis to be tested is a null hypothesis; in this context that ‘there is no relationship between log size and the number of invertebrate animals found underneath them’. Most univariate statistical tests examine the likelihood of the null hypothesis being true (see Chapter 5). A null hypothesis should meet the following criteria:
be a single, clear and testable statement – where more complex research questions are asked, you should break these hypotheses down into individual statements that are treated separately and tested in turn;
have an outcome, typically either ‘accept’ or ‘reject’ the null hypothesis;
be readily understandable to someone who is not a scientist.
Reviewing the literature
You should always review the planning and implementation of each stage of your research project by using current information, either from others who have been involved in similar research, or using texts, papers in journals, or other information sources (e.g. the internet), or a combination of these. Be aware of possible biases in the information used, especially where this is obtained from websites belonging to individuals (rather than respected organisations) that have not been independently validated. Most papers in reputable journals and many textbooks have been examined by independent referees, although even these may contain factual inaccuracies and personal opinions that may not conform to current opinion. Although considered the gold‐standard of information sources, even peer‐reviewed journals are subject to bias against the publication of negative results. It is important to start your review of the literature as early as possible, since it is an ongoing process throughout your research and should inform each stage of your project. At the very least you should begin by reading the literature to establish that your proposed idea has not been already published and to define the gaps in knowledge that you will attempt to fill. It is likely that as you read one paper, you will find references to other work that may be important. Expect to read more than 100 papers in your field and to actively use a third to half of these in your thesis.
If you are new to a subject matter, you should first try and locate seminal piece(s) of work in the field or a recent review. Typically, this will be close to the top of a search list of highly cited papers and can be found by ordering a search by ‘times cited’. Take a detailed look at the seminal paper(s), the reference list, and who is citing that paper. In journal databases (e.g. Web of Knowledge), citation networks can be viewed to examine the connectedness between a seminal paper and all those papers that cite it. This is useful because it can elucidate key papers in the field and reduce the search effort dramatically. Typically, your first search should include seminal works and a collection of the most recent papers in the field (i.e. from the last few years). It might be helpful to order these by journal impact factor (if available), since parochial journals may not contain as high quality science, although sometimes smaller research papers with less apparent impact can provide valuable information in the form of species lists, new methods, and negative findings that are often not reported in more mainstream journals. An additional word of warning: highly cited papers can also be poor papers in the field since other authors might simply be referencing them to make an example of that piece of work (e.g. ‘Black and White's (2000) experimental design has been shown here and by others to be flawed’). Knowledge of the literature can assist in avoiding ‘blind alleys’ and unfruitful lines of enquiry or techniques. There are two main types of literature: primary and secondary.
Primary literature
This is first‐hand information; for example, articles in specialist journals, reports, MSc and PhD theses by those who have done the work and generated data. Journals that publish only refereed papers (i.e. those that have been through a peer‐review process) are the most important sources of primary, up‐to‐date information, and where possible your literature review should focus on this type of source. Other primary sources include technical reports, management plans, consultancy reports, and species lists (e.g. from annual recorder reports). All of these can be useful sources of information for ecological projects, but you should be aware that they may not have been edited or their quality controlled.
Secondary literature
This is prepared from other sources of information – including textbooks, review articles, opinion pieces, and letters to the editor – which often express views on primary research. If you are lucky, there may be specialised books covering your subject area. These may provide a good starting point since books are secondary sources of information, while journals are a preferred source of reference for most research projects. The coverage in student textbooks is usually rather more superficial than that in specialist texts. If there are review articles on your subject, these may be useful to obtain an overview and as a source of new references. Reviews are found in edited book sections, journals that specialise in reviews (e.g. Trends in Ecology and Evolution)3 and journals that have occasional review papers. Review papers in established scientific journals have usually been subject to peer review.
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