Practical Field Ecology. C. Philip Wheater
Alternatively, we might wish to look at the range of species found in each of several woodlands and see which woodlands have similar species types. This is a similarity or clustering analysis and, depending on the technique used to calculate the similarities, data are normally recorded as a matrix (of species by woodlands) that contains either measurements (e.g. counts), ranks (e.g. ranked abundance), or binary data (e.g. species presence or absence). A similar technique to clustering enables us to visualise patterns in either the individuals (in this example, the woodlands) and/or the variables (here, the types of species). This is known as ordination and there are a number of different methods available depending on the algorithm (i.e. statistical formula). Such methods can utilise data comprising measurements, ranks, or binary information.
Summary
This chapter has identified the range of aspects that should be carefully considered when planning your project. Case Study 1.3 describes how one researcher approached her work, using the current literature to develop her techniques and adopting appropriate protocols for working overseas, in potentially hazardous environments. Ensure that you take sufficient time in the planning phase of your research project to cover all of the component parts. This includes health and safety and legal issues as well as making sure that your aims and objectives are focused and that any methods employed are appropriate to gather and analyse data. At each stage, consider the details of the implementation, whether this is in the practicalities of sampling or data management. Box 1.9 gives some general guidelines that should be ticked off in advance of implementing your project.
Case Study 1.8 Monitoring dung beetle richness in East Africa
Dr Roisin Stanbrook is a Post‐doctoral fellow at the University of Central Florida. She uses dung beetles to assess the impact of habitat modification on dung beetle communities, and models how changes in mammalian diversity in protected areas in East Africa affect dung beetle community composition. She has long held a passion for the little things that run our world, and for the need to increase awareness of insect conservation. This case study examines the different aspects of using baited pitfall trapping, which is most commonly employed method to determine dung beetle diversity, and the challenges encountered when working in protected areas in East Africa.
Model organism and research challenges faced
Scarabaeinae, or true dung beetles, comprise one of the most species‐rich groups of coprophagous insects with almost 7000 species found globally. Dung beetles have a widespread distribution, which is centred around the species‐rich tropics, with diversity gradually declining in higher latitudes. This ubiquity means that dung beetles are often used as indicators of habitat quality and barometers of habitat change due to species' associations with habitat types, and reductions in diversity when habitats are negatively affected by disturbance. One of the benefits of using dung beetles as an eco‐indicator is the ease with which large data sets can be gathered in a short timeframe, and consequentially used to form a rapid impact assessment (Bicknell et al. 2014). However, there are many challenges one may encounter when used baited pitfall traps.
One major issue with pitfall trapping is obtaining an accurate relative sample of dung beetle diversity. Without adequate sampling effort, dominant species are often over‐represented and rare species may be missed entirely. Traps frequently generate large numbers of common species over a short time period, but longer trapping periods of up to one month may be needed in species‐rich tropical locations where dung beetle niches are smaller. Factors such as the quantity of moonlight, or seasonal shifts in temperature could determine if rare species are detected or not. Another common issue when using baited pitfall traps is trap disturbance by other animals. Once traps are set, they are left unattended until the observer returns. This allows inquisitive species such as hyenas (Crocuta crocuta), or animals such as mongooses (e.g. Mungos mungo) which like to feed on captured beetles, ample time to disrupt trapping effort and consume valuable data.
Once trap data have been collected, the samples need to be sorted and identified to species or morphospecies. This typically requires a high‐powered microscope and access to many intricately written identification keys. Identifying dung beetles to species level requires time and tenacity, and access to existing collections to verify identifications can be beneficial. This can be challenging when collecting species internationally, but can be circumnavigated by using collections belonging local or national museums.
How the challenge was resolved
A dung beetle project's success will largely depend on the amount and length of time pitfall traps are deployed. It is recommended that a pilot study be conducted in the same location, and during the same season, for at least one entire trapping effort. Traps should be set and collected daily for a minimum of 8 days. A species accumulation curve should then be constructed. Species accumulation curves are easy to construct and are readily interpretable to give the researcher an indication of the minimum sampling effort required for an adequate inventory, which avoids incurring extra time and fieldwork costs.
Standard methods for pitfall traps usually employ dung suspended over a bucket which is placed into the ground with the lip of the bucket flush with the soil surface. One method of avoiding trap loss by other animals is to use pitfall traps with built‐in mesh enclosures. The trap is constructed from a one‐gallon sturdy container, such as a paint can with the lid placed on the container but the centre of the lid removed and replaced with strong chicken wire. This design means that even if the trap is disturbed, captured beetles remain inside the container and the sample will not be lost.
Sorting and identifying dung beetles to species can be tricky. Forging strong collaborations with scientists and museums in‐country allows access to holotype specimens found in their collections, and if export for further analyses are required these collaborations will ensure that the export process conforms with both national and international law. Roisin worked closely with National Museums Kenya in Nairobi and deposited specimens in their collection to leave a permanent record of Kenyan dung beetle diversity for future dung beetle enthusiasts.
Advice for students wanting to study dung beetles
Dung baited pitfall traps are a relatively easy and enjoyable method of assessing habitat modification and its associated effects. There are, however, health risks associated with using animal dung as bait. The handling of dung and other contaminants expose scientists to an increased risk of gastrointestinal infection, and care must be taken to minimise exposure and employ strict hygiene routines. Regular handwashing in conjunction with the use of disposable gloves are often the minimum requirements to avoid infection.
Dung beetle species richness is highest in the tropical forests and grasslands of Africa. These habitats also contain the world's highest density large wild animal populations, and an increased awareness of working in such locations is necessary to collect meaningful data safely. Studying fantastic insects such as dung beetles can be incredibly worthwhile, especially as there are still numerous new species found every year (e.g. Roggero et al. 2017).
Box