Protocols for Surveying Rhynchocyon
In the next couple of years there will be numerous teams surveying the flora and fauna in several Tanzanian forests. Many of these teams have agreed to include sengis (elephant-shrews) in their surveys. The material on these pages is intended to try and achieve some consistency in the information gathered by a large number of people with varying backgrounds in the BIOLOGY OF SENGIS.
The natural history of giant forest sengis is unusual and thus the methods included in most manuals of field techniques are inadequate. The methods described below are intended to supplement those found in more comprehensive manuals, which often will include general techniques such as determining random points, positioning transects, measuring distances along transects, flagging methods, preparing voucher specimens, etc. Good manuals that are published include:
SPECIAL CONCERN because of the destruction of their forest habitats. Petrodromus also occurs in woodlands throughout much of central and eastern Africa and because it is so widespread it is of little conservation concern. Therefore, these protocols will focus on the two species of Rhynchocyon. There are several issues with regard to the IDENTIFICATION and DISTRIBUTION of Rhynchocyon in Tanzania that are basic to the development of conservation plans. Briefly, it is known that R. petersi occurs in the Eastern Arc forests from north to south as far as the northern Udzungwa Mountains, where it meets R. cirnei from the south. It is not clear where these two species come together – there is evidence that there may be a population of R. petersi surrounded by R. cirnei in the West Kilombero forests or perhaps even some kind of fine-grained separation of these two species within the same forests in this area. Of particular interest in understanding the distribution of these two species are the following FORESTS (235 KB PDF) in the northerneastern Udzungwa Mountains: Luhombero, Ndundulu, Nyumbanitu, Ukami, Lyondo, Iwonde, Nyanganje, Magombero and Mwanihana. There is also evidence that both species may occur in the Nguru Mountains. The presence or absence of Rhynchocyon in the isolated forests on the Mahenge and Malundwe mountains also needs to be established.
Davies, G. (ed.). 2002. African Forest Biodiversity: a field survey manual for vertebrates. Earthwatch Institute (Europe), Oxford . 161 pp.
Sutherland, W.J. (ed.). 1996. Ecological Census Techniques – a handbook. Cambridge University Press, Cambridge . 336 pp.
Wilson , D.E., F.R. Cole, J.D. Nichols, R. Rudran, and M.S. Foster (eds.). 1996. Measuring and Monitoring Biological Diversity – standard methods for mammals. Smithsonian Institution Press, Washington. 409 pp.
There is also some question surrounding the distribution of Rhynchocyon in the coastal forests in the Lindi District and to the south into Mozambique. Specifically, does the Rufiji River indeed separate R. petersi to the north and R. cirnei to the south along the coast. Additionally, it is unclear how far inland along riparian forests of this region Rhynchocyon extends.
Before deciding which of various different survey methods to use, specific objectives must be clearly defined. I believe that the four most important objectives for surveying Rhynchocyon in Tanzanian forests are as follows:
- Determine which species of giant sengi occur in each of the fragmented coastal forests and isolated forests of the Eastern Arc Mountains.
- Determine the relative abundance of Rhynchocyon in selected forests.
- Determine the general forest condition in those forests where abundance surveys are completed for Rhynchocyon (see number 2 above).
- Collect and curate fresh tissue from each taxon or form of Rhynchocyon from as many sites as possible for subsequent molecular analyses to elucidate the taxonomy and phylogeography of the different forms that occur in Tanzania.
Because of logistical, personnel, and time limitation not all objectives can be done at all sites being surveyed in Tanzania. Also, not all forests are of equal interest in terms of sengis (see list of forests that are of greatest interest above). The leaders of the various projects must decide what can be accomplished in terms of sengi surveys. The easiest and most compatible objective with other survey aims is number 1 above. Objectives 2 and 3 will take considerably more focused effort, but will yield more detailed information on conservation status. The most difficult objective is number 4, but this has the greatest potential for producing significant biological results.
As indicated above, the type of survey that should be used mostly depends on the objective, but also on the availability of field crews, logistics, and time. In general, visual encounter surveys are used to determine if giant sengis are present. An estimate of abundance and the condition of habitat can be done with nest surveys. Various methods of capture are needed so that voucher specimens and tissues can be collected and analysed to resolve the phylotaxonomy of giant sengis.
Giant sengis are diurnal, so that they are relatively easy to see during the day, although making positive identification to species can be difficult because of their swift antelope-like behaviours and the poor lighting in forest habitats. Making positive species identifications is especially difficult in some areas of Tanzania , where the distribution of taxa meet or overlap and where pelage colours and patterns are not as distinct as often shown in field guides and portrait PHOTOS.
The presence of Rhynchocyon (but not to species) can be implied from indirect sign or SPOOR, which includes feeding and nest building. Although giant sengis do not generally vocalize, they do produce characteristic sounds while moving about on the forest floor leaf litter. I assume that the behaviour and ecology of all Rhynchocyon are similar, so survey participants not familiar with sengis may find my MONOGRAPH [21 MB PDF] on R. chrysopygus of Kenya useful. For biologists that are more familiar with sengis, I have assembled selected pages from the monograph that describe the most relevant BEHAVIOURS [655 KB PDF] for conducting effective visual encounter surveys. Camera traps can also be used to determine the presence of giant sengis (see below).
Because numerous people with different backgrounds are likely to be involved in forest surveys, it is important that all observers record the same information in the same way. This is best done with a standardized FIELD DATASHEET [20 KB PDF] with clearly defined categories and standardized abbreviations. This datasheet only includes the minimum information needed for sengis; if other mammals or birds are also being surveyed the sengi information could be incorporated into a datasheet that is designed for a broader range of species and a larger array of environmental and habitat factors. If carefully designed, the data on sengis can easily be extracted after the information is entered into data management software.
Because of the difficulty of consistently sighting giant sengis during visual encounter surveys, the resulting data are not suitable for estimating abundance. However, a quantitative method of estimating the number of animals in an area has been developed based on the number of LEAF NESTS on the forest floor encountered on a transect. These same transects also can be used to characterize the habitat. The details of this method are fully described in a published paper by FITZGIBBON AND RATHBUN [462 KB PDF]. Because of the difficulty of spotting nests on the forest floor, these transects should not be used simultaneously for other purposes. A nest survey datasheet, which includes all the necessary data to carry out the estimation calculations and is similar in format to the visual encounter survey field datasheet above, will need to be developed.
Developing a search image for the cryptic nests is time-consuming. An alternative is to hire a local resident, who is already familiar with nests, to assist in transect counts. It is difficult to cut dedicated paths for nest surveys, so an alternative is to use existing game trails that are relatively straight. It is assumed (but not known) that existing game trails do not influence the occurrence of sengi nests. The calibration of nest counts for each form of Rhynchocyon and different forest types is beyond the scope of these protocols; it is assumed at this point that the method developed for the golden-rumped sengi is applicable to all Rhynchocyon.
There are several options for capturing giant sengis, depending on the objectives along with logistical, personnel and time restraints. If a specimen in-hand is needed for positive identification or biopsy, often the most effective method is to pay a bounty to local residents (especially if they normally capture animals for bush meat or traditional medicine). However, these specimens are often seriously injured or killed in the capture and transportation process and may not be fresh. Shooting sengis with a shotgun guarantees fresh tissue and a good voucher specimen. Rhynchocyon can not be captured in normal small mammal traps (e.g., Sherman or similar traps) because they generally are not attracted to bait (remember, they are antelope-like). Snaring can be effective, but it requires skill and the sengis usually break one or both rear legs. NETTING [88 KB PDF] is the most effective method of capturing un-injured animals. Sengis that become ENTANGLED in fishing nets strung vertically along the forest floor can be carefully and completely photographed, the tip of the tail removed for TISSUE [26 KB PDF], and then released. However, if it is suspected that a new or unique form or taxon has been found, at least one voucher specimen should be collected so that a careful study of the skin and skull can be made after it has been deposited and catalogued into a museum RESEARCH COLLECTION.
The data that need to be collected from live or dead animals include date, location (GPS latitude and longitude), collector, weight (bag + animal minus bag), sex (penis sheath is at the base of sternum and very obvious), and what tissues and photos were taken. Also, some kind of habitat description, including elevation above sea level. These data can be entered into a field notebook, but a standardized field datasheet will help ensure that all data are recorded.
The use of CAMERA TRAPS [221 KB PDF], usually set for other animals such as antelopes, have opportunistically captured IMAGES of giant forest sengis. However, because sengis occur at relatively low densities and do not usually use paths or trails, it is difficult to obtain enough captures for population estimation. However, even a single image can be used to determine presence, especially if the image is of good quality.
If dead or live sengis are captured, photographs (film or digital) should be taken. Make sure to completely photograph the pelage colouration and pattern on the sides, back, rump, and tail. Also, the forehead and sides of the head.
These protocols benefited from comments made by Clare FitzGibbon, Nike Doggart, and Francesco Rovero.