Field Report: Homopus signatus
In a part of 1999 and 2000, I have worked
on setting up a field project on the
this first fieldwork period, two Americans, a German, and two Dutch, including
myself, participated. In the end of the period, two South Africans from the
University of the
The study of Homopus is a private initiative,
although important input from the University of the
H. s. signatus is found in northwestern
Although H. s. signatus occupies a harsh
area, there is nevertheless a number of threats to the survival of this
herbivorous species on the long term. First of all, the species has a
relatively small distribution area, emphasizing its fundamental vulnerability.
Additionally, the natural habitat is threatened by mining activity (mainly
copper and granite), overgrazing and road traffic. As a result of mining
activity, habitat is being destroyed, and mines furthermore produce dust,
decreasing plant growth, and therefore reducing food availability for
herbivores. Overgrazing by goats and sheep occurs mainly in the communal areas,
where increasing numbers of - less selective - goats are kept due to increasing
drought. Overgrazing reduces food availability for herbivorous species, among
others as a result of shifts in species composition of the vegetation,
increasing the relative abundance of unpalatable species. Traffic, finally,
causes many road causalities. Potential threats are furthermore droughts due to
climatic change (rainfall has decreased during the past decades) and captive
husbandry. Huge amount of money are paid for H. s. signatus in the commercial
wildlife trade. So far
In case there may be a moment that survival of H. s. signatus becomes critical, wildlife management measures will need to be taken. This is only possible with sufficient knowledge on the species. For instance, a reserve can only be founded when it is known whether the required food items are available in that area, as well as sites required for reproduction, hibernation, aestivation, when the size of the area will meet the species’ demands, et cetera. In order to have this knowledge, research is necessary. One part of the research can be conducted in captivity (this is also carried out within the Homopus Research Foundation, but for some aspects research in the wild is inevitable. Field research on H. s. signatus can furthermore provide insight in suitability of evaluated research methods for small tortoise species in rocky areas, since hardly any research has been carried on such species until now.
In order to gather data on population characteristics and activity of the species, a 36,000 m2 field site was chosen in August 2000. This area was subdivided in microhabitats, such as relatively leveled habitat with many flowering herbs (in August), rocky hill, extremely steep stone slabs, et cetera. All these microhabitats were methodically inspected for tortoises, during six weeks. Morphometrics, mass, sex, scute annuli number, presence of ticks, supernumeral scutes and shell damage, exact location in the field work area, et cetera was recorded. Moreover it was noted in what microhabitat each tortoise was located, and in what activity it was engaged. When a tortoise was hiding, details about the hiding place were written down. Finally the soil temperature was measured, as well as whether a tortoise was sitting in the sun or in the shade, and the current weather condition. Obviously all qualitative data were recorded as predefined classes, to allow later (statistical) analyses. Fecal samples were collected, together with a reference collection of all plant species that potentially could be food items, in order to determine the diet of the species. Female tortoises were x-rayed for reproductive data. Upon completion of data collection from a specimen, it was uniquely marked by means of small dots of black nail polish, and identification 35 mm color slides were made, to allow identification during later studies.
An average of ten tortoises was followed throughout the fieldwork period by means of thread-trailing. Thread cocoons were fixed on the shell using surgical adhesive tape, allowing tracking of each specimen every 24 hours, to gather information on path followed, distance moved and new location. Every 24 hours the cocoon was renewed.
Throughout the fieldwork period, over eighty tortoises were located, with approximately the same number of males and females. The specimens turned out not to be homogeneously distributed in the area, but it seemed as if they had a preference for specific microhabitats. The ultimate adaptation of H. s. signatus to its rocky habitat was clearly illustrated when specimens entered steep rock slabs that were almost impossible barriers to the researchers. The tortoises were also very well camouflaged in their habitat, making it difficult to locate them, especially in combination with their shy nature. Many specimens were infected by ticks.
H. s. signatus was mainly active during the warmest hours of the day. During the night, and during days with bad weather, they hide in rock crevices or in other hiding places. Differences were noticed, possibly indicating preferences for specific types of hiding places. The difference tortoises moved on a day varied greatly. On an average, tortoises moved several tens of meters per day. For none of the studied aspects there appeared to be differences between males and females.
Scute annuli have been described in literature as a suitable method to determine the age of many tortoise species in the wild. This needs to be proved for H. s. signatus too, before scute rings can be counted as if they were years. It will be tried to examine this in a follow-up project on H. s. signatus in 2001. At this moment, it can only be concluded that scute rings were relatively easily counted, and that the maximum scute ring number counted was fourteen, in an old female.
The collected fecal samples and the x-ray photographs still have to be analyzed entirely, and therefore it is impossible to provide results in the current field report.
As mentioned in the introduction, the described research on H. s. signatus is part of an ongoing study on the ecology of H. s. signatus and H. s. cafer. Preparations for a follow-up field study on H. s. signatus, to be carried out in 2001, are well underway. This project will be carried out by two Germans, a Swedish researcher, a South African and myself. This study will also depend entirely on donations. In that respect I would like to ask you to consider making a donation too. Costs consist mainly of costs for research materials, whereas travel expenses for travelling to South Africa, as well as housing and food, and a significant part of the research materials will be paid for by the researchers themselves. The advantage of small scale projects like this one is that even small donations make a large difference. The total budget of the study is only a few thousands of dollars. Please contact me in case you would like to receive details about how to make a donation. Alternatively, donations can be made through the Tortoise Trust.
Additions to the information provided here can be found on the internet site of the Homopus Research Foundation, http://www.homopus.org. From this site the proposals for the research projects can be downloaded. Naturally it is also possible to contact me directly in case you have any questions.
This study was permitted by Northern Cape Nature Conservation (permit numbers 137/99, NNO 1/10/2 and 084/99, NNO 3/5/4). Sincere thanks to the participants in the field, Mark Klerks, Chris Hobson, Fabian Schmidt and Tom Licitra, and Ernst Baard, Retha Hofmeyr, Brian Henen and Nicolas Bayoff, who commented on the project proposal, improving it greatly. Additionally, Retha Hofmeyr and Brian Henen have provided important information on reproduction, by performing ultrasound scans during the fieldwork. The project would not have been possible without donations of money (Dutch Foundation for the Advancement of Herpetology (Stichting tot Bevordering van de Herpetologie), Tortoise Trust USA, Dutch Turtle/Tortoise Society, private turtle enthusiasts), and research materials (Röbke Agenturen (Netherlands), Barbour Threads (Netherlands), South Africa OnLine, Roland’s Uitspan (South Africa), Microscoop Service Rob Engelhard (Netherlands), Cellpack bv (Netherlands)). The offer to use facilities was gratefully accepted from Springbok Hospital (South Africa), Wageningen University and Utrecht University (both Netherlands). Ernst Baard (South Africa) has been encouraging us throughout the process of realizing the project.
Victor J.T. Loehr
3402 EC IJsselstein