The hippopotamus amphibius is presently considered "vulnerable" by the IUCN « Hippo Specialist Group », they are listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Today, hippopotami range over most of sub-Saharan Africa. The estimated total number of hippopotami in Africa is in the order of 125'000-148'000 individuals. The species is believed to face an overall decline of 7 to 20%, mainly due to habitat loss, habitat fragmentation and poaching.
Some of the most significant threats to wildlife today are health related. Especially for threatened and endangered species, or such that might become threatened in the foreseeable future, baseline data on diseases, their spread and consequences are a key factor for sustainable management. For Gabon like for most Western African countries there is no good area-wide data concerning hippopotami numbers or their health status.
Due to the dense forests in this country, hippopotami are only found locally; population is thought to number around 250 individuals. The common hippopotamus is fully protected by Gabonese law (law of July 22nd 1982); hunting, capturing, and trading of hippopotami or their body parts are specifically prohibited on the entire territory. Yet poaching for meat as well as habitat fragmentation is thought to constitute the biggest threat for this species in Gabon.
The Gamba Complex of Protected Areas, where this study was performed, is situated in south-western Gabon. The complex, a protected area network of 11'320 km² shows a mosaic of very diverse habitat types, the equatorial climate is hot and humid and the hydrologic landscape is a complex network of lagoons, rivers and different types of marshes. It is said to be the region with the highest density of hippopotami in the Gabon.
The overall aim of this study was the assessment of the conservation status of the hippopotamus in the Gamba complex of protected area as the basis for effective protection and management strategies as well as the investigation of the possibility of extracting parasites and assessing parasite type from faeces of the common hippopotamus. The specific objectives were firstly the assessment of the Hippopotamus population in the complex as well as the assessment of the key habitats for daily resting and the nightly foraging; secondly, the testing of a useful non-invasive method for the evaluation of gastrointestinal parasites of free ranging hippopotami.
Researches were performed during dry seasons between the beginning of June and the beginning of October in 2010 and 2011. Regions in the Gamba complex appearing suitable for hippopotamus in respect to water resources and nearby grasslands were investigated as well as areas known to harbour hippopotami. In total we covered an area of about 1500 km in 12 different regions. Hippopotami seen in the water were counted, on land all signs testifying for the presence of the animals were recorded, be it the hippopotamus lawns, foot prints, faeces or remain of the animal itself for example bones.
For the evaluation of potentially important habitat variables, different parameters (water depth, current and temperature) were recorded in places where hippopotami occurred. Water depth and temperature were measured using an echo-sounder. The current was measured by anchoring and using a folding rule and a floater.
Over 1100 GPS points showing the presence of hippopotami were recorded.
Water depth did not exceed 3.2 m where hippopotami were detected, invariably of the region water temperatures always was 26°C ±1°C and the maximum current measured near hippopotami was 0.5m/s. 77 faecal samples were collected. About 10 - 15 g of faecal material was fixed using a dilution of 15g sodium acetate in 20ml acetic acid, 40 ml formalin (37 %) and 925ml tap water. Each sample was analysed separately using flotation as well as sedimentation to extract the different parasitic stages. We found parasites in 70 out of the 77 samples collected. In the sediment of 61 samples eggs of fasciola spp. could be demonstrated. 42 were positive for Eimeria, while four samples contained larvae of Strongyloides, one of which belonged to the genus Dictyocaulus. To the best of the authors' knowledge, no representative of the genus Dictyocaulus has ever been described as a parasite infesting hippopotami before. One sample contained a deformed egg that presumably belongs to a nematode.1 oocyte from Isospora was found. In 13 of the samples eggs of mites (Acarina) were identified. The results of this study have been communicated to all local and international stakeholders i.e. organisations such as the WWF, WCS, the local NGO H2O and the Gabonese centre for research CENAREST to support the long term conservation and management of the hippopotamus in the Gamba complex.
Rietmann, S; Walzer, C
(2014): Parasitological examination of common hippopotamus (Hippopotamus amphibius) faeces in the Gamba Complex of Protected Area in Gabon.
Wien Tierarztl Monat (101), 3-4 66-73.