Mammal presence along the Mascoitania Stream was monitored using a series of track traps over a period of one week. Paca and ocelot tracks were most frequently recorded. Environmental factors along the stream bank were assessed and a negative correlation demonstrated between gradient and number of tracks recorded at each site. Results provide a baseline for monitoring species presence and activity in the future as eco-tourism and deforestation begin to impact on the environmental health of the Madre de Dios region.

River-banks and streams provide ideal locations for monitoring mammal activity within lowland rainforests. They provide essential watering holes for many mammals whose trails are easily identified at crossing points. The exposed nature of the river course and the substrate along its banks facilitate the recording of tracks. The discrete nature of many mammals coupled with their nocturnal or crepuscular activity often limits observation of them, so by utilising the tracks they leave behind our knowledge of their movements can be better understood. Additionally, rivers within rainforest habitats have frequently been associated with collpars, where clay-rock cliffs offer a focal point for animal visitations.

The aim of this short research project was to investigate the prevalence of mammal species around the Mascoitania stream, Madre de Dios region, Peru. The data collected may subsequently be used as a baseline indicator of species abundance in the area. Future monitoring may then highlight the influence that forest regeneration, and potentially, tourist impact, will have on the mammal population.

In addition to mammal prevalence we recorded the influence of environmental factors on the mammal distribution down the length of the stream. Our hypothesis was that mammal occurrence is evenly distributed along the stream bank.

A 300m stretch of the Mascoitania stream was measured along the waterline of the north bank from its confluence with the Madre de Dios river up to the point where the Union trail crosses it (GPS 19L 0240097;8584214 to 0239955;8584228). Every 10m a 1m squared area of stream bank was cleared of stones and debris. The substrate of these areas were either sand, clay or soil, and we recorded which type it was. If necessary we imported sand to the area. They were then watered and the surface smoothed to form our 30 trap tracks.

Over a period of 7 days form 30th July to 5th August 2005 each trap was visited every morning, and the number of tracks was recorded and the species identified. Digital photos were taken to aid identification. The number of individuals that passed through the trap could not be identified.

The environmental and topographic features of the river-bank were recorded for analysis with the mammal trap data. River depth was measured at the centre of the stream. Gradient of the quadrant was measured using a clinometer to give a measure of the bank steepness. We also compiled an exposure score for each trap from an average of density and height vegetation measurements. A segmented toilet tube was used to assess the proportion of vegetation density both above the trap and horizontal to the bank, while the average height of surrounding vegetation was estimated. In addition the presence of animal and human trails in the area was noted. Although there are many other factors that we could have measured, these were the ones that we believed were most likely to influence mammal presence.

The high number of paca recordings is not incidental. Paca are commonly found in open river bank habitats. Since ocelot are the main predator of the paca, the similarly high occurance of ocelot tracks might also be expected.

The negatively correlated relationship between number of tracks and gradient of bank could be expected as access to the river via steep slopes is likely to be more hazardous and less desirable for most animals. As an aside interestingly we had the highest number of tracks in trap 30 next to the Union trail suggesting mammals prefer to use existing paths where possible.

Why were river depth and exposure not important factors? River depth does not change dramatically along the 300 metre stretch so immediately reduces significance and secondly depth does not necessarily affect animals that come to drink rather than cross. Exposure may be important to some species but less so to nocturnal mammals or to predators.

If we were to continue monitoring it would be interesting to explore whether differentiation can be made of factor importance between prey and predator species. We would also like to set up a camera trap at site 21 as on both occasions when tapir tracks were found it was at this precise location and there was also evidence of peccaries next to but not within our trap. It is possible that this is a new collpa site since the bank is clay substrate.

As little as a week of monitoring has provided a good overview of mammal presence around the stream and a baseline for future monitoring. Information collected on the environment could also be used for long term monitoring river and land changes. Finally the project has highlighted some behavioural aspects of mammal activity such as the use of existing trails and possible discovery of a previously unidentified collpa.