Introduction

Saguinus is the most diverse of the Neotropical primate genera, with 13 –15 species and 33 recognized forms (Hershkovitz, 1977; Rylands et al., 2000). There have been detailed studies of the feeding ecology, social organization, and behavioral ecology of the majority of the extant Saguinus species. S. leucopus is notable for the deficiency of information about it (Snowdon and Soini, 1988; Calle, 1992; Vargas and Solano, 1996; Poveda, 2000, and Cuartas-Calle, 2001), and perhaps the least known is S. inustus. The latter occurs in southeastern Colombia west of the Andes, between the Río Mesay and the frontier with Brazil, and between the Ríos Guayabero-Guaviare and Caquetá. There is still no accurate delimitation of the eastern and western boundaries of its geographical range in Colombia (Defler, 2003). S. inustus also occurs in western Brazil, between the Rios Negro and Japurá and the Colombian border. Here we present preliminary data on some aspects of the ecology of this species on the lower Río Caquetá, Colombian Amazonia and briefly discuss the importance of conducting further research on its ecology in the region.

Subjects, Study Site and Data Collection

Mottled-face tamarins are small: head-body = 208–259 mm (n = 10) with a tail slightly longer, between 330 and 410 mm (n = 10) (Hershkovitz, 1977). On the lower Río Caquetá they are known as “hueviblanco” because the males have naked external genitalia and a white scrotal sac. Otherwise black, they have white patches of skin on each side of the muzzle, which makes them easily recognizable from a distance.

The study was carried out in the interfluvial forests adjacent to the lower Ríos Caquetá and Apaporis, Colombian Amazonia. Observations were made in the vicinity of Comeyafú (1°17′S, 69°34′W), a 19,000-ha indigenous reserve on the left margin of the Río Caquetá in the state of Amazonas (Fig. 1). We first met with the community in order to tell them the purpose of conducting the study and to select people to participate in the fieldwork. With the help of field assistants we found a group of five animals frequently seen near the community. Existing trails in the area were used to search for and follow them, and additional trails were cut to cover the group's known range. We observed the group from March to June 2003, which included the end of the dry season (early rainy season) and the rainy season. For a period of 18 days we attempted to follow the group for the entire day, but this was achieved on only five days because of the lack of a more extensive trail grid. Daily ranges were drawn on a map scale 1:1000 and were measured using the distances between consecutive group positions recorded during the day. Home range size was calculated using the convex polygon method, which although possibly overestimating the range (Albernaz, 1997), was the most appropriate because the quadrate method requires a comprehensive trail grid. Trees used as feeding sources were marked with colored flagging tape and later revisited to obtain botanic specimens for identification. Information on feeding by S. inustus was limited to the animal and plant species we saw them eat.

Results and Discussion

Foods

The mottled-face tamarins were seen to eat the fruits of 23 plant species from 12 families and 13 genera (Table 1). These plant species were spread through terra firma (primary and secondary forest) and flooded forest, and all, except for the liana Mendoncia ovata, were trees.

Table 1.

Fruits eaten by a group of S. inustus on the lower Río Caquetá, Colombian Amazonia.

Some of these fruits were typically found in the secondary forest. For instance, Mendoncia ovata was commonly seen growing in the low and high rastrojo, as was Inga thibaudiana. Other species, such as the two Pourouma spp., grow near large forest gaps and along the borders between the primary and secondary forest and the cultivated plots. Buchenavia sp. and two of the Inga species, on the other hand, were found only in the flooded forest.

As reported for other tamarins, S. inustus was also seen to eat small spiders, orthopterans, and ant larvae. These resources were commonly obtained as the tamarins foraged in the middle and lower levels of the forest, especially in the low rastrojo, where they were often seen moving about only 0.5 m above the forest floor.

Conservation Aspects

S. inustus is ranked as of Least Concern under the IUCN categorization (2001). It seems to be common around Indian villages along the lower Ríos Caquetá and Apaporis interfluvium. In general, one sees more tamarins in habitats that have been disturbed by human activities. Peres (1999), for example, found that densities of S. fuscicollis, S. mystax, and S. imperator were higher in areas subject to moderate to heavy hunting pressure than in those where hunting was minimal or non-existent. Density comparisons of the same set of species, and including S. geoffroyi, in protected and unprotected areas have shown that these species are more abundant and comprise a greater proportion of the total primate density in the latter (Freese et al., 1977; Soini, 1987). Nevertheless, some unprotected sites show densities as low or lower than those in protected sites (Muckenhirn et al., 1975; Freese et al., 1982). Plots cultivated by Indians, peasant crops, and small-scale logging have transformed many areas of the mottled-face tamarin's natural habitat. Slash-and-burn is the prevalent agricultural practice in the region, but can be considered of low impact in forest conversion only when human population densities are very low. Rural populations are growing considerably, concentrating their numbers in certain areas and making increasing demands on forest resources. The interfluvium between the Ríos Caquetá and Apaporis, east to the mouth of the Río Miriti, is a case in point, where a very large proportion of the region's indigenous population is concentrated (1.24 people/km²) and where numbers will continue to increase through immigration.

Much (60–70%) of the range of S. inustus in Colombia falls within the boundaries of indigenous reserves (Defler, 2003), along with smaller areas on the lower Río Caquetá settled by peasant families. It will be important to continue studying these tamarins and monitoring their densities along with current trends of forest clearing and other human activities, so that we can attain a better understanding of the ecology and conservation status of the species. These actions will, we hope, both continue our learning about the ecology of this interesting primate, and provide a mechanism to involve local people in joint conservation measures in their lands.