STUDY SITE AND SUBJECTS
A group of initially five and later four moustached tamarins, Saguinus mystax mystax, was observed for 345 hr between June 15 and September 5, 1990 in the study area of the
Estación Biológica Quebrada Blanco (EBQB). The EBQB is located on the right bank of the Rio Blanco, a tributary of the Rio Tahuayo, at about 4'40'S, 73'W, in northeastern Peru. The study area is characterized by high-ground, non-inundatable rain forest standing on a slightly undulating terrain ["bosque de colina (ENCARNACION, 1985) or "tierra firme"] and interspersed with small swampy areas ["palmal de altura" (ENCARNACION, 1985)]. The area is drained by the white-water Quebrada Blanco and by the clear-water Quebrada Choroyo. The altitude of the study site is about 110 m above sea level. Annual rainfall at the nearest meteorological station (Tamshiyacu, about 40 km northwest of the EBQB) averaged about 3,000 mm between 1980 and 1989; the period from June to September is relatively dry with July and August receiving less than 200 mm rainfall on average.
Observations of the study group were generally conducted from the early morning when the tamarins left their sleeping site until the afternoon when the tamarins retired. While systematic data on activity patterns and home-range use and other aspects of the tamarins' behaviour were collected at 5-min intervals, unusual events like geophagy were recorded with an ad libitum sampling technique, describing the behaviour and the circumstances as detailed as possible.
ANALYTICAL METHODS
Soil samples were collected directly from the sites where the moustached tamarins had been feeding and were stored in Nalgene bottles. Upon return from the field, the samples were kept at 8 - 10'C in a refrigerator until they were analyzed.
All elements were measured by x-ray fluorescence (XRF) techniques using a Philips PW1480 automated sequential spectrometer. Data processing was controlled by the Philips X40 software package. For calibration of major and trace elements we used a wide variety of international geochemical reference samples, which cover most typical rock compositions (from the US Geological Survey, the International Working Group "Analytical Standards of Mineral, Ores, and Rocks," the National Research Council Canada, the Geological Survey of Japan etc.).
The glass disks used for both the major and trace elements determination were prepared using mixtures of prefused lithium tetraborate, lithium metaborate, and LiF. For the dilution, 6.0 g of this flux and 1.0 g of the soil powder were weighed into platinum-gold crucibles and fused for 30 min at 1,150'C. The melt was poured into pre-heated, polished 40 mm-diameter molds. All elements were analyzed using a 3-kW rhodium target x-ray tube for sample excitation. Pulse-height selection was used to reduce interference from higher 9rder spectral lines and background noise.
