Neotropical 12(2).text.2.indd Neotropical Primates 12(2), August 2004 55 role of predation risk, proximity to feeding sites, and ter- ritorial defence. Ethology 105(12): 1035–1051. Heymann, E. W. 1995. Sleeping habits of tamarins, Sagui- nus mystax and Saguinus fuscicollis (Mammalia, Primates, Callitrichidae), in northeastern Peru. J. Zool., Lond. 237: 211–226. Huang, C., Wei, F., Li, W., Li, Y. and Sun, R. 2003. Sleep- ing cave selection, activity pattern and time budget of white-headed langurs. Int. J. Primatol. 24(4): 813–824. Jones, C., Jones, C. A., Jones Jr., J. K. and Wilson, D. E. 1996. Pan troglodytes. Mammalian Species 529: 1–9. Liu, Z. H. and Zhao, Q. K. 2004. Sleeping sites of Rhi- nopithecus bieti at Mt. Fuhe, Yunnan. Primates 45(4): 241–248. Lorenzi, H. and Souza, H. M. 1996. Palmeiras no Brasil: Nativas e Exóticas. Nova Odessa, São Paulo. Miranda, G. H. B. and Faria, D. S. 2001. Ecological aspects of black-pincelled marmoset (Callithrix penicillata) in the cerradão and dense cerrado of the Brazilian central plateau. Brazil. J. Biol. 61(3): 397–404. Spironello, W. R. 2001. The brown capuchin monkey (Cebus apella): Ecology and home range requirements in central Amazonia. In: Lessons from Amazonia: The Ecol- ogy and Conservation of a Fragmented Forest, R. O. Bier- regaard Jr., C. Gascon, T. E. Lovejoy and R. Mesquita (eds.), pp.271–283. Yale University Press, New Haven, Connecticut. Stevenson, M. F. and Rylands, A. B. 1988. The genus Cal- lithrix. In: Ecology and Behavior of Neotropical Primates, Vol. 2, R. A. Mittermeier, A. B. Rylands, A. F. Coimbra- Filho and G. A. B. da Fonseca (eds.), pp.131–222. World Wildlife Fund – US, Washington, DC. Zhang, S. Y. 1995. Sleeping habits of brown capuchin mon- keys (Cebus apella) in French Guiana. Am. J. Primatol. 36: 327–335. ON THE OCCURRENCE OF THE OWL MONKEY (AOTUS AZARAI ) IN CERRO LEON, CHACO, PARAGUAY Juan Manuel Campos, Ivon Benítez Dennis A. Meritt Jr. The owl monkey, Aotus azarai, has been described from various parts of northern Argentina and Paraguay (see Stall- ings, 1984, 1985; Fernandez-Duque et al., 2001). One of the earliest reports is found in Kerr (1950), in a descrip- tion of a pioneering exploration of the Chaco from 1889 to 1891 along the Río Pilcomayo. The most recent review de- tailing this primate’s distribution in northern Argentina and Paraguay is provided by Neris et al. (2002). In the northern Paraguayan Chaco, they describe low canopy scrub forest and high canopy forest as suitable Aotus habitat. They de- scribe its activities in Paraguay as mainly crepuscular, al- though sometimes active on cloudy or overcast days. During fieldwork on the Chacoan peccary, Catagonus wagneri, in the Chaco Central in the austral spring of 2003, an opportunity presented itself to investigate two locations in the extreme north and west of the country. One of these was the Defensores del Chaco National Park and its unusual land formation, Cerro Leon. These are the only places one may find rocks of any type in the entire Chaco region. The observation reported here provides an additional location for Aotus azarai in Paraguay, verifying that it is capable of survival and reproduction in a xero- phytic habitat. Defensores del Chaco and Cerro Leon are located from 19°45’ to 20°45’S, and 59°30’ to 61°10’W in the Depart- ment of Alto Paraguay and a small portion of Boquerón. Av- erage annual rainfall is from 500 to 800 mm, and tempera- ture ranges from 0–42°C. The park has a xerophytic fauna and flora, locally referred to as seca—literally dried up, arid and barren. At the time of our visit the region had been suf- fering from an extended period of extreme drought. While visiting Cerro Leon during late October of 2003, we observed an adult pair of Aotus azarai with a very young infant in a candelabra tree cactus (Cereus sp.), near a foot trail leading to the summit of the highest ridge. The day was cloudless, with bright sun and an ambient tempera- ture of about 40°C. The adults were alert but not obvi- ously alarmed; the infant was clinging to an adult’s neck and upper back. It was movement by the adults that clued us to their presence. There were no vocalizations, and we saw no aggressive behavior, such as the typical rapid and jerky movement of the head and upper body. We observed the pair and their offspring closely for more than twenty minutes, after which time—and perhaps in response to our attempts to take photographs—the trio moved rapidly out of the tree cactus, into the adjacent shrubby vegetation and out of sight. Given the steepness of the hillside and the density of the thorny vegetation, it was not possible to follow them. The environment in which this family group of Aotus was found is a stunted, thorny, dry forest region with no large trees or emergent vegetation, except for occasional Palo Borracho trees (Chorisia insignis) in the infrequent and somewhat more humid lowland areas. The “soil” at Cerro Leon is largely broken rocks of various sizes, making human movement and climbing noisy and extremely dif- ficult. The large amount of rock present at this site is un- characteristic of the Chaco—a flat, plain-like habitat that is without stone or rocks of any type. All stone and rock used there for road building or construction is either im- ported or brought from the eastern and southern part of the country. Chaqueños tell the folk story of the Chaco being a great inland sea whose bottom was devoid of rock or stone. Plant growth is precarious; rainfall is limited and subject to rapid runoff, and there is little natural shade. Overall the vegetation rarely exceeds 3 m, with the excep- tion of the occasional tree cactus (Cereus sp.) or Palo Bor- racho tree. Given these circumstances, we were unable to determine whether or not these owl monkeys were demonstrating Neotropical Primates 12(2), August 200456 cathemeral activity. However, given the nature of the habi- tat, and the obviously restricted food resources, one could logically conclude that such activity was likely in order to ensure survival. A careful survey of the habitat revealed a number of small tree holes, cactus tangles, and other suitable retreats of sufficient size to accommodate an adult Aotus or a small family group. Those which we investigated did not contain any owl monkeys or other mammals, nor did they show any signs of recent use, such as food remnants, waste, hair, or rub marks. This is the furthest north that we have observed Aotus in the Chaco, although Handen et al. (1994) documented the presence of owl monkeys in a location identified as Area II in the northernmost department, the Chaco. Mul- tiple observations of a pair with and without offspring be- tween 1989 and 1997 have been made in a farming area outside of the Mennonite colony of Neuland in the Chaco Central (D. Meritt Jr., unpublished observation: it is un- clear if they were of the same pair, their offspring or un- related animals). The habitat is considerably different in that location, as are the potential food resources. Neuland is part of the Mennonite colony located near Filadelphia in the Chaco Central. It is typical Chaco, without rocks and with dense thorny shrubs and an abundance of trees. The region is several hundred kilometers south and west of Defensores del Chaco and Cerro Leon, and consider- ably wetter. Redford and Eisenberg (1992) report the presence of infant Aotus in the Paraguayan Chaco in August, Sep- tember, and October. This corresponds with the present observation and those mentioned above in Neuland (D. Meritt Jr., unpublished). A number of authors have previ- ously reported the presence of Aotus in large tree cacti, including Rathbun and Gache (1980), Stallings (1984, 1985), Stallings and Mittermeier (1983) and Stallings et al. (1989). At the time of year when this observation was made, there were no fruits or seeds present in or on the vegetation and no flowers to be seen. There were a number of small lizards and infrequent small birds, but no large flying insects. A search for Aotus droppings to try to determine possible food sources was unsuccessful. Acknowledgments: The authors are grateful for permission to carry out scientific studies in Paraguay through the cour- tesy and authority of the Ministro, Secretaria del Medio Ambiente. Partial support for this work was provided by the Chacoan Peccary Species Survival Plan (SSP) of the Ameri- can Zoo & Aquarium Association (AZA) through funds provided by M. Scott for “Proyecto Tagua”. Juan Manuel Campos, DVM and Ivon Benítez, Proyecto Tagua Toledo, Chaco, Paraguay, and Dennis A. Meritt Jr., Department of Biological Science, DePaul University, 2325 North Clifton Avenue, Chicago, IL 60614, USA. E-mail: . References Fernandez-Duque, E., Rotundo, M. and Sloan, C. 2001. Density and population structure of owl monkeys in the Argentinean Chaco. Am. J. Primatol. 53: 99–108. Handen, C. E., Unger, J. and Meritt, D. 1994. Current status of the tagua (Catagonus wagneri ) in Paraguay. Zool. Garten N. F. 64(6): 329–337. Kerr, J. G. 1950. A Naturalist in the Gran Chaco. Syndics of Cambridge University Press, Boston. Neris, N., Colman, F., Ovelar, E., Sukigara, N. and Ishii, N. 2002. Kato’s Data Book on Larger Mammals of Paraguay — Distribution, Population Trends, and Utilization. Secretaria de Ambiente, Madame Lynch 3.500 C/Primer Presidente, Asunción, Paraguay. Rathbun, G. B. and Gache, M. 1980. Ecological survey of the night monkey, Aotus trivirgatus, in Formosa Province, Argentina. Primates 21: 211–219. Redford, K. H. and Eisenberg, J. F. 1992. Mammals of the Neotropics: The Southern Cone. Volume 2. Chile, Argentina, Uruguay, Paraguay. The University of Chicago Press, Chi- cago. Stallings, J. R. 1984. Status and conservation of Paraguayan primates. Master’s thesis, University of Florida, Gainesville. Stallings, J. R. 1985. Distribution and status of primates in Paraguay. Primate Conserv. (6): 51–58. Stallings, J. R. and Mittermeier, R. A. 1983. The black-tailed marmoset, Callithrix argentata melanura, recorded from Paraguay. Am. J. Primatol. 4: 159–163. Stallings, J. R., West, L., Hahn, W. and Gamarra, I. 1989. Primates and their relation to habitat in the Paraguayan Chaco. In: Advances in Neotropical Mammalogy, K. H. Redford and J. F. Eisenberg (eds.), pp. 425–442. Sandhill Crane Press, Gainesville, Florida. THE USE OF CAMERA-TRAPS IN A SURVEY OF THE BUFF-HEADED CAPUCHIN MONKEY, CEBUS XANTHOSTERNOS Maria Cecília Martins Kierulff, Gabriel Rodrigues dos Santos Gustavo Canale, Carlos Eduardo Guidorizzi Camila Cassano Introduction The buff-headed or yellow-breasted capuchin monkey (Cebus xanthosternos) is endemic to a restricted region of the Atlantic Forest of eastern Brazil, one of the richest and most threat- ened ecosystems in the world (SOS Mata Atlântica et al., 1998; Myers et al., 2000). Due mostly to habitat destruction and hunting, this once-abundant species is rapidly declining in number, and is one of the 25 most endangered primates in the world (Mittermeier and Konstant, 2000; Konstant et al., 2002; Mittermeier et al., in prep.). In 2002 we began a survey of the remaining yellow-breasted capuchin monkey populations throughout its original distribution, in order to establish the conservation status of the species and to iden- tify the threats to its survival.