University of Los Andes

About: University of Los Andes is a education organization based out in Bogotá, Colombia. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 17616 authors who have published 25555 publications receiving 413463 citations.

Ecological strategies of woolly monkeys (Lagothrix lagotricha) at Tinigua National Park, Colombia.

Abstract: Information on the use of space, activity patterns, diet, and social interactions were recorded for a group of woolly monkeys (Lagothrix lagotricha) during 13 months at Tinigua National Park, Macarena, Colombia. In this region, fruit abundance changes throughout the year with a peak during March-April (beginning of the rainy season) and less fruit during September-November (end of rainy season). Woolly monkeys spent most of their time in mature forest where fruit abundance is higher than in opendegraded or flooded forests. Changes in habitat used by monkeys were coupled with changes in fruit supply across vegetation types. On an annual basis, woolly monkeys spent 24% of point samples locomoting, 36% resting, 36% feeding, and 4% on other activities. However, these proportions varied across the year depending on fruit availability. Based on instantaneous samples, the diet consisted mostly of fruits (60%), arthropods (23%), vegetative parts and flowers (17%), and other items (1%). Non-lactating females and juveniles spent more time eating insects than adult males and lactating females; however, significant differences between classes were detected only during the period of fruit scarcity. These differences are probably due to the high extent to which non-lactating females and juveniles were excluded from fruiting trees by males. The high proportion of arthropods in their diet is unusual for primates with large body size and is a possible factor influencing group cohesiveness in woolly monkeys. © 1994 Wiley-Liss, Inc.

The CIDA variability survey of Orion OB1. I. The low-mass population of Ori OB1a and 1B

Abstract: We present results of a large-scale, multiepoch optical survey of the Orion OB1 association, carried out with the QUEST camera at the Venezuela National Astronomical Observatory. We identify for the first time the widely spread low-mass, young population in the Ori OB1a and OB1b subassociations. Candidate members were picked up by their variability in the V band and position in color-magnitude diagrams. We obtained spectra to confirm membership. In a region spanning ~68 deg2, we found 197 new young stars; of these, 56 are located in the Ori OB1a subassociation and 141 in Ori OB1b. The spatial distribution of the low-mass young stars is spatially coincident with that of the high-mass members but suggests a much sharper edge to the association. Comparison with the spatial extent of molecular gas and extinction maps indicates that the subassociation Ori OB1b is concentrated within a ringlike structure of radius ~2°(~15 pc at 440 pc), centered roughly on the star Ori in the Orion belt. The ring is apparent in 13CO and corresponds to a region with an extinction AV ≥ 1. The stars exhibiting strong Hα emission, an indicator of active accretion, are found along this ring, whereas the center is populated with weak Hα-emitting stars. In contrast, Ori OB1a is located in a region devoid of gas and dust. We identify a grouping of stars within a ~3 deg2 area located in Ori OB1a, roughly clustered around the B2 star 25 Ori. The Herbig Ae/Be star V346 Ori is also associated with this grouping, which could be an older analog of σ Ori. Using several sets of evolutionary tracks, we find an age of 7–10 Myr for Ori OB1a and of ~4–6 Myr for Ori OB1b, consistent with previous estimates from OB stars. Indicators such as the equivalent width of Hα and near-IR excesses show that the number of accreting low-mass stars decreases sharply between Ori OB1b and Ori OB1a. These results indicate that although a substantial fraction of accreting disks remain at ages ~5 Myr, inner disks are essentially dissipated by 10 Myr.