in 22.7% of the feeding observations. The following lists the range of preference observed in this study: 22.7% Jessenis polycarpa (Arecaceae), 7.9% Ocotea no. 1 (Lauraceae); 6.6% Tachigalia sp. (Caesalpiniaceae); 5.9% Beilschmiedia sp. (Lauraceae); 5.8% Ocotea no. 2 (Lauraceae); 4.8% unidentified; 3.5% unidentified; 3.5% Guatteria sp. (Annonaceae); 3.4% Annona sp. (Annonaceae); 2.4% unidentified; 2.0% unidentified; Guatteria sp. (Annonaceae); 1.9% Duguetia sp. (Annonaceae). Palacios & Rodríguez and Palacios et al. identified 62 species from 32 plant familias in the diet of a study group of black titis in the Estación Biológica Caparú in eastern Colombia. The preference values of each family, according to species utilized is as follow: Myristicaceae (25.02%); Euphorbiaceae (15.28%); Moraceae (14.37%); Arecaceae (8.68%); Caesalpiniaceae (7.85%) Rubiaceae (5.10%); Chrysobalanaceae (4.41%); Annonaceae (4.19%); Cecropiaceae (4.03%); Araceae (1.95%); Elaeocarpaceae (1.78%); Dilleniaceae (1.69%), Combretaceae (1.17%), Apocynaceae (1%); Aquifoliaceae (1%), Meliaceae (0.88%); Sapotaceae (0.85%); Burseraceae (0.81%); Apocynaceae (0.67%); Monimiaceae (0.23%); Piperaceae (0.22%); Melastomaceae (0.18%); Humiriaceae (0.13%) Celastracezae (0.11%); Myrtaceae (0.09%); Lecythidaceae (0.08%); Aquifoliaceae (0.07%); Sterculiaceae (0.07%); Solanaceae (0.05%); Clusiaceae (0.02%). The most important species consumed during six months in this study are listed as follows: 13.88% Sandwithia heterocalyx (Euphorbiaceae); 10% Virola melinonii (Myristicaceae); 8.35% Iryanthera ulei (Myristicaceae); 7.06 Oenocarpus bataua (Arecaceae); 6.53% Heterostemon conjugatus (Caesalbiniaceae); 5.10% Coussarea sp. (Rubiaceae); 5.02% Ficus sp. (Moraceae); 4.53% Iryanthera crassifolia (Myristicaceae); 3.84% Helicostylis tomentosa (Moraceae); 3.39% Brosimum rubescens (Moraceae). Reproduction The estrus cycle seems to be about 16 days, based on observations of 14 cycles of a tame, free-ranging female which lived at the Estación Biológica Caparú (Vaupés, Colombia). During the period of receptivity (which lasts 2–3 days) the black labia and the clitoris became swollen and hard and behavior changes occurred. During the receptive period the female became much more affectionate towards its human "parents", purred loudly, somewhat like a cat and crouched in a lordotic position when the base of the tail was stimulated. Contrariwise to her increased affection towards her perceived "family unit" (or two humans), she became much more aggressive than normal towards any "outsiders" (i.e. other human beings). During estrus the female tongue-flicked frequently, using this signal in two opposite contexts; she tongue-flicked as she attempted to approach her favorite humans while she also tongue-flicked as a preliminary to attach on other (especially male) humans. One recognizable pair at the Estación Biológica Caparú had been observed together for 14 years and was said to be still together at least four years more