For arboreal primates, ground use may increase dispersal opportunities, tolerance to habitat change, access to ground-based resources, and resilience to human disturbances, and so has conservation implications. We collated published and unpublished data from 86 studies across 65 localities to assess titi monkey (Callicebinae) terrestriality. We examined whether the frequency of terrestrial activity correlated with study duration (a proxy for sampling effort), rainfall level (a proxy for food availability seasonality), and forest height (a proxy for vertical niche dimension). Terrestrial activity was recorded frequently for Callicebus and Plecturocebus spp., but rarely for Cheracebus spp. Terrestrial resting, anti-predator behavior, geophagy, and playing frequencies in Callicebus and Plecturocebus spp., but feeding and moving differed. Callicebus spp. often ate or searched for new leaves terrestrially. Plecturocebus spp. descended primarily to ingest terrestrial invertebrates and soil. Study duration correlated positively and rainfall level negatively with terrestrial activity. Though differences in sampling effort and methods limited comparisons and interpretation, overall, titi monkeys commonly engaged in a variety of terrestrial activities. Terrestrial behavior in Callicebus and Plecturocebus capacities may bolster resistance to habitat fragmentation. However, it is uncertain if the low frequency of terrestriality recorded for Cheracebus spp. is a genus-specific trait associated with a more basal phylogenetic position, or because studies of this genus occurred in pristine habitats. Observations of terrestrial behavior increased with increasing sampling effort and decreasing food availability. Overall, we found a high frequency of terrestrial behavior in titi monkeys, unlike that observed in other pitheciids.

Neotropical Entomology 37(6): 641-645 (2008) El Primero que Llegue, Primero se Sirve: Comportamiento "Sentarse y Esperar" en los Escarabajos del Estiércol en la Fuente de Excremento de Primate RESUMEN -Los Escarabajos del estiércol (Coleoptera: Scarabaeidae: Scarabaeinae) compiten intensamente por excrementos, un recurso escaso por el cual muchas especies forrajean en el sotobosque en bosques tropicales. En este artículo describimos el comportamiento particular de una especie de escarabajo del estiércol, Canthon aff. quadriguttatus (Olivier), asociado a dos especies de primates en Perú. Observamos esta especie de escarabajo en la región genital y anal de monos "tocones", Callicebus brunneus (Wagner), y subsecuentemente cayendo con excrementos que los monos defecaron. De manera similar, observamos individuos de esta especie de escarabajo asociados a monos "huapos", Pithecia irrorata irrorata (Gray). Mediante un comportamiento de "sentarse y esperar" a la fuente, C. aff. quadriguttatus llega primero a la fuente de excremento y aparentemente supera a otras especies de escarabajos en la competencia por el mismo recurso. Este artículo representa el primer registro de C. aff. quadriguttatus en asociación a dos especies de primate en la Amazonía del sureste de Perú. Discutimos este comportamiento en el contexto de competencia y distribución de recursos y especulamos sobre la razón por la cual este escarabajo está asociado a ambas especies de primates. PALABRAS-CLAVE: Competencia, distribución de recursos, foresia, especialización de nichoABSTRACT -Dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae) compete intensively for dung resources, and most species forage in the understory. Here, we describe the unique behavior of one dung beetle species, Canthon aff. quadriguttatus (Olivier), associated with two species of monkeys from Peru. We observed this beetle species on the genital and anal regions of the brown titi monkey, Callicebus brunneus (Wagner), and subsequently falling with dung as the monkeys defecated. The same association was also observed with the bald-faced saki monkey, Pithecia irrorata irrorata (Gray).Using the "sit and wait" at the source behavior, C. quadriguttus may arrive fi rst at the dung resource, possibly out-competing other dung beetle species. This paper is the fi rst report of this behavior for C. aff. quadriguttatus on the brown titi monkey and bald-faced saki monkey from southeastern, Amazonian Peru. We discuss this behavior in the context of competition and resource partitioning, and also speculate as to why C. aff. quadriguttatus has been found on both monkey species.

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