Terrestrial behavior in titi monkeys (Callicebus, Cheracebus, and Plecturocebus) : potential correlates, patterns, and differences between genera

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 We collated published and unpublished data from 86 studies across 65 localities to assess titi monkey (Callicebinae) terrestriality.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

Antiphonal four-part synchronized chorusing in a Neotropical wren

Plain-tailed wrens (Thryothorus euophrys) live in groups that sing synchronized choruses, the contributions of females and males alternating with each other in cycles, within which each sex sings two of the four parts, the whole achieving near perfect synchrony. As each bird has a repertoire of ca 20 phrases of each type, the synchrony also requires them to choose the same type at the same time as others of their sex. Songs can last up to 2 min, during which individuals join in and drop out. This must be one of the most complex singing performances yet described in a non-human animal

A comparative study of song form and duetting in neotropical <em>Thryothorus</em> wrens

The traditionally-defined wren genus Thryothorus is notable for its diversity of singing styles with some species producing highly coordinated duets or choruses in various formats while, at the other extreme, songs are performed almost exclusively by males. In this comparative study, we document the singing styles of almost all of the 27 or so species in this group, relating these to a molecular phylogeny in an effort to identify the conditions that have led to the evolution of duetting and chorus singing. In a previous study, we used molecular data to demonstrate that Thryothorus is actually paraphyletic, leading us to propose its splitting into three genera ( one newly described) in addition to Thryothorus. Here we show that most species within each of these four genera usually sing with the same style, and that these styles tend to differ between the genera. We also show that a few species have songs that differ markedly from those most typical of their genus. We argue that these exceptional cases will provide important insights into the origins of duetting behavior, and tentatively suggest factors that may have played a role in determining the extent to which male and female birds combine their vocalizations together.</p

Duetting Patterns of Titi Monkeys (Primates, Pitheciidae: Callicebinae) and Relationships with Phylogeny

Long-range vocal communication in socially monogamous titi monkeys is mediated by the production of loud, advertising calls in the form of solos, duets, and choruses. We conducted a power spectral analysis of duets and choruses (simply “duets” hereafter) followed by linear discriminant analysis using three acoustic parameters—dominant frequency of the combined signal, duet sequence duration, and pant call rate—comparing the coordinated vocalizations recorded from 36 family groups at 18 sites in Bolivia, Peru and Ecuador. Our analysis identified four distinct duetting patterns: (1) a donacophilus pattern, sensu stricto, characteristic of P. donacophilus, P. pallescens, P. olallae, and P. modestus; (2) a moloch pattern comprising P. discolor, P. toppini, P. aureipalatii, and P. urubambensis; (3) a torquatus pattern exemplified by the duet of Cheracebus lucifer; and (4) the distinctive duet of P. oenanthe, a putative member of the donacophilus group, which is characterized by a mix of broadband and narrowband syllables, many of which are unique to this species. We also document a sex-related difference in the bellow-pant phrase combination among the three taxa sampled from the moloch lineage. Our data reveal a presumptive taxonomic incoherence illustrated by the distinctive loud calls of both P. urubambensis and P. oenanthe within the donacophilus lineage, sensu largo. The results are discussed in light of recent reassessments of the callicebine phylogeny, based on a suite of genetic studies, and the potential contribution of environmental influences, including habitat acoustics and social learning. A better knowledge of callicebine loud calls may also impact the conservation of critically endangered populations, such as the vocally distinctive Peruvian endemic, the San Martin titi, P. oenanthe

Terrestrial Behavior in Titi Monkeys (Callicebus, Cheracebus, and Plecturocebus): Potential Correlates, Patterns, and Differences between Genera

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. © 2019, Springer Science+Business Media, LLC, part of Springer Nature