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Despite many explorations and surveys, the geographic distribution of many primate species, particularly in the neotropics, is not yet well known. In this paper, we provide evidence that extends the range of Spix's saddle-back tamarin in Peru.

As part of our study on coppery titi monkeys in the Peruvian Amazon, we observed an individual rubbing his belly with leaves from a potentially medicinal plant. He climbed down from high above and grabbed a handful of leaves from an understory tree, which made it look like a deliberate action. Sitting on a liana he then chewed on the leaves before rubbing them slowly on his belly for a couple of minutes. The plant genus is known in traditional medicine and is used for various effects.

The Manyara monkey was described as a new subspecies of the Cercopithecus mitis species complex in 2020. We sequenced a part of its mitochondrial genome and reconstructed the phylogeny of the mitochondrial lineages. The reconstruction suggests that the Manyara monkey clusters in the youngest of three major C. mitis clades. Our data support the phylogeographic hypothesis of a west-east range expansion of gentle monkeys into eastern and southern Africa.

From November 2011 through to November 2019, we carried out seasonal road transect surveys and estimated population densities of Manyara monkeys and vervet monkeys in Lake Manyara National Park. Both species occurred at relatively high densities, and their population trends remained fairly stable over the study period. Our research highlights the value of long-term monitoring and the importance of Lake Manyara National Park as a stronghold for the endemic and endangered Manyara monkey.

Alfaxalone is a general anesthetic used widely in veterinary medicine and has a chemical structure similar to progesterone. Here we report an unexpectedly high serum progesterone value in a female common marmoset following the treatment with alfaxalone. Cross-reactivity of the antibody used in the progesterone assay with alfaxalone most likely explains this finding, and therefore evaluation of serum progesterone results in animals treated with alfaxalone should be done with caution.

A camera trap captured the moment in which a group of collared peccaries attacked and killed a howler monkey at a clay lick in the Taricaya Ecological Reserve, Madre de Dios, Peru. This novel behaviour helps us understand the myriad risks howler monkeys face when descending to the forest floor while also indirectly emphasizing the importance of geophagy for these animals.