Tool use by black-horned capuchins: Three nut species (Syagrus romanzoffiana, Acrocomia aculeata, and Terminalia catappa) are processed. Nut-cracking behavior shows no large seasonal differences, and active choice of the hammers is suggested.

Infection of mantled howler monkeys (Alouatta palliata) by the botfly Cuterebra baeri results in an increase in activity, including more time feeding and moving.

Graphical abstract showing the main results of this article.

Alouatta macconnelli river crossing, Guyana.

Handedness Index scores show that olive baboons have strong hand preferences during a cognitive task but much weaker and more varied hand preferences during natural behaviors.

Our result showed that anthropogenic food from humans attracted monkey groups to the provisioned sites, leading to more intergroup contact there. Due to the ample anthropogenic food, the intergroup competition was mitigated and there was no strict linear dominance relationship among monkey groups.

Image by Brianna Anderson.

We present two important results of our research: (1) The middle ear structures that distinguish major groups of primates are already apparent at birth. Here, we show the middle ear of the Owl Monkey (Aotus nancymaae) as a newborn (left) and as an adult (right). The middle ear cavity is divided into the central tympanic cavity (TC, in white), the anterior accessory cavity (AAC, in the dark purple), and the posterior accessory cavity (PAC, in gray-green). The middle ear bones are housed within the TC: malleus (red), incus (blue), and stapes (purple). The inner ear (yellow) is shown for context. (2) We also describe how Old World Monkeys, represented by the Rhesus Macaque (Macaca mulatta), have a greater degree of middle ear complexity compared to Lemurs/Lorises, represented by the Slender Loris (Loris tardigradus); this is shown in both the newborn (top row) and the adult stages (bottom row).

The figure illustrates the impact of pre-rescue housing conditions and age at rescue on abnormal behavior in sanctuary chimpanzees. Chimpanzees isolated prior to rescue (yellow data points) show a positive relationship between age at rescue and scans spent displaying abnormal behaviors—rescues occurring later in life are associated with higher percentages of scans displaying these behaviors. In contrast, chimpanzees housed socially pre-rescue (green data points) do not show this trend, as their age at rescue does not influence the frequency of abnormal behavior.

Circ-annual enamel thinning in Japanese macaque canine tooth.

Image summarizing the main results of the study.

Vocal and gestural communicative signals showing evidence for cultural variation in the wild.

Photo by Nicholas Chapoy. Females and their new infants are of great interest to group members in white-faced capuchins.

We increased the efficiency of breeding within our marmoset colony by allowing females to choose their mate using a partner-preference “love maze.” When exposed to pairs of several eligible males, female marmosets showed a clear and repeated preference for one male only by directing affiliative behaviors toward him including proceptive tongue-flicking and face grooming behavior. Her self-directed choice of male was a major determinant of her reproductive success compared with females who were randomly paired.

This is a graphical representation of physiological and environmental factors on hematological parameters in chimpanzees.

Mother-offspring stable nitrogen isotope (δ¹⁵N) differences by offspring age. Data point colors are different individuals, squares are hairs collected singly, while circles are hairs collected in a group. Diagonal line shows trend line.

The theoretical amount of mental effort an animal should exert depending on how routine a situation is, how accurately a cue or signal predicts an outcome, or how computationally complex a problem is.

Map of Kibale National Park, Uganda, showing the location of the censuses.

A photo of Nau, a Japanese macaque who was born with one eye, and the key highlights from the review article.

Losing lemurs: declining populations and land cover changes over space and time.

Density estimates (individual/ha) and their respective lower and upper 95% confidence limit for M. murinus and M. ravelobensis.

In the first 6 months of life, colobus infants participate in more nonmaterial handling when they engage in more maternal handling or less nursing. There is no association between nonmaternal handling time and maternal handling or nursing times in older infants.

Primate Conservation is a Public Issue

Lemurs in the same social group have similar microbiomes over time.

We examined the how forest structure boundaries affect the population structure and genetic connectivity of western black crested gibbons in Yunnan China. Both high-altitude rhododendron thickets and lowland anthropogenic deforestation are restricting gene flow in these critically endangered apes.

Relationship between fruit productivity and arthropodivory in black lion tamarins.

What sets male and female vervet monkey alarm calls apart? Exploring sex differences in terrestrial alarm call structure.

Heat map showing the mean percentage difference for dietary measures (% time feeding fruit, richness, Shannon–Wiener diversity index, Holmes–Pitelka overlap index) in which deviation was measured between each subsample and the full data set.

Carpal tunnel syndrome is a highly prevalent neuropathy in humans. This syndrome consists of compression suffered by the median nerve inside the carpal tunnel. The detailed anatomical study of the carpal tunnel and the structures that pass through it, the median nerve and the tendons of the flexor muscles of the fingers, in humans and other primate species, may shed light on the etiopathogenesis of tunnel syndrome. Mainly, this analysis can provide information on whether carpal tunnel syndrome is due to the anatomical characteristics of the carpal tunnel in humans or whether other more functional factors should be considered.

Platynosomosis: life cycle and pathological features.

Feeding trees drive black lion tamarins' trajectories in all areas. Depending on the environmental context, landmarks located at route intersections are used for spatial orientation before reaching the final objective.

Vervet monkey life-history estimates.

“When and why do white-faced capuchins eat plant pith? We investigated how ecological variables and plant traits shape patterns of pith consumption. We find that pith foraging occurs primarily during seasonal transitions, and that dietary pith species contain relatively more pith, are softer, and have a different odor profile than non-dietary species.“