Individuals must decide how to allocate their time based on their priorities at different life stages. Juvenile and subadult sifaka prioritize social activity compared to adults, potentially due to its significance towards behavioral development. Sex differences in social activity emerge before adulthood, but sex differences in other activities emerge later.

Infant being handled by mother.

Data indicate that, across 3 years, significant elevations in urinary norepinephrine result from housing relocations compared to baseline (Time 1).

Telemetry data indicate that longer term pairing of heterosexual cynomolgus macaques results in lower blood pressure and increased body temperature consistent with the literature on loneliness in humans which is associated with elevated blood pressure and reduced body temperature.

Geladas produce yawn vocalizations, yawn more, and in a larger variety of contexts than hamadryas. Geladas are more susceptible to others' yawns that hamadryas. Yawn contagion in hamadryas is mostly shown by males. Pictures by V. Maglieri and M. Francesconi.