What makes a long tail short? Testing Allen's rule in the toque macaques of Sri Lanka.

Allen's rule (1877) predicts ecogeographical anatomical variation in appendage proportions as a function of body temperature regulation. This phenomenon has been tested in a variety of animal species. In macaques, relative tail length (RTL) is one of the most frequently measured appendages to test Allen's rule.

A multidisciplinary view on cultural primatology: behavioral innovations and traditions in Japanese macaques.

Cultural primatology (i.e., the study of behavioral traditions in nonhuman primates as a window into the evolution of human cultural capacities) was founded in Japan by Kinji Imanishi in the early 1950s.

Stone handling behavior in rhesus macaques (Macaca mulatta), a behavioral propensity for solitary object play shared with Japanese macaques.

Stone handling (SH) behavior was systematically studied in a captive troop of rhesus macaques housed at the Primate Research Institute of Kyoto University, and compared with the results of long-term studies of this behavior in Japanese macaques, to evaluate the similarities of SH behavior in these two closely related species. Similar to Japanese macaques, rhesus macaques showed age-related differences in SH. Young animals were more active and displayed more SH patterns and bouts than did adults.

Comparison of stone handling behavior in two macaque species: implications for the role of phylogeny and environment in primate cultural variation.

This study describes the stone handling (SH) behavior of captive rhesus macaques and compares it with that of a captive troop of Japanese macaques with reference to the relative contributions of phylogeny-driven behavioral propensities, environmental differences and socially facilitated learning to the formation of culture. These systematically collected data demonstrate for the first time that two closely related macaque species might share a common cultural behavior, SH. The rhesus troop displayed SH behavioral patterns that was already described in Japanese macaque troops.

Stone-throwing by Japanese macaques: form and functional aspects of a group-specific behavioral tradition.

Throwing is a major behavioral component of hominid evolution. Comparison of this behavior across a broad range of non-human primate species is needed to elucidate the phylogenetic constraints on throwing behavior. In this study of stone-throwing in Japanese macaques, we present a systematic multi-group comparison of the frequency and prevalence of this behavior as well as detailed descriptions and quantitative data on the form, context, and possible social transmission of stone-throwing.

Age-specific functions of stone handling, a solitary-object play behavior, in Japanese macaques (Macaca fuscata).

Stone handling (SH) in Japanese macaques, a form of solitary-object play, is newly acquired only by young individuals, and is the first example of a directly nonadaptive behavior that is maintained as a behavioral tradition within free-ranging provisioned social troops. We report here the first systematic investigation of this behavior in a stable captive social troop, the Takahama troop, which is housed in an outdoor enclosure of the Primate Research Institute (PRI), Kyoto University, Japan. This study was conducted to evaluate relevant competing hypotheses regarding the function of object play (e.