Adolescent male chimpanzees do not form a dominance hierarchy with their peers

Dominance hierarchies are a prominent feature of the lives of many primate species. These hierarchies have important fitness consequences, as high rank is often positively correlated with reproduction. Although adult male chimpanzees strive for status to gain fitness benefits, the development of dominance relationships is not well understood. While two prior studies found that adolescent males do not display dominance relationships with peers, additional research at Ngogo in Kibale National Park, Uganda, indicates that adolescents there form a linear dominance hierarchy. These conflicting findings could reflect different patterns of rank acquisition across sites. An alternate possibility arises from a recent re-evaluation of age estimates at Ngogo and suggests that the report describing decided dominance relationships between adolescent males may have been due to the accidental inclusion of young adult males in the sample. To investigate these issues, we conducted a study of 23 adolescent male chimpanzees of known age during 12 months at Ngogo. Adolescent male chimpanzees exchanged pant grunts, a formal signal of submission, only 21 times. Recipients of pant grunts were late adolescent males, ranging between 14 and 16 years old. In contrast, younger adolescent males never received pant grunts from other males. Aggression between adolescent males was also rare. Analysis of pant grunts and aggressive interactions did not produce a linear dominance hierarchy among adolescent males. These data indicate that adolescent male chimpanzees do not form decided dominance relationships with their peers and are consistent with the hypothesis that the hierarchy described previously at Ngogo resulted from inaccurate age estimates of male chimpanzees. Because dominance relationships develop before adulthood in other primates, our finding that adolescent male chimpanzees do not do so is surprising. We offer possible explanations for why this is the case and suggest future studies that may help clarify the matter.     

Macronutrients along the sediment profile in a subtropical monsoonal wetland in India

We analyzed 144 composite sediment samples to appraise the seasonal variation in select major nutrients in the bed sediments of Keoladeo National Park (KNP), Bharatpur, a subtropical monsoonal wetland system in India, from September 2003 to July 2005. Total organic carbon (TOC, %) and total nitrogen (TN, %) in the sediments were in the range of 0.61–14.01 and 0.26–0.68, respectively. The total available phosphorus (TAP, %) and total available sulphur (TAS, %) ranged from 0.001 to 0.034 and from 0.001 to 0.012, respectively. While C:N ratio was within a narrow range (1.38–13.56), C:P ratios varied widely (18.81–5995.83). Similar wide variations were seen in C:S ratio (352.2–3929.5) as well as N:P ratio (9.34–56.6). All the parameters except TAS showed depth-wise declines along the sediment profile. In contrast, the pH gradually increased along the depth. Most of the parameters significantly varied across months and sediment layers. A positive correlation (Two-tailed, P < 0.05) existed between TOC and all the nutrients and their ratios except TAP and N:P. TAP was positively correlated with electrical conductivity (EC) and water soluble substances (WSS), suggesting the contribution of phosphate to the dissolved salts. During certain months elements such as P were comparatively low in concentration, in spite of input through agricultural runoff and large scale bird droppings, probably due to its higher uptake by macrophytes growing luxuriantly in the wetland. Organic materials appear to decay at a faster rate during the drier periods as indicated by the fall in TOC and the rise in TN. Principal Component Analysis (PCA) shows that three components contributed to 68.9% of the total variance. The first component that accounted for 26.4% of the total variance reflects the importance of total organic carbon in wetland sediments and the ratio of carbon to other nutrients. The second one accounting for 23.7% of the variance correlated with water soluble substances (EC, WSS and TAS). The third component accounting for 18.7% of the variance reflects the influence of two major nutrients, nitrogen and phosphorus, in sediments those affect the biogeochemical processes in wetlands. Thus, the three PCA components can be characterized as ‘sediment organic carbon and its ratios with other elements’, ‘WSS, TAS’ and ‘the limiting nutrients such as N and P’, respectively.     

A preliminary analysis of wound care and other-regarding behavior in wild chimpanzees at Ngogo,Kibale National Park,Uganda

Primates - Caring for others is a key feature of human behavior. Mothers, fathers, siblings, grandparents, and other group members provide care in the form of provisioning, protection, and first...