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Lameira A.R.,University Utrecht | Delgado R.A.,University of Southern California | Wich S.A.,Great Ape Trust of Iowa | Wich S.A.,University of Zurich
Journal of Evolutionary Psychology | Year: 2010

Human speech shows an unparalleled richness in geographic variation. However, few attempts have been made to understand this linguistic diversity from an evolutionary and comparative framework. Here, we a) review extensively what is known about geographic variation of acoustic signals in terrestrial mammals, using common terminology adopted from linguistics to define different forms of variation (i.e. accents and dialects), and b) examine which factors may determine this variation (i.e. genetic, environmental and/or social). Heretofore, terminology has been used inconsistently within and across taxa, and geographic variation among terrestrial mammals has never been defined as in human speech. Our results show that accents, phonologically different varieties, occur widely in terrestrial mammals. Conversely, dialects, lexically and phonologically different varieties, have only been documented thus far in great white-lined bats, red deer, chimpanzees and orangutans. Although relatively rare among terrestrial mammals, dialects are thus not unique to humans. This finding also implies that such species possess the capacity for acoustic learning. Within primates, the two great apes showing dialects are those who also show extensive cultures in the wild, suggesting that, in hominoids, intricacy of acoustic geographic variation is potentially associated with cultural complexity; namely, both have derived from selection increasingly favoring social learning across varied contexts, including the acoustic domain. © 2010 Akadémiai Kiadó, Budapest.

Jaeggi A.V.,University of Zurich | Dunkel L.P.,University of Zurich | van Noordwijk M.A.,University of Zurich | Wich S.A.,Great Ape Trust of Iowa | And 3 more authors.
American Journal of Primatology | Year: 2010

Studies of social learning in the wild are important to complement findings from experiments in captivity. In this field study, immature Bornean orangutans rarely foraged independently but consistently followed their mothers' choices. Their diets were essentially identical to their mothers' even though not all mothers had the same diet. This suggests vertical transmission of diet by enhancement. Also, immatures selectively observed their mothers during extractive foraging, which increased goal-directed practice but not general manipulation of similar objects, suggesting observational forms of learning of complex skills. Teaching was not observed. These results are consistent with the reported presence of food traditions and skill cultures in wild orangutans. We suggest that food traditions can develop wherever association commonly allows for social learning. However, the capacity for observational learning, and thus more complex culture, is more likely to evolve among extractive foragers with prolonged association between adults and immatures. © 2009 Wiley-Liss, Inc.

Bastian M.L.,Duke University | Zweifel N.,University of Zurich | Vogel E.R.,George Washington University | Wich S.A.,Great Ape Trust of Iowa | And 3 more authors.
American Journal of Physical Anthropology | Year: 2010

This study explores diet differences between two populations of wild Bornean orangutans (Pongo pygmaeus wurmbii) to assess whether a signal of social learning can be detected in the observed patterns. The populations live in close proximity and in similar habitats but are separated by a river barrier that is impassable to orangutans in the study region. We found a 60% between-site difference in diet at the level of plant food items (plant species-organ combinations). We also found that individuals at the same site were more likely to eat the same food items than expected by chance. These results suggest the presence of diet (food selection) traditions. Detailed tests of three predictions of three models of diet acquisition allowed us to reject a model based on exclusive social learning but could not clearly distinguish between the remaining two models: one positing individual exploration and learning of food item selection and the other one positing preferential social learning followed by individual fine tuning. We know that maturing orangutans acquire their initial diet through social learning and then supplement it by years of low-level, individual sampling. We, therefore, conclude that the preferential social learning model produces the best fit to the geographic patterns observed in this study. However, the very same taxa that socially acquire their diets as infants and show evidence for innovation-based traditions in the wild paradoxically may have diets that are not easily distinguished from those acquired exclusively through individual learning. © 2010 Wiley-Liss, Inc.

Faust L.J.,Alexander Center for Applied Population Biology | Cress D.,Pan African Sanctuary Alliance | Farmer K.H.,Pan African Sanctuary Alliance | Farmer K.H.,University of Stirling | And 2 more authors.
International Journal of Primatology | Year: 2011

Wildlife sanctuaries rescue, rehabilitate, reintroduce, and provide life-long care for orphaned and injured animals. Understanding a sanctuary's patterns in arrival, mortality, and projected changes in population size can help managers plan carefully for future needs, as well as illuminate patterns in source populations of wildlife. We studied these dynamics for chimpanzees (Pan troglodytes) in 11 sanctuaries of the Pan African Sanctuary Alliance (PASA). We analyzed historic demographic patterns and projected future population dynamics using an individual-based demographic model. From 2000 to 2006, the population in these sanctuaries has been growing at a rate of 15% per year. This growth is driven by arrivals of new individuals, with an average of 56 arrivals per year. The median age of the 760 chimpanzees living in these sanctuaries as of 2007 was 9 yr, with 76% of the population <15 yr. We found no significant difference in survivorship to age 20 between these chimpanzees and those maintained in North American accredited zoos. The size of the population in 20 yr is projected to be between 550 and 1800, depending on different assumptions about arrival and reintroduction rates. Projected shifts in age structure, including increases in the proportions of adolescent (9-19 yr of age) and older (35+) chimpanzees, may necessitate adjustments to management, veterinary care, and housing. This research illustrates how data on historic population dynamics can be modeled to inform future sanctuary capacity and management needs, allowing sanctuaries to plan better for their populations' long-term care. © 2011 Springer Science+Business Media, LLC.

Spillmann B.,University of Zurich | Dunkel L.P.,University of Zurich | van Noordwijk M.A.,University of Zurich | Amda R.N.A.,National University of Indonesia | And 3 more authors.
Ethology | Year: 2010

Long calls by flanged male Bornean orang-utans (Pongo pygmaeus wurmbii) serve as a long-distance communication signal in this semi-solitary species and allow individuals to adjust their ranging behavior. Long calls can be heard up to circa 1 km in dense rainforest. Only flanged males emit them, in various contexts: spontaneously (where no disturbances from the environment are perceived by human observers), when highly aroused by another male's long call or a falling tree nearby, or right after having pushed over a dead tree themselves. In this study, acoustic analyses of orang-utan long calls at Tuanan in Central Kalimantan not only confirm the discrimination of individual males by their long calls but also demonstrate the discrimination of context based on the long calls' acoustic structure, which is further supported by the females' ranging responses according to long call contexts. Females with dependent offspring move away from spontaneous long call sources but appear to ignore long calls elicited by disturbance. Hence, Bornean orang-utan females perceive measurable differences in acoustic characteristics of long calls given in different contexts. These findings concur with vocal discrimination of contexts in other non-human primates. © 2010 Blackwell Verlag GmbH.

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