Patrícia Izar | Universidade de São Paulo (original) (raw)
Papers by Patrícia Izar
Journal of Comparative Psychology, 2017
Female wild bearded capuchins (Sapajus libidinosus) living at Serra da Capivara National Park (SC... more Female wild bearded capuchins (Sapajus libidinosus) living at Serra da Capivara National Park (SCNP) that use stone and stick tools during foraging occasionally toss or throw stones at the male during courtship. We report similar behaviors in a different population that uses stones as tools in foraging. We video-recorded the sexual behavior of four females (27 days during nine proceptive periods) belonging to a group of wild capuchins living in Fazenda Boa Vista (FBV), 320 km from SCNP. Three females used stones or branches when they solicited the alpha male (79 episodes). The female that did not use objects was the sole female to solicit a subordinate male. The vast majority of episodes (95%) involved pushing or dropping branches, both loose and attached to the tree, toward the male. Females used objects only during the one-way courtship phase, before the male reciprocated the female's solicitations. In 93% of the episodes in which a female used objects, she performed affiliative behaviors immediately before or after using the objects. We conclude that throwing or pounding stones and pushing or dropping branches by females in SCNP and FBV in the sexual context have a clear affiliative meaning (to attract the male's attention). Given the tool-using status of both populations where these behaviors have been reported, it is important to determine whether they appear in populations that do not use tools, or are restricted to populations already primed to use objects in other contexts.
PLOS ONE
In most group-living animals, a dominance hierarchy reduces the costs of competition for limited ... more In most group-living animals, a dominance hierarchy reduces the costs of competition for limited resources. Dominance ranks may reflect prior attributes, such as body size, related to fighting ability or reflect the history of self-reinforcing effects of winning and losing a conflict (the winner-loser effect), or both. As to prior attributes, in sexually dimorphic species, where males are larger than females, males are assumed to be dominant over females. As to the winner-loser effect, the computational model DomWorld has shown that despite the female’s lower initial fighting ability, females achieve some degree of dominance of females over males. In the model, this degree of female dominance increases with the proportion of males in a group. This increase was supposed to emerge from the higher fraction of fights of males among themselves. These correlations were confirmed in despotic macaques, vervet monkeys, and in humans. Here, we first investigate this hypothesis in DomWorld and...
A representative bearded capuchin monkey, Teimoso (body mass = 3.6 kg), is striking an intact pia... more A representative bearded capuchin monkey, Teimoso (body mass = 3.6 kg), is striking an intact piaçava nut with a 1.91 kg hammer.
A representative bearded capuchin monkey, Teimoso (body mass = 3.6 kg), is striking an intact pia... more A representative bearded capuchin monkey, Teimoso (body mass = 3.6 kg), is striking an intact piaçava nut with a 1.48 kg hammer.
A representative bearded capuchin monkey, Teimoso (body mass = 3.6 kg), is striking an intact pia... more A representative bearded capuchin monkey, Teimoso (body mass = 3.6 kg), is striking an intact piaçava nut with a 1.01 kg hammer.
SSRN Electronic Journal, 2022
We analysed the patterns of coordination of striking movement and perceptuomotor control of stone... more We analysed the patterns of coordination of striking movement and perceptuomotor control of stone hammers in wild bearded capuchin monkeys, <i>Sapajus libidinosus</i> as they cracked open palm nut using hammers of different mass, a habitual behaviour in our study population. We aimed to determine why these monkeys cannot produce conchoidally fractured flakes as do contemporary human knappers or as did prehistoric hominin knappers. We found that the monkeys altered their patterns of coordination of movement to accommodate changes in hammer mass. By altering their patterns of coordination, the monkeys kept the strike's amplitude and the hammer's velocity at impact constant with respect to hammer mass. In doing so, the hammer's kinetic energy at impact—which determines the propagation of a fracture/crack in a nut—varied across hammers of different mass. The monkeys did not control the hammer's kinetic energy at impact, the key parameter a perceiver-actor should control while knapping stones. These findings support the hypothesis that the perceptuomotor control of stone hammers in wild bearded capuchin monkeys is inadequate to produce conchoidally fractured flakes by knapping stones, as do humans.
bioRxiv, 2021
The family Cebidae (capuchin and squirrel monkeys) form a remarkable platyrrhine clade exhibiting... more The family Cebidae (capuchin and squirrel monkeys) form a remarkable platyrrhine clade exhibiting among the largest primate encephalisation quotients. Each cebid lineage is characterised by notable lineage-specific traits, with capuchins showing striking similarities to Hominidae including high sensorimotor intelligence with tool use, advanced cognitive abilities, and behavioural flexibility. Here, we take a comparative genomics approach, analysing five cebid branches including successive lineages, to infer a stepwise timeline for cebid adaptive evolution. We uncover candidate targets of selection across various periods of cebid evolution that may underlie the emergence of lineage-specific traits. Our analyses highlight shifting and sustained selective pressures on genes related to brain development, longevity, reproduction, and morphology, including evidence for cumulative and diversifying neurobiological adaptations over cebid evolutionary history. In addition to generating a new,...
Civil War History, 2020
This study was funded by NASA-Develop National Program granted to AP and CR. Salisbury University... more This study was funded by NASA-Develop National Program granted to AP and CR. Salisbury University grant to AP. The University of Georgia grant to RS. EthoCebus research at FBV is funded by FAPESP (2011/21032-2; 2012/20107-1; 2013/192192) and CNPq (303306/2009-2) grants to PI, CAPES (017/2012; 20131537) grants to NS and MPV, FAPEMA UNIVERSAL (00613/15) to RRS.
Rapid Communications in Mass Spectrometry, 2020
RATIONALE This study analyzes variability in the diets of wild bearded capuchin monkeys, Sapajus ... more RATIONALE This study analyzes variability in the diets of wild bearded capuchin monkeys, Sapajus libidinosus, by analyzing stable carbon (δ13 C value) and nitrogen (δ15 N values) isotope ratios and elemental concentrations (%C and %N) of fecal samples and food items. Developing isotopic and elemental correlates for diets of habituated subjects is a necessary step toward applying similar methods to interpret diets of unhabituated or cryptic subjects. METHODS Fecal samples from wild capuchins and their foods were collected at Fazenda Boa Vista, Brazil. Fecal samples from laboratory-housed Sapajus spp. and their foods were analyzed to establish diet-feces offsets for δ13 C, δ15 N, %C, and %N. Samples were dried, powdered, and measured for isotopic and elemental values. A Bayesian mixing model commutes isotopic and elemental data from wild capuchins into likely proportions of different food categories. RESULTS The captive study shows small diet-feces spaces for Sapajus spp. of -0.8±0.7‰ for δ13 C, -0.2±0.4‰ for δ15 N, -6.1±1.7% for %C, and -1.0±0.6% for %N. The wild study shows omnivorous diets based on a C3 , C4 , and CAM plants, and fauna. Subject diets are highly varied within and between days. Fecal data show age-related differences in diet and crop-raiding. There is no consistent isotopic or elemental difference between mothers and infants. CONCLUSION Fecal stable isotope and elemental evidence employed in a Bayesian mixing model reflects the highly varied diets of capuchin monkeys in an isotopically heterogeneous environment. The isotopic and elemental variability reported here will aid similar diet reconstructions among unhabituated subjects in the future, but precludes tracking weaning isotopically among capuchins in this environment.
American Journal of Primatology, 2020
Animal personality is defined as consistent individual differences across time and situations, bu... more Animal personality is defined as consistent individual differences across time and situations, but little is known about how or when those differences are established during development. Likewise, several studies described the personality structure of adult capuchin monkeys, without assessing the ontogeny of these personality traits. We analyzed the behavioral repertoire of 12 wild infants (9 males, 3 females) yellowbreasted capuchin monkeys (Sapajus xanthosternos), in Una Biological Reserve (Bahia, Brazil). Each infant was observed and filmed weekly from birth until 36 months, through daily focal sampling. We analyzed the behavior of each individual in 10 developmental points. By means of component reduction (principal component analysis), we obtained four behavioral traits: Sociability, Anxiety, Openness, and Activity. We investigated whether there were developmental effects on those traits by fitting regression models for the effect of time on behavioral traits, controlling for monkey identity, sex, and cohort. Sociability (decreasing) and Anxiety (increasing) changed significantly along development. By means of repeatability analysis, we did not find intra-individual consistency across time in those traits, so we cannot discriminate stable personality traits in early ontogeny. Our results show that the personality structure of capuchin monkeys is not established during early development, in agreement with the literature on human personality.
Psicologia USP, 2019
Resumo Quando buscamos entender o comportamento humano, comparações com primatas não humanos são ... more Resumo Quando buscamos entender o comportamento humano, comparações com primatas não humanos são especialmente relevantes para identificar homoplasias (características semelhantes que evoluem independentemente em diferentes espécies). Neste artigo, apresentamos um estudo longitudinal de dois anos sobre o comportamento materno de macacos-prego (Sapajus spp.) em condições naturalísticas. Nossos resultados permitiram identificar estilos de cuidado distintos dentro de um contínuo de permissividade a proteção. O desenvolvimento observado do vínculo entre mães e filhotes sugere que o período de dependência de filhotes de macaco-prego envolve, além de processos de maturação física, o estabelecimento e desenvolvimento de processos psicológicos associados ao sistema de apego. É possível que a variabilidade de estilos maternos resultante da combinação de características de mães, filhotes e contextos socioecológicos, aliada ao prolongamento do vínculo de apego, pavimente caminhos para diferent...
Evolutionary Ecology and Human Behavior, 2017
Population ecology is concerned with the growth (and decline) of populations of plants and animal... more Population ecology is concerned with the growth (and decline) of populations of plants and animals, including humans. This interest, of course, is also shared by demography, economics, and several other disciplines. Population ecology differs in its emphasis on ecology and evolution-the ecological interactions among individuals and among species, and the evolutionary forces that shape these interactions. Earlier chapters in this volume discuss how natural selection shapes the characteristics of individuals: their use of resources, their distribution across the landscape, their life histories, and so forth. This chapter is concerned with the effects that these characteristics have on the dynamics and stability of populations. It will show that these effects are profound, and have important practical consequences.
Biology letters, 2018
We analysed the patterns of coordination of striking movement and perceptuomotor control of stone... more We analysed the patterns of coordination of striking movement and perceptuomotor control of stone hammers in wild bearded capuchin monkeys, Sapajus libidinosus as they cracked open palm nut using hammers of different mass, a habitual behaviour in our study population. We aimed to determine why these monkeys cannot produce conchoidally fractured flakes as do contemporary human knappers or as did prehistoric hominin knappers. We found that the monkeys altered their patterns of coordination of movement to accommodate changes in hammer mass. By altering their patterns of coordination, the monkeys kept the strike's amplitude and the hammer's velocity at impact constant with respect to hammer mass. In doing so, the hammer's kinetic energy at impact-which determines the propagation of a fracture/crack in a nut-varied across hammers of different mass. The monkeys did not control the hammer's kinetic energy at impact, the key parameter a perceiver-actor should control while k...
International Journal of Psychological Research, 2016
Variación en los niveles de glucocorticoides: demandas de supervivencia y reproducción en capuchi... more Variación en los niveles de glucocorticoides: demandas de supervivencia y reproducción en capuchinos negros salvajes (Sapajus nigritus) (Sapajus nigritus)
Animal Cognition, 2015
The spontaneous use of stone tools for cracking nuts by tufted capuchin monkeys, now known to be ... more The spontaneous use of stone tools for cracking nuts by tufted capuchin monkeys, now known to be habitual among wild populations in savanna environments, was first described in a semifree group living in the Tietê Ecological Park (SP, Brazil). Nut-cracking at TEP was first observed by our team in 1995 (Ottoni and Mannu in Int J Primatol 22(3):347-358, 2001), and its ontogeny and associated social dynamics, with inexperienced observers highly interested in the activities of proficient individuals, greatly tolerant to scrounging, support hypotheses about social biases on tool-use learning. Here we further analyze the social learning biases, better characterizing: the social context of nut-cracking in which observation by conspecifics occurs, the quality of the nut-cracking behavior itself and whether scrounging may be the motivation behind this behavior. We confirm that the choice of observational targets is an active one; monkeys do not simply observe those who they are socially close to. We investigate social learning strategies, describing how young capuchins choose to observe older, more proficient and dominant individuals during nut-cracking bouts. Monkeys with higher productivity rates were also more frequently targeted by observers, who were tolerated scroungers, further supporting the scrounging hypothesis. Finally, based on changes of the demographic patterns of tool use and observation, we set to retrace data from 14 years of continuous studies. We argue that we have followed the dissemination of the behavior (Transmission Phase) almost from its beginning, when juveniles were the most frequent nutcrackers, to a more common pattern where adults are the most active tool users (Tradition Phase).
Journal of Comparative Psychology, 2017
Female wild bearded capuchins (Sapajus libidinosus) living at Serra da Capivara National Park (SC... more Female wild bearded capuchins (Sapajus libidinosus) living at Serra da Capivara National Park (SCNP) that use stone and stick tools during foraging occasionally toss or throw stones at the male during courtship. We report similar behaviors in a different population that uses stones as tools in foraging. We video-recorded the sexual behavior of four females (27 days during nine proceptive periods) belonging to a group of wild capuchins living in Fazenda Boa Vista (FBV), 320 km from SCNP. Three females used stones or branches when they solicited the alpha male (79 episodes). The female that did not use objects was the sole female to solicit a subordinate male. The vast majority of episodes (95%) involved pushing or dropping branches, both loose and attached to the tree, toward the male. Females used objects only during the one-way courtship phase, before the male reciprocated the female's solicitations. In 93% of the episodes in which a female used objects, she performed affiliative behaviors immediately before or after using the objects. We conclude that throwing or pounding stones and pushing or dropping branches by females in SCNP and FBV in the sexual context have a clear affiliative meaning (to attract the male's attention). Given the tool-using status of both populations where these behaviors have been reported, it is important to determine whether they appear in populations that do not use tools, or are restricted to populations already primed to use objects in other contexts.
PLOS ONE
In most group-living animals, a dominance hierarchy reduces the costs of competition for limited ... more In most group-living animals, a dominance hierarchy reduces the costs of competition for limited resources. Dominance ranks may reflect prior attributes, such as body size, related to fighting ability or reflect the history of self-reinforcing effects of winning and losing a conflict (the winner-loser effect), or both. As to prior attributes, in sexually dimorphic species, where males are larger than females, males are assumed to be dominant over females. As to the winner-loser effect, the computational model DomWorld has shown that despite the female’s lower initial fighting ability, females achieve some degree of dominance of females over males. In the model, this degree of female dominance increases with the proportion of males in a group. This increase was supposed to emerge from the higher fraction of fights of males among themselves. These correlations were confirmed in despotic macaques, vervet monkeys, and in humans. Here, we first investigate this hypothesis in DomWorld and...
A representative bearded capuchin monkey, Teimoso (body mass = 3.6 kg), is striking an intact pia... more A representative bearded capuchin monkey, Teimoso (body mass = 3.6 kg), is striking an intact piaçava nut with a 1.91 kg hammer.
A representative bearded capuchin monkey, Teimoso (body mass = 3.6 kg), is striking an intact pia... more A representative bearded capuchin monkey, Teimoso (body mass = 3.6 kg), is striking an intact piaçava nut with a 1.48 kg hammer.
A representative bearded capuchin monkey, Teimoso (body mass = 3.6 kg), is striking an intact pia... more A representative bearded capuchin monkey, Teimoso (body mass = 3.6 kg), is striking an intact piaçava nut with a 1.01 kg hammer.
SSRN Electronic Journal, 2022
We analysed the patterns of coordination of striking movement and perceptuomotor control of stone... more We analysed the patterns of coordination of striking movement and perceptuomotor control of stone hammers in wild bearded capuchin monkeys, <i>Sapajus libidinosus</i> as they cracked open palm nut using hammers of different mass, a habitual behaviour in our study population. We aimed to determine why these monkeys cannot produce conchoidally fractured flakes as do contemporary human knappers or as did prehistoric hominin knappers. We found that the monkeys altered their patterns of coordination of movement to accommodate changes in hammer mass. By altering their patterns of coordination, the monkeys kept the strike's amplitude and the hammer's velocity at impact constant with respect to hammer mass. In doing so, the hammer's kinetic energy at impact—which determines the propagation of a fracture/crack in a nut—varied across hammers of different mass. The monkeys did not control the hammer's kinetic energy at impact, the key parameter a perceiver-actor should control while knapping stones. These findings support the hypothesis that the perceptuomotor control of stone hammers in wild bearded capuchin monkeys is inadequate to produce conchoidally fractured flakes by knapping stones, as do humans.
bioRxiv, 2021
The family Cebidae (capuchin and squirrel monkeys) form a remarkable platyrrhine clade exhibiting... more The family Cebidae (capuchin and squirrel monkeys) form a remarkable platyrrhine clade exhibiting among the largest primate encephalisation quotients. Each cebid lineage is characterised by notable lineage-specific traits, with capuchins showing striking similarities to Hominidae including high sensorimotor intelligence with tool use, advanced cognitive abilities, and behavioural flexibility. Here, we take a comparative genomics approach, analysing five cebid branches including successive lineages, to infer a stepwise timeline for cebid adaptive evolution. We uncover candidate targets of selection across various periods of cebid evolution that may underlie the emergence of lineage-specific traits. Our analyses highlight shifting and sustained selective pressures on genes related to brain development, longevity, reproduction, and morphology, including evidence for cumulative and diversifying neurobiological adaptations over cebid evolutionary history. In addition to generating a new,...
Civil War History, 2020
This study was funded by NASA-Develop National Program granted to AP and CR. Salisbury University... more This study was funded by NASA-Develop National Program granted to AP and CR. Salisbury University grant to AP. The University of Georgia grant to RS. EthoCebus research at FBV is funded by FAPESP (2011/21032-2; 2012/20107-1; 2013/192192) and CNPq (303306/2009-2) grants to PI, CAPES (017/2012; 20131537) grants to NS and MPV, FAPEMA UNIVERSAL (00613/15) to RRS.
Rapid Communications in Mass Spectrometry, 2020
RATIONALE This study analyzes variability in the diets of wild bearded capuchin monkeys, Sapajus ... more RATIONALE This study analyzes variability in the diets of wild bearded capuchin monkeys, Sapajus libidinosus, by analyzing stable carbon (δ13 C value) and nitrogen (δ15 N values) isotope ratios and elemental concentrations (%C and %N) of fecal samples and food items. Developing isotopic and elemental correlates for diets of habituated subjects is a necessary step toward applying similar methods to interpret diets of unhabituated or cryptic subjects. METHODS Fecal samples from wild capuchins and their foods were collected at Fazenda Boa Vista, Brazil. Fecal samples from laboratory-housed Sapajus spp. and their foods were analyzed to establish diet-feces offsets for δ13 C, δ15 N, %C, and %N. Samples were dried, powdered, and measured for isotopic and elemental values. A Bayesian mixing model commutes isotopic and elemental data from wild capuchins into likely proportions of different food categories. RESULTS The captive study shows small diet-feces spaces for Sapajus spp. of -0.8±0.7‰ for δ13 C, -0.2±0.4‰ for δ15 N, -6.1±1.7% for %C, and -1.0±0.6% for %N. The wild study shows omnivorous diets based on a C3 , C4 , and CAM plants, and fauna. Subject diets are highly varied within and between days. Fecal data show age-related differences in diet and crop-raiding. There is no consistent isotopic or elemental difference between mothers and infants. CONCLUSION Fecal stable isotope and elemental evidence employed in a Bayesian mixing model reflects the highly varied diets of capuchin monkeys in an isotopically heterogeneous environment. The isotopic and elemental variability reported here will aid similar diet reconstructions among unhabituated subjects in the future, but precludes tracking weaning isotopically among capuchins in this environment.
American Journal of Primatology, 2020
Animal personality is defined as consistent individual differences across time and situations, bu... more Animal personality is defined as consistent individual differences across time and situations, but little is known about how or when those differences are established during development. Likewise, several studies described the personality structure of adult capuchin monkeys, without assessing the ontogeny of these personality traits. We analyzed the behavioral repertoire of 12 wild infants (9 males, 3 females) yellowbreasted capuchin monkeys (Sapajus xanthosternos), in Una Biological Reserve (Bahia, Brazil). Each infant was observed and filmed weekly from birth until 36 months, through daily focal sampling. We analyzed the behavior of each individual in 10 developmental points. By means of component reduction (principal component analysis), we obtained four behavioral traits: Sociability, Anxiety, Openness, and Activity. We investigated whether there were developmental effects on those traits by fitting regression models for the effect of time on behavioral traits, controlling for monkey identity, sex, and cohort. Sociability (decreasing) and Anxiety (increasing) changed significantly along development. By means of repeatability analysis, we did not find intra-individual consistency across time in those traits, so we cannot discriminate stable personality traits in early ontogeny. Our results show that the personality structure of capuchin monkeys is not established during early development, in agreement with the literature on human personality.
Psicologia USP, 2019
Resumo Quando buscamos entender o comportamento humano, comparações com primatas não humanos são ... more Resumo Quando buscamos entender o comportamento humano, comparações com primatas não humanos são especialmente relevantes para identificar homoplasias (características semelhantes que evoluem independentemente em diferentes espécies). Neste artigo, apresentamos um estudo longitudinal de dois anos sobre o comportamento materno de macacos-prego (Sapajus spp.) em condições naturalísticas. Nossos resultados permitiram identificar estilos de cuidado distintos dentro de um contínuo de permissividade a proteção. O desenvolvimento observado do vínculo entre mães e filhotes sugere que o período de dependência de filhotes de macaco-prego envolve, além de processos de maturação física, o estabelecimento e desenvolvimento de processos psicológicos associados ao sistema de apego. É possível que a variabilidade de estilos maternos resultante da combinação de características de mães, filhotes e contextos socioecológicos, aliada ao prolongamento do vínculo de apego, pavimente caminhos para diferent...
Evolutionary Ecology and Human Behavior, 2017
Population ecology is concerned with the growth (and decline) of populations of plants and animal... more Population ecology is concerned with the growth (and decline) of populations of plants and animals, including humans. This interest, of course, is also shared by demography, economics, and several other disciplines. Population ecology differs in its emphasis on ecology and evolution-the ecological interactions among individuals and among species, and the evolutionary forces that shape these interactions. Earlier chapters in this volume discuss how natural selection shapes the characteristics of individuals: their use of resources, their distribution across the landscape, their life histories, and so forth. This chapter is concerned with the effects that these characteristics have on the dynamics and stability of populations. It will show that these effects are profound, and have important practical consequences.
Biology letters, 2018
We analysed the patterns of coordination of striking movement and perceptuomotor control of stone... more We analysed the patterns of coordination of striking movement and perceptuomotor control of stone hammers in wild bearded capuchin monkeys, Sapajus libidinosus as they cracked open palm nut using hammers of different mass, a habitual behaviour in our study population. We aimed to determine why these monkeys cannot produce conchoidally fractured flakes as do contemporary human knappers or as did prehistoric hominin knappers. We found that the monkeys altered their patterns of coordination of movement to accommodate changes in hammer mass. By altering their patterns of coordination, the monkeys kept the strike's amplitude and the hammer's velocity at impact constant with respect to hammer mass. In doing so, the hammer's kinetic energy at impact-which determines the propagation of a fracture/crack in a nut-varied across hammers of different mass. The monkeys did not control the hammer's kinetic energy at impact, the key parameter a perceiver-actor should control while k...
International Journal of Psychological Research, 2016
Variación en los niveles de glucocorticoides: demandas de supervivencia y reproducción en capuchi... more Variación en los niveles de glucocorticoides: demandas de supervivencia y reproducción en capuchinos negros salvajes (Sapajus nigritus) (Sapajus nigritus)
Animal Cognition, 2015
The spontaneous use of stone tools for cracking nuts by tufted capuchin monkeys, now known to be ... more The spontaneous use of stone tools for cracking nuts by tufted capuchin monkeys, now known to be habitual among wild populations in savanna environments, was first described in a semifree group living in the Tietê Ecological Park (SP, Brazil). Nut-cracking at TEP was first observed by our team in 1995 (Ottoni and Mannu in Int J Primatol 22(3):347-358, 2001), and its ontogeny and associated social dynamics, with inexperienced observers highly interested in the activities of proficient individuals, greatly tolerant to scrounging, support hypotheses about social biases on tool-use learning. Here we further analyze the social learning biases, better characterizing: the social context of nut-cracking in which observation by conspecifics occurs, the quality of the nut-cracking behavior itself and whether scrounging may be the motivation behind this behavior. We confirm that the choice of observational targets is an active one; monkeys do not simply observe those who they are socially close to. We investigate social learning strategies, describing how young capuchins choose to observe older, more proficient and dominant individuals during nut-cracking bouts. Monkeys with higher productivity rates were also more frequently targeted by observers, who were tolerated scroungers, further supporting the scrounging hypothesis. Finally, based on changes of the demographic patterns of tool use and observation, we set to retrace data from 14 years of continuous studies. We argue that we have followed the dissemination of the behavior (Transmission Phase) almost from its beginning, when juveniles were the most frequent nutcrackers, to a more common pattern where adults are the most active tool users (Tradition Phase).