Usage of outdoor runs and defaecation behaviour of fattening pigs
Authors: Höne U., Krause E. T., Bussemas R., Traulsen I., Schrader L. (2023)
Access to an outdoor run improves the housing conditions of fattening pigs by an enlarged space allowance, access to different climatic conditions and environmental stimulation. One central conflicting issue regarding outdoor runs is the emission of harmful gases such as ammonia resulting from faeces and urine. However, by establishing appropriate functional areas in fattening pens, the area soiled by faeces and urine can potentially be reduced. Here, we investigated the usage of an outdoor run and the frequencies and locations of defaecation behaviour of fattening pigs kept in groups of ten in eight pens. Usage of the outdoor run was registered by scan sampling at the group level in three observation periods (pigs at 16, 19, and 22 weeks of age). Furthermore, in each pen, two focal pigs were individually marked and continuously observed for 24 h in each observation period to record defaecation behaviour. At the group level, the fattening pigs used the outdoor run mainly during the daytime between 06:00 h and 20:00 h. A total of 99.4% of defaecation events occurred in the outdoor run, most often in the corner next to the wall of the barn. On average, 11.08 ( ± SD 3.06) defaecation events per pig per day were recorded, whereby the time of day significantly affected the relative frequencies of defaecation behaviour (GLMER, X12 = 4.11, P < 0.043). Fattening pigs defaecated more often during the daytime than during the nighttime. The number of daily defaecations decreased with age. In pens as used in our study, fattening pigs perform nearly all defaecations in the outdoor run and within a small area. This may enable technical possibilities to reduce ammonia emissions in pig pens with outdoor runs, such as regular cleaning of dunging areas by an automatic floor scraper.
Organic pig farming; Fattening pigs; Outdoor runs; Elimination areas; Defaecation behaviour
Continue reading >>>
Lateralization and Performance Asymmetries in the Termite Fishing of WildChimpanzees in the Goualougo Triangle, Republic of Congo
Authors: CRICKETTE M. SANZ, DAVID B. MORGAN, AND WILLIAM D. HOPKINS
The nearly universal right hand preference manifested by human populations is one of the most pronounced manifestations of population-level lateralization. Morphological and archeological evidence indicate that this behavioral specialization may have emerged among our hominin ancestors. Whether population-level behavioral asymmetries are evident in non-human animals remains a topic of considerable scientific debate, with the most consistent evidence of population-level trends emerging from studies of chimpanzees (Pan troglodytes). However, previous studies of population-level lateralization in wild apes have relied upon data sets pooled across populations to reach adequate sample sizes. Our aim was to test for population-level handedness within a single wild chimpanzee population, and also to determine if performance asymmetries were associated with handedness. To address these questions, we coded handedness and duration of fishing probe insertions from remote video footage of chimpanzee visitation to termite nests (totaling 119 hr) in the Goualougo Triangle, Republic of Congo. Similar to reports from other populations, chimpanzees in the Goualougo Triangle showed robust individual hand preferences for termite fishing. There were 46 righthanded, 39 left-handed, and 4 ambiguously-handed individuals. Though we did not detect an overall significant population-level handedness (t(88)¼0.83, n.s.) in this study, males showed a greater right hand preference than females. Further, we found that average dipping latencies were significantly faster for right- compared to left-handed chimpanzees. Possible explanations and evolutionary implications of taxa- and task-specific patterns of population-level laterality are discussed.Download
Am. J. Primatol. 78:1190–1200, 2016. © 2016 Wiley Periodicals, Inc.
The ontogeny of termite gathering among chimpanzees in the Goualougo Triangle, Republic of Congo
Authors: Musgrave, S., Lonsdorf, E., Morgan, D., and Sanz, C. (2020)
Acquiring tool‐assisted foraging skills can potentially improve dietary quality and increase fitness for wild chimpanzees (Pan troglodytes). In contrast to chimpanzees in East and West Africa, chimpanzees in the Congo Basin use tool sets and brush‐tipped fishing probes to gather termites. We investigated the ontogeny of these tool skills in chimpanzees of the Goualougo Triangle, Republic of Congo, and compared it to that for chimpanzees at Gombe, Tanzania. We assessed whether chimpanzees acquired simple tool behaviors and single tool use before more complex actions and sequential use of multiple tool types.
Materials and Methods
Using a longitudinal approach, we scored remote video footage to document the acquisition of termite‐gathering critical elements for 25 immature chimpanzees at Goualougo.
All chimpanzees termite fished by 2.9 years but did not manufacture brush‐tipped probes until an average of 4.3 years. Acquisition of sequential tool use extended into juvenility and adolescence. While we did not detect significant sex differences, most critical elements except tool manufacture were acquired slightly earlier by females.
These findings contrast with Gombe, where chimpanzees learn to both use and make fishing probes between ages 1.5–3.5 and acquire the complete task by age 5.5. Differences between sites could reflect tool material selectivity and design complexity, the challenge of sequential tool behaviors, and strength requirements of puncturing subterranean termite nests at Goualougo. These results illustrate how task complexity may influence the timing and sequence of skill acquisition, improving models of the ontogeny of tool behavior among early hominins who likely used complex, perishable technologies.
Learn more >>>
Effects of sounds of different quality on the behaviour and heart beat parameters of goats
Authors: Johns, J., Patt, A., Hillmann, E. (2015)
In alpine regions, bells are used to relocate free-ranging grazers like cows and goats. Considering that goats have a well-developed hearing capacity, sounds (e.g. a chime of a bell) mayact as stressors depending on their characteristics. The aim of this study was to test whethera non-uniform sound (chime of a bell) varying in amplitude and frequency and a uniform sound (sinusoidal tone) with continuously increasing amplitude and constant frequency lead to stress responses in terms of behaviour and heart beat. Twenty-nine goats were tested individually in a test arena in two sessions, each lasting five consecutive days with one trial per day. A day before the first trial, reference values were collected without playback. During the following five trials, playbacks were conducted. Differences in behaviour and heart beat parameters between test and reference values were analysed by using generalised linear mixed-effects models. During the first trial, the relative feeding duration was decreased and the relative alertness duration was increased during both stimuli, but more when goats were exposed to the non-uniform than the uniform sound. For both stimuli, the relative feeding duration increased (trial × stimulus: P = 0.05) and the relative alertness duration decreased (trial × stimulus: P = 0.004) from the first to the fifth trial but returned to the levels of the reference values sooner when goats were exposed to the uniform than the non-uniform sound. Cardiac activity was not affected by the stimuli. Altogether, the chime of a bell led to higher behavioural arousal than the uniform sinusoidal tone, indicating a potential of the chime to being more aversive to goats than a uniform sound. With repeated exposure to the stimuli, goats habituated to both stimuli, but habituation was faster to the sinusoidal sound than to the chime of a bell. Free-ranging goats in alpine regions usually are equipped with bells 24 h a day during the summer season. Thus, the question arises whether the long-term exposure to the chime of a bell might have negative effects on animal welfare.
Learn more >>>
Does nest size matter to laying hens?
Authors: Ringgenberg, N., Fröhlich, E., Harlander-Matauschek, A., Würbel, H., Roth, B. (2014)
Laying hens in loose housing systems have access to group-nests which provide space for several hens at a time to lay their eggs. They are thus rather large and the trend in the industry is to further increase the size of these nests. Though practicality is important for the producer, group-nests should also cater to the egg-laying behaviour of hens to promote good welfare. One of the factors playing a role in the attractiveness of a nest is the amount of enclosure: hens prefer more enclosure when having a choice between different nest types. The aim of this study was to investigate if hens prefer smaller group-nests to lay their eggs given that they may seem more enclosed than larger nests.
The relative preference of groups of laying hens for two nest sizes – 0.43 m2 vs. 0.86 m2 – was tested in a free-access choice test. The experiment was conducted in two consecutive trials with 100 hens each. They were housed from 18 to 36 weeks of age in five groups of 20 animals and had access to two commercial group-nests differing in internal size only. We counted eggs daily as a measure of nest preference. At 28 and 36 weeks of age, videos were taken of the pens and inside the nests on one day during the first 5 h of lights-on. The nest videos were used to record the number of hens per nest and their behaviour with a 10 min scan sampling interval. The pen videos were observed continuously to count the total number of nest visits per nest and to calculate the duration of nest visits of five focal hens per pen.
We found a relative preference for the small nest as more eggs, fewer nest visits per egg and longer nest visit durations were recorded for that nest. In addition, more hens – including more sitting hens – were in the small nests during the main egg-laying period, while the number of standing hens did not differ. These observations indicate that even though both nests may have been explored to a similar extent, the hens preferred the small nest for egg-laying.
Learn more >>>
Insect prey characteristics affecting regional variation in chimpanzee tool use
Authors: Sanz, C., Deblauwe, I., Tagg, N., Morgan, D. (2014)
It is an ongoing interdisciplinary pursuit to identify the factors shaping the emergence and maintenance of tool technology. Field studies of several primate taxa have shown that tool using behaviors vary within and between populations. While similarity in tools over spatial and temporal scales may be the product of socially learned skills, it may also reflect adoption of convergent strategies that are tailored to specific prey features. Much has been claimed about regional variation in chimpanzee tool use, with little attention to the ecological circumstances that may have shaped such differences. This study examines chimpanzee tool use in termite gathering to evaluate the extent to which the behavior of insect prey may dictate chimpanzee technology. More specifically, we conducted a systematic comparison of chimpanzee tool use and termite prey between the Goualougo Triangle in the Republic of Congo and the La Belgique research site in southeast Cameroon. Apes at both of these sites are known to use tool sets to gather several species of termites. We collected insect specimens and measured the characteristics of their nests. Associated chimpanzee tool assemblages were documented at both sites and video recordings were conducted in the Goualougo Triangle. Although Macrotermitinae assemblages were identical, we found differences in the tools used to gather these termites. Based on measurements of the chimpanzee tools and termite nests at each site, we concluded that some characteristics of chimpanzee tools were directly related to termite nest structure. While there is a certain degree of uniformity within approaches to particular tool tasks across the species range, some aspects of regional variation in hominoid technology are likely adaptations to subtle environmental differences between populations or groups. Such microecological differences between sites do not negate the possibility of cultural transmission, as social learning may be required to transmit specific behaviors among individuals.
Learn more >>>
Investigation of distances covered by fattening pigs measured with VideoMotionTracker
Authors: Julia Brendle, Steffen Hoy
The investigation was carried out with altogether 144 pigs kept in groups of 6 or 12. Every pen was equipped with perforated floor. Water and the in-house compound feed with different elements depending on the fattening period were available ad libitum during the whole fattening period. At the beginning of each fattening period all pigs were weighed and the individual rank place was calculated based on 72 h continuous infrared video-recordings. At the beginning, in the middle and at the end of the fattening period the distances covered by focus animals during 24 h were measured using the VideoMotionTracker (VMT) software tool (Mangold). The VideoMotionTracker is a software solution to allow tracking animals on a video recording using the PC mouse or a touch-screen terminal to measure distances that were covered. This measurements on pigs resulted in highly significant differences between the covered distances at the different fattening stages (at the beginning: 582 m; in the middle: 391 m; at the end: 261 m on average). Fattening pigs kept in groups of 12 each covered longer distances during the fattening period compared with pigs kept in groups of 6 (459 m versus 333 m). The differences between the means were highly significant (p < 0.001). On average female pigs covered a longer distance than castrated male pigs (443 m versus 349 m). The factor rank position did not show any significant influence on the covered distance of each focus animal. Pigs with high rank positions on average covered 399 m whereas pigs with low rank positions covered with 393 m a marginally shorter distance. Furthermore the interaction between fattening period and rank position was examined but did not show any significance either. The influence of the factor pen within group size was highly significant (p < 0.001) and the parameters live weight and covered distances were negatively correlated.Download
Tool Use in Animals
Authors: C. Sanz, J. Call, C. Boesch
Capuchin Monkeys cracking nuts with stones or chimpanzees catching termites with sticks. These are examples of animals that use tools inventively – mostly to tap into food sources. The book, “Tool Use in Animals”, offers the interdisciplinary insight into the topic of tool use in animals, recently published by Cambridge Publishing House.
The book examines the cognitive abilities and environmental factors that have shaped the tool development and tool use in animals. What makes this book extremely special: The animals were not observed in laboratory studies, but in the wild. Thus, the publication is a fascinating read and is not only aimed at scientific readership.
“Tool Use in Animals” presents contributions from several leading authors from psychology, biology and anthropology. The editors are Dr. Crickette Sanz, anthropologist at Washington University, Dr. Josep Call, psychologist at Max-Planck-Institute and Professor Christophe Boesch, director of the Max-Planck-Instituts for Evolutionary Anthropology.
Dr. Crickette Sanz is also a member of the Mangold Scientific Council and engaged in the Goualougo Triangle Ape Project which is dedicated to research and preservation of great apes in the Congo.
Contextualised behavioural measurements of personality differences obtained in behavioural tests and social observations in adult capuchin monkeys (Cebus apella)
Authors: Jana Uher, Elsa Addessi, Elisabetta Visalberghi
We applied a new framework for behavioural research on personality differences in 26 adult tufted capuchin monkeys. Using the Behavioural Repertoire x Environmental Situations Approach, we generated systematically 20 non-lexical emic personality constructs that have high ecological validity for this species. For construct operationalisation, we obtained 146 contextualised behavioural measures repeatedly in 15 experimental situations and 2 group situations using computerised and video-assisted methods. A complete repetition after a 2–3-week break within a 60-day period yielded significant test–retest reliability from individual-oriented and variable-oriented viewpoints at different levels of aggregation. In accordance with well-established findings on cross-situational consistency, internal consistency was only moderate. This new and important finding highlights fundamental differences between behavioural approaches and judgment-based approaches to personality differences.
Link to "Journal of Research in Personality" >>>
Aping expressions: Chimpanzees produce distinct laugh types when responding to laughter of others
Authors: M. Davila Ross, B. Allcock, C. Thomas, K.A. Bard
Humans have the ability to replicate the emotional expressions of others even when they undergo different emotions. Such distinct responses of expressions, especially positive expressions, play a central role in everyday social communication of humans and may give the responding individuals important advantages in cooperation and communication.Download
A dual function of echolocation: bats use echolocation calls to identify familiar and unfamiliar individuals
Authors: Silke L. Voigt-Heucke, Michael Taborsky, Dina K.N. Dechmann
Bats use echolocation for orientation during foraging and navigation. However, it has been suggested that echolocation calls may also have a communicative function, for instance between roost members. In principle, this seems possible because echolocation calls are species specific and known to differ between the sexes, and between colonies and individuals for some species. We performed playback experiments with lesser bulldog bats, Noctilio albiventris, to which we presented calls of familiar/unfamiliar conspecifics, cohabitant/noncohabitant heterospecifics and ultrasonic white noise as a control. Bats reacted with a complex repertoire of social behaviours and the intensity of their response differed significantly between stimulus categories. Stronger reactions were shown towards echolocation calls of unfamiliar conspecifics than towards heterospecifics and white noise. To our knowledge, this is the first time that bats have been found to react to echolocation calls with a suite of social behaviours. Our results also provide the first experimental evidence for acoustical differentiation by bats between familiar and unfamiliar conspecifics, and of heterospecifics. Analysis of echolocation calls confirmed significant individual differences between echolocation calls. In addition, we found a nonsignificant trend towards group signatures in echolocation calls of N. albiventris. We suggest that echolocation calls used during orientation may also communicate species identity, group affiliation and individual identity. Our study highlights the communicative potential of sonar signals that have previously been categorized as cues in animal social systems.
Genetic Architecture of Tameness in a Rat Model of Animal Domestication
Authors: Frank W. Albert
Abstract of the main publication: A common feature of domestic animals is tameness—i.e., they tolerate and are unafraid of human presence and handling. To gain insight into the genetic basis of tameness and aggression, we studied an intercross between two lines of rats (Rattus norvegicus) selected over.60 generations for increased tameness and increased aggression against humans, respectively. We measured 45 traits, including tameness and aggression, anxiety-related traits, organ weights, and levels of serum components in .700 rats from an intercross population. Using 201 genetic markers, we identified two significant quantitative trait loci (QTL) for tameness. These loci overlap with QTL for adrenal gland weight and for anxiety-related traits and are part of a five-locus epistatic network influencing tameness. An additional QTL influences the occurrence of white coat spots, but shows no significant effect on tameness. The loci described here are important starting points for finding the genes that cause tameness in these rats and potentially in domestic animals in general.
Link to Genetics website >>>
Rapid facial mimicry in orangutan play
Authors: Marina Davila Ross, Susanne Menzler and Elke Zimmermann
Emotional contagion enables individuals to experience emotions of others. This important empathic phenomenon is closely linked to facial mimicry, where facial displays evoke the same facial expressions in social partners. In humans, facial mimicry can be voluntary or involuntary, whereby its latter mode can be processed as rapid as within or at 1 s. Thus far, studies have not provided evidence of rapid involuntary facial mimicry in animals.
This study assessed whether rapid involuntary facial mimicry is present in orangutans (Pongo pygmaeus; NZ25) for their open-mouth faces (OMFs) during everyday dyadic play. Results clearly indicated that orangutans rapidly mimicked OMFs of their playmates within or at 1 s. Our study revealed the first evidence on rapid involuntary facial mimicry in non-human mammals. This finding suggests that fundamental building blocks of positive emotional contagion and empathy that link to rapid involuntary facial mimicry in humans have homologues in non-human primates.
Responding to inequities: gorillas try to maintain their competitive advantage during play fights
Authors: Edwin Van Leeuwen, Elke Zimmermann and Marina Davila Ross
Abstract: Humans respond to unfair situations in various ways. Experimental research has revealed that non-human species also respond to unequal situations in the formof inequity aversions when they have the disadvantage. The current study focused on play fights in gorillas to explore for the first time, to our knowledge, if/how non-human species respond to inequities in natural social settings. Hitting causes a naturally occurring inequity among individuals and here it was specifically assessed how the hitters and their partners engaged in play chases that followed the hitting. The results of this work showed that the hitters significantly more often moved first to run away immediately after the encounter than their partners. These findings provide evidence that non-human species respond to inequities by trying to maintain their competitive advantages. We conclude that non-human primates, like humans, may show different responses to inequities and that they may modify them depending on if they have the advantage or the disadvantage.Download
Kin recognition in the grey mouse lemur (Microcebus murinus)
Authors: Institute of Zoology, University of Veterinary Medicine Hannover / Lab course: Experimental Behavioural Biology
Kin recognition is a prerequisite for kin selection. Kin selection has been theorized as a driving force behind the evolution of group-living in primates. vocal recognition of kin has been observed in haplorhine primates (Rendall, 2004) and in the diurnal, gregarious strepsirrhine, Lemur catta (Nunn, 2000). Much less research has been done on the vocalizations of the nocturnal, solitarily foraging strepsirrhines. Our study is the first to test for vocal recognition of kin in a nongregarious strepsirrhine. Mouse lemurs are small-boiled, nocturnal, solitarily foraging strepsirrhine primates that have dispersed social networks (Braune et al., 2008). We have testet whether M. murinus females respond differently to and whistles, an alarm call (Braune et al., 2008), and trills, advertisement calls, given by their father and by unrelated males.
Food preference in two mouse lemur species (Microcebus lehilahytsara & Microcebus murinus)
Authors: Institute of Zoology, University of Veterinary Medicine Hannover / Lab course: Experimental Behavioural Biology
Two different species of mouse lemurs (Microcebus lehilahytsara and M. murinus) were tested for their food preferences. Four different food items were presented in a two paired choice test to find the most adequate reward for upcoming behavioural tests.
Acoustic cues of caller identity and affect intensity in communication calls of tree shrews (Tupaia belangeri)
Authors: Institute of Zoology, University of Veterinary Medicine Hannover / Lab course: Experimental Behavioural Biology
Comparative studies on the vocalisation of humans and animals have shown that structural and temporal variations in communication sounds serve several functions, such as to reliably transmit the affective state and individuality of the sender. These variations within a call type are named acoustic cues and are ghoutght to be important factors in the communication process of social living animals. In the present study, we have examined attention calls of tree shrews (Tupaia belangeri) for acoustic cues conveying the affective state and/or individuality of the sender. Any general physiological activation of the nervous system in a tree shrew leads to defined changes in its behavioural patterns. When aroused, it raises its tail/ruffles its tail hair and sometimes utters attention calls (von Holst, 1977). Tree shrews utter these calls in their natural habitat, when they are confronted with new environmental stimuli (Emmons, 2000).
Personality in the behaviour of great apes - temporal stability, cross-situational consistency
Authors: Jana Uher, Jens B. Asendorpf and Josep Call
Using a multidisciplinary approach, the present study complements ethological behaviour measurements with basic theoretical concepts, methods and approaches of the personality psychological trait paradigm. Its adoptability and usefulness for animal studies is tested exemplarily on a sample of 20 zoo-housed great apes (five of each of the following species): bonobos, Pan paniscus; chimpanzees, Pan troglodytes verus; gorillas, Gorilla gorilla gorilla; and orang-utans, Pongo pygmaeus abelii. Data on 76 single trait-relevant behaviours were recorded in a series of 14 laboratory based situations and in two different group situations. Data collection was repeated completely after a break of two weeks within a 50-day period. All behaviour records were sufficiently reliable. Individual- and variable-oriented analyses showed high/substantial temporal stability on different levels of aggregation. Distinctive and stable individual situational and response profiles clarified the importance of situations and of multiple trait-relevant behaviours. The present study calls for a closer collaboration between personality psychologists and behavioural biologists to tap the full potential of animal personality research.
Personality assessment in the Great Apes: Comparing ecologically valid behavior measures, behavior ratings, and adjective ratings
Authors: Jana Uher and Jens B. Asendorpf
Three methods of personality assessment (behavior measures, behavior ratings, adjective ratings) were compared in 20 zoo-housed Great Apes: bonobos (Pan paniscus), chimpanzees (Pan troglodytes verus), gorillas (Gorilla gorilla gorilla), and orangutans (Pongo pygmaeus abelii). To test a new bottom-up approach, the studied trait constructs were systematically generated from the species’ behavioral repertoires. The assessments were reliable, temporally stable, and showed substantial cross-method coherence. In most traits, behavior ratings mediated the relations between adjective ratings and behavior measures. Results suggest that high predictability of manifest behavior is best achieved by behavior ratings, not by adjectives. Empirical evidence for trait constructs beyond current personality models points to the necessity of broad and systematic approaches for valid inferences on a species’ personality structure.
Cooperative Activities in Young Children and Chimpanzees
Authors: Felix Warneken, Frances Chen and Michael Tomasello
Human children 18 – 24 months of age and 3 young chimpanzees interacted in 4 cooperative activities with a human adult partner. The human children successfully participated in cooperative problem-solving activities and social games, whereas the chimpanzees were uninterested in the social games. As an experimental manipulation, in each task the adult partner stopped participating at a specific point during the activity. All children produced at least one communicative attempt to reengage him, perhaps suggesting that they were trying to reinstate a shared goal. No chimpanzee ever made any communicative attempt to reengage the partner. These results are interpreted as evidence for a uniquely human form of cooperative activity involving shared intentionality that emerges in the second year of life.
Computer Supported Measurement of Distance Moved by Rabbits a day by Mangold Video Motion Tracker
Authors: Steffen Hoy, Justus Liebig University of Gießen
Because of several reasons it was necessary to develop and to test a new software solution to analyze the distance moved by farm animals in the field.
Teaching varies with task complexity in wild chimpanzees
Authors: Stephanie Musgravea, Elizabeth Lonsdorf, David Morgan, Madison Prestipino, Laura Bernstein-Kurtycze, Roger Mundry, and Crickette SanzEnter author(s)
Cumulative culture is a transformative force in human evolution, but the social underpinnings of this capacity are debated. Identi-fying social influences on how chimpanzees acquire tool tasks of differing complexity may help illuminate the evolutionary origins of technology in our own lineage. Humans routinely transfer tools to novices to scaffold their skill development. While tool transfers occur in wild chimpanzees and fulfill criteria for teaching, it is unknown whether this form of helping varies between populations and across tasks. Applying standardized methods, we compared tool transfers during termite gathering by chimpanzees in the Goualougo Triangle, Republic of Congo, and in Gombe, Tanzania. At Goualougo, chimpanzees use multiple, different tool types sequentially, choose specific raw materials, and perform modifications that improve tool efficiency, which could make it challenging for novices to manufac-ture suitable tools. Termite gathering at Gombe involves a single tool type, fishing probes, which can be manufactured from various materials. Multiple measures indicated population differences in tool-transfer behavior. The rate of transfers and probability of transfer upon request were significantly higher at Goualougo, while resistance to transfers was significantly higher at Gombe. Active transfers of tools in which possessors moved to facilitate possession change upon request occurred only at Goualougo, where they were the most common transfer type. At Gombe, tool requests were typically refused. We suggest that these population differences in tool-transfer behavior may relate to task complexity and that active helping plays an enhanced role in the cultural transmission of complextechnology in wild apes.Download