Ontogeny of heart rate in embryonic and nestling crows (Corvus corone and Corvus macrorhynchos)

The developmental patterns of mean heart rate (MHR) and instantaneous heart rate (IHR) were investigated in embryos and chicks of altricial Corvuscorone and Corvus macrorhynchos. The MHR of embryos increased linearly with time from 250 beats · min⁻¹ at mid-incubation to 290 beats · min⁻¹ in hatchlings. MHR during the pipping period was maximal, but only marginally higher than in hatchlings. MHR was stable at about 290–300 beats · min⁻¹ during the 1st week after hatching. Spontaneous heart rate (HR) decelerations and accelerations were found in embryos and chicks, disturbing the baseline HR with increasing frequency during development. However, the IHR accelerations developed later and were less frequent than in precocial species. IHR and body temperature decreased during mild cold exposure (23–25 °C) and IHR accelerations were reduced in nestlings during the 1st week. We suggest that the development of parasympathetic control of HR in crows occurs at 60% of incubation, similar to precocial embryos, but sympathetic control may be delayed and suppressed in contrast to precocial embryos. Accepted: 3 March 1999     

Categorical learning between 'male' and 'female' photographic human faces in jungle crows (Corvus macrorhynchos)

We trained jungle crows to discriminate among photographs of human face according to their sex in a simultaneous two-alternative task to study their categorical learning ability. Once the crows reached a discrimination criterion (greater than or equal to 80% correct choices in two consecutive sessions; binomial probability test, p < .05), they next received generalization and transfer tests (i.e., greyscale, contour, and ‘full’ occlusion) in Experiment 1 followed by a ‘partial’ occlusion test in Experiment 2 and random stimuli pair test in Experiment 3. Jungle crows learned the discrimination task in a few trials and successfully generalized to novel stimuli sets. However, all crows failed the greyscale test and half of them the contour test. Neither occlusion of internal features of the face, nor randomly pairing of exemplars affected discrimination performance of most, if not all crows. We suggest that jungle crows categorize human face photographs based on perceptual similarities as other non-human animals do, and colour appears to be the most salient feature controlling discriminative behaviour. However, the variability in the use of facial contours among individuals suggests an exploitation of multiple features and individual differences in visual information processing among jungle crows.     

Dominance in assamese macaques (Macaca assamensis)

A field study of 64 assamese macaques (Macaca assamensis) was conducted at a temple site in Assam, India. Focal and all occurrence scan techniques were used to collect data on agonistic, grooming, and sexual behavior. More than 1,000 hr of data were summarized into agonistic dominance, grooming, and mounting matrices. Rank hierarchies were constructed for all three and compared. We also directly compared each cell in each matrix with the corresponding cells in the other matrices. A nearly linear agonistic dominance hierarchy was found, but it did not correlate with the directionality of mounting or grooming. Adult males mounted females, generally were dominant to females and groomed females more often than they were groomed by females. Younger males groomed older males and were also generally subordinate to older males. These age and sex effects produced some inter‐correlations among grooming, mounting, and dominance but only for specific age‐sex classes. Theoretical models of social exchange were not considered useful in predicting the complex patterns of grooming, mounting, and dominance seen in the present group. Whereas such models may "explain" existing data for some groups and have gained widespread acceptance, they must be empirically tested. Am. J. Primatol. 48:283–289, 1999. © 1999 Wiley‐Liss, Inc.     

Formation of linear dominance relationship in captive jungle crows (Corvus macrorhynchos): implications for individual recognition

Jungle crows (Corvus macrorhynchos) flexibly change their social forms depending on their age, time of the day, and the season. In the daytime, paired adults behave territorially and unpaired subadults form small flocks of ten birds, whereas at night hundreds of birds roost together. In the breeding season, pairings remain in their nest all day. This fission-fusion raises questions about the underlying social structure and the cognitive capability of jungle crows. In this study, dyadic encounters were used to investigate dominance relationships (linear or non-linear) and the underlying mechanisms in captive jungle crows. Fourteen crows were tested in 455 encounters (i.e., 5 encounters per dyad), and a stable linear dominance relationship emerged. Sex and aggressiveness were determinants as individual characteristics for dominance formation. Males dominated females, and more aggressive individuals dominated less aggressive ones. Aggressive interactions in dyads occurred primarily during the first encounter and drastically declined during subsequent encounters without any signs of a confidence effect. These results suggest that, in captive jungle crow, a linear form of dominance is intrinsically determined by sex and aggressiveness and maintained extrinsically by memories of past outcomes associated with specific individuals, implying individual recognition.     

Foot-use laterality in the Japanese jungle crow (Corvus macrorhynchos)

Laterality of foot-use behaviour was examined in jungle crows (Corvus macrorhynchos). Consistency of laterality was also verified in comparison with two different behaviours. One was beak-scratching, and another was food-holding. Significant bias of foot-use laterality was found in 11 of 13 tested subjects for beak-scratching and in 10 of 12 tested subjects for food-holding. Bias of foot-use laterality was not common among footed subjects, suggesting no population-level bias. However, a significant number of footed subjects (10 of 12) who were tested in both behaviours showed consistent laterality irrespective of behavioural differences. These results suggest that jungle crows have strong individual-level laterality in foot-use behaviour.     

Cooperative problem solving in rooks (Corvus frugilegus)

Recent work has shown that captive rooks, like chimpanzees and other primates, develop cooperative alliances with their conspecifics. Furthermore, the pressures hypothesized to have favoured social intelligence in primates also apply to corvids. We tested cooperative problem-solving in rooks to compare their performance and cognition with primates. Without training, eight rooks quickly solved a problem in which two individuals had to pull both ends of a string simultaneously in order to pull in a food platform. Similar to chimpanzees and capuchin monkeys, performance was better when within-dyad tolerance levels were higher. In contrast to chimpanzees, rooks did not delay acting on the apparatus while their partner gained access to the test room. Furthermore, given a choice between an apparatus that could be operated individually over one that required the action of two individuals, four out of six individuals showed no preference. These results may indicate that cooperation in chimpanzees is underpinned by more complex cognitive processes than that in rooks. Such a difference may arise from the fact that while both chimpanzees and rooks form cooperative alliances, chimpanzees, but not rooks, live in a variable social network made up of competitive and cooperative relationships.     

Apoptosis-mediated seasonal testicular regression in the Japanese Jungle crow (Corvus macrorhynchos)

The present study investigated effects of apoptosis observed during seasonal testicular regression in Japanese Jungle Crows. The study was conducted during January to June 2008, 2009. Testes from adults captured during non-breeding (January), prebreeding (February to mid-March), main-breeding (late March to early May), transition (mid-May to late May), and post-breeding (June) seasons were analyzed. Apoptosis was assessed by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay. Paired-testis volume increased 95-fold from the non-breeding to the main-breeding season (P < 0.05), and subsequently decreased 26-fold from the main breeding to the post-breeding season (P < 0.05). Testicular activity was evaluated from the total germ cell count and sperm index, which increased 42- and 5-fold, respectively, in the main-breeding season, and subsequently decreased 33- and 5-fold in the post-breeding season. In testes, TUNEL-positive germ cells were at low levels in the non-breeding season, absent in the prebreeding and the main-breeding seasons, and highest in mid-May (P < 0.05). In contrast, TUNEL-positive Sertoli cells occurred only in late-April. In addition, TUNEL-positive fibroblast-like cells were observed in the outer zone of the tunica albuginea in the post-breeding season. Collectively, these data suggested that the seasonal rise in the testicular competence occurred slowly in Japanese Jungle Crows; however, testis function was terminated rapidly after the breeding season. Furthermore, we concluded, similar to other avian species, Sertoli cell apoptosis followed by massive germ cell death was responsible for rapid testicular regression in Jungle Crows.     

Advances in the understanding of same-sex and opposite-sex sexual harassment

Sexual harassment has traditionally been studied as men's harassment of women. This has led to a lack of knowledge about same sex harassment, and women harassing peers. This has also downplayed the inherent sexual nature of sexual harassment acts. While keeping in mind that sexual harassment is undesirable and causes distress, one needs to consider that many acts that are perceived as unwanted may not primarily be motivated by a wish to derogate but rather by an interest in soliciting short-term sex. In the current study we examined both perpetrators as well as victims of harassment, and specified both sex of perpetrator and target (a total of eight sex constellations). We reproduced the previously found association between unrestricted sociosexuality and sexual harassment in a representative sample of 1326 high school students (57% women). In all regression models sociosexuality outcompeted traditional measures such as porn exposure, rape stereotypes and hostile sexism. Based on the original work we divided the harassment acts into two groups of tactics: sexual solicitation and competitor derogation. Men were particularly subject to derogatory tactics from other men, while women were particularly subject to solicitation from opposite sex peers. Sexual harassment may be understood better from a human sexual strategies perspective, including competitor derogation and mate solicitation. As such, sociosexual orientation predicts both same sex derogation and opposite sex solicitation. The current results highlight the importance of considering the sex of both perpetrator and target. This advanced understanding of the inherently sexual nature of sexual harassment needs to inform future prevention studies. Unrestricted sociosexuality predicts sexual harassment in all constellations better than traditional social science models.     

Effect of rearing style on the development of social behaviour in young ravens (Corvus corax)

Early social experiences can affect the development and expression of individual social behaviour throughout life. In particular, early-life social deprivations, notably of parental care, can later have deleterious consequences. We can, therefore, expect rearing procedures such as hand-raising—widely used in ethology and socio-cognitive science—to alter the development of individual social behaviour. We investigated how the rearing style later affected (a) variation in relationship strength among peers and (b) individuals’ patterns of social interactions, in three captive groups of juvenile non-breeders consisting of either parent-raised or hand-raised birds, or a mix of both rearing styles. In the three groups, irrespectively of rearing style: strongest relationships (i.e., higher rates of association and affiliations) primarily emerged among siblings and familiar partners (i.e., non-relatives encountered in early life), and mixed-sex and male–male partners established relationships of similar strength, indicating that the rearing style does not severely affect the quality and structure of relationships in young ravens. However, compared to parent-raised ravens, hand-raised ravens showed higher connectedness, i.e., number of partners with whom they mainly associated and affiliated, but formed on average relationships of lower strength, indicating that social experience in early life is not without consequences on the development of ravens’ patterns of social interaction. The deprivation of parental care associated with the presence of same-age peers during hand-raising seemed to maximize ravens’ propensity to interact with others, indicating that besides parents, interactions with same-age peers matter. Opportunities to interact with, and socially learn from peers, might thus be the key to the acquisition of early social competences in ravens.     

Early Ontogeny of the Behavior of Young in Large-Billed Crows (Corvus macrorhynchos) in Their Natural Habitat

Biology Bulletin - The early ontogeny of behavior of corvid juveniles in their natural habitat was studied, and the large-billed crow (Corvus macrorhynchos) taken as an example. Research was...     

Using biological markets principles to examine patterns of grooming exchange in Macaca thibetana

Biological markets principles offer testable hypotheses to explain variation in grooming exchange patterns among nonhuman primates. They predict that when within-group contest competition (WGC) is high and dominance hierarchies steep, grooming interchange with other "commodity" behaviors (such as agonistic support) should prevail. In contrast, when WGC is low and gradients shallow, market theory predicts that grooming reciprocity should prevail. We tested these predictions in a wild, provisioned Tibetan macaque (Macaca thibetana) group across six time periods during which the group had been subjected to varying degrees of range restriction. Data on female-female aggression, grooming, and support were collected using all-occurrences and focal animal sampling techniques, and analyzed using ANCOVA methods and correlation analyses. We found that hierarchical steepness varied significantly across periods, but did not correlate with two indirect indicators of WGC (group size and range restriction) in predicted directions. Contrary to expectations, we found a negative correlation between steepness and group size, perhaps because the responses of group members to external risks (i.e. prolonged and unavoidable exposure to humans) may have overshadowed the effects of WGC. As predicted, grooming reciprocity was significant in each period and negatively correlated with steepness, even after we controlled group size, kinship, rank differences, and proximity. In contrast, there was no evidence for grooming interchange with agonistic support or for a positive relationship between interchange and steepness. We hypothesize that stressful conditions and/or the presence of stable hierarchies during each period may have led to a greater market demand for grooming than support. We suggest that future studies testing these predictions consider more direct measures of WGC and commodities in addition to support, such as feeding tolerance and access to infants.     

No Short‐Term Contingency Between Grooming and Food Tolerance in Barbary Macaques (Macaca sylvanus)

The exchange of services such as allo‐grooming, allo‐preening, food tolerance and agonistic support has been observed in a range of species. Two proximate mechanisms have been proposed to explain the exchanges of services in animals. First, an animal can give a service to a partner depending on how the partner behaved towards it in the recent past. This mechanism is usually tested by examining the within‐dyad temporal relation between events given and received over short time periods. Second, the partner choice mechanism assumes that animals give favours towards specific partners but not others, by comparing how each partner behaved towards them over longer time frames. As such, the partner choice mechanism does not make specific predictions on a temporal contingency between services received and given over short time frames. While there is evidence for a long‐term positive correlation between services exchanged in animals, results for short‐term contingencies between services given and received are mixed. Our study investigated the exchange of grooming for food tolerance in a partially provisioned group of Barbary macaques, by analysing the short‐term contingency between these events. Tolerance over food was compared immediately after grooming and in control condition, using food of different shareability. We found no evidence that grooming increases food tolerance or decrease aggression around food in the short term. Food tolerance was affected by the shareability of the food and the sex of the partners. The exchanges of grooming and food tolerance in non‐human primates may be little affected by recent single events. We suggest that long‐term exchanges between services given and received and social partner choice may play a more important role in explaining social interactions than short‐term contingent events.     

Grooming in mandrills and the time frame of reciprocal partner choice

In this study, we examined the time frame of reciprocal partner choice in the grooming interactions of captive mandrills (Mandrillus sphinx) in order to test the hypothesis that the cognitive limitations of primates constrain the occurrence of reciprocation to short time intervals. In contrast to this hypothesis, mandrills groomed preferentially those individuals that groomed them more even when cases of immediate reciprocation were excluded from the analysis. These results show that mandrills were not limited to reciprocating grooming over short time intervals. It is proposed that a system of emotional bookkeeping may support the ability of primates to reciprocate over long time frames. Am. J. Primatol. 71:884–888, 2009. © 2009 Wiley‐Liss, Inc.     

On the evolutionary and ontogenetic origins of tool‐oriented behaviour in New Caledonian crows (Corvus moneduloides)

New Caledonian crows (Corvus moneduloides) are prolific tool users in captivity and in the wild, and have an inherited predisposition to express tool‐oriented behaviours. To further understand the evolution and development of tool use, we compared the development of object manipulation in New Caledonian crows and common ravens (Corvus corax), which do not routinely use tools. We found striking qualitative similarities in the ontogeny of tool‐oriented behaviour in New Caledonian crows and food‐caching behaviour in ravens. Given that the common ancestor of New Caledonian crows and ravens was almost certainly a caching species, we therefore propose that the basic action patterns for tool use in New Caledonian crows may have their evolutionary origins in caching behaviour. Noncombinatorial object manipulations had similar frequencies in the two species. However, frequencies of object combinations that are precursors to functional behaviour increased in New Caledonian crows and decreased in ravens throughout the study period, ending 6 weeks post‐fledging. These quantitative observations are consistent with the hypothesis that New Caledonian crows develop tool‐oriented behaviour because of an increased motivation to perform object combinations that facilitate the necessary learning. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 870–877.     

Tolerance and Social Facilitation in the Foraging Behaviour of Free‐Ranging Crows (Corvus corone corone; C. c. cornix)

Social foraging provides animals with opportunities to gain knowledge about available food. Studies indicate that animals are influenced by social context during exploration and are able to learn socially. Carrion and hooded crows, which are opportunistic generalists with flexible social systems, have so far received little focus in this area. We combined observational and experimental approaches to investigate social interactions during foraging and social influences on crow behaviour within a free‐ranging population at Vienna Zoo, which included 115 individually marked crows. We expected the crows to be tolerant of conspecifics during foraging due to high food abundance. We predicted that social context would enhance familiar object exploration, as well as a specific foraging strategy: predation by crows on other species. We found that crows were highly tolerant of one another, as reflected by their high rates of cofeeding – where they fed directly beside conspecific(s) – relative to affiliative or agonistic interactions. Evidence for social facilitation – when the observer's behaviour is affected by the mere presence of a model – was found in both object exploration and predation behaviour. Specifically, crows touched the objects more frequently when others were present (whilst only approaching the objects when alone), and conspecifics were present more frequently during predation events involving the high‐risk target species. Evidence for enhancement during object exploration – where the observer's attention is drawn to a place or object by a model's actions – was not confirmed in this context. Our results highlight the role played by the presence of conspecifics across different contexts: natural foraging behaviour, familiar object exploration and a specific foraging strategy. To our knowledge, this is one of the first corvid studies aimed at teasing apart specific social influence and learning mechanisms in the field. These crows therefore make promising candidates for studying social learning and its consequences under naturalistic conditions.     

Effects of early rearing experience on adult behavior and nesting in captive Hawaiian crows (Corvus hawaiiensis)

Behavioral data were collected during the breeding season on eight pairs of Hawaiian crows (Corvus hawaiiensis) housed at two facilities on different islands. All data were collected from videocamera time‐lapse recordings of the nesting platforms. Behaviors included frequency of nest cup manipulation, percent of time spent on nest, allopreening, play, and stereotypy. The number of breeding pairs increased from four in 1996 to six in 1997, to seven in 1998, and to eight in 1999. Five of the older birds (three males and two females) were solitary‐reared for most if not all of their first year, while the remaining 12 birds were all socially reared. Significant differences were found between isolate‐ and socially‐reared birds, with isolate‐reared birds having higher rates of solo play (P = 0.0041) and stereotypies (P = 0.0090). Pairs that were comprised of at least one isolate‐reared bird engaged in significantly less allopreening (P = <0.0001) than pairs in which both birds were socially reared. From 1996 to 1999, 87 eggs were laid, with a mean of 1.88 ± 0.24 SEM eggs per clutch. Only three females produced clutches every year, and they were responsible for 85.1% of the eggs laid. Although not significant, the mean number of clutches produced per pair decreased from 2.50 ± 0.65 in 1996 to 0.87 ± 0.99 in 1999. Age of females does not appear to be a critical factor in the decrease in clutch production. New pairing combinations are under way in an effort to improve propagation in this highly endangered species. Zoo Biol 21:59–75, 2002. © 2002 Wiley‐Liss, Inc.