Barking in domestic dogs: context specificity and individual identification

In this study we sought to determine whether dog barks could be divided into subtypes based on context. We recorded barking from 10 adult dogs, Canis familiaris, of six breeds in three different test situations: (1) a disturbance situation in which a stranger rang the doorbell, (2) an isolation situation in which the dog was locked outside or in a room isolated from its owner and (3) a play situation in which either two dogs or a human and a dog played together. We analysed spectrograms of 4672 barks using macros that took 60 sequential frequency measurements and 60 sequential amplitude measurements along the length of the call. Statistical analyses revealed that barks are graded vocalizations that range from harsh, low-frequency, unmodulated calls to harmonically rich, higher-frequency, modulated calls. The harsh, low-frequency, unmodulated barks were more commonly given in the disturbance situation, and the more tonal, higher-pitch, modulated barks were more commonly given in the isolation and play situations. Disturbance barks were also longer in duration with more rapid repetition than the barks given in other contexts. Discriminant analysis revealed that dog barks can be divided into different subtypes based on context even within individual dogs, and that dogs can be identified by their bark spectrograms despite the context of the bark.     

Distress Calls of a Fast-Flying Bat (Molossus molossus) Provoke Inspection Flights but Not Cooperative Mobbing

Many birds and mammals produce distress calls when captured. Bats often approach speakers playing conspecific distress calls, which has led to the hypothesis that bat distress calls promote cooperative mobbing. An alternative explanation is that approaching bats are selfishly assessing predation risk. Previous playback studies on bat distress calls involved species with highly maneuverable flight, capable of making close passes and tight circles around speakers, which can look like mobbing. We broadcast distress calls recorded from the velvety free-tailed bat, Molossus molossus, a fast-flying aerial-hawker with relatively poor maneuverability. Based on their flight behavior, we predicted that, in response to distress call playbacks, M. molossus would make individual passing inspection flights but would not approach in groups or approach within a meter of the distress call source. By recording responses via ultrasonic recording and infrared video, we found that M. molossus, and to a lesser extent Saccopteryx bilineata, made more flight passes during distress call playbacks compared to noise. However, only the more maneuverable S. bilineata made close approaches to the speaker, and we found no evidence of mobbing in groups. Instead, our findings are consistent with the hypothesis that single bats approached distress calls simply to investigate the situation. These results suggest that approaches by bats to distress calls should not suffice as clear evidence for mobbing.     

Receivers respond differently to chick-a-dee calls varying in note composition in Carolina chickadees, Poecile carolinensis

The chick-a-dee call of the avian genus Poecile is a structurally complex vocal system because it possesses a set of simple rules that governs how the notes of the call are ordered, and variable numbers of each of the note types strung together can generate an extraordinary number of unique calls. Whereas it has been hypothesized that chick-a-dee calls with different notes may convey different information, no experimental evidence has been offered in support of the hypothesis. Previously published studies suggested that flock members use chick-a-dee calls in the context of moving to or from a feeding site. Here, we tested Carolina chickadees' responses to playbacks of chick-a-dee calls that differed in note composition. Playbacks were conducted in the field in the context of a novel food source. Our pilot data had indicated that chick-a-dee calls with relatively large numbers of ‘C’ notes were given by birds on their first contact with a novel seed stand. In the present study, we found that chickadees flew in close to the playback speaker and subsequently took seed from a seed stand more often during playbacks of chick-a-dee calls containing C notes than chick-a-dee calls not containing C notes or than control playbacks. Vocal responses of chickadees to the playbacks also differed in relation to the particular vocal signal being played back. These results indicate that receivers respond differently to chick-a-dee calls containing different compositions of note types and represent a first step to link variation in note composition and ordering in these calls to possible meanings.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved .     

Acoustic recognition in macaroni penguins: an original signature system

Penguins use vocal signatures as cues to identify their kin in dense colonies. Experimental studies of four species in two genera have pointed out that vocal signatures depend on the breeding ecology of the birds. Penguins that have a meeting site for pair members and chicks (genus Pygoscelis), as in many seabirds, have a less complex vocal signature than penguins that have no nests (genus Aptenodytes). To investigate whether this pattern would extend to other nest-building penguins, we studied the vocal signature in a species of the genus Eudyptes, the macaroni penguin, E. chrysolophus. Temporal and spectral features of signatures were analysed to determine which were likely to encode individual identity. Using a methodology derived from the theory of information, we measured and compared the amount of information given by each of these parameters by means of a stereotypy index. We then tested their effective efficiency in playback experiments of modified calls. Like Aptenodytes species, the macaroni penguins used a double coding system that integrated information in both the temporal and spectral domains. The encoding was made through the tempo given by the successive syllables of the call and the harmonic content of the call. However, information was not complementary but was mostly repeated in both domains, and variables were unidimensional as in Pygoscelis signatures. These results point out an original and simple signature system in macaroni penguins. Although they support the hypothesis of simpler systems in nest-building species they also reveal more subtle differences within this category.     

Third-Party Ranks Knowledge in Wild Vervet Monkeys (Chlorocebus aethiops pygerythrus)

The Machiavellian/Social Intelligence Hypothesis proposes that a complex social environment selected for advanced cognitive abilities in vertebrates. In primates it has been proposed that sophisticated social strategies like obtaining suitable coalition partners are an important component of social intelligence. Knowing the rank relationships between group members is a basic requirement for the efficient use of coalitions and the anticipation of counter-coalitions. Experimental evidence for such knowledge currently exists in only few species. Here, we conducted rank reversal playback experiments on adult females belonging to three different groups of free-ranging vervet monkeys (Chlorocebus aethiops pygerythrus) to test their knowledge of the female hierarchy. Playbacks simulating rank reversals (subordinate aggressing a dominant) induced longer looking times than playbacks simulating a dominant aggressing a subordinate. Vervet monkey females therefore seem to compute the rank relationships between other females. Our results suggest that detailed social knowledge about rank relationships may be widespread in primates and potentially also in other species living in stable groups.     

Interspecific and Geographic Variation in the Diets of Sympatric Carnivores: Dingoes/Wild Dogs and Red Foxes in South-Eastern Australia

Dingoes/wild dogs (Canis dingo/familiaris) and red foxes (Vulpes vulpes) are widespread carnivores in southern Australia and are controlled to reduce predation on domestic livestock and native fauna. We used the occurrence of food items in 5875 dingo/wild dog scats and 11,569 fox scats to evaluate interspecific and geographic differences in the diets of these species within nine regions of Victoria, south-eastern Australia. The nine regions encompass a wide variety of ecosystems. Diet overlap between dingoes/wild dogs and foxes varied among regions, from low to near complete overlap. The diet of foxes was broader than dingoes/wild dogs in all but three regions, with the former usually containing more insects, reptiles and plant material. By contrast, dingoes/wild dogs more regularly consumed larger mammals, supporting the hypothesis that niche partitioning occurs on the basis of mammalian prey size. The key mammalian food items for dingoes/wild dogs across all regions were black wallaby (Wallabia bicolor), brushtail possum species (Trichosurus spp.), common wombat (Vombatus ursinus), sambar deer (Rusa unicolor), cattle (Bos taurus) and European rabbit (Oryctolagus cuniculus). The key mammalian food items for foxes across all regions were European rabbit, sheep (Ovis aries) and house mouse (Mus musculus). Foxes consumed 6.1 times the number of individuals of threatened Critical Weight Range native mammal species than did dingoes/wild dogs. The occurrence of intraguild predation was asymmetrical; dingoes/wild dogs consumed greater biomass of the smaller fox. The substantial geographic variation in diet indicates that dingoes/wild dogs and foxes alter their diet in accordance with changing food availability. We provide checklists of taxa recorded in the diets of dingoes/wild dogs and foxes as a resource for managers and researchers wishing to understand the potential impacts of policy and management decisions on dingoes/wild dogs, foxes and the food resources they interact with.     

Resource partitioning among cape foxes,bat-eared foxes,and black-backed jackals in South Africa

Cape foxes (Vulpes chama) and bat-eared foxes (Otocyon megalotis) are sympatric with black-backed jackals (Canis mesomelas) over much of southern Africa, although competition with and/or predation by jackals may suppress local populations of both fox species. From 2005 to 2008, we captured, radio-collared, and monitored 11 cape foxes, 22 bat-eared foxes, and 15 black-backed jackals on a game ranch in South Africa to investigate their spatial, habitat, temporal, and dietary resource overlap. Mean annual home-range sizes were 27.7 km² for cape foxes, 5.0 km² for bat-eared foxes, and 17.8 km² for jackal family groups. Home ranges overlapped completely between species, although core areas overlapped less (<45%), with cape foxes and jackals overlapping the least (12%). When active, cape foxes, but not bat-eared foxes, used core areas of jackal groups less than expected. Additionally, both fox species used jackal core areas less than expected for their den sites, suggesting areas outside jackal core areas were used as refuges by foxes. Strong levels of habitat partitioning were not apparent at the study site or home-range levels, although habitat selection for den sites differed between jackals and cape foxes. Jackals were the most diurnal across seasons, whereas cape foxes were the most nocturnal. Diets overlapped little (R₀ = 0.20–0.34) among the canid species, with bat-eared foxes overlapping the least with the others. Jackals killed at least 5 collared bat-eared foxes and 1 collared cape fox, indicating potential interference competition, probably for exclusive use of territorial space rather than over shared resources. We conclude that bat-eared foxes coexisted with jackals primarily by their dietary specialization and group living. Cape foxes coexisted with jackals by exhibiting high levels of spatial, habitat, temporal, and dietary partitioning. Surprisingly, the fox species exhibited positive associations with each other. Our results show the mechanisms that may allow jackals to suppress fox populations, yet also show how foxes, in turn, use different mechanisms to coexist with a dominant canid. © 2012 The Wildlife Society.     

Behavior and blood catecholamines of captive belugas during playbacks of noise from an oil drilling platform

Belugas (Delphinapterus leucas) depend on sounds for communication and echolocation. To address the concerns that noise from oil platforms may have adverse effects, we examined behavioral responses of four captive belugas to playbacks of noise from SEDCO 708, a semi-submersible drilling platform. Swim patterns, social groups, and respiration/dive rates were not statistically different before and during playbacks. We assayed levels of blood catecholamines before and after playbacks as a measure of stress. Blood epinephrine and norepinephrine levels measured immediately after playbacks were not elevated. Using the parameters we selected, we could not detect any short-term behavioral or physiological effects of drilling noise playbacks on these captive belugas. However, care should be taken in extrapolating these results to the behavior of wild belugas around oil platforms.     

Individual and Species Differences in Quail Calls (Coturnix c. japonica,c. c. coturnix and a Hybrid)

Male European and Japanese male quail have very stereotyped calls. This study examined which parameters best discriminated between individuals, and which between the two sub-species and a hybrid of the two (European father x Japanese mother). Recordings were made of several calls from individual Japanese, European and hybrid quail, from which sonograms were made and analyzed. We found that parameters describing the time structure of the call discriminated best between individuals. Time structure also showed the greatest differences between the two sub-species and the hybrid. Hybrid calls were extremely variable, individual hybrids often producing more than one call type, occasionally of both sub-species types. However, individuals could still be identified from the call parameters. In addition, we investigated responses of males to playbacks of calls from all three quail types. European and Japanese males responded most strongly, with calling, to the playbacks of the calls of their own sub-species, intermediately to playbacks of the hybrid and least to those of the other sub-species.     

Decline and fall: The causes of group failure in cooperatively breeding meerkats

In many social vertebrates, variation in group persistence exerts an important effect on individual fitness and population demography. However, few studies have been able to investigate the failure of groups or the causes of the variation in their longevity. We use data from a long‐term study of cooperatively breeding meerkats, Suricata suricatta, to investigate the different causes of group failure and the factors that drive these processes. Many newly formed groups failed within a year of formation, and smaller groups were more likely to fail. Groups that bred successfully and increased their size could persist for several years, even decades. Long‐lived groups principally failed in association with the development of clinical tuberculosis, Mycobacterium suricattae, a disease that can spread throughout the group and be fatal for group members. Clinical tuberculosis was more likely to occur in groups that had smaller group sizes and that had experienced immigration.     

Social monitoring via close calls in meerkats

Social monitoring of the actions of group members is thought to be a key development associated with group living. Humans constantly monitor the behaviour of others and respond to them in a flexible way depending on past interactions and the current social context. While other primates have also been reported to change their behaviour towards other group members flexibly based on the current state of their relationship, empirical evidence is typically linked to contextually specific events such as aggressive or reproductive interactions. In the cooperatively breeding meerkat (Suricata suricatta), we investigated whether subordinate females use frequently emitted, non-agonistic close calls to monitor the location of the dominant female and whether they subsequently adjust their response based on recent social interactions during conflict and non-conflict periods. Subjects discriminated between the close calls of the dominant female and control playbacks, responding by approaching the loudspeaker and displaying submissive behaviour only if they were currently threatened by eviction. Our results suggest that meerkats assess the risk for aggressive interactions with close associates depending on social circumstances, and respond accordingly. We argue that social monitoring based on non-agonistic cues is probably a common mechanism in group-living species that allows the adjustment of behaviour depending on variation in relationships.     

The Emergence of Groups and Inequality through Co-Adaptation

The emergence of groups and of inequality is often traced to pre-existing differences, exclusionary practices, or resource accumulation processes, but can the emergence of groups and their differential success simply be a feature of the behaviors of a priori equally-capable actors who have mutually adapted? Using a simple model of behavioral co-adaptation among agents whose individual actions construct a common environment, we present evidence that the formation of unequal groups is endemic to co-adaptive processes that endogenously alter the environment; agents tend to separate into two groups, one whose members stop adapting earliest (the in-group), and another comprising agents who continue to adapt (the out-group). Over a wide range of model parameters, members of the in-group are rewarded more on average than members of the out-group. The primary reason is that the in-group is able to have a more profound influence on the environment and mold it to the benefit of its members. This molding capacity proves more beneficial than the persistence of adaptivity, yet, crucially, which agents are able to form a coalition to successfully exert this control is strongly contingent on random aspects of the set of agent behaviors. In this paper, we present the model, relevant definitions, and results. We then discuss its implications for the study of complex adaptive systems generally.     

Experimental evidence for group hunting via eavesdropping in echolocating bats

Group foraging has been suggested as an important factor for the evolution of sociality. However, visual cues are predominantly used to gain information about group members'' foraging success in diurnally foraging animals such as birds, where group foraging has been studied most intensively. By contrast, nocturnal animals, such as bats, would have to rely on other cues or signals to coordinate foraging. We investigated the role of echolocation calls as inadvertently produced cues for social foraging in the insectivorous bat Noctilio albiventris. Females of this species live in small groups, forage over water bodies for swarming insects and have an extremely short daily activity period. We predicted and confirmed that (i) free-ranging bats are attracted by playbacks of echolocation calls produced during prey capture, and that (ii) bats of the same social unit forage together to benefit from passive information transfer via the change in group members'' echolocation calls upon finding prey. Network analysis of high-resolution automated radio telemetry confirmed that group members flew within the predicted maximum hearing distance 94±6 per cent of the time. Thus, echolocation calls also serve as intraspecific communication cues. Sociality appears to allow for more effective group foraging strategies via eavesdropping on acoustical cues of group members in nocturnal mammals.     

Pathology and Epidemiology of Ceruminous Gland Tumors among Endangered Santa Catalina Island Foxes (Urocyon littoralis catalinae) in the Channel Islands,USA

In this study, we examined the prevalence, pathology, and epidemiology of tumors in free-ranging island foxes occurring on three islands in the California Channel Islands, USA. We found a remarkably high prevalence of ceruminous gland tumors in endangered foxes (Urocyon littoralis catalinae) occurring on Santa Catalina Island (SCA)—48.9% of the dead foxes examined from 2001–2008 had tumors in their ears, and tumors were found in 52.2% of randomly-selected mature (≥ 4 years) foxes captured in 2007–2008, representing one of the highest prevalences of tumors ever documented in a wildlife population. In contrast, no tumors were detected in foxes from San Nicolas Island or San Clemente Island, although ear mites (Otodectes cynotis), a predisposing factor for ceruminous gland tumors in dogs and cats, were highly prevalent on all three islands. On SCA, otitis externa secondary to ear mite infection was highly correlated with ceruminous gland hyperplasia (CGH), and tumors were significantly associated with the severity of CGH, ceruminous gland dysplasia, and age group (older foxes). We propose a conceptual model for the formation of ceruminous gland tumors in foxes on SCA that is based on persistent, ubiquitous infection with ear mites, and an innate, over exuberant inflammatory and hyperplastic response of SCA foxes to these mites. Foxes on SCA are now opportunistically treated with acaricides in an attempt to reduce mite infections and the morbidity and mortality associated with this highly prevalent tumor.     

Distributed leadership in semifree-ranging white-faced capuchin monkeys

We investigated the initiation of group movements in white-faced capuchin monkeys, Cebus capucinus, with the aim of determining whether a single individual with high dominance status consistently leads movements or whether leadership is distributed between group members. The group studied was reared in semifree-ranging conditions. A multivariate analysis followed by univariate analyses demonstrated that leadership was not concentrated on a single individual in this species. All individuals could initiate a collective movement. Nearly half of group members regularly succeeded in recruiting at least three followers. Although both sexes had similar rates of start attempts, females succeeded more frequently than males. We found no significant effect of the dominance status on the percentage of successful attempts. The use of a slow speed, looking back towards the other group members, or trills by the initiator heightened the likelihood of success in group movement initiation. An initiator starting from a core position in a clumped group was more successful than one starting from an edge position in a clumped group or from a dispersed group. Furthermore, the probability of successful start attempts was higher when the group remained stationary for a long period. Leadership in white-faced capuchins appears to be distributed between group members rather than exclusively concentrated on high-ranking individuals. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

Vocalization toward conspecifics in silver foxes (Vulpes vulpes) selected for tame or aggressive behavior toward humans

We examined the production of different vocalizations in three strains of silver fox (unselected, aggressive, and tame) attending three kinds of behavior (aggressive, affiliative, and neutral) in response to their same-strain conspecifics. This is a follow-up to previous experiments which demonstrated that in the presence of humans, tame foxes produced cackles and pants but never coughed or snorted, whilst aggressive foxes produced coughs and snorts but never cackled or panted. Thus, cackle/pant and cough/snort were indicative of the tame and aggressive fox strains respectively toward humans. Wild-type unselected foxes produced cough and snort toward humans similarly to aggressive foxes. Here, we found that vocal responses to conspecifics were similar in tame, aggressive and unselected fox strains. Both cackle/pant and cough/snort occurred in foxes of all strains. The difference in the use of cackle/pant and cough/snort among these strains toward humans and toward conspecifics suggest that silver foxes do not perceive humans as their conspecifics. We speculate that these vocalizations are produced in response to a triggering internal state, affiliative or aggressive, that is suppressed by default in these fox strains toward humans as a result of their strict selection for tame or aggressive behavior, whilst still remaining flexible toward conspecifics.     

Moving calls: a vocal mechanism underlying quorum decisions in cohesive groups

Members of social groups need to coordinate their behaviour when choosing between alternative activities. Consensus decisions enable group members to maintain group cohesion and one way to reach consensus is to rely on quorums. A quorum response is where the probability of an activity change sharply increases with the number of individuals supporting the new activity. Here, we investigated how meerkats (Suricata suricatta) use vocalizations in the context of movement decisions. Moving calls emitted by meerkats increased the speed of the group, with a sharp increase in the probability of changing foraging patch when the number of group members joining the chorus increased from two up to three. These calls had no apparent effect on the group's movement direction. When dominant individuals were involved in the chorus, the group's reaction was not stronger than when only subordinates called. Groups only increased speed in response to playbacks of moving calls from one individual when other group members emitted moving calls as well. The voting mechanism linked to a quorum probably allows meerkat groups to change foraging patches cohesively with increased speed. Such vocal coordination may reflect an aggregation rule linking individual assessment of foraging patch quality to group travel route.     

Alarm Calls of Marmosets (Callithrix geoffroyi) to Snakes and Perched Raptors

Communication about the presence of predators is an important benefit of group living. Critical information about the nature of danger can be conveyed through referential alarm calls. Raptors pose a significant predatory threat to callitrichid species. Unlike a raptor in flight, a perched raptor cannot attack suddenly at great speed, and it can be monitored from a safe distance. In this sense a perched bird may pose a threat more similar to that of a terrestrial predator such as a snake. Here we compare predatory contexts by addressing these two questions: 1) Do marmosets produce acoustically distinct alarm calls to snake models and perched raptor models? 2) Do the visual responses of the marmosets to the playbacks of perched raptor–elicited calls differ from those given to the playbacks of calls given in response to snakes? We recorded alarm calls from two groups of outdoor-housed Geoffroy’s marmosets (Callithrix geoffroyi) in response to predator models. Later, we played back stimuli created from these recordings to the marmosets and scored their gaze direction. Results show that calls given to models of perched raptors are acoustically distinct from those given to models of snakes. Further, the relative number of upward to downward looks while listening to the playbacks of perched raptor–elicited calls was significantly greater than it was for snake-elicited calls. Reactions to airborne raptors are known to elicit freezing or rapid flight, neither of which occurred in response to our playbacks. Our data suggest a greater complexity in the alarm call repertoire of marmosets than previously demonstrated.     

Responses of Redfronted Lemurs to Experimentally Modified Alarm Calls: Evidence for Urgency-Based Changes in Call Structure

Abstract The aim of this study was to investigate how information about the affective state is expressed in vocalizations. Alarm calls can serve as model systems with which to study this general question. Therefore, we examined the information content of terrestrial predator alarm calls of redfronted lemurs ( Eulemur fulvus rufus ), group-living Malagasy primates. Redfronted lemurs give specific alarm calls only towards raptors, whereas calls given in response to terrestrial predators (woofs) are also used in other situations characterized by high arousal. Woofs may therefore have the potential to express the perceived risk of a given threat. In order to examine whether different levels of arousal are expressed in call structure, we analysed woofs given during inter-group encounters or in response to playbacks of a barking dog, assuming that animals engaged in inter-group encounters experience higher arousal than during the playbacks of dog barks. A multivariate acoustic analysis revealed that calls given during group encounters were characterized by higher frequencies than calls given in response to playbacks of dog barks. In order to examine whether this change in call structure is salient to conspecifics, we conducted playback experiments with woofs, modified in either amplitude or frequencies. Playbacks of calls with increased frequency or amplitude elicited a longer orienting response, suggesting that different levels of arousal are expressed in call structure and provide meaningful information for listeners. In conclusion, the results of our study indicate that the information about the sender's affective state is expressed in the structure of vocalizations.     

The Movement Ecology of the Straw-Colored Fruit Bat,Eidolon helvum,in Sub-Saharan Africa Assessed by Stable Isotope Ratios

Flying foxes (Pteropodidae) are key seed dispersers on the African continent, yet their migratory behavior is largely unknown. Here, we studied the movement ecology of the straw-colored fruit bat, Eidolon helvum, and other fruit bats by analyzing stable isotope ratios in fur collected from museum specimens. In a triple-isotope approach based on samples of two ecologically similar non-migratory pteropodids, we first confirmed that a stable isotope approach is capable of delineating between geographically distinct locations in Sub-Saharan Africa. A discriminant function analysis assigned 84% of individuals correctly to their capture site. Further, we assessed how well hydrogen stable isotope ratios (δ²H) of fur keratin collected from non-migratory species (n = 191 individuals) records variation in δ²H of precipitation water in sub-Saharan Africa. Overall, we found positive, negative and no correlations within the six studied species. We then developed a reduced major axis regression equation based on individual data of non-migratory species to predict where potentially migratory E. helvum (n = 88) would come from based on their keratin δ²H. Across non-migratory species, δ²H of keratin and local water correlated positively. Based on the isoscape origin model, 22% of E. helvum were migratory, i.e. individuals had migrated over at least 250 km prior to their capture. Migratory individuals came from locations at a median distance of about 860 km from the collection site, four even from distances of at least 2,000 km. Ground-truthing of our isoscape origin model based on keratin δ²H of extant E. helvum (n = 76) supported a high predictive power of assigning the provenance of African flying foxes. Our study highlights that stable isotope ratios can be used to explain the migratory behavior of flying foxes, even on the isotopically relatively homogenous African continent, and with material collected by museums many decades or more than a century ago.