Singing behavior and singing functions of black‐crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang,central Yunnan,China

We used data on loud duetted and solo songs collected from one habituated polygynous group of black‐crested gibbons (Nomascus concolor jingdongensis) on Mt. Wuliang, Yunnan, to test several hypotheses about the functions of these songs. The major functions proposed for loud gibbon songs include resource defense, mate defense, pairbonding, group cohesion and mate attraction. Duet bouts are generally initiated by adult males, who select the highest trees near to ridges or on steep slopes as singing trees. Such trees facilitate voice transmission and inter‐group communication. Singing trees tended to be located near important food patches and sleeping sites, which supports the resource defense hypothesis. The adult male and two adult females always sang interactively, alternating male phrases with the females' stereotyped great calls, to produce the duets, and females rarely produced great calls if they were more than 30 m from the male. The two females usually produced great calls synchronously during the duet, especially when they were close together. These features support both the mate defense and pairbonding hypotheses. The number of great calls and their degree of synchrony transmit information about spatial relationships and possibly pairbond strength to members to neighboring groups and floating animals. During or after the duet bouts, the adult females and juvenile moved toward to the adult male; and group members maintained a close spatial relationship, which supports the group cohesion hypothesis. Other incidents observed suggest a mate competition role for duets. The adult male always sang when the females started duetting with the subadult male. The subadult male sang solo bouts, but they were not more frequent or longer than bouts initiated by the adult male. Although mate attraction is the likely function of subadult solos, it was not convincingly demonstrated. In conclusion, all hypotheses concerning the function of singing are supported by at least some of the data, and none can be excluded. Am. J. Primatol. 71:539–547, 2009. © 2009 Wiley‐Liss, Inc.     

Red Deer (Cervus elaphus) Hinds Discriminate Between the Roars of Their Current Harem-Holder Stag and Those of Neighbouring Stags

During the period of reproduction red deer stags gather harems and roar loudly and repeatedly, both toward competing stags and toward the hinds that they actively herd. It has been proposed that red deer hinds may actively choose their mate on the basis of a comparison of the roaring rate of competing stags. Hinds may also choose to mate with the male that is most familiar to them, i.e. that male who spent most time and effort in retaining them within his harem and in roaring at them. Such a mechanism of female choice implies that females are able to discriminate individual characteristics in the stags' roars. We investigated this possibility by conducting playback experiments based on the habituation–discrimination paradigm. Our results show that hinds are able to discriminate between the roars of their current harem-holder stag and those of other neighbouring stags and suggest that this ability, a necessity for individual recognition, may be important in female mate choice in red deer.     

四川梅花鹿发情期的几种发声行为

2006 年9 ～11 月在四川省若尔盖县铁布自然保护区,对四川梅花鹿发情期的声行为进行了初步观测,结果表明:在发情期,四川梅花鹿的发声行为可分为雌、雄鹿的报警叫声,雄鹿的吼叫声和求偶叫声。雌鹿的报警叫声持续时间257 ～ 539 ms,频率范围1409. 5 ～ 4474. 6 Hz,主频率3534. 8 ±89.12 Hz;雄鹿的报警叫声持续时间136 ～187 ms,频率范围271.8 ～3910.5 Hz,主频率3244.3 ±79.32 Hz;两者在持续时间、最低频率、最高频率上差异极显著(P < 0.01),在间隔时间上差异不显著(P = 0.624)。吼叫是雄鹿的主要发情行为之一。雄鹿每次吼叫1 声,持续时间1580 ～4972 ms,频率范围234.6 ～6171.4 Hz,主频率2264.6 ± 166.44 Hz。雄鹿吼叫声的主频率存在显著的个体差异(P <0.01)。在整个吼叫过程中,一只雄鹿的吼叫常会引起周围其它雄鹿的吼叫反应。雄鹿每日吼叫的次数与其在繁殖群中的等级序列有关,不同序列等级雄鹿的吼叫频次存在显著差异(P<0.01)。雄鹿的吼叫声在白天和夜晚均能听到,但主要发生在06:00 ～ 08:00、17:00 ～ 19:00 和01:00 ～ 03:00 三个时间段。四川梅花鹿雄鹿的求偶叫声有4 种,其生物学意义与发情炫耀、追逐、激惹和爬跨等行为有关。     

Maternal grouping as a defense against infanticide by males: evidence from field playback experiments on African lions

Female lions roar in order to stay in contact with their pridematesand to defend their territory against other prides. In doingso, however, they risk attracting die attention of potentiallyinfanticidal nonresident males. We used playback experimentsto demonstrate that nonresident males are indeed specificallyattracted to female roars, approaching the roars of female,but not male, conspecifics. However, diere was also evidencediat males adjust their behavior according to the probabilitythat they might execute a successful takeover. Alien male lionswere more reluctant to approach playbacks of three females roaringdian of a single female roaring; single males were more reluctantdian pairs to approach female roars; and old males were morereluctant than younger males to approach female roars. Previousobservational studies have shown diat female lions living ingroups are more successful than singletons at defending theircubs in direct interactions widi potentially infanticidal males.Our results suggest that maternal groups may also, by roaringin chorus, minimize the chances that diese encounters occurat all.     

Role of loud calls in brown howlers,Alouatta fusca

The loud calls of brown howler monkeys were studied during a year at the Santa Genebra Reserve, in southeastern Brazil. The study group emitted roars and barks on a total of 47 occasions, the majority of which (92%) were restricted to intergroup visual encounters. Loud calls were also elicited by the roars of distant groups (6%) and during intragroup agonistic interactions (2%). Intergroup visual encounters (n = 42) occurred predominantly in seldom used quadrats of the study group home range. In these instances, the loud calls were produced chiefly by the adult male alone (69% of cases), while the study group's two adult females joined the male in the remaining cases. Intergroup physical aggression, such as chase and displacement, was observed during 15 encounters (35% of cases). A dawn chorus does not occur in Santa Genebra—the loud calls were heard most frequently in mid-morning and again during mid-afternoon—and they were more abundant during the dry season, when the availability of food (new leaves) in the forest was lower. The data presented here provide some support for the hypothesis that roars of howler adult males are used in assessment of opponents, providing an alternative to energetically expensive chases and fights. However, given the relatively high rate of physical aggression observed during intergroup encounters, a result probably related to the high density of howlers and the consequent high frequency of intergroup encounters observed in this forest (0.7/day), ritualized aggression, in the form of loud calling, is apparently often insufficient to settle disputes. © 1995 Wiley-Liss, Inc.     

Incubation feeding by male Scarlet Tanagers: a mate removal experiment

ABSTRACT Incubation feeding, where males feed their mates, is a common behavior in birds and may improve female condition, nest attentiveness, and nesting success. We used behavioral observations and a temporary mate removal experiment to test the female nutrition hypothesis for incubation feeding by male Scarlet Tanagers (Piranga olivacea). All males (N= 20) were observed incubation feeding and fed females both at the nest (x? 1.36 trips/h) and away from the nest (x? 20.1 trips/h). Male feeding rate off‐nest was negatively correlated with the duration of female foraging bouts and positively correlated with the total time females spent incubating per hour. Eggs were predated at seven of 19 (37%) nests, but nest survival during incubation was not related to either female incubation behavior or male feeding rate. During temporary removal experiments (N= 12), female Scarlet Tanagers remained on the nest significantly longer and did not have longer foraging bouts. An unexpected outcome of the removal experiments was a dramatic change in female vocal behavior. All 12 experimental females gave chik‐burr calls during the male‐removal experiments (x? bout length = 11.7 min), but during normal observation periods only six of 20 females at the incubation stage gave chik‐burr calls (x? bout length = 0.7 min, N= 20). Our results suggest that female tanagers likely gain nutritional benefits from incubation feeding, but male feeding may not improve immediate reproductive success. Nine of 54 (17%) nestlings in five of 17 broods (29%) were extra‐pair young (EPY), indicating that males could potentially benefit from incubation feeding via mate retention and fidelity as well as, or instead of, through immediate gains in reproductive success. Our study indicates that females benefit from incubation feeding and do not simply passively accept food from their mates, but instead may influence male feeding rates through direct (e.g., mate following and vocalizing) and indirect (the threat of mate abandonment or cuckoldry) means.     

Arctic roars – laryngeal anatomy and vocalization of the muskox (Ovibos moschatus Zimmermann, 1780, Bovidae)

The impressive roaring of adult male muskoxen most often occurs during rutting contests. Roaring in adult females is primarily relevant to mother–infant communication. Loud roars are produced by taking up a specific roaring posture. Acoustic recordings were made in a small herd of zoo muskoxen during three successive rutting seasons. Earlier recordings of a different herd were used for comparison. Head-and-neck specimens were subjected to vascular injection, macroscopic anatomical dissection, computer tomographic analysis and skeletonization. Isolated preserved larynges of young animals were dissected for ontogenetic comparison. Despite a pronounced sexual dimorphism of head mass, larynx size is almost identical in adult male and female muskoxen, as is the fundamental frequency of their roars. Remarkably, the larynges of both sexes of muskoxen are provided with an unpaired ventrorostral ventricle. Probably, this ventricle is inflated during the initial phase of a roar. The ventricle may have two functions: to increase the amplitude of roaring and to darken the timbre of the roars by acting as an additional resonance space. The vocal fold of adult female and young individuals has a sharp rostral edge and a vocal ligament is still present. During male ontogeny the vocal ligament becomes transformed into a large fat pad extending into the wall of the laryngeal vestibulum. Accordingly, the glottic region in the adult male lacks any sharp edges of the mucosa. In both sexes the thyroarytenoid muscle is divided into three portions. A single roar may comprise phases of different sound volume. The roars of both muskox sexes are characterized by a pulsed structure. We suggest that two oscillating systems are involved in the production of roars: one comprising only the medial portion of the vocal fold and one including its lateral portion.     

Do Red Deer Stags (Cervus elaphus) Use Roar Fundamental Frequency (F0) to Assess Rivals?

It is well established that in humans, male voices are disproportionately lower pitched than female voices, and recent studies suggest that this dimorphism in fundamental frequency (F0) results from both intrasexual (male competition) and intersexual (female mate choice) selection for lower pitched voices in men. However, comparative investigations indicate that sexual dimorphism in F0 is not universal in terrestrial mammals. In the highly polygynous and sexually dimorphic Scottish red deer Cervus elaphus scoticus, more successful males give sexually-selected calls (roars) with higher minimum F0s, suggesting that high, rather than low F0s advertise quality in this subspecies. While playback experiments demonstrated that oestrous females prefer higher pitched roars, the potential role of roar F0 in male competition remains untested. Here we examined the response of rutting red deer stags to playbacks of re-synthesized male roars with different median F0s. Our results show that stags’ responses (latencies and durations of attention, vocal and approach responses) were not affected by the F0 of the roar. This suggests that intrasexual selection is unlikely to strongly influence the evolution of roar F0 in Scottish red deer stags, and illustrates how the F0 of terrestrial mammal vocal sexual signals may be subject to different selection pressures across species. Further investigations on species characterized by different F0 profiles are needed to provide a comparative background for evolutionary interpretations of sex differences in mammalian vocalizations.     

Replacement female house sparrows regularly commit infanticide: gaining time or signaling status?

Although the killing of unrelated young (usually designed asinfanticide) has been typically considered a male behavior,recent research has shown that females may commit infanticideeven more frequently than do males. In rodents and primates,female infanticide represents a strategy associated to competitionfor resources or infant exploitation, but little is known aboutthe causes and reproductive consequences of the killing of conspecificsby females in other vertebrates. In the present article, I focuson infanticide committed by females that replace mates of territorialmales in a population of the house sparrow. I show that (1)replacement females regularly committed infanticide, (2) experiencedfemales committed infanticide more frequently than did novelfemales and tended to select polygynous males to take over theirnests, and (3) laying date and reproductive success after aterritory takeover did not differ between infanticidal and noninfanticidalfemales. These results seem to indicate that infanticide hasnot evolved in females because of the short-term reproductivebenefits it accrues to the perpetrator. I suggest that the killingof unrelated young by females relates to dominance status amongpotential female breeders and that this behavior benefits theperpetrators in terms of mate selection.     

Sexual selection and adult male orangutan long calls

Long calls given by adult male orangutans (Pongo pygmaeus) have been hypothesized to mediate interindividual spacing among male orangutans and to attract female orangutans, to high-ranking mates over long distances. To test these two hypotheses I conducted observations of calling behaviour and a series of experimental playbacks of recorded long calls. The findings were consistent with the male-spacing hypothesis but did not support the mate-attraction hypothesis. Experimental playbacks demonstrate that long calls regulate spacing between males through an approach-avoidance system based on dominance relationships: the highest-ranking adult male approaches calls, while lower-ranking, males avoid calls. The results of playbacks also reveal that sexually active females do not move toward long calls, and therefore do not indicate that long calls function in attracting mates. This latter finding suggests that female mate choice may not have been an important selective factor during the evolution of long calls.     

Territorial behavior in Southeast Asian langurs: Resource defense or mate defense?

Between-group antagonism or territoriality in primates may serve two different but compatible functions: resource defense or mate defense. Females are expected to be involved more strongly in the first, males in the second. The resource defense hypothesis predicts that home range overlap should decrease as defensibility and population density increase, and that females should be involved in hostile between-group interactions. The mate defense hypothesis predicts that between-group relations should be hostile and that males should take the primary role in antagonistic encounters. In a comparative study of 12 populations of 6 Presbytis species in Southeast Asia, we found support for the mate defense hypothesis; only males produce loud calls, between-group antagonism is entirely a male affair, and neither defensibility nor population density determine spatial exclusivity or the level of antagonism. We discuss the differences between our findings and traditional interpretations of territorial behavior.     

Monogamy in a feeding generalist, <Emphasis Type="Italic">Chaetodon trichrous</Emphasis>, the endemic Tahitian Butterflyfish

Butterflyfishes have been well studied for their feeding ecology and mating systems. In particular, studies of corallivorous butterflyfishes have supported models of monogamy based on their predictable, low quality food; a patch of coral that is economically defensible by a pair. Moreover, pairs often exhibit trade-offs in territorial defense (greater by males) and feeding (greater by females) that improve their reproductive success. However, this model has not been well tested for more generalist feeders. In addition, recent hypotheses for monogamy in fish have emphasized parental care, but butterflyfishes do not provide parental care. This study tests five hypotheses for monogamy in the endemic Tahitian butterflyfish, Chaetodon trichrous: 1) uniform distribution of limiting resources, 2) joint defense of a territory, 3) low mate availability, 4) predator detection, and 5) benefits of cooperative behavior. Chaetodon trichrous was the most abundant butterflyfish in bays. Pairs jointly patrolled feeding territories. They preferentially fed over hard substrate other than live coral, however, this substrate was available outside of territories. They also ate plankton. Pairs were sorted positively for size, and all pairs were heterosexual. Males were larger than their partners, but females fed at higher rates. These results suggest that C. trichrous is monogamous, but reject the hypotheses that pairs form for joint defense of a territory (pairs swam together), that pairs remain together because of low mate availability (frequent interactions with neighbors), or that pairs form for predator detection (no homosexual pairs). Monogamy in C. trichrous is associated with the uniform distribution of hard substrate, although this resource is not limiting. Further, the higher feeding rate of females may represent a benefit provided by their monogamous mates.     

Food Resource Characteristics in Two Nocturnal Lemurs with Different Social Behavior: Avahi occidentalis and Lepilemur edwardsi

I present results from a comparative field study on the feeding behavior of the gregarious Avahi occidentalis and the solitary-but-social Lepilemur edwardsi to evaluate hypotheses relating to social organization and food resources. While Avahi and Lepilemur are both nocturnal, have comparable body weights and positional behaviors, and are both folivorous, they differ in their social organization. Therefore, they present an ideal model for assessing food resource characteristics through comparisons of food selection in both species with regard to forest composition. The monogamous Avahi tend to select under-represented resources. They are repeatedly exploited, which suggests that their location must be known. It is worthwhile and probably imperative to defend those resources. Such defense imposes ranging limitations on male Avahi. Females may prefer familiar mates that will share their knowledge of resource location and defend the resources. A stable monogamous pattern could be the optimal strategy. In contrast, food selection by Lepilemur is based on common resources to a higher degree, but they show a lower degree of exploitation. Lepilemur males would be less restricted and could potentially opt for a different strategy, e.g., a dispersed harem. It is unclear whether this strategy is realized or not. I discuss other possible correlates of monogamy—infanticide protection, predation avoidance—but the gregarious pattern in Avahi may best be seen as a retention, and its nocturnal activity as a secondary adaptation.     

The Function of Howling in the Ring-Tailed Lemur (Lemur catta)

Long calls are sex-specific vocalizations used for mate attraction or mate defense in many animal species. Ring-tailed lemurs (Lemur catta), female-dominant strepsirrhines, have a male-specific long call termed a howl, with proposed functions that have never been empirically tested. I aimed to investigate why ring-tailed lemur males howl and to test whether the mate defense and mate attraction hypotheses for long-calling were applicable to this species. From March to July 2010, I collected 600 h of focal data on 25 males aged ≥3 year at Beza Mahafaly Special Reserve, Madagascar. I observed each male continuously for 30 min at a time and noted all agonism using one–zero sampling at 2.5-min intervals. I calculated male dominance rank from these data. I recorded days when female estrus occurred and noted howling and intergroup encounters using all-occurrences sampling. Howling rate was not significantly related to female estrus or male dominance rank, providing no support for the mate attraction hypothesis or the intragroup mate defense hypothesis. In contrast, the intergroup mate defense hypothesis was strongly supported. During intergroup encounters, male howling rate significantly increased compared to howling rate at times without other groups present, and a greater number of males participated in multimale howling choruses when compared to times without nongroup members present. My results suggest that male ring-tailed lemurs howl to advertise their presence and location to other groups, but not to male or female members of their own group. Howling could discourage male immigration by advertising the number of males already present in a group. Long calls are used for similar mate defense purposes during intergroup encounters by other primates, including Thomas langurs (Presbytis thomasi) and chacma baboons (Papio ursinus).     

Foraging Behavior and Activity Patterns of Alouatta caraya in the Northeastern Argentinean Flooded Forest

Howling monkeys (Alouatta spp.) are colonizer species, showing a plasticity in behavior that allows them to inhabit different sorts of forests. There is a series of hypotheses relating demography to behavioral and ecological characteristics of howlers: (1) as howler density increases, home range size will decrease; (2) howler groups occupying small home ranges will have a high proportion of leaves in their diet; and, (3) the proportion of mature leaves in the diet is negatively correlated with group daily travel distance. To test hypotheses about howler diet and ranging pattern in relation to food resources, we studied the foraging ecology and general activity patterns of 2 groups of black howlers (Alouatta caraya) inhabiting in flooded forest of Paraná River (Argentina), the habitat with the highest density recorded for Alouatta. We found, in addition to the highest densities, also the smallest home ranges for Alouatta (Group I: 1.7 ha and Group II: 2.2 ha). However, diet was not dominated by leaves, and high quality items—flowers, fruits, new leaves—were a high proportion of the diet all year. Also, daily travel distance is not correlated with the proportion of mature leaves in the diet, but is positively correlated with the number of group confrontations. Finally, we propose a model integrating and interpreting our results as a function of the spatial and temporal distribution of high quality food resources in the Argentinean flooded forest.     

Reduced geographic variation in roars in different habitats rejects the acoustic adaptation hypothesis in the black-and-gold howler monkey (Alouatta caraya)

Vocalizations used for long-range communication must disperse without significant structural changes to be decoded by receivers. The acoustic adaptation hypothesis (AAH) holds that, since acoustic signals are influenced by the habitat in which they disperse, sounds will possess specific structural characteristics to diminish sound degradation. Additionally, vocalizations can also be influenced by genetics, anatomy, and/or cultural aspects. Here, we tested the AAH through quantitative comparisons of roars in four allopatric populations of the black-and-gold howler monkey (Alouatta caraya) across an environmental gradient from open to closed, in northeastern Argentina. At each site, we obtained good-quality recordings from three adult males, also between July and November 2013, conducted vegetation surveys (measuring tree density, canopy closure, and vertical structure), evaluated potential masking of roars by gathering environmental sound samples, and assessed sound attenuation of a synthetic tone at three different distances: 10 m (landmark reference distance), 50, and 100 m. We also tested the alternative hypothesis that acoustic properties of roars could be explained by population genetic divergence. Our results did not support the AAH. Although our four study sites were significantly different in vegetation structure, conforming to an open-to-closed gradient, roars of A. caraya were not different among populations. Likewise, although environmental sound differed between sites, we found no evidence of environmental sound affecting the acoustic properties of roars. The attenuation of the synthetic tone was only near significant at 100 m distance between both extreme sites from the environmental gradient. The four A. caraya study populations grouped into three genetically differentiated clusters. Since roar features were independent from population genetic clustering, we reject the genetic hypothesis too. The combination of high amplitude and low peak frequency of roars, coupled to small home range size and extensive overlap between neighboring groups, allows roars to keep their communication value across habitats without need of specific environmental tuning.     

Loud calls of adult male red howling monkeys (Alouatta seniculus)

Loud calls of adult male red howlers (Alouatta seniculus) inhabiting a deciduous and semideciduous open woodland site in Venezuela were recorded opportunistically and categorized by ear and sonographically as barks and roars. Five to six different bark syllables were identified as occurring singly or in sequences of doublets and triplets. In barks, spectral energy was concentrated in bands at 350-400 Hz, 900-1,100 Hz, 1,800-2,200 Hz and 3,000-3,500 Hz, but not all higher bands were present in each syllable. Roars appeared sonographically like prolonged barks composed of a pulsated preface, a long legato climax and a brief, fractionated and at times pulsated coda; each part varied internally to the ear and in acoustic structure. All loud calls were of the noisy type (nonharmonic energy over a broad frequency range). Acoustic characteristics of the calls are interpreted in terms of the subserving vocal tract anatomy. I compare loud calls of red howlers with those of mantled (A. palliata) and black (A. caraya) howlers.     

Predator and non-predator long-distance calls in Guereza colobus monkeys

East African Guereza colobus monkey males are known for their conspicuous roaring behaviour; a spectacle that can dominate the predawn hours of African forests. Recent research has shown that these monkeys also produce roars during daytime hours in response to predators. While roars to leopards and eagles differ in how roaring phrases are assembled into sequences, there are no obvious structural differences between predawn roars and roars to eagles. Although recipients could use daytime information to disambiguate between the two contexts, this may be a risky strategy because eagles can be active before dawn. We carried out acoustic analyses, which showed that the duration of the first roaring phrase was significantly longer in predawn roars compared to eagle roars. Furthermore, the initial call repetition rate was faster in response to eagle roars compared to predawn roars. Apart from these two differences, all other acoustic characteristics were identical between the two contexts. Although these monkeys exhibit some of the most basic vocal behaviour found in non-human primates, callers are able to provide reliable contextual information by varying the duration and assemblage of individual vocal units. Playback experiments are needed to confirm whether recipients relate these acoustic differences to different contexts.     

The Evolution of Exploitation in Humans: ‘Surrounded by Strangers I Thought Were My Friends’1

Early humans were obligately social, living in nested kin groups or close associations of related individuals. Theoretical and empirical research has demonstrated that group life is characterized by both costs (e.g. increased likelihood of disease transmission) and benefits (e.g. enhanced predator defense). This paper addresses the evolution of exploitation in humans (e.g. slavery, infanticide) as a response to within‐group competition for limiting resources (e.g. food, mates), a potential cost of living in groups. Exploitation is defined as one individual's use of another for selfish ends, in particular, the acquisition and/or use of another's resources for the optimization of inclusive fitness. It is argued that exploitation is most likely to occur in relationships characterized by asymmetries such as dependence, intimacy, and/or differential access to resources. A simple mathematical treatment assesses exploitation as a facultative response to local competition among relatives, providing insights into the conditions favorable and adverse to exploitation of conspecifics. Possible applications of the formulations are discussed, including the conditions under which intraspecific exploitation may be beneficial to both actor and recipient(s). Constraints on the evolution of exploitation in humans are identified, and suggestions are made for testing hypotheses related to the differential costs and benefits of exploitation to conspecifics. Future studies may promote the mitigation of exploitation's deleterious effects in Homo sapiens, a body of research which may apply, as well, to other social mammals.