Acoustical variations in sexually dimorphic features of distance calls in domesticated zebra finches (Taeniopygia guttata castanotis)

Species-specific distance calls (DCs) were recorded from Zebra finches (Taeniopygia guttata castanotis) obtained from three different breeding stocks: Japanese breeders that use Bengalese finches as fostering parents, and Japanese and American breeders that let natural parents rear Zebra finches. These calls were analyzed for five acoustic parameters that were shown to be sexually dimorphic in wild Zebra finches. Male Zebra finches had DCs that were variable among breeding stocks and among individuals. Female DCs recorded from Bengalese-fostered birds were generally longer in duration and higher in pitch than those recorded from Zebra-finch-reared birds, males and females in each breeding stock differed in at least one acoustic parameter, but that parameter was unique in each of the breeding stocks. These results suggest that although sexual dimorphism in Zebra finch DCs has gradually disappeared during the process of domestication, at least one acoustic attribute which allows discrimination between the calls of the sexes has been preserved.     

Geographic and Temporal Variation of the Male Zebra Finch Distance Call

Temporal and geographic variation of acoustic signals can provide insights into dispersal patterns, population history and speciation. Vocalizations that are transmitted from one generation to the next are of particular value in this respect because they can reveal patterns of gene flow, effectively behaving as population markers. The male zebra finch Taeniopygia guttata distance call is one such vocalization; sons learn their father's distance call in the first 40 d of life and it is individually stereotyped thereafter. We investigated geographic variation in the zebra finch by comparing the structure of distance calls recorded from 61 males from six populations across the continent‐wide range of the Australian subspecies T. g. castanotis. Intra‐population variation was high, in many cases greater than the variation among all males recorded, possibly because of population interchange. However, three of six call variables measured, including the newly discovered modulated element, varied geographically although the pattern of distance call variation did not agree with that of geographic proximity of populations. The proportion of calls with a modulated element increased dramatically over 7 yr in central Australia but there was no change over a similar period of time in south‐eastern Australia where no calls contained the element. The findings suggest that interchange among widely separated populations may be commonplace in Australian zebra finches, with the possible exception of those from south‐eastern Australia.     

Is there variation in the response to contact call playbacks across the hybrid zone of the parrot Platycercus elegans?

Learned vocal signals could be important in the formation of prezygotic isolation between two hybridising taxa. This study examined whether vocal variation in the parrot Platycercus elegans facilitates the separation of individuals from two subspecies, P. e. elegans (CR) and P. e. flaveolus (YR). CR and YR have very different plumage coloration, respectively deep crimson and pale yellow, but hybridise where they meet creating an intermediate population (WS). In a factorial design playback experiment, we conducted 108 playback trials on three focal populations (YR, WS, CR), in and around this area of hybridisation, to test if they respond differently to contact calls from their own or another population. We also analysed whether differences in acoustic variables of the stimulus calls predicted the response to the call. We did not find any indication that individuals from the three focal populations responded differently to calls sampled from their own or another subspecies. We did find an effect of two of the five acoustic variables that we used to describe and classify contact calls from the three source populations. Specifically, duration of the stimulus call positively affected the response from individuals from WS and negatively the response from CR, and CR responded more to stimulus calls with a lower peak frequency. Overall, we found no indication that acoustic variation in contact calls on a subspecies level is involved in maintaining plumage colour differences between P. e. elegans and P. e. flaveolus subspecies.     

Sex recognition in brown skuas: do acoustic signals matter?

Bird vocalisations are often essential for sex recognition, especially in species that show little morphological sex dimorphism. Brown skuas (Catharacta antarctica lonnbergi), which exhibit uniform plumage across both sexes, emit three main calls: the long call, the alarm call and the contact call. We tested the potential for sex recognition in brown skua calls of 42 genetically sexed individuals by analysing 8–12 acoustic parameters in the temporal and frequency domains of each call type. For every call type, we failed to find sex differences in any of the acoustic parameters measured. Stepwise discriminant function analysis (DFA) revealed that sexes cannot be unambiguously classified, with increasing uncertainty of correct classification from contact calls to long calls to alarm calls. Consequently, acoustic signalling is probably not the key mechanism for sex recognition in brown skuas.     

Vocal individual discrimination in Japanese monkeys

The present study determines which features of the coo call are used by Japanese monkeys Macaca fuscata for vocal individual discrimination. First, two female Japanese monkeys were trained to discriminate conspecific individuals vocally, using an operant conditioning. Using as stimuli three unknown individuals with 30 calls per individual, the two monkeys succeeded in discriminating new call exemplars from the three stimulus individuals. A discriminant analysis performed on calls used as stimuli indicated that start frequency of the fundamental and call duration were variables that can differentiate individuals efficiently. Then, playbacks of acoustically modified signals were used to indicate which vocal features are used by monkeys for the individual discrimination. Stimuli signals containing modified pitch or duration, or filtered so as to keep only the fundamental component, were tested. Results indicated that Japanese monkeys use multiple acoustical cues to perform vocal individual discrimination, including at least pitch, call duration, and harmonics. However, harmonics seem to be less important for discrimination than pitch and call duration.     

Acoustic behaviour and phonotaxis in the duetting ephippigerines,Steropleurus nobrei* and Steropleurus stali (Tettigoniidae)

Both sexes of the ephippigerines Steropleurus stall and S. nobrei can stridulate and produce multisyllabic calls which are described. Female stridulation is in response to the conspecific male call. In both species cither sex can perform phonotaxis on the call of the conspecific member of the opposite sex, but ignore the calls of other species. The parameters of the calls are examined with the conclusion that the only reliably distinctive feature is the modal or carrier frequency generated during stridulation. There are frequency differences between male and female calls in both species. Males only perform phonotaxis on female replies generated in response to their own call, implying that there is also some time window involved. Male phonotaxis was faster and more accurate than that of the female. Acoustic rivalry and aggression were also noted, particularly in females.     

Systematics of the Hipposideros turpis complex and a description of a new subspecies from Vietnam

• 1 Hipposideros turpis is traditionally known as a species composed of three subspecies, H. t. turpis, H. t. alongensis and H. t. pendleburyi, distributed disjunctly in south‐west Japan, north‐east Vietnam and south‐west Thailand, respectively. Prior to the present study, the systematic status of forms within the species remained unclear.
• 2 Using morphological (external, bacular, cranial and dental characters), genetic and echolocation data, we demonstrate that turpis, alongensis and pendleburyi represent three distinct species, and that these species are endemic to Japan, Vietnam and Thailand, respectively. They are very distinct genetically and do not even form a monophyletic group.
• 3 We also prove that H. alongensis is composed of two subspecies, H. a. alongensis and H. a. sungi. The latter subspecies is described as new to science. To date, H. a. alongensis appears to be restricted to the Cat Ba Island of Cat Ba National Park, west Ha Long Bay, whereas H. a. sungi ssp. nov. is known from three localities in mainland northeast Vietnam. These two subspecies are distinguished by body size, molecular data and the frequency of the constant‐frequency component of their echolocation signals.

     

Keeping a low profile: small hive beetle reproduction in African honeybee colonies

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Response of Hawaiian Moorhens to broadcast of conspecific calls and a comparison with other survey methods

ABSTRACT Accurate population surveys are critical for effective management of species of conservation concern. Traditional visual and aural surveys are ineffective for behaviorally cryptic species such as rails, but incorporating call‐broadcast into surveys can increase their detection rate. From 2004 to 2006, we surveyed wetlands (N= 67) on Kauai and Oahu for endangered Hawaiian Moorhens (Gallinula chloropus sandvicensis) with the goal of comparing the effectiveness of visual and aural observations to that of call‐broadcast surveys. We evaluated six different Hawaiian Moorhen calls, including the “squeal” call of young moorhens. We also compared the results of surveys conducted using the broadcast of Hawaiian Moorhen calls to those of extended time (75 min) surveys and surveys where the calls of the North American subspecies of moorhen (G. c. cachinnans) were broadcast. We found that broadcast of Hawaiian Moorhen calls increased detection rates by 56% on Kauai and 30% on Oahu. Territorial and chick‐distress calls elicited the greatest response. We also found a nonlinear positive relationship between the estimated population of Hawaiian Moorhens at a wetland and the improvement in detection due to call‐broadcast, suggesting social facilitation of responses. Survey periods of 60 min produced results similar to those obtained using call‐broadcast. However, long survey periods require more time than call‐broadcast surveys and increase the likelihood of double counting individuals. Broadcast of the calls of the North American subspecies of moorhen failed to increase detection rates above those obtained using visual and aural surveys. Our results suggest that the population of Hawaiian Moorhens is larger than previously estimated, but is likely well below the 2000 individuals recommended for removal from the Endangered Species list. We recommend the use of call‐broadcast during surveys of Hawaiian Moorhens to improve estimates of population sizes and trends.     

Bioacoustic analysis of frog calls from northeast India

Mating calls of three frog species abundant in northeast IndiaRana tigerina,Rana cyanophlyctis andRana limnocharis were recorded in the fields of Assam and Meghalaya during their breeding season (July-August, 1991). The calls were analysed for their temporal and spectral characters. They were species specific, with distinct call duration and call period, number of pulses per call and interpulse interval, and dominant frequency and frequency domain. A comparison of the mating calls ofRana cyanophlyctis with those of the siblingRana ehrenbergi from Yemen showed differences in their temporal and spectral characters, supporting the suggestion that these two species are distinct species, rather than subspecies of the same species. Differences in the temporal and spectral pattern were found in the mating calls of morphologically alike specimens ofRana limnocharis, indicating that the present morphotypeRana limnocharis in northeast India is composed of several species.     

Differences in distress: Variance and production of American Crocodile (Crocodylus acutus) distress calls in Belize

Acoustic communication of American Crocodiles (Crocodylus acutus) is relatively understudied. Our overall aim was to determine the acoustic structure of wild American Crocodile distress calls, distinguish call differences among size classes (hatchling, juvenile, sub‐adult, and adult), and investigate call production on a gradient of human disturbance. American Crocodile distress calls have strong frequency modulation and are comprised of multiple harmonics in a downsweeping pattern. Measured parameters (total duration, first quartile duration, maximal frequency, first quartile frequency, end frequency, slope of first quartile, slope of last quartiles) differed significantly among size classes (p < .05). Hatchling distress calls are higher in frequency and strongly modulated, whereas calls produced by sub‐adults and adults showed little modulation, are lower in frequency, and have greater overall duration. Proportion of crocodiles that produced distress calls during capture differed by size class and sampling location, particularly adult distress calls which are reported here to be produced with undocumented frequency. We determined that American Crocodiles of all size classes produce distress calls at varying rates among study sites. Our results demonstrate that American crocodiles produce distress call more frequently at sites with higher anthropogenic activity. Measured call parameters of juveniles and hatchling American crocodiles also varied among sites in relation to human disturbance. Calls recorded at sites of high anthropogenic impact have increased duration and less modulation which may adversely affect response to emitted distress calls. Proportional and call parameter variances suggest anthropogenic activity as a driver for increased call production and alteration of call parameters at high human‐impacted sites.     

Geographical and individual variation in echolocation calls of the intermediate leaf‐nosed bat,Hipposideros larvatus

The cause and significance of variation in echolocation call frequency within hipposiderid bats is not well understood despite an increasing number of allopatric and sympatric examples being documented. We examined variation patterns in the resting frequency (RF) of echolocation calls emitted by the intermediate leaf‐nosed bat, Hipposideros larvatus, on a broad geographical scale. Data mining technology and Kruskal–Wallis test both showed substantial variation with a longitudinal pattern in RF in H. larvatus among colonies, and this variation was associated with geographical distance and not body size. In addition, we found that a high degree of variability between individuals was hidden under the geographical variation. The results support an effect of random cultural drift, and challenge the prey detection hypothesis. Moreover, an acoustic difference among local island colonies may be indicative of a vocal dialect. We found that each colony of H. larvatus seems to maintain a ‘private bandwidth’, which could be used for colony identity and individual communication thus helping individuals and colonies to get a number of fitness benefits.     

Subspecific divergence in a loud call of the ruffed lemur (Varecia variegata)

A loud call of the ruffed lemur (Varecia variegata) was analyzed for subspecific and gender differences according to four variables: pulse rate, median pulse duration, median high frequency, and median low frequency. These vocalizations of black-and-white and red ruffed lemurs and one hybrid ruffed lemur were recorded at the Duke University Primate Center (Durham, NC). Significant differences were found between subspecies but not between the sexes. Quantitative differences in this loud call of ruffed lemur subspecies indicate that these prosimians exhibit subspeciation trends similar to anthropoid primates for which comparable data exist. Preliminary data are presented that support the hypothesis that the vocalization functions as a terrestrial predator alarm call.     

Advertisement calls of Guenther’s frog Hylarana guentheri (Anura: Ranidae) during the breeding season

Acoustic signalling is the most important form of communication in anuran amphibians. Here we recorded and analysed the calls of 18 male Guenther’s frogs (Hylarana guentheri) from the wild during the breeding season. The advertisement calls of H. guentheri were composed of from a single note to five notes, with three-note calls the most recorded. All individuals produced calls around 600 Hz but calls ranged from 470 to 2600 Hz. Comparing the differences between individuals calls, we found within-male coefficients of variation (CV_w) of call intensity, the fundamental frequency, the first formant, the second formant, the third formant and the fourth formant were static (less than 5% variation), whereas those of note duration, call duration, call interval, numbers of pulses and dominant frequency were dynamic (larger than 15% variation). Comparisons of the call characteristics of H. guentheri in this study with other studies from China, Singapore and Vietnam found call characteristics varied greatly between the five different locations.     

Similarity in the begging calls of nestling Red‐winged Blackbirds

ABSTRACT Although individually distinct begging calls may permit parents to recognize their offspring, birds nesting in dense breeding colonies where fledglings intermingle might benefit from additional adaptations. For example, if the calls of all nestlings in a brood were similar, parents would need to recognize only one brood call instead of the identity calls of each nestling. We recorded nestling Red‐winged Blackbirds (Agelaius phoeniceus) to determine whether their calls function to identify individuals (identity call hypothesis) or broods (brood call hypothesis). We used spectrogram cross‐correlation and dynamic time warping as well as call duration, peak frequency, and frequency range to estimate the similarity of begging calls of nestling Red‐winged Blackbirds. We recorded individual nestlings on day 5 and on day 9 of the nestling period to determine whether calls of individuals were more similar than calls of different nestlings, and whether calls of broodmates were more similar than calls of nestlings from different broods. We found that calls of 8‐d‐old individuals were more similar than calls of different nestlings, but the calls of broodmates were not more similar than those of nestlings from different broods. These results were consistent with the identity call hypothesis. We then compared begging calls of pairs of nestlings recorded separately and together on day 9. We found that the calls of 8‐d‐old nestlings recorded together were more similar than when they were recorded separately. In addition, using playback of begging calls from normal broods and artificial “broods” constructed from the calls of single nestlings, we found that females returned with food sooner in response to the calls of single nestlings (with enhanced call similarity) than to those of normal broods. Our results suggest that similar begging calls may be beneficial for both nestlings and parents, with broodmates fed at higher rates when their calls are more similar and, after fledging, parents needing to recognize only one brood call instead of the identity calls of each fledgling.     

Does body mass restrict call peak frequency in echolocating bats?

1. Echolocation is the ability of some animals to orient themselves through sound emission and interpretation of the echoes. This is bats’ main sense for orientation and recognising biotopes that provide food, water, and roosts. It is widely accepted that echolocation call frequency is related to body mass, and this relationship has been described as the ‘allometric hypothesis’, which proposes a negative correlation between these variables.
2. There is evidence that, in many cases, the allometric hypothesis does not apply. Additionally, studies supporting this hypothesis were done at the family level, resulting in a broad range of correlation values with r ranging from −0.36 to −0.76, and only insectivorous bats were included. Due to the notable exceptions and the lack of a quantitative synthesis of this hypothesis including all echolocating bats, we evaluated the allometric hypothesis of echolocation calls for this group.
3. Using a meta-analysis and phylogenetic generalised least-squares techniques, we evaluated the relationship between echolocation call peak frequency and the body mass of bats.
4. We found a negative relationship between body mass and echolocation call peak frequency for the 85 bat species that were included in our analysis (r = −0.3, p = 0.005). The relationship was consistent when we analysed the data at the insectivorous guild level, and in bats belonging to the families Vespertilionidae, Rhinolophidae, Emballonuridae, and the genus Myotis. However, the wide range of r values suggests that the strength of the relationship between peak frequency and body mass varies within the order Chiroptera.
5. Our results support the allometric hypothesis of sound production in echolocating bats. However, the low coefficient we found suggests that factors other than body mass may influence the peak frequency of echolocation calls produced by bats.

     

The use of chemical composition as a population marker in insects: a study of the Brimstone butterfly

ABSTRACT.

• 1 The elemental composition of 249 adult Brimstone butterflies (Gonepteryx rhamni L.) was studied by wavelength dispersive X-ray fluorescence spectrometry, to determine whether site/population-specific differences could be detected. The chemical elements studied were K, Ca, Fe, Cu, Zn, Ti, P, CI and S.
• 2 Marked differences were found in the chemical composition of the two sexes, and between individuals caught on different sites and in different years and seasons.
• 3 Multivariate analyses of the data using principal component analysis and canonical variate analysis showed a clear separation of the butterflies by sex, and within each sex, by seasons. Of the elements studied, the main discriminating ones for this butterfly were K, Ca, P, Zn, CI and S.
• 4 Whilst differences in chemical composition appear to result from variations in the composition of soil and food-plants in different localities, any site/population-specific differences are soon masked by the passage of time, as adults age and feed. This makes the technique of limited value in the study of dispersal in this species.