ACOUSTIC COMMUNICATION AND MATING BEHAVIOUR IN WATER BUGS OF THE GENUS MICRONECTA

ABSTRACT

The role of male sounds in attracting females and in mating was investigated in the three most common species of Micronecta found in ponds 60 km NE of Melbourne, Australia: M. concordia, M. tasmanica and M. robusta. In playback experiments using recorded male signals, females were attracted to signals of conspecific males, in preference to signals of heterospecific sympatric males. Studies of mating behaviour, using video recording, showed that signals were obligatory for mating. These findings strongly suggest that acoustic signalling is important in reproductive isolation in Micronecta. Comparisons between matings and rejected matings showed that, within each species, copulation only occurred following a certain minimum number of acoustic signals with more pulse-trains than the mean for the species. Low amplitude sounds (after signals) were also important in courtship, immediately preceding mating. No sounds occurred during copulation.     

STRIDULATORY ORGAN AND ULTRASONIC EMISSION IN CERTAIN SPECIES OF PONERINE ANTS (GENUS: ECTATOMMA AND PACHYCONDYLA,HYMENOPTERA, FORMICIDAE)

ABSTRACT

Five species of neotropical Ponerinae ants, Ectatomma permagnum Forel, E. quadridens Fabr., E. ruidum Roger, E. tuberculatum Olivier and Pachycondyla apicalis Latreille, were studied. The genus Ectatomma, consisting of 14 species in the tropical forests of Central and South America, has been studied previously in relation to the stridulatory organ only. Stridulations were heard, in the four species considered in this paper, during artificial disturbance of individuals or of the whole colony; so the role of sound production during normal life is still uncertain. Pachycondyla apicalis, belonging to Central American forests, is occasionally present in cocoa and coffee plantations.

The recordings made under laboratory conditions revealed the emission of pulse trains with very clear pulses extending in frequency to more than 75 kHz. The sounds recorded from the workers of the genus Ectatomma appeared homogeneous in their acoustic structure. They were typically emitted in long sequences and were made of pulse-trains consisting of two subunits (disyllabic chirps) characterized by pulses with opposite phase, produced by the alternate movement of the simple plectrum against the pars stridens. In sounds recorded from workers of Pachycondyla we found sequences of monosyllabic chirps, made by single trains of pulses. Pictures and measurements on the stridulatory apparatus were made with a scanning electron microscope.     

Plant community patterns in Moroccan temporary ponds along latitudinal and anthropogenic disturbance gradients

Background: Temporary ponds, an abundant habitat in the Maghreb region and notably in Morocco, have a high conservation value. However, they are mainly known from the north of the country.

Aims: The aim of this work was to characterise the vegetation of Moroccan temporary ponds along a combined gradient of latitude and anthropogenic pressure.

Methods: Eighty-five ponds distributed along a north–south gradient of 750 km were sampled. For each pond, all vegetation was surveyed (flooded and dry parts) and the local abiotic characteristics were measured during two successive hydrological cycles. The prevailing anthropogenic pressures were also identified and were attributed an impact score.

Results: Eighty-one characteristic pond species (including 17 rare species) were recorded, with several new distribution data in the southern part of the latitudinal gradient. Plant communities were related to climatic and anthropogenic factors, but mostly to local factors, such as maximum water depth and soil pH. The northern ponds (wettest macroclimate) were rich in characteristic species and rare species, while the southern (driest macroclimate) ponds were more species poor.

Conclusions: In addition to the direct impact of increasing human activity, a further reduction of the floristic richness of temporary ponds is expected due to climatic changes. This is particularly the case for characteristic species which have a high conservation value.     

A PRELIMINARY REPORT ON THE ACOUSTIC COMMUNICATION IN URUGUAYAN CTENOMYS (RODENTIA,OCTODONTIDAE): BASIC SOUND TYPES

ABSTRACT

Subterranean rodents are interesting organisms for communication studies because of their fossorial way of life. Acoustic communication in the South American genus Ctenomys has not yet been studied even though this species is geographically widespread. This paper represents a preliminary survey of Ctenomys vocalizations. Three types of vocal signals were identified: S-, C- and G-signals. Using field, laboratory and literature data, we provide interpretations on the possible functions of these signals. S-signals are harsh and low-pitched putative spatial localization signals that may also encode for sexual identification. C-signals are relatively high-pitched and narrow-banded FM vocalizations that are sexual signals used by females in a copulatory context. Finally, G-signals are harsh and patternless sounds that are aggressive signals used in direct encounters with con- or hetero- specific individuals.     

COMPARATIVE ANALYSIS OF SWIMBLADDER (DRUMMING) AND PECTORAL (STRIDULATION) SOUNDS IN THREE FAMILIES OF CATFISHES

ABSTRACT

Among teleosts, only representatives of several tropical catfish families have evolved two sonic organs: pectoral spines for stridulation and swimbladder drumming muscles. Pectoral mechanisms differ in relative size between pimelodids, mochokids and doradids, whereas swimbladder mechanisms exhibit differences in origin and insertion of extrinsic muscles. Differences in vocalization among families were investigated by comparing distress calls in air and underwater. High frequency broad-band pulsed sounds of similar duration were emitted during abduction of pectoral spines in all three families. Adduction sounds were similar to abduction signals in doradids, shorter and of lower sound pressure in mochokids, and totally lacking in pimelodids. Simultaneously or successively with pectoral sounds, low frequency harmonic drumming sounds were produced by representatives of two families. Drumming sounds were of similar intensity as stridulatory sounds in pimelodids, fainter in doradids, and not present in mochokids. Swimbladder sounds were frequency modulated and the fundamental frequency was similar in pimelodids and doradids. The ratio of stridulatory to drumming sound amplitude was higher in air than underwater in both doradids and one of the pimelodids. Also, overall duration of pectoral sounds, compared to swimbladder sounds, was longer in air than underwater in one doradid and pimelodid species. This first comparison of vocalization within one major teleost order demonstrates a wide variation in occurrence, duration, intensity and spectral content of sounds and indicates family- and species-specific as well as context- (receiver-) dependent patterns of vocalization.     

BIOACOUSTIC PUBLICATIONS, 1989

ABSTRACT

Coruros Spalacopus cyanus, social fossorial rodents from Chile, use a complex acoustic repertoire with eleven different true vocalisations and one mechanical sound in various behavioural contexts. The complex of contact calls is particularly well differentiated. Juvenile coruros produced six true vocalisations of which four were structurally identical to adult calls. One vocalisation had components of two adult sounds and one occurred only in juvenile animals. Certain calls from the adult repertoire were lacking. The frequencies of sounds of juveniles were considerably higher than those of adults, with many sounds reaching the ultrasonic range. Nevertheless, pure ultrasonic sounds were not recorded.

The frequencies of the analysed sounds of coruros extended from 0.17 to 20.33 kHz with dominant frequency components between 0.17 and 10 kHz. The acoustic properties of calls are suitable for transmission above and below ground, thus providing further indirect evidence that coruros are not strictly confined to an underground way of life. Indeed, the great variability of frequency ranges, with lower frequencies always being included, reflects a specialisation for communication in variable acoustic environments.

The most distinctive and unique vocalisation of coruros is the long duration musical trilling (lasting up to two minutes), which is a long-distance call emitted in alarm and arousal contexts. Recordings of this call from natural burrows in the field in Chile showed similar structural features to vocalisations from captive colonies in the laboratory.

Our findings provide a further example of matching physical properties of vocalisations to the acoustic conditions of the habitat. However, vocalisations in subterranean rodents consist almost exclusively of short-distance calls, the trilling of coruros being the notable exception. Since the selective pressure of the acoustic environment upon the evolution of short-distance vocalisations is probably minimal, we suggest that during their evolution, subterranean mammals have matched their vocalisations primarily to their hearing range and not directly to the acoustics underground. Hearing probably has been the primary target of natural selection, serving not only for communication but also for detection of predators (and, in carnivores, of prey).     

Aspects of Species Recognition by Sound in Four Species of Damselfishes,Genus Eupomacentrus (Pisces: Pomacentridae)

Members of four sympatric species of Eupomacentrus carry out reproductive activities at the same time of the year and produce similar pulsed courtship sounds. Such sounds are known to facilitate courtship among conspecifics. Consequently, members of the four species in the field and in the laboratory were tested with the various sounds to determine if they could distinguish their own species sounds from those produced by congeners. The differential responses clearly demonstrate species specific recognition by sound and indicate that the pulse interval and the number of pulses per sound are the important parameters for this recognition.     

Nesting habitat and nest features of Water Rails Rallus aquaticus and Little Crakes Zapornia parva on large wetlands

ABSTRACT

Capsule: In large and medium wetlands with extended reed beds Phragmites and cattail Typha dominated areas, Water Rails Rallus aquaticus and Little Crakes Zapornia parva show higher differences in nesting sites in contrast with other populations from small and fragmented wetlands, where the ranges of values for environmental variables at nesting sites overlap greatly.

Aims: To investigate the nesting sites and nesting habitats of both species to a fine scale, on medium and large wetlands, to evaluate the potential overlapping of nesting habitat and to compare data with those obtained in small wetlands.

Methods: In the study area, the Fize? Basin, Romania, 17 wetlands, ponds and reed beds ranging from 11.78 to 252.68 ha were investigated. The species were present on 4 wetlands, which were subsequently surveyed for nests. Between April and August 2010–2012, a total of 83 Water Rail and 46 Little Crake nests were found, measured and analysed in terms of nesting habitat and nest features.

Results: Principal component analyses suggest no overlap in nest site selection and a partial overlap in the nest features. An analysis of similarity confirmed significant nest structural differences. A discriminant function analysis highlights the main factors dividing the nest features of both species being: water depth and distance between the nest and a water surface. Little Crakes build their nests in cattail Typha sloped clumps, while Water Rails build their nests near reed Phragmites strains.

Conclusion: In large and medium wetlands, Water Rails nest deep in the reed bed rather than in other types of habitats, contrary to what has been reported for small ponds areas. Little Crakes nest in cattail independently of the size of the wetland where they occur.     

Comparative experiments on temperature responses of bryophytes: assimilation,respiration and freezing damage

Abstract

(1) Temperature-net assimilation and temperature-respiration curves based on manometric measurements at high carbon dioxide concentrations are presented for twenty-three mosses and five hepatics.

(2) In most of the species, the optimum temperature for net assimilation under the experimental conditions was about 25°–30°C and the temperature compensation point about 35°–40°C.

(3) Substantially lower optima and maxima were found in Orthothecium rufescens, Plagiopus oederi, Acrocladium trifarium, Fontinalis squamosa, Nardia compressa and Hookeria lucens.

(4) Several northern and montane species (e.g. Anthelia julacea, Andreaea nivalis, Rhacomitrium lanuginosum) did not differ substantially from the majority of lowland species in the response of net assimilation to temperature. Some substantial differences were found between species of differing habitats.

(5) Most of the mosses and leafy liverworts tested withstood rapid cooling to ?5°C for 6 hr. They are evidently protected from intracellular freezing at normal rates of cooling by the withdrawal of water to form extracellular ice.

(6) Conocephalum conicum, Targionia hypophylla and Pellia epiphylla were killed by rapid cooling to ?5°C.

(7) Plagiochila spinulosa and Myurium hebridarumwithstood periods of 1–2 weeks at ?5°C. Survival of bryophytes for long periods of low temperatures appears to be principally a matter of desiccation resistance.     

CHARACTERISTICS OF FINBACK BALAENOPTERA PHYSALUS VOCALIZATIONS IN THE ST. LAWRENCE ESTUARY

ABSTRACT

Sounds produced by Finback Whales Balaenoptera physalus were recorded from a stationary hydrophone in the St. Lawrence Estuary from June to September. The vocalizations consisted of frequencies below 120 Hz; impulsive sounds had frequencies up to 1 kHz. Over 80% of the sounds were downsweeping calls. Frequency variations in the downsweeps were correlated with social context. Constant calls, upsweeps, wavers and a frequency and amplitude modulated call were rare and may be context specific. Vocalization rates varied with the number of animals present and context, but could not be used as a census technique. Comparisons are made with the data from other investigators in both the Northwest Atlantic and the Northeast Pacific. Frequency and time characteristics for Finback downsweeps are summarized and discussed as components important for species recognition.     

EQUIPMENT REVIEW

ABSTRACT

The Northern White Rhinoceros Ceratotherium simum cottoni is a subspecies of the White Rhino that is almost extinct in the wild. We studied the last reproducing herd kept in Zoo Dvur Kralove to describe its vocal repertoire. The calls produced by eight individuals were recorded and analysed as concerned both sound properties and behavioural contexts in which they were emitted. We distinguished 11 calls belonging to four categories: (1) tonal harmonic sounds, (2) puffing sounds, (3) growling sounds, and (4) repetitive sounds. We found an apparent similarity between acoustic parameters of homologous calls recorded in both white rhino subspecies. We further confirmed that the repertoire of white rhino calls is much larger than that reported in other rhino species. We tentatively interpret this finding as an adaptation to increased sociality. Four calls reach the infrasound range; nevertheless, they are probably not used for communication over distance. This is obvious in the case of the grouch call, which contains the highest infrasound component. There are, however, other candidates for such a communication function: the repetitive pant sound, which is not known in other rhino species. We hypothesise that the repetitions may enhance their audibility in the typical open habitats of white rhinos.     

Effects of environmental heterogeneity on species diversity and composition of terrestrial bryophyte assemblages in tropical montane forests of southern Ecuador

Background: Most studies on tropical bryophytes deal with epiphytic species. This is the first ecological study of tropical forests that focuses specifically on terrestrial bryophytes.

Aim: To investigate the differences between slope and ridge environments in upper montane forests of southern Ecuador in terms of species diversity (richness, abundance), species composition and life forms of terrestrial bryophytes.

Methods: We used Non-metric Multidimensional Scaling (NMDS) to group bryophyte relevés by study location, habitat type and exposure class. Species indicator values were calculated and compared for different habitats.

Results: In total, 140 species were recorded, the majority being liverworts. NMDS analyses and Mantel correlations clearly separated between slope and ridge relevés, and between sunny and shaded microhabitats on ridges. Bryophyte life forms also showed different distribution patterns in slope and in ridge habitats. Mosses were more prominent in sunny than in shaded microhabitats.

Conclusions: Environmental differentiation between ridges and slopes, and small-scale variation in microclimatic conditions caused by differences in exposure, were stronger predictors of species richness and composition than geographical distance between study sites.     

A PORTABLE DIGITAL SOUND EMITTER FOR INTERACTIVE PLAYBACK OF ANIMAL VOCALISATIONS

ABSTRACT

A new portable digital sound emitter (DSE) for normal and interactive playback of sound signals in the field and in the laboratory is described together with two examples of applications of the DSE in interactive field experiments. The DSE may be loaded with a broad spectrum of digitised sounds, e.g. artificial signals or natural animal vocalisations, and it is controlled via the keyboard of a portable PC running a dedicated program. This program, which can be tailored to support a vast number of different demands, enables the experimenter to start and stop the analog output from the DSE at any time and to choose freely between the available sounds and playback modes. The use of the DSE for interactive playback experiments therefore is only limited by the ability of the operator to perceive the vocalisations of the participating animal and to operate the keyboard of the PC.     

Courtship Sounds Advertise Species Identity and Male Quality in Sympatric Pomatoschistus spp. Gobies

Acoustic signals can encode crucial information about species identity and individual quality. We recorded and compared male courtship drum sounds of the sand goby Pomatoschistus minutus and the painted goby P. pictus and examined if they can function in species recognition within sympatric populations. We also examined which acoustic features are related to male quality and the factors that affect female courtship in the sand goby, to determine whether vocalisations potentially play a role in mate assessment. Drums produced by the painted goby showed significantly higher dominant frequencies, higher sound pulse repetition rates and longer intervals between sounds than those of the sand goby. In the sand goby, male quality was predicted by visual and acoustic courtship signals. Regression analyses showed that sound amplitude was a good predictor of male length, whereas the duration of nest behaviour and active calling rate (i.e. excluding silent periods) were good predictors of male condition factor and fat reserves respectively. In addition, the level of female courtship was predicted by male nest behaviour. The results suggest that the frequency and temporal patterns of sounds can encode species identity, whereas sound amplitude and calling activity reflects male size and fat reserves. Visual courtship duration (nest-related behaviour) also seems relevant to mate choice, since it reflects male condition and is related to female courtship. Our work suggests that acoustic communication can contribute to mate choice in the sand goby group, and invites further study.     

Mating calls of three prochilodontid fish species from Brazil

Passive acoustic monitoring (PAM) of fish sounds has been used as a means of detecting the presence and abundance of fishes. Prior to PAM, bioacoustical analyses of sounds are needed to characterize species-specific characteristics of calls. With hydrophones placed in outdoor ponds, we recorded the mating calls of three species of prochilodontid fishes (Prochilodus argenteus, P. costatus, P. lineatus). Fish were induced to spawn and call by injection of carp (Cyprinus carpio) pituitary gland extract. We recorded a total of 394 pulse train calls and additional single pulse calls that were not associated with trains. The trains of all three species were similar in nature - series of low frequency pulses that lasted from 1 to 11 s, often with an initial rapid rise followed by a slow tapering of pulse amplitude. Dominant frequency of single pulses and trains was greatest in P. lineatus, with P. costatus and P. argenteus exhibiting lower single pulse dominant frequencies, and P. costatus having lower train dominant frequency. With data from the three species combined, the dominant frequency of pulses significantly increased with fish standard length. There was also a significant linear relationship between the dominant frequency of pulses and trains. Discriminant function analysis showed that differences in train dominant frequency, pulse duration, and pulse period between the three species were significant enough to discriminate between them. This study was the first to fully characterize the sounds of these three Prochilodus species, and should assist fisheries biologists monitoring spawning behavior in these species.     

THE COMMUNICATIVE SIGNIFICANCE OF TONALITY IN BIRDSONG: RESPONSES TO SONGS PRODUCED IN HELIUM

ABSTRACT

“Pure tones” are a distinctive acoustic feature of many birdsongs. Recent research on songbird vocal physiology suggests that such tonal sounds result from a coordinated interaction between the syrinx and a vocal filter, as demonstrated by the emergence of harmonic overtones when a bird sings in helium. To investigate the communicative significance of vocal tract filtration in the production of birdsong, we used field playback experiments to compare the responses of male swamp sparrows Melospiza georgiana to normal songs and those same songs recorded in helium. We also measured responses to pure tone songs that had been shifted upward in frequency to match the average spectra of those songs with added harmonics. Male sparrows were significantly more responsive to the playback of normal songs than to either helium songs with added harmonics or frequency- shifted pure tone songs. Songs with harmonics retained a high degree of salience, however. We conclude that explanations for the occurrence of tonal sounds in birdsongs must consider perceptual attributes of songs as communicative signals, as well as problems of song production and transmission.     

The changing bird phenology of Mid Deeside,Scotland 1974–2010

Capsule Marked changes were observed in the spring phenology of birds and were more apparent in residents and short‐distance migrants than in trans‐Mediterranean migrants.

Aims To examine changes in first songs and arrivals of birds in northeast Scotland.

Methods First song or first observations of 38 species were recorded between 1974 and 2010. Trends through time, and relationships with regional variation in temperature, were both examined.

Results There was a strong tendency for first song/first arrival dates to advance, with the average change being an advance of 25 days over the 37 years of study (or 0.7 days per year). Change was greater in the dates of first song of resident species than in the first detection of short‐distance and trans‐Mediterranean migrants. Relationships with temperature were apparent, but were significant for fewer than half of the species.

Conclusion Bird species vary greatly in their phenological response to climate warming. The recent decade of sustained higher spring temperatures has enabled greater detection of change in long‐term time series, and milder winters (except 2009/10) have also increased the incidence of wintering in short‐distance migrants.