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Calling Rate (calling + rate)
Selected AbstractsLong-range call use in dominance-structured Crested Tit Parus cristatus winter groupsJOURNAL OF AVIAN BIOLOGY, Issue 1 2000Indri?is Krams In this study on free-ranging Crested Tits Parus cristatus, I examine the relationship between social dominance and the frequency of use of long-range communication calls. Calling rates of trills were highest among socially dominant individuals and they gave more calls when close to the boundary of their territories. Dominant females uttered fewer calls than their mates. However, they gave significantly more calls than subordinate males and subordinate females, the latter calling least. A removal and playback experiment revealed a relationship between the utterance of trilled calls and the defence of the winter territory in the Crested Tit. Although territorial vocalizations could incur costs, territorial individuals may gain from improved winter survival by decreasing the risk of food stealing by Crested Tits from adjacent territories. [source] COSTS OF AN INDUCED IMMUNE RESPONSE ON SEXUAL DISPLAY AND LONGEVITY IN FIELD CRICKETSEVOLUTION, Issue 10 2004Alain Jacot Abstract Immune system activation may benefit hosts by generating resistance to parasites. However, natural resources are usually limited, causing a trade-off between the investment in immunity and that in other life-history or sexually selected traits. Despite its importance for the evolution of host defense, state-dependent fitness costs of immunity received little attention under natural conditions. In a field experiment we manipulated the nutritional condition of male field crickets Gryllus campestris and subsequently investigated the effect of an induced immune response through inoculation of bacterial lipopolysaccharides. Immune system activation caused a condition-dependent reduction in body condition, which was proportional to the condition-gain during the preceding food-supplementation period. Independent of nutritional condition, the immune insult induced an enduring reduction in daily calling rate, whereas control-injected males fully regained their baseline level of sexual signaling following a temporary decline. Since daily calling rate affects female mate choice under natural conditions, this suggests a decline in male mating success as a cost of induced immunity. Food supplementation enhanced male life span, whereas the immune insult reduced longevity, independent of nutritional status. Thus, immune system activation ultimately curtails male fitness due to a combined decline in sexual display and life span. Our field study thus indicates a key role for fitness costs of induced immunity in the evolution of host defense. In particular, costs expressed in sexually selected traits might warrant the honest advertisement of male health status, thus representing an important mechanism in parasite-mediated sexual selection. [source] Acoustic estimation of wildlife abundance: methodology for vocal mammals in forested habitatsAFRICAN JOURNAL OF ECOLOGY, Issue 3 2010Mya E. Thompson Abstract Habitat loss and hunting pressure threaten mammal populations worldwide, generating critical time constraints on trend assessment. This study introduces a new survey method that samples continuously and non-invasively over long time periods, obtaining estimates of abundance from vocalization rates. We present feasibility assessment methods for acoustic surveys and develop equations for estimating population size. As an illustration, we demonstrate the feasibility of acoustic surveys for African forest elephants (Loxodonta africana cyclotis). Visual surveys and vocalizations from a forest clearing in the Central African Republic were used to establish that low-frequency elephant calling rate is a useful index of elephant numbers (linear regression P < 0.001, radj.2 = 0.58). The effective sampling area was 3.22 km2 per acoustic sensor, a dramatic increase in coverage over dung survey transects. These results support the use of acoustic surveys for estimating elephant abundance over large remote areas and in diverse habitats, using a distributed network of acoustic sensors. The abundance estimation methods presented can be applied in surveys of any species for which an acoustic abundance index and detection function have been established. This acoustic survey technique provides an opportunity to improve management and conservation of many acoustically-active taxa whose populations are currently under-monitored. Résumé La perte d'habitat et la pression de la chasse menacent des populations de mammifères dans le monde entier, ce qui entraîne des contraintes de temps critiques pour l'évaluation des tendances. Cette étude présente une nouvelle méthode de recherche qui échantillonne sur de longues périodes de façon constante et non intrusive et qui permet d'obtenir des estimations d'abondance à partir des taux de vocalisation. Nous présentons les méthodes d'évaluation de la faisabilité d'études acoustiques et nous développons des équations pour estimer la taille des populations. Pour illustrer ceci, nous montrons la faisabilité d'études acoustiques chez les éléphants de forêts africains Loxodonta africana cyclotis. Nous avons utilisé des études visuelles et des vocalisations d'une clairière forestière de République Centrafricaine pour établir que le taux d'appel à basse fréquence des éléphants est un indice intéressant du nombre d'éléphants (régression linéaire P < 0,001, radj² = 0,58). La superficie d'échantillonnage effective était de 3,22 km² par senseur acoustique, ce qui est une augmentation spectaculaire par rapport à la couverture des transects d'études par comptage des crottes. Ces résultats appuient le recours aux études acoustiques pour estimer l'abondance des éléphants dans de vastes zones retirées et dans des habitats variés, en utilisant un réseau de senseurs acoustiques bien répartis. Les méthodes d'estimation de l'abondance présentées peuvent être appliquées à toute espèce pour laquelle on a établi un indice d'abondance acoustique et une fonction de détection. Cette technique d'étude acoustique donne la possibilité d'améliorer la gestion et la conservation de nombreux taxons actifs au point de vue acoustique et dont les populations sont actuellement trop peu suivies. [source] Do temperature and social environment interact to affect call rate in frogs (Crinia signifera)?AUSTRAL ECOLOGY, Issue 2 2004Bob B. M. Wong Abstract Acoustic displays are pervasive and conspicuous forms of sexual advertisement used by animals to attract mates. Evidence suggests that individuals may use environmental cues and/or the presence of other displaying animals to select the best times for display to optimize the chances of mating. Less well-known is how the physical and social environment might interact to affect the actual content of the display itself. We examined the effects of social environment and temperature on calling rate in a frog Crinia signifera. We found that both variables interacted to affect call rate but only among continuous callers. Call rate increased with temperature in individuals calling continuously on their own but no relationship was found in frogs calling continuously in the presence of others, either in a duet or in a group calling situation. We suggest that the temperature sensitivity of calling rate in frogs could depend on the social environment of the caller. As such, we suggest caution in generalizing about the way temperature affects calling rates in frogs and encourage greater consideration of how physical and social environments might interact to influence the signal content of acoustic displays. [source] Patterns of Vocal Interactions in a Bullfrog (Rana catesbeiana) Chorus: Preferential Responding to Far NeighborsETHOLOGY, Issue 8 2000Su L. Boatright-Horowitz In chorusing species, males seem to be spaced non-randomly, and their vocal interactions may be governed by particular behavioral rules. We monitored patterns of vocal interactions in a natural bullfrog (Rana catesbeiana) chorus to determine the probability with which calls of individual frogs would follow each other's in dyadic sequences. Expected probabilities of responses in a dyad were calculated based upon the joint probabilities of calling (relative calling rates) of the individual frogs; observed probabilities of response reflected the actual number of following responses in each dyad. Results of statistical tests comparing observed and expected probabilities of responding revealed that, when dyads were closely spaced, observed probabilities of a following response were significantly less than the expected probabilities. Conversely, when dyads were composed of more distant males, observed probabilities of responding were significantly greater than expected. Observed probabilities of response were correlated with inter-male distances; males called more frequently than expected following calls of far neighbors, and less frequently than expected following calls of near neighbors. These data suggest that males attend to both nearby and distant callers, and adjust the onset of their own vocalizations appropriately. Males may be actively inhibited by calls of their near neighbors, and their calling may be actively elicited by the calls of their far neighbors. [source] Heard but not seen: an acoustic survey of the African forest elephant population at Kakum Conservation Area, GhanaAFRICAN JOURNAL OF ECOLOGY, Issue 1 2010Mya E. Thompson Abstract This study, designed to survey forest elephants (Loxodonta africana cyclotis) at Kakum Conservation Area, Ghana, is the first to apply acoustic methods to elephant abundance estimation and to compare results with independent survey estimates. Nine acoustic sensors gathered sound continuously for 38 days. Low-frequency calling rates have been established as useful elephant abundance indices at a Namibian watering hole and a central African forest clearing. In this study, we estimated elephant population size by applying an abundance index model and detection function developed in central Africa to data from simultaneous sampling periods on Kakum sensors. The sensor array recorded an average of 1.81 calls per 20-min sampling period from an effective detection area averaging 10.27 km2. The resulting estimate of 294 elephants (95% CI: 259,329) falls within confidence bounds of recent dung-based surveys. An extended acoustic model, estimating the frequency with which elephants are silent when present, yields an estimate of 350 elephants (95% CI: 315,384). Acoustic survey confidence intervals are at least half as wide as those from dung-based surveys. This study demonstrates that acoustic surveying is a valuable tool for estimating elephant abundance, as well as for detecting other vocal species and anthropogenic noises that may be associated with poaching. Résumé Cette étude, conçue pour étudier les éléphants de forêt (Loxodonta africana cyclotis) de l'Aire de conservation de Kakum, au Ghana, est la première qui applique des méthodes acoustiques pour l'estimation de l'abondance des éléphants et qui compare les résultats avec des estimations indépendantes. Pendant 38 jours, neuf senseurs acoustiques ont récolté les sons en continu. Le rythme des appels à basse fréquence est un indice utile de l'abondance des éléphants que l'on a pu établir à un point d'eau en Namibie et dans une clairière d'une forêt d'Afrique centrale. Ici, nous estimons la taille d'une population d'éléphants en appliquant un modèle d'indice d'abondance et une fonction de détection mis au point en Afrique centrale à des données provenant des senseurs de Kakum pour des périodes d'échantillonnage simultanées. La batterie de senseurs a enregistré une moyenne de 1.81 appel par 20 min, pour une superficie de détection réelle de 10.27 km² en moyenne. L'estimation qui en résulte, qui est de 294 éléphants (95% IC 259,329), tombe dans les limites de confiance de récentes études basées sur les crottes. Un modèle acoustique étendu, qui estime aussi la fréquence à laquelle les éléphants sont silencieux pendant leur présence, donne une estimation de 350 éléphants (95% IC 315,384). Les intervalles de confiance d'une étude acoustique sont au moins la moitié de ceux des études par les crottes. Cette étude montre que l'étude acoustique est un outil intéressant pour estimer l'abondance des éléphants et aussi pour détecter d'autres espèces bruyantes et les bruits d'origine anthropique qui pourraient être associés au braconnage. [source] Do temperature and social environment interact to affect call rate in frogs (Crinia signifera)?AUSTRAL ECOLOGY, Issue 2 2004Bob B. M. Wong Abstract Acoustic displays are pervasive and conspicuous forms of sexual advertisement used by animals to attract mates. Evidence suggests that individuals may use environmental cues and/or the presence of other displaying animals to select the best times for display to optimize the chances of mating. Less well-known is how the physical and social environment might interact to affect the actual content of the display itself. We examined the effects of social environment and temperature on calling rate in a frog Crinia signifera. We found that both variables interacted to affect call rate but only among continuous callers. Call rate increased with temperature in individuals calling continuously on their own but no relationship was found in frogs calling continuously in the presence of others, either in a duet or in a group calling situation. We suggest that the temperature sensitivity of calling rate in frogs could depend on the social environment of the caller. As such, we suggest caution in generalizing about the way temperature affects calling rates in frogs and encourage greater consideration of how physical and social environments might interact to influence the signal content of acoustic displays. [source] | ||||||||||