Signal Of Need Research Articles

Nestling cuckoos, Cuculus canorus, exploit hosts with begging calls that mimic a brood

Nestling cuckoos, Cuculus canorus , eject host eggs or young from the nest and are then raised alone by the hosts. Using reed warblers, Acrocephalus scirpaceus , as hosts, we investigated how the single cuckoo chick can command the same provisioning rate as a whole brood of host young. Large size alone is not sufficient to stimulate adequate provisioning because single blackbird, Turdus merula , or song thrush, T. philomelos , chicks of the same mass as a cuckoo were fed at a lower rate. Our experiments show that the key stimulus is the cuckoo chick9s rapid begging call (‘si, si, si, si ...’), which sounds remarkably like a whole brood of host chicks, and which it matched in calling rate. When single blackbird or song thrush chicks were accompanied by loudspeakers that broadcast either cuckoo begging calls or calls of a brood of reed warblers, the hosts increased their provisioning rate to that for a cuckoo chick. We suggest that the cuckoo needs vocal trickery to stimulate adequate care to compensate for the fact that it presents a visual stimulus of just one gape.

Instability of signaling resolution models of parent-offspring conflict.

Recent signaling resolution models of parent-offspring conflict have provided an important framework for theoretical and empirical studies of communication and parental care. According to these models, signaling of need is stabilized by its cost. However, our computer simulations of the evolutionary dynamics of chick begging and parental investment show that in Godfray's model the signaling equilibrium is evolutionarily unstable: populations that start at the signaling equilibrium quickly depart from it. Furthermore, the signaling and nonsignaling equilibria are linked by a continuum of equilibria where chicks above a certain condition do not signal and we show that, contrary to intuition, fitness increases monotonically as the proportion of young that signal decreases. This result forces us to reconsider much of the current literature on signaling of need and highlights the need to investigate the evolutionary stability of signaling equilibria based on the handicap principle.

Mouth colour is a reliable signal of need in begging canary nestlings

Begging passerine chicks display brightly coloured mouths as they solicit food from their parents. Despite a range of hypotheses, the function of vivid nestling mouth colour remains unknown. Here I report that mouth colour functions as a signal of need in canary nestlings, in the days immediately following hatching. Changes in mouth colour accurately reflect a nestling's state of need: the more food deprived the chick, the more intensely coloured its mouth. In controlled experiments with two nestlings, parents were offered the opportunity to choose which nestling to feed. When the mouth colour of one offspring was artificially reddened using food colouring, parents gave it more food. These results demonstrate a novel function for nestling mouth colour and are consistent with recent models of the resolution of parent–offspring conflict.

Begging signals and parent–offspring conflict: do parents always win?

Apparently costly begging behaviour has recently been explained as a means by which offspring communicate their need, allowing parents to provide them with a level of resource equal to that which would be optimal (for the parents) in the absence of begging. This hypothesis contrasts with earlier explanations, which suggest that solicitation induces parents to provide more resources than it would otherwise (in the absence of begging) be optimal for them to do. Here, I develop an extended model of costly begging as a signal of need, which unlike previous analyses allows offspring to adjust their level of begging over time in response to parental feeding. I show that under these more realistic conditions, a signalling resolution of parent-offspring conflict also leads parents to allocate more resources than would otherwise be optimal for them, in order to reduce the subsequent level of costly solicitation by their young.

Signaling of Need between Parents and Young: Parent-Offspring Conflict and Sibling Rivalry

The young of birds and mammals frequently solicit food and other resources from their parents in ways that appear to be costly either in terms of energetic expenditure or because they may attract predators. Costly solicitation has been explained as a means by which the young manipulate their parents into providing more resources than the parental optimum. Alternatively, communication between parents and young can be interpreted as an evolutionarily stable signaling system. A model is developed of two young in a brood who compete for a fixed amount of resources distributed by their parents. It is shown that an evolutionarily stable signaling system can exist in which the parent obtains accurate information about the resource needs of its young and on which it bases its resource distribution decisions. Young with greater resource requirements solicit at higher levels, but the system is stable because any misrepresentation is selected against. Essential for stability is that signaling must be costly; it is t...

When do canary parents respond to nestling signals of need?

Parent birds at the nest face a brood of nestlings that are jostling, gaping, calling and posturing. Recent empirical work on food distribution among the brood has demonstrated a strong effect of close proximity to the parent in determining the amount of food allocated to each chick. Chick position in the size hierarchy and level of chick food deprivation have previously been shown separately to influence chick proximity to the feeding parent, but it is not clear how these two factors interact. Experiments on canaries, described here, aimed first to investigate the interaction of size and hunger on chick proximity to the feeding parent and, second, to discover whether parents responded to any other chick behaviours when distributing food within the brood. Manipulations of levels of food deprivation with respect to chick size indicated that although size had the strongest effect on chick proximity to the parent, hunger level could also play a part. When chick position in the nest was controlled experimentally, parents responded to other cues when allocating food. It is suggested that the broad food distribution patterns of the parents are influenced by size-dependent chick behaviours, such as proximity to the parent. Within these broad patterns parents respond to short-term fluctuations in chick hunger as signalled by the posturing and calling behaviours of the chick.

Human breasts: evolutionary origins as a deceptive signal of need for provisioning and temporary infertility

Les poitrines des femmes se developpent pendant la grossesse et la lactation. Pendant cette periode qui profite le plus a l'enfant, les hommes sont des pourvoyeurs plus genereux pour les femmes ayant une forte poitrine. Les hommes dominateurs considerent cependant une forte poitrine comme non attirante sexuellement. Ce comportement permet a ces femmes d'etre librement courtisees par des hommes non-dominateurs. Le courtisage implique l'approvisionnement des femmes, ce qui ameliore le bien-etre de l'enfant. Ainsi les femmes a forte poitrine etaient mieux « entretenues ». Les femmes ayant des genes favorisant le depot de graisse dans leur poitrine avaient des descendants plus nombreux afin que de tels genes soient selectionnes. Chez les primates non-humains chez lesquels l'approvisionnement par le mâle n'etait pas important, les depots de graisse preferentiels n'apparaissaient pas car de tels depots ne pouvaient conduire a un meilleur approvisionnement

Calling by domestic piglets: reliable signals of need?

Two manipulations were performed on domestic piglets to determine whether differences in calling during periods of separation from the mother can indicate differences in need. In both cases, the aim was to manipulate the piglet's need for the sow's attention. In the first manipulation a ‘thriving’ piglet (i.e. the piglet with the heaviest weight and most rapid weight gain) and a ‘non-thriving’ one (lightest and slowest weight gain) were selected from each of 15 litters. The two piglets were removed from the sow and litter and recorded for 13 min in separate isolated enclosures. For the second manipulation, two piglets of intermediate weight and weight gain were selected from each of the same 15 litters and were removed from the sow during nursing under one of two conditions. The ‘unfed’ piglet was removed just before the milk ejection and the ‘fed’ one just after receiving milk. Both were recorded as in the first manipulation. ‘Non-thriving’ and ‘unfed’ piglets called more and used more high-frequency calls, longer calls, and calls that rose more in frequency than their ‘thriving’ and ‘fed’ litter-mates. By means of a playback experiment, the assumption that sows respond to these piglet calls was tested. Sows were more likely to vocalize and approach the loudspeaker during playback of the piglet isolation calls than during playback of white noise. It is argued that if a piglet's calls provide reliable information about its need for the sow's resources, then this calling can be used as a measure of its welfare. These results are consistent with theoretical models of honst signalling.

Cold-Induced Calling and Shivering in Young American White Pelicans: Honest Signalling of Offspring Need for Warmth in a Functionally Integrated Thermoregulatory System

AbstractVocal regulation of body temperature in thermally dependent offspring can occur when cold-induced vocalizations elicit appropriate brooding and rewarming by a parent or surrogate. I tested the ability of young American white pelicans to regulate vocally body temperature in the laboratory by exposing them to moderate chilling (20-23°C), either continuously, or punctuated by brief (usually 2 min) periods of warmth in response to cold-induced calling. When continuously chilled, they began to call almost immediately (median latency 35 s), and body temperature began to drop. At 1 and 2 weeks of age, visible shivering also occurred, but was not sufficient to arrest the decline in body temperature. When chilling was then ameliorated by brief periods of warmth in response to cold-induced calling, body temperature shifted upwards, indicating a vocal thermoregulatory ability similar to, but somewhat faster, than that previously reported for late-stage embryos in this species. At 1 day of age, cold-induced calling occurred with a shorter latency and at a higher rate at lower body temperatures, as expected in a compensatory thermoregulatory system. After the onset of shivering thermogenesis at 1 and 2 weeks of age, the compensatory response decreased, but calling still occurred in response to chilling, as required by a simple on-off regulatory system. Begging for food was inhibited at body temperatures low enough to elicit shivering, suggesting that vocal maintenance of a relatively high body temperature may be of importance to normal begging and food acquisition prior to the full development of endothermy in this species. Effective functioning of the vocal thermoregulatory system requires that information about offspring body temperature be accurate. This requirement suggests a strong parallel between vocal thermoregulation and the concept of honest signalling in animal communication. Honest signalling of need by offspring has received recent theoretical support, but is controversial and has rarely been tested experimentally. I used the occurrence of shivering, which is the main source of endothermic heat in birds, as a standard against which to test empirically the honesty of cold-induced calls as signals of need for warmth. When 1 and 2-week old chilled, shivering chicks began to warm up during vocal regulation sessions, shivering eventually became periodic, starting each time a bird was chilled and ending during each subsequent period of rewarming. Calling at this time invariably (84 of 84 cases) began only after the onset of shivering, then ended while shivering was still in progress. To the extent that shivering is an honest, perhaps unfakable indicator of a biologically relevant need for warmth, the vocalizations associated with it appear to be honest signals indicating the presence of that need. Results are also consistent with a recent theoretical model of honest signalling of need by offspring, but it remains to be determined whether honest solicitation of warmth prevails when chicks are in naturally competitive situations at the nest.

The Interactional Theory of Depression: A Meta-Analysis of the Research Literature

Coyne's (1976a) interactional theory of depression states that depressed people induce a negative mood in others through social interaction and hence elicit rejection from them. A meta-analysis was conducted to ssess the relationship between (1) depression and negative mood in others, (2) depression and rejection by others, and (3) negative mod and rejection by others. The results indicate strong support for the rejection component of the theory, but rather modest support for the negative mood induction hypothesis. Negative mood seems to show a curvilinear (inverted-U) relationship with depression

Signalling of need by offspring to their parents

THE young of birds and mammals often solicit food from their parents in ways that appear to be costly and to reduce their fitness1, 2. Thus birds in the nest beg vigorously for food, incurring energetic costs and possibly attracting predators3; the behaviour of young mammals requiring to suckle (bleating or crying, for example) similarly appears costly1, 2. If solicitation is a means by which the young communicate need to their parents, why has a less expensive form of communication not evolved4? An answer to this question is provided by the theory of parent–offspring conflict: natural selection acting on genes expressed in the young will lead to greater demands for parental resources than is optimal for the parent1, 5. The accurate communication of offspring need is evolutionarily unstable as offspring will be selected to demand extra resources. Models of parent–offspring conflict have shown that an evolutionarily stable equilibrium can exist at which an offspring solicits resources in a way that reduces its fitness, and a parent provides extra resources to prevent further expensive solicitation6–11. I present an alternative explanation for costly solicitation by showing that the level of offspring solicitation can be a true reflection of offspring need as long as solicitation is costly and the benefits of extra resources increase with need. My analysis suggests that the parent normally allocates resources using accurate information about the condition of the young. The requirement that the signalling system is costly is a direct consequence of the potential for parent–offspring conflict.

Understanding anorexia in the elderly: Formulating BioPsychological Research strategies

Anorexia in the elderly may arise from a disregulated system rather than from the operation of an isolated pathological mechanism. The properties of a disregulated system can be diagnosed through a functional analysis. Anorexia could arise through a weak read-out of metabolic signals of need rather than from hyperactive satiety agents. Serotonin systems may integrate regulatory actions.

An investigation of crying in the newborn in relation to maternal and infant factors

SummaryTotal 24 hour crying times were measured in 182 babies on various postnatal days during the first week, using a specially designed cry recorder. The mean 24 hour crying time was 25 minutes (range 4 seconds - 1 hour 48 minutes). Of 44 factors analysed for their effect on crying. 11 were found to be related. Factors associated with increased crying included high maternal age. low maternal anxiety. multiparity. maternal hypertension, twinning, caesarean section, and mixed breast and bottle feeding. Factors associated with reduced crying included very young mothers. high maternal anxiety. forceps delivery and admission to the neonatal unit. Some of these factors reflect alterations in the babies' excitability and others reflect variations in maternal attitudes and responses. The data form a base for the examination of later infant behaviour.A baby's cry is a signal of need and as such has a compelling effect on the mother (Oswald, 1972). Babies cry when hungry or in pain, as a particularly effective me...