Food allocation in crimson rosella broods: parents differ in their responses to chick hunger

Food allocation in many asynchronously hatching bird species favours large, competitively superior chicks. In contrast, food is usually distributed equally within broods of crimson rosellas, Platycercus elegans, implying that parents do not simply feed the most competitive chick. We used two temporary removal experiments to manipulate hunger of: (1) individual first- or last-hatched chicks, or (2) the whole brood. When only a single chick was hungry, parents compensated fully and chicks gained the same mass over the day as during controls. Mothers and fathers, however, responded in different ways to chick hunger. Mothers did not strongly alter their food allocation when a single chick was hungry, and controlled the distribution of food by refusing to feed first-hatched chicks when they were hungry and by moving more during feeds. In contrast, fathers allocated more food to hungry last-hatched chicks. When the whole brood was hungry, parents were unable to compensate chicks and all chicks lost mass over the day. In these conditions, mothers preferentially fed first-hatched chicks, while fathers fed all chicks equally. Our results show that both mothers and fathers were able to discriminate and selectively feed chicks, but that parents responded differently to changes in chick hunger within the brood. Fathers responded more strongly to variation in chick hunger within the brood, suggesting they reallocate food based on short-term changes in hunger. Mothers distributed food preferentially to last-hatched chicks except when the whole brood was hungry, when they switched to favouring first-hatched chicks. This pattern is consistent with a strategy of adaptive brood reduction when food is scarce. Copyright 2000 The Association for the Study of Animal Behaviour.     

Transient changes in the pattern of food intake following a simulated time-zone transition to the east across eight time zones

Twelve healthy adults were studied, singly or in groups of up to four, in an Isolation Unit before (control days) and for 3 days after a simulated time-zone transition to the east across 8 time zones (the clock being changed from 15:00 to 23:00 h). Subjects were free to choose how to pass their waking hours (though naps were forbidden), and to eat what and when they wanted. A wide selection of food was provided, though the subjects had to prepare it. Subjects completed food intake questionnaire on waking and at 3 h intervals during the waking day. This questionnaire assessed the reasons for choosing not to eat a meal or, if a meal was eaten, the reasons for doing so, the type of meal chosen and the reasons for this choice, and subjective responses to the meal (hunger before, enjoyment during, and satiety afterwards). Subjects also recorded the incidence and degree of indigestion and jet lag at 3 h intervals after the time-zone transition. Following the time-zone transition, the subjects experienced significant amounts of jet lag and recorded a significant increase in the incidence of indigestion. They also showed significant changes in their pattern of food intake, but, whereas the patterns of food intake were no longer significantly different from control days by the third post-shift day, the symptoms of jet lag and indigestion were still present then. The distribution of daytime meals was significantly affected on the first post-shift day, with a redistribution of the times that the main, hot meals were eaten; these times indicated some influence of an unadjusted body clock. On this day also, the reasons for determining food intake continued to be dominated by hunger and appetite (hunger even increasing in the frequency with which it was cited), and the reason for not eating a meal, by a lack of hunger. On both control and post-shift days, there was a marked effect of meal type upon the responses to food intake, with cold food being rated least and large hot meals most when appetite before the meal, enjoyment during it, and satiety afterward were considered. However, evidence suggested that the degree to which larger hot meals were preferred to cold meals was significantly less marked after the time-zone transition. On control days, sleep was unbroken; whereas, after the time-zone transition, all subjects woke on at least one of the 3 nights studied. During the first post-shift night, about half of the subjects ate a meal, the reason given being that they were “hungry.” On those occasions when subjects woke but did not eat a meal, the reason cited was because they “could not be bothered” as frequently as because they were “not hungry.”. A simulated time-zone transition is associated with significant changes to the incidence of indigestion, pattern of food intake, and subjective responses to food. However, these changes are generally transient and are only weakly linked to the sensation of jet lag.     

Parental Distribution of Resources in Relation to Larval Hunger and Size Rank in the Burying Beetle Nicrophorus vespilloides

In altricial birds, the parents' distribution of resources within the brood is influenced by variation in at least two components of nestling condition: hunger level and size rank. Here, we examine whether variation in larval hunger and size rank had similar influences on the parents' distribution of resources in the burying beetle Nicrophorus vespilloides . To this end, we analyzed hitherto unpublished data on parental resource distribution among individual larvae derived from three previous experiments. Our first experiment showed that resource distribution was biased towards hungry larvae at the expense of control larvae, but that actively begging hungry larvae were as likely to obtain resources from parents as actively begging control larvae. Thus, resource distribution was biased towards hungry larvae because hungry larvae spent more time begging than control larvae. Our second experiment showed that actively begging senior larvae (i.e. larvae that were older and larger) were more likely to obtain resources than actively begging junior larvae, suggesting that senior larvae had a competitive advantage or were treated preferentially by the parents. Our third experiment found no evidence that the interaction between larval hunger and size rank had an effect on parental resource distribution, suggesting that hunger level had a similar effect on resource distribution to seniors and juniors. We conclude that offspring hunger and size rank have remarkably similar effects in the burying beetle N. vespilloides as reported in studies on altricial birds.     

State-dependent decisions in nest site selection by a web-building spider

Foraging decisions may reflect a trade-off between food intake and safety and can also be influenced by the animal's internal state. Foraging in the web-building spider Stegodyphus lineatus depends on a capture web associated with a retreat (the nest). The relocation of nests, including the take-over of conspecific nests, may be viewed as a foraing decision, which depends on risk of exposure, cost of silk production and hunger state. We investigated a possible state-dependent trade-off in nest site choice of S. lineatus spiderlings. The philopatric nature ofS. lineatus implies a high risk of encounters with potentially cannibalistic conspecifics and a potential loss of inclusive fitness because encountered conspecifics are likely to be kin. To test for state dependence of foraging decisions, we compared preferences of well-fed and hungry spiders for their own nests and those of siblings and nonsiblings. We expected satiated spiders to prefer their own to conspecific nests and hungry spiders to choose the risky option of a conspecific nest. SinceS. lineatus is less aggressive towards kin, we tested the ability of spiders to discriminate kin by silk-bound cues. Because of this reduced aggression, preference for kin nests should be safer than preference for nonkin nests. A strong preference for self-nests demonstrated self-recognition in well-fed spiders. However, neither well-fed nor hungry spiders discriminated between nests of siblings and nonsiblings. Well-fed spiders preferred self-nests to empty chambers, but showed no discrimination between nonself-nests and empty chambers. Hungry spiders showed a reduced preference for self-nests, suggesting that hunger elicits a more risky foraging strategy. A tendency of hungry spiders to adopt the nests of conspecific spiders may reflect a silk-saving strategy. We conclude that S. lineatus spiders show state-dependent decision making in nest site selection. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Taste reactivity patterns in domestic cats (Felis silvestris catus)

The present study is aimed at finding taste reactivity patterns in domestic cats (Felis silvestris catus) which reflect 'liking' or perceived palatability. Three groups of nonstressed cats living in households were formed which a priori were expected to differ in motivational state for eating food items (more or less hungry), and which were offered two different food items differing in general taste properties (more or less flavourful food, MFF and LFF, respectively) around the time that they were fed their normal food. Analysis of the amount of food eaten showed that MFF was consumed regardless of hunger level and that LFF was consumed depending on the hunger level of cats: the more hungry cats ate more of LFF than the less hungry cats. Analysis of post-meal behavioural sequences showed that the 'MFF consumption sequence' differed from the 'LFF refusal sequence' and that the 'LFF consumption sequence' strongly resembled the 'MFF consumption sequence' but also contained elements of the 'LFF refusal sequence'. Subsequent analysis of the frequencies and total durations of behavioural patterns showed that two kinds of patterns existed, possibly reflecting two 'palatability dimensions': hedonic taste reactivity patterns (lick/sniff feeding bowl, lip lick and groom face) and aversive taste reactivity patterns (lick/sniff food and lick nose). These dimensions may be combined to obtain a single palatability score.     

Effects of Structural Refuge and Density on Foraging Behaviour and Mortality of Hungry Tadpoles Subject to Predation Risk

Theoretical models of prey behaviour predict that food‐limited prey engage in risk‐prone foraging and thereby succumb to increased mortality from predation. However, predation risk also may be influenced by factors including prey density and structural cover, such that the presumed role of prey hunger on predation risk may be obfuscated in many complex predator–prey systems. Using a tadpole (prey) – dragonfly larva (predator) system, we determined relative risk posed to hungry vs. sated prey when both density and structural cover were varied experimentally. Overall, prey response to perceived predation risk was primarily restricted to increased cover use, and hungry prey did not exhibit risk‐prone foraging. Surprisingly, hungry prey showed lower activity than sated prey when exposed to predation risk, perhaps indicating increased effort in search of refuge or spatial avoidance of predator cues among sated animals. An interaction between hunger level and predation risk treatments indicated that prey state affected sensitivity to perceived risk. We also examined the lethal implications of prey hunger by allowing predators to select directly between hungry and sated prey. Although predators qualitatively favoured hungry prey when density was elevated and structural cover was sparse, the overall low observed variation in mortality risk between hunger treatments suggests that preferential selection of hungry prey was weak. This implies that hunger effects on prey mortality risk may not be readily observed in complex landscapes with additional factors influencing risk. Thus, current starvation‐predation trade‐off theory may need to be broadened to account for other mechanisms through which undernourished prey may cope with predation risk.     

Begging in Common Redstart Nestlings: Scramble Competition or Signalling of Need?

Begging behaviour by the young affects parental food distribution among nestlings of altricial birds. We present an analysis of two types of begging behaviour (assuming the front nest positions and gaping) based on videotaped natural nestling feeding in European common redstart (Phoenicurus phoenicurus). We test whether these types of begging support the predictions of two mathematical models: scramble competition with competitive asymmetries between nestlings [Anim. Behav. 27 (1979) 1210] or honest signalling model [Nature 352 (1991) 328]. None of the measured variables of nestling or parental behaviour were affected by body weight differences between siblings. In contrast, both gaping and nest positioning were affected by individual differences in nestling hunger. In agreement with the honest signalling model, hungrier nestlings gaped with higher probability and started to gape sooner after the arrival of the parent than did their less hungry nestmates. Those nestlings with the shortest latency to gape also received food more often. Nest positioning was related to nestling hunger in a way unforeseen by the existing models. The intervals between nestling position changes were several times longer than the intervals between parental feeding visits, and parents preferred to feed nestlings in front positions, so nestlings in front positions were always less hungry than nestlings in back. Hence the pattern of movements influenced the feeding decision in favour of the more satiated nestlings and acted against the effect of gaping. Nestling movement seemed to be caused by the less hungry nestlings moving actively from front to rear positions. Low mortality of individual nestlings within broods that survived to fledging and small within‐brood variation in fledging weights indicated low competition among nestmates. We suggest that there are two behavioural mechanisms that contribute to the equalization of fledging weights in common redstart nestlings: the signalling of need through gaping and the regular turnover of nestlings at front positions.     

Motherhood and the “Madness of Hunger”: <Emphasis Type="Italic">“…Want Almal Vra vir My vir ‘n Stukkie Brood”</Emphasis> (“…Because Everyone Asks Me for a Little Piece of Bread”)

It is widely assumed that the social and economic conditions of poverty can be linked to common mental disorders in low-, middle- and high-income countries. Despite the considerable increase in quantitative studies investigating the link between poverty and mental health, the nature of the connection between poverty and emotional well-being/distress is still not fully comprehended. In this qualitative study, exploring how one group of Coloured South African women, diagnosed with depression and residing in a semi-rural low-income South African community, subjectively understand and experience their emotional distress, data was collected by means of in-depth semi-structured interviews and social constructionist grounded theory was used to analyse the data. We will attempt to show (1) that the depressed women in this group of respondents frequently refer to the emotional distress caused by hungry children and (2) that the emotional distress described by the respondents included emotions typically associated with depression (such as sadness, hopelessness and guilt), but also included emotions not necessarily associated with depression (such as anxiety, anger and anomie). In our attempt to understand (both psychologically and politically) the complex emotional response of mothers to their children’s hunger, we argue that powerful gender and neo-liberal discourses within which mothers are interpellated to care for children, and more specifically, to make sure that children are not hungry, mean that the mothers of hungry children felt that they were not fulfilling their responsibilities and thus felt guilty and ashamed. This shame seemed, in turn, to lead to anger and/or anomie, informing acting out behaviours ranging from verbal and physical aggression to passive withdrawal. A vicious cycle of hunger, sadness and anxiety, shame, anger and anomie, aggression and withdrawal, negative judgement, and more shame, are thus maintained. As such, the unbearable rebukes of hungry children can be thought of as evoking a kind of “madness” in low-income mothers.     

Trading off safety against food: state dependent habitat choice and foraging in crucian carp

The influence of hunger level and predation risk on habitat choice and foraging in crucian carp, Carassius carassius, were studied in a laboratory experiment. Experiments were carried out in aquaria with or without a predator (pike, Esox lucius). Habitat use and foraging activity of three-fish foraging groups of either fed or hungry crucian carp were studied. Fish were allowed to choose between an open (risky) habitat with Tubifex worms and a habitat with dense vegetation (safe) without food. Habitat use was significantly affected by both risk of predation and hunger level. Crucian carp spent less time in the open habitat when there was a predator present and they also spent less time there when fed than when hungry. Furthermore, there was a significant interaction between risk of predation and hunger level, indicating a state-dependent trade-off between food acquisition and predator avoidance.     

Interference competition in ant-lion (Macroleon quinquemaculatus) larvae

Abstract.

• 1 The effects of density, feeding regime, and body size on interference competition in the pit-digging larvae of the ant-lion Macroleon quinquemaculatus (Hagen) were investigated in laboratory experiments.
• 2 Competition had little effect on the pit size of winners but losers constructed much smaller pits than isolated larvae. Losers were less likely to dig or maintain pits and more likely to move than winners.
• 3 Competition was much stronger between well-fed larvae than between hungry ones, and well-fed competitors showed reduced growth rates. Well-fed larvae orientated themselves so that they could throw sand into their neighbour's pit whereas hungry larvae faced away from each other. Differences in hunger level reversed the competitive advantage of larger larvae only when individuals were of similar size.
• 4 Cannibalism was density-dependent and most frequent in hungry, similar-sized, larvae; the smaller larva was usually the victim.
• 5 Displays/challenges between larvae affected the distance between pits. Body size was the main determinant of contest outcome though pit ownership and hunger level also had an effect.

     

Overestimating resource value and its effects on fighting decisions

Much work in behavioral ecology has shown that animals fight over resources such as food, and that they make strategic decisions about when to engage in such fights. Here, we examine the evolution of one, heretofore unexamined, component of that strategic decision about whether to fight for a resource. We present the results of a computer simulation that examined the evolution of over- or underestimating the value of a resource (food) as a function of an individual's current hunger level. In our model, animals fought for food when they perceived their current food level to be below the mean for the environment. We considered seven strategies for estimating food value: 1) always underestimate food value, 2) always overestimate food value, 3) never over- or underestimate food value, 4) overestimate food value when hungry, 5) underestimate food value when hungry, 6) overestimate food value when relatively satiated, and 7) underestimate food value when relatively satiated. We first competed all seven strategies against each other when they began at approximately equal frequencies. In such a competition, two strategies--"always overestimate food value," and "overestimate food value when hungry"--were very successful. We next competed each of these strategies against the default strategy of "never over- or underestimate," when the default strategy was set at 99% of the population. Again, the strategies of "always overestimate food value" and "overestimate food value when hungry" fared well. Our results suggest that overestimating food value when deciding whether to fight should be favored by natural selection.     

Assessing Projection Bias in Consumers’ Food Preferences

The aim of this study is to test whether projection bias exists in consumers’ purchasing decisions for food products. To achieve our aim, we used a non-hypothetical experiment (i.e., experimental auction), where hungry and non-hungry participants were incentivized to reveal their willingness to pay (WTP). The results confirm the existence of projection bias when consumers made their decisions on food products. In particular, projection bias existed because currently hungry participants were willing to pay a higher price premium for cheeses than satiated ones, both in hungry and satiated future states. Moreover, participants overvalued the food product more when they were delivered in the future hungry condition than in the satiated one. Our study provides clear, quantitative and meaningful evidence of projection bias because our findings are based on economic valuation of food preferences. Indeed, the strength of this study is that findings are expressed in terms of willingness to pay which is an interpretable amount of money.     

云斑尖塘鳢消化酶活力的研究

本文采用酶学分析方法研究了云斑尖塘鳢在正常摄食状态与饥饿的状态下胃、肠及肝胰脏组织中蛋白酶、淀粉酶和脂肪酶的活性。结果显示,在30℃的条件下,正常摄食组样本在酸性条件下的蛋白酶活力表现为:胃后肠肝胰脏前肠,中性和碱性条件下:后肠肝胰脏前肠及胃;饥饿组样本仅有胃表现出较高的酸性蛋白酶活性,其他器官的蛋白酶活性均很低。在正常和饥饿实验组中肝胰脏的淀粉酶活性均高于其他器官,胃肠的淀粉酶活性均较低。正常摄食组中脂肪酶活力后肠肝胰脏;而在饥饿组中仅有肝胰脏检测到脂肪酶活性。结果表明,云斑尖塘鳢适度饥饿组较正常摄食组消化酶活性大幅降低;其高蛋白酶活力及中等脂肪酶活力与其肉食性相一致;此外云斑尖塘鳢也具备少量的淀粉消化能力。     

Effect of prey density and hunger state on capture of krill, Nyctiphanes australis Sars, by Australian salmon, Arripis trutta (Bloch & Schneider)

When hungry salmon were offered a simulated (unattainable) swarm of krill with high central density, the density of the region first attacked increased with increasing attack readiness (measured as snout contacts). When allowed to capture krill in a range of prey densities, hungry salmon captured krill most successfully (in terms of capture/contacts) in the lowest density and less efficiently with increasing densities. However, salmon still captured a greater number of krill in a given time in high compared to low densities. When salmon in three different hunger states were exposed to a simulated swarm of krill, those with the lowest hunger level most often attacked the lowest prey densities first. Salmon with a high hunger level most often attacked the highest prey density first. Those fish with a moderate hunger level chose an intermediate prey density. This behaviour can be interpreted as a hunger-dependent feeding strategy. The ways in which swarming of the prey might influence capture by the predator are considered.     

Modification of egg production and packaging in response to food availability by Nassarius pauperatus

Summary Adjacent populations of Nassarius pauperatus differ significantly in how hungry their members are. The numbers of eggs and egg capsules produced are positively correlated with how hungry members of a population are, but the average number of eggs per capsule is negatively correlated with hunger. These results were confirmed in a laboratory experiment using two groups from the same population maintained with different levels of food.The significance of this behaviour is discussed and the hypothesis proposed that the flexibility of reproductive patterns is correlated with dispersive ability.     

Measurement of, and some reasons for, differences in eating habits between night and day workers

A questionnaire was designed to assess the following: why working people chose to eat or not to eat at a particular time of day; the factors that influenced the type of food eaten; and subjective responses to the meal (hunger before, enjoyment during, satiety afterward). Self-assessments were done every 3 h during a typical week containing work and rest days, by one group of 50 day workers and another group of 43 night workers. During the night work hours compared to rest days, night workers evidenced a significantly altered food intake, with a greater frequency of cold rather than hot food (p < 0.001). The type and frequency of meals were influenced significantly more (p < 0.05) by habit and time availability and less by appetite. This pattern continued into the hours immediately after the night shift had ended. In day workers food intake during work hours, compared to rest days, was also influenced significantly more often (p < 0.05) by time availability than hunger, but less so than with night workers. Moreover, day workers were less dependent than night workers upon snacks (p = 0.01), and any significant differences from rest days did not continue beyond work hours. Not only did night workers change their eating habits during work days more than did day workers but also they looked forward to their meals significantly less (p < 0.001) and felt more bloated after consuming them (p < 0.05), such effects being present to some extent during their rest days also. These findings have clear implications for measures designed to ease eating problems that are commonly problematic in night workers.     

Freedom of Choice About Incidental Findings Can Frustrate Participants' True Preferences

Ethicists, regulators and researchers have struggled with the question of whether incidental findings in genomics studies should be disclosed to participants. In the ethical debate, a general consensus is that disclosed information should benefit participants. However, there is no agreement that genetic information will benefit participants, rather it may cause problems such as anxiety. One could get past this disagreement about disclosure of incidental findings by letting participants express their preferences in the consent form. We argue that this freedom of choice is problematic. In transferring the decision to participants, it is assumed that participants will understand what they decide about and that they will express what they truly want. However, psychological findings about people's reaction to probabilities and risk have been shown to involve both cognitive and emotional challenges. People change their attitude to risk depending on what is at stake. Their mood affects judgments and choices, and they over‐ and underestimate probabilities depending on whether they are low or high. Moreover, different framing of the options can steer people to a specific choice. Although it seems attractive to let participants express their preferences to incidental findings in the consent form, it is uncertain if this choice enables people to express what they truly prefer. In order to better understand the participants' preferences, we argue that future empirical work needs to confront the participant with the complexity of the uncertainty and the trade‐offs that are connected with the uncertain predictive value of genetic risk information.     

Trait Anxiety Has Effect on Decision Making under Ambiguity but Not Decision Making under Risk

Previous studies have reported that trait anxiety (TA) affects decision making. However, results remain largely inconsistent across studies. The aim of the current study was to further address the interaction between TA and decision making. 304 subjects without depression from a sample consisting of 642 participants were grouped into high TA (HTA), medium TA (MTA) and low TA (LTA) groups based on their TA scores from State Trait Anxiety Inventory. All subjects were assessed with the Iowa Gambling Task (IGT) that measures decision making under ambiguity and the Game of Dice Task (GDT) that measures decision making under risk. While the HTA and LTA groups performed worse on the IGT compared to the MTA group, performances on the GDT between the three groups did not differ. Furthermore, the LTA and HTA groups showed different individual deck level preferences in the IGT: the former showed a preference for deck B indicating that these subjects focused more on the magnitude of rewards, and the latter showed a preference for deck A indicating significant decision making impairment. Our findings suggest that trait anxiety has effect on decision making under ambiguity but not decision making under risk and different levels of trait anxiety related differently to individual deck level preferences in the IGT.     

Possible entrainment of ghrelin to habitual meal patterns in humans

Ghrelin is reportedly a meal-initiation signal based on observations that concentrations increase before meals coincident with rising hunger. However, evidence that ghrelin peaks vary with feeding schedules suggests that it rises in anticipation of an expected meal, rather than eliciting feeding. To explore the entrainment of ghrelin profiles, this study investigated the association between varying habitual meal patterns and plasma ghrelin concentrations. Lean and obese adults following either a short intermeal interval (SII) pattern, with 2.5-3.5 h between their habitual breakfast and lunch times, or a long intermeal interval (LII) pattern, with 5.5-6.5 h between these eating occasions, participated. Food intake and appetite were recorded for 2 baseline days. On the subsequent test day, blood samples were collected over 8 h while participants ate a breakfast and lunch matched to their customary meals and pattern. Appetite ratings were obtained and ghrelin, insulin, glucose, and leptin concentrations were measured. Peak ghrelin concentrations differed significantly by group and occurred prior to each group's respective lunch time. Ghrelin concentrations directly correlated with subjective hunger. This association was stronger when hunger preceded ghrelin, a pattern inconsistent with ghrelin causing the hunger rise. Ghrelin concentrations were inversely correlated with insulin, and peak insulin concentrations preceded nadir ghrelin concentrations postprandially. Ghrelin concentrations periprandially, and over the entire test session, did not differ by meal group, likely because of similar intakes between groups. These data demonstrate that the timing of ghrelin peaks is related to habitual meal patterns and may rise in anticipation of eating rather than eliciting feeding.