The tactics of mutual mate choice and competitive search

A model of mutual mate choice is described, formulated as a dynamic game, which yields predictions about mating behaviour under the influence of time constraints, choice costs and competition for mates. These variables were examined because they may result in a change in the distribution of qualities among unmated individuals of both sexes over the course of the breeding season. The model predicts that mutual choice gives rise to assortative mating, although high costs of choice and/or inaccurate assessment both lead to lower overall correlations between the qualities (or the attractiveness) of mates. When all individuals are present from the start of the breeding season, the correlation between the qualities of individuals pairing at a given time declines throughout the season, so that mates are more closely matched among individuals who pair early than among those who pair late (and extra-pair copulation may thus be more common among the latter). Delayed arrival of lower-quality individuals may, however, lead to an increase in this correlation with time during the early part of the season. The mean quality of unmated males and females declines over time, because more attractive individuals tend to mate sooner. As a result of this decline, and because of time constraints, superior individuals become less choosy as the season progresses. If choice is costly, however, then inferior individuals become more selective with time during the early part of the season, and the level of choosiness peaks later for such individuals. Received: 28 March 1996 / Accepted after revision: 21 September 1996     

Deception by helpers in cooperatively breeding white-winged choughs and its experimental manipulation

White-winged choughs (Corcorax melanorhamphos) are obligate cooperative breeders, living in groups which may contain up to 20 birds. Although breeding is dominated by a single pair, all birds contribute to rearing young, including the provisioning of nestlings. However, some birds which have carried food to the nest, even to the point of placing the food in the gaping mouth of a nestling, consume the food themselves rather than provision the nestlings. Birds which fail to feed nestlings are typically young, and are only likely to fail to deliver food when they cannot be observed by other group members. Birds which have just failed to deliver food are more likely to engage in alternative helping behaviours such as allopreening the nestlings than are helpers which have just delivered food in the conventional manner. Failure to deliver food is almost eliminated when foraging constraints are experimentally reduced by supplemental feeding of the group. Collectively these observations suggest that young white-winged choughs act deceptively by simulating helping behaviours without sacrificing food supplies. Received: 24 January 1997 / Accepted after revision: 6 June 1997     

How Kentish plovers,<Emphasis Type="Italic"> Charadrius alexandrinus</Emphasis>, cope with heat stress during incubation

Biparental incubation is frequent among shorebirds and is expected when the survival prospects of offspring increase relative to uniparental incubation. To understand why this occurs, it is important to identify the factors that constrain uniparental incubation. It is assumed that birds choose nesting sites that provide an appropriate microclimate for incubation. Many shorebirds nest in sites with no or little cover, where ambient temperatures at ground level might be >50°C during very hot days. Shorebirds nest in exposed sites because predation risk on incubating adults is higher in covered sites. In hot environments, incubating shorebirds might experience heat stress in exposed sites, and this may compromise nesting success if adults are unable to attend their nests continuously, limiting the possibilities of uniparental incubation and thus the expression of a sexual conflict over incubation. The operative temperatures of Kentish plovers (Charadrius alexandrinus) were recorded in exposed and covered sites, and the thermal behaviour and incubating tactics of pair members were studied in a hot environment. During the hottest part of the day, there was a difference of 10–15°C in the operative temperatures of plovers between covered and exposed sites. Plovers in covered sites did not exhibit any thermoregulatory behaviour indicative of thermal stress, probably because the thermal range encountered by them in such places during most of the daytime was close to the thermo-neutral zone. The frequency with which plovers in exposed sites exhibited thermoregulatory behaviour was related to ambient temperature. Under very hot conditions, incubating birds were probably unable to maintain homeostasis for long periods and pair members resorted to shortening incubation bouts. Female Kentish plovers mainly incubate in the daytime and males during the night. However, the probability of diurnal incubation by males increased with ambient temperature in exposed nests, but not in covered ones. In fact, the frequency of participation in diurnal incubation by males was greater in exposed than in covered sites, suggesting that the participation of males in diurnal incubation may be related to the inability of females to stay at the nest during long periods when the ambient temperature is high. Even after resorting to shortened incubation bouts, the plovers may be unable to attend their nests continuously during heat waves, and the nests may be deserted. The propensity of plovers to desert their nests was affected by proximity to water, with nests located close to water being deserted less frequently. It seems likely that susceptibility to thermal stress changed in relation to proximity to water because in sites close to water it was possible to belly-soak, which would allow a more continuous nest attendance. Therefore, despite the adoption of behavioural solutions to face heavy heat loads, nesting success was vulnerable to these solutions because heat stress during extended periods may constrain parental nest attendance, and this may limit the opportunities for sexual conflicts over incubation.Communicated by J. Graves     

Futurecoast: Predicting the future coastal evolution of England and Wales

Analysis of shoreline change is often based exclusively upon the littoral cell concept and modelling of hydrodynamic processes. The Futurecoast study has considered fresh approaches to assessing shoreline evolution, which have been used to provide an analysis of future long-term evolution for the entire shoreline of England and Wales. This has been based upon an improved understanding of coastal systems and their behavioural characteristics. The study has included a range of supporting studies, focussing upon maximizing use of existing information and experience. A number of additional data sets have also been produced. The integration of leading expertise from different areas of coastal research to collectively consider this information has been the foundation for the study. The key outputs from this research are: (1) Improved understanding of coastal behaviour; (2) Assessment of future shoreline evolution; (3) Supporting information and data; (4) Delivery of results on an interactive CD-ROM.     

Social foraging and dominance relationships: the effects of socially mediated interference

In socially foraging animals, it is widely acknowledged that the position of an individual within the dominance hierarchy of the group has a large effect upon its foraging behaviour and energetic intake, where the intake of subordinates can be reduced through socially mediated interference. In this paper, we explore the effects of interference upon group dynamics and individual behaviour, using a spatially explicit individual-based model. Each individual follows a simple behavioural rule based upon its energetic reserves and the actions of its neighbours (where the rule is derived from game theory models). We show that dominant individuals should have larger energetic reserves than their subordinates, and the size of this difference increases when either food is scarce, the intensity of interference suffered by the subordinates increases, or the distance over which dominant individuals affect subordinates increases. Unlike previous models, the results presented in this paper about differences in reserves are not based upon prior assumptions of the effects of social hierarchy and energetic reserves upon predation risk, and emerge through nothing more than a reduction in energetic intake by the subordinates when dominants are present. Furthermore, we show that increasing interference intensity, food availability or the distance over which dominants have an effect also causes the difference in movement between ranks to increase (where subordinates move more than dominants), and the distance over which dominants have an effect changes the size of the groups that the different ranks are found in. These results are discussed in relation to previous studies of intra- and interspecific dominance hierarchies.     

Defence effectiveness of easy bleeding sawfly larvae towards invertebrate and avian predators

Summary. Easy bleeding is a phenomenon discovered in some tenthredinid insects which possess a particularly low mechanical resistance of the integument, leading under mechanical stress to haemolymph exudation. It has a defensive effect against ants and wasps through harmful plant compounds which are sequestered in the haemolymph. Here we describe etho-ecological and some chemical aspects of the defence of easy bleeders and specify the range of predators to which easy bleeding might be effective. Beside a high haemolymph deterrence associated with low integument resistance across sawfly species, we also detected toxicity of the haemolymph of some species to workers of the ant Myrmica rubra. The behaviour of easy bleeders is to move slowly and, once disturbed, to become motionless, thereby probably impeding the tendency of a predator to attack. This behaviour had no beneficial effect for easy bleeders when attacked by the predatory bug Podisus maculiventris. Bugs could successfully and without harm prey on sawfly larvae without evoking easy bleeding. For the easy bleeder Athalia rosae, host plants with different secondary metabolite profiles, and, consequently, changes in haemolymph chemistry only slightly affected the feeding behaviour of the bugs. To test the effectiveness of easy bleeding towards a vertebrate predator, easy bleeders were offered to birds, Sturnus vulgaris. The body colouration of the sawfly larvae was of prime importance in determining the predators response when testing birds in a group. It is likely that easy bleeding is a defence strategy directed primarily towards foraging insects with biting-chewing mandibles and that it is much less active towards predatory insects with piercing-sucking mandibles as well as birds. The involvement of chemical and/or physical cues in the strategy is discussed with respect to these types of predators.     

Analysis of the causal components of assortative mating in water striders

Field studies demonstrate that natural populations of a group of water striders (Heteroptera: Gerridae) that share a common mating system are characterized by weak assortative mating by size and by large sizes of mating males and females relative to single individuals. This study presents an experimental assessment of the components of mating that may contribute to these mating patterns. The effects of male and female body size on each of three components of mating were studied in three water strider species in the laboratory. Large females of all three species mated more frequently, copulated for longer and were guarded longer than small females. Large males mated more frequently than small males in all three species, and also guarded females for longer in the two species where the average of mate guarding was long. However, we found an antagonistic effect of male size on copulation duration: small males copulated for longer than large males in all three species. We show that the combined effects of these size biases mimic the mating patterns found in the wild, e.g. weak and variable assortative mating, and stronger and less variable size ratios of mating versus non-mating females relative to males. We suggest that the antagonistic effects of male size on copulation and guarding duration may be a key source of interpopulational variation in assortative mating and sexual selection on male size. Further, neither spatial or temporal covariation in size, nor mechanical constraints, caused the assortative mating observed here in this group of water striders. Some combination of male and female choice (either active or passive forms) of large mates and male-male exploitation competition for mates play potentially important roles in producing population level assortative mating in water striders. Received: 17 March 1995/Accepted after revision: 28 October 1995     

Towards sustainable consumption: Predicting the impact of social‐psychological factors on energy conservation intentions in Northern Cyprus

The incessant demand and consumption of energy services among individuals’ is increasing throughout the world. Individuals’ electricity consumption in Northern Cyprus has risen considerably. However, the demand for electrical energy services on the island is heavily reliant on imported fossil fuels. Burning fossil fuels has adverse effects on its environment. Therefore, sustainable energy consumption is required and individuals are targeted for energy conservation to reduce electricity consumption. Against this background, using the Structural Equation Modeling approach, this research incorporates social‐psychological factors; personal norms, positive and negative emotions into the theory of planned behaviour (TPB) model to assess the relationships among the variables, explain their impact on consumers’ electricity conservation intentions and enhance the explanatory power of the model. Data was conveniently obtained from a quantitative sample of 400 electricity consumers. The results indicate that negative emotions have the strongest significant influence on intentions, but personal norms have the least effect on intentions to save electricity. Furthermore, the study revealed that our expanded TPB model can provide improved explanatory power more than the original TPB. Policy implications, limitations and future research are discussed.     

Fighting rules and rival recognition reduce costs of aggression in male lizards, Podarcis hispanica

The establishment of fighting rules and the ability to recognise individual conspecifics and to assess their fighting ability and/or roles may help to reduce costs of fighting. We staged encounters between males of the lizard Podarcis hispanica to examine whether lizards used fighting strategies and whether a previous agonistic experience affects the outcome and characteristics of a subsequent encounter. The results showed that simple rules such as body size differences and residence condition were used to determine the outcome of agonistic interactions as quickly as possible. Thus, larger males were dominant in most encounters. However, when size differences between opponents are smaller, they may be more difficult to estimate and, then, residence condition was more important. In addition, the intensity of interactions between males could be explained according to the ”sequential assessment game”, supporting the idea that P. hispanica males acquire information about fighting ability gradually during the progress of a fight. Our results also showed that the second fight of the same pair of males was less aggressive, even when its outcome was the opposite of the first. This result suggests that male P. hispanica can recognise individual opponents and that they use this information to reach a contest outcome more quickly, thus reducing unnecessary aggression levels in subsequent interactions. These fighting strategies and assessment mechanisms may help to stabilise the social system of this lizard. Received: 2 November 1999 / Revised: 26 August 2000 / Accepted: 4 September 2000     

Mass communication and pro-environmental behaviour: waste recycling in Hong Kong

Treatment of domestic waste has been one of the major environmental problems in Hong Kong. The Government has a stated policy to advocate the minimization of waste disposal through the encouragement of waste reduction, re-use and recycling. The current study applies Ajzen's theory of planned behaviour to predict behavioural intention and actual behaviour of voluntary use of waste recycling receptacles. A systematic random sample of 173 household members in a public housing estate were interviewed. The results indicated that attitude was the major factor in predicting behavioural intention, followed by behavioural control and social norms. Attitude, subjective norm and perceived control together explained 44% of the variance of behavioural intention. Perception of mass media as a major source of subjective norm was first introduced and tested. Mass communication stood out as one of the major sources of influence in establishment of subjective norms. The study has the implication that more publicity messages should be put on the mass media to promote green behaviours.