Behavioural correlates of testosterone and seasonal changes of steroids in red-winged blackbirds

I studied the relationship between behaviour and plasma testosterone level (T) and the seasonal changes in T and plasma corticosterone levels (B) in male red-winged blackbirds, Agelaius phoeniceus. I measured T and B using radioimmunoassay, and on the day after taking blood, I observed each male's behaviour for 60 min. The time that males spent conspicuously perched and the number of songs were positively correlated with T, but the proportion of time spent conspicuously perched and the frequency of song were not correlated with T. The frequency of aggressive encounters, sexual chases, epaulet exposure when singing and flights within the territory were positively correlated with T, suggesting a direct role for circulating testosterone influencing male aggressive behaviour. Both T and B increased early in the breeding season, peaked when the first females were receptive, and decreased through the remainder of the breeding season. Late in the season, the presence of a receptive female caused males to have increased T. The peak in T when the first females were receptive, the positive correlation between aggression and T, and the response to a receptive female with increased T support predictions of the challenge hypothesis. T was positively correlated with B, suggesting a cost to the males of maintaining high T. When a receptive female was present on the male's territory, T was negatively correlated with date. Male red-winged blackbirds in Indiana may respond less to receptive females late in the season when benefits associated with protecting paternity and gaining extra-pair fertilizations decrease.Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Proteins in urine scent marks of male house mice extend the longevity of olfactory signals

The binding of volatile semiochemicals to lipocalin proteins in many mammalian scent marks may provide a gradual release of volatile ligands, extending the life of airborne odour signals. We tested this by using menadione to displace semiochemical ligands from major urinary proteins (MUPs) in urine streaks obtained from adult male house mice, Mus domesticus, and assessed the responses of other males to these and to intact urine marks as they aged. Dominant male mice scent-mark their territories extensively with urine streaks; MUPs in these marks bind at least two semiochemically active molecules, 2-sec-butyl-4,5-dihydrothiazole (thiazole) and 2,3-dehydro-exo-brevicomin (brevicomin), associated with the males' aggressive status. Wild-caught males (N=24), housed in individual enclosures, were presented with two glass slides, behind mesh to prevent contact, on which 10 μl of both unfamiliar urine and 0.5 mg/ml menadione in ethanol had been streaked. On one slide the urine and menadione solution were mixed to displace ligands; on the other they were separate (intact urine). We carried out tests 0, 0.5, 1 or 24 h after deposition, and matched them to changes in the concentration of thiazole and brevicomin within the intact and displaced marks. Males were hesitant to approach intact urine up to 1 h old but, when ligands were displaced, or were reduced to low levels by natural evaporation from intact urine streaks aged 24 h, their approach was similar to that to water and to menadione controls. Ligands did not appear to cause any longer term avoidance and, after the first approach, investigation increased with the freshness of urine regardless of when the ligands were displaced. This is the first direct demonstration that proteins evince a slow release of olfactory signals from mammalian scent marks. The nature of their response suggests that, from a distance, mice may be unable to tell whether airborne signals emanate from scent marks or from the donor himself and we suggest that this may provide territory owners with a major advantage in defending their territories.Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

The self-esteem motive in social influence: agreement with valued majorities and disagreement with derogated minorities

We conducted three experiments to examine variables that might influence the longevity of socially induced food preferences in Norway rats. The duration of social influence on the food choices of 42-day-old rats (1) increased with both increasing numbers of demonstrators and increasing numbers of demonstrations by a single demonstrator, (2) varied with the temporal distribution of demonstrations, but (3) did not vary with the age of demonstrators. The results suggest that a single episode of social learning produces short-term, but not long-term, effects on a Norway rat's food choices. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Is sperm galactosyltransferase a signaling subunit of a multimeric gamete receptor?

The influence of relatedness on the pre- and post-emergent survival of honey bee queens was investigated. Workers did not preferentially rear sisters over non-siblings under conditions of natural queen replacement. After queen emergence, however, there was a significant effect of a queen's relatedness to the workers on her survivorship during fights with rival queens. The mechanism of this bias towards related queens is unknown, and several hypotheses are discussed. The difference in post-emergent survivability suggests that kin selection may operate during competition among adult queens at this crucial stage of honey bee reproduction. Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.     

Mechanisms of sex-ratio adjustment in domestic swine: reply to James

No abstract. Copyright 1998 The Association for the Study of Animal Behaviour.     

Multiple mechanisms may affect birth sex ratio in domestic pigs

No abstract. Copyright 1998 The Association for the Study of Animal Behaviour.     

Certainty of paternity and paternal investment in eastern bluebirds and tree swallows

Extra-pair paternity is common in many socially monogamous passerine birds with biparental care. Thus, males often invest in offspring to which they are not related. Models of optimal parental investment predict that, under certain assumptions, males should lower their investment in response to reduced certainty of paternity. We attempted to reduce certainty of paternity experimentally in two species, the eastern bluebird, Sialia sialis, and the tree swallow, Tachycineta bicolor, by temporarily removing fertile females on two mornings during egg laying. In both species, experimental males usually attempted to copulate with the female immediately after her reappearance, suggesting that they experienced the absence of their mate as a threat to their paternity. Experimental males copulated at a significantly higher rate than control males. However, contrary to the prediction of the model, experimental males did not invest less than control males in their offspring. There was no difference between experimental and control nests in the proportion of male feeds, male and female feeding rates, nestling growth and nestling condition and size at age 14 days. We argue that females might have restored the males' confidence in paternity after the experiment by soliciting or accepting copulations. Alternatively, males may not reduce their effort, because the fitness costs to their own offspring may outweigh the benefits for the males, at least in populations where females cannot fully compensate for reduced male investment. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Two cooperatively social populations of the theridiid spider Anelosimus studiosus in a temperate region

The quality of an individual's odour can allow potential mates to discriminate against individuals of low social class, poor health status or unsuitable genotype. Competitive scent marking provides a further mechanism which could allow mates to discriminate between individuals of apparently high quality. The presence or absence of fresh countermarks from competitors within an owner's territory or area marked by a dominant animal provides a reliable indicator of the owner's ability to defend its territory or dominate competitors. This could be used by potential mates to discriminate between individuals advertising their apparently high competitive ability through their scent-marking behaviour and odour quality. We tested this by manipulating scent marks in the neighbouring territories of wild-caught male house mice, Mus domesticus. As predicted, oestrous females used scent marks to select males apparently able to defend exclusive territories over those unable to exclude intruders. Females were more strongly attracted to the odour of owners of exclusively marked territories and showed more sexually related behaviour when interacting with these males. Furthermore, while females preferred a territory containing a better protected nest site regardless of the owner's apparent competitive ability, they still used the presence or absence of intruder countermarks when selecting a potential mate. This suggests that females use scent marks as a reliable signal of the best-quality mate among neighbouring males independently of their nest location. Since assessment depends on both the territory holder's own marks and those of competitor males, countermarking is likely to be an important mechanism of competition for mates between neighbours. Copyright 1998 The Association for the Study of Animal Behaviour     

Interactions between cleaning gobies and territorial damselfish on coral reefs

We studied the interactions between cleaning gobies, Elacatinus spp., at cleaning stations and territorial dusky damselfish, Stegastes fuscus, on a Barbadian fringing reef to enhance our understanding of the behavioural impact of cleaning stations on members of a coral reef community. Cleaning stations within damselfish territories were visited by significantly fewer species and fewer individuals than those outside damselfish territories. At cleaning stations within damselfish territories, the main client was the territory holder itself. Client behaviour did not differ between the two types of cleaning station; however, cleaning gobies at stations within damselfish territories spent less time cleaning clients, their cleaning bouts were shorter, and their feeding rate on clients was slower. These effects appear to be due to the repeated aggression of territorial damselfish towards fish intruding on to their territories to visit cleaning stations. The overlap between a territorial damselfish and a cleaning station therefore appears to have detrimental impacts on cleaning goby foraging. The presence of cleaning stations within damselfish territories exerted some effects on the territory owners. Although the rates of intrusions were similar on territories with and without cleaning stations, damselfish with cleaning stations tended to chase intruders more often, had a lower foraging rate, and were at higher risk of egg predation because of increased intrusions by egg predators. A potential benefit to territorial damselfish is regular access to a cleaning station; however, the magnitude of this benefit is unknown. This study reveals that damselfish, which are ubiquitous on coral reefs, can generate significant variation in levels of use of cleaning stations, which leads to new questions relating to the settlement behaviour of both cleaning gobies and damselfish. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Predator discrimination error and the benefits of Müllerian mimicry

Müllerian mimicry has traditionally been thought to benefit both unpalatable mimic and model species but recently its existence has been questioned. Even if both mimic and model species are unpalatable, they are unlikely to be equally unpalatable. It has been argued that the more unpalatable species will suffer a cost of increased predation because the presence of the more palatable mimic will increase its perceived palatability (by the predator), similar to that experienced by a model in Batesian mimicry. Yet, previous models of Müllerian mimicry have assumed that a predator can discriminate perfectly between available prey. We argue that this is not the case and that discrimination error is an important factor in determining the nature of mimetic relationships. Using computer simulations we show that the nature of a mimetic relationship will depend on the trade-off between the cost of an increase in perceived palatability and the benefits of a reduction in predator discrimination error. We show that mimicry can be unequivocally Müllerian, with both species benefiting, and propose that palatability should no longer be used as the sole defining characteristic of a mimetic relationship. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Fluctuating asymmetry, mate choice and experimental designs

No Abstract Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour     

Experimental design and the signalling properties of fluctuating asymmetry

No Abstract Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour     

Territorial intrusions and copulation behaviour in the great skua, Catharacta skua

Birds of many species intrude on to territories in order to obtain extra-pair copulations, and frequent within-pair copulations are thought to be a response to cuckoldry where mate guarding is not possible. Great skuas are colonial birds in which females are left alone in the breeding territory while males forage for the pair. Opportunities for cuckoldry are therefore numerous, and it could be predicted that sperm competition should be intense in this species. We tested several hypotheses that attempt to explain territorial intrusions by female great skuas. Few intrusions coincided with the main fertile period and extra-pair copulations were almost never solicited, and therefore the sperm competition hypothesis was rejected. Only 0.9% of the copulations observed (N=339) were extra-pair. Thus opportunity for cuckoldry is a very poor predictor of the intensity of sperm competition, in spite of the relevance given to this factor in the literature. Of three extra-pair copulations observed, two involved unpaired territorial males. This suggests that genetic benefits were not the aim of unfaithful females. All three were preceded by courtship feeding, while only 26% of within-pair copulations followed successful food begging. This statistically significant difference constitutes evidence for a trade of copulations for food in a monogamous bird. Evidence is presented supporting hypotheses that females intrude on to territories in order to induce males to give away some food, and to become familiarized with potential partners for future breeding seasons.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour     

The changing trade-off between food finding and food stealing in juvenile oystercatchers

When juvenile oystercatchers, Haematopus ostralegus, first arrived on the wintering grounds in August and September, they regularly stole mussels, Mytilus edulis, from other, mainly older, oystercatchers. By October, however, juveniles stole far fewer mussels and found almost all their mussels independently for themselves on the mussel bed. Although stealing a mussel was always less profitable than taking a mussel from the mussel bed, a simple rate-maximizing optimality model showed that, in August and September, juveniles increased both their net and gross rates of energy intake by stealing because they were rather inefficient at foraging for themselves. By October, their greater efficiency at finding good quality mussels, combined with the increased resistance of potential victims to kleptoparasitic attacks, resulted in higher intake rates if juveniles stopped stealing mussels and took mussels only from the mussel bed. Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.     

Temporal manipulation of ejaculate components by newly fertilized Drosophila melanogaster females

Observations of newly mated Drosophila melanogaster females suggest that females control the times at which components of the ejaculate cause behavioural and physiological changes characteristic of fertilized females. Females that were assayed immediately after they mated elicited as much courtship as they did when they were virgins, but were unreceptive to copulation. Within a few minutes of when they disengaged from copulation, most females performed ovipositor extrusion, which has been classified as a rejection behaviour, in response to courting males or males that had previously performed courtship. Most females that were assayed immediately after mating had already ovulated. The females, however, do not begin to lay eggs until 4-6 h after mating, at which time they elicit very little courtship (Scott & Richmond 1985, Anim. Behav., 33, 817-824). Our observations suggest that neither ovipositor extrusion nor male-synthesized pheromones that are transferred to females' cuticles during copulation inhibit males' courtship of newly fertilized females. Thus, males cannot determine that newly fertilized females are unreceptive to copulation. These observations also indicate that the failure of newly fertilized females to mate with males is not a consequence of the females' inability to elicit vigorous courtship. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Yellowhammers get fatter in the presence of a predator

According to predictions from theoretical models, body mass and the daily foraging pattern of small birds in winter should be sensitive to predation risk. With increased risk of predation birds are expected to lower their body mass and shift their foraging to the afternoons. I studied the effect of predator presence on daily mass gain in captive yellowhammers, Emberiza citrinella. The birds were tested in unisex pairs, one bird being dominant over the other. In the first treatment the amount of food was restricted, and the daily pattern of mass gain was recorded. The second treatment was identical to the first, but, in addition, a stuffed sparrowhawk, Accipiter nisus, was displayed to the birds in the morning. Contrary to predictions from some theoretical models and other studies, the birds gained weight on days when the hawk was shown. Furthermore, the increased foraging happened mainly in the first half of the day, which also contradicts predictions from models. These results could be explained as a response to interrupted foraging, decreasing the probability of the birds acquiring the critical evening body mass. Alternatively, the birds increased their body reserves in preparation to leave a dangerous situation. Both dominance classes showed a similar response. The results suggest that the effects of predators on foraging interruptions should be included in models of daily routines of reserve accumulation. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Triterpenoid saponins and sapogenins from Vaccaria segetalis

When two species have predators in common, animals might be able to obtain important information about predation risk from the alarm calls produced by the other species. The behavioural responses of adult yellow-bellied marmots, Marmota flaviventris, and golden-mantled ground squirrels, Spermophilus lateralis, to conspecific and heterospecific alarm calls were studied to determine whether interspecific call recognition occurs in sympatric species that rarely interact. In a crossed design, marmot and squirrel alarm calls were broadcast to individuals of both species, using the song of a sympatric bird as a control. Individuals of both species responded similarly to conspecific and heterospecific anti-predator calls, and distinguished both types of alarms from the bird song. These results indicate that both marmots and squirrels recognized not only their own species' anti-predator vocalizations, but also the alarm calls of another species, and that these vocalizations were discriminated from an equally loud non-threatening sound. These findings suggest that researchers ought to think broadly when considering the sources of information available to animals in their natural environment. Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.     

The importance of behavioural studies in conservation biology

The exciting research developments in animal behaviour over the last two decades have had a negligible impact on conservation. I list 20 subjects in which the study of animal behaviour can make a significant contribution to conservation. Behaviour may in itself be worth conserving. I also suggest how behavioural ecologists could become more involved in conservation. Copyright 1998 The Association for the Study of Animal Behaviour.     

Prey availability and selective foraging in shorebirds

Accurate measurements of prey availability are vital to our understanding of foraging behaviour, particularly prey selectivity. In the present study, observations of shorebirds foraging for fiddler crabs on intertidal mudflats demonstrate that prey availability depends both on the temporal variation in crab activity and on the crabs' responses to the presence of foraging shorebirds. Our results suggest that measurements of prey availability that do not specifically account for prey activity patterns and their responses to predators are neccessarily inaccurate. Furthermore, our results also show that tests for foraging selectivity are extremely sensitive to the way in which prey availability is measured and can even indicate active prey selectivity when more accurate measures of prey availability show predators to be non-selective. Because inaccurate measures of food resources greatly reduce our ability to detect food preferences, greater care must be taken to account for prey activity patterns and their responses to predators in measurements of prey availability. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Functions of mudballing behaviour in the European fiddler crab Uca tangeri

European fiddler crabs place mudballs around their burrow openings. Both males and females placed mudballs, but there were major differences between the sexes in mudballing behaviour, suggesting that the female's mudballs were a by-product of digging out the burrow whereas the male's may have additional functions. When the male's mudballs were removed experimentally, the number and intensity of male-male agonistic interactions increased significantly. Experimentally visually isolated males spent longer making mudballs and less time waving. In a binary choice test, females were more likely to approach dummy males with mudballs, spent longer near these males and were more likely to enter their burrows than dummy males without mudballs. The same pattern was apparent for males with 30 rather than 20 mudballs. These results are consistent with a dual function for mudballs in U. tangeri: to reduce the number and intensity of aggressive interactions between neighbouring males and to attract females. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.