Dominance between booby nestlings involves winner and loser effects

Two-chick broods of the blue-footed booby, Sula nebouxii, ordinarily exhibit stable dominance-subordinance, with the senior (first-hatched) chick habitually aggressive and the junior one habitually submissive (Nelson 1978, The Sulidae: Gannets and Boobies. London: Oxford University Press). But are both the subordinate and the dominant chick affected in their agonistic tendencies by early social experience? To answer this, we permanently paired subordinate and dominant chicks, 2-3 weeks old, with singletons (chicks lacking experience with a nestmate) by cross-fostering. During the first 4 h after pairing, subordinate chicks were seven times less aggressive than singletons and twice as likely to be submissive; dominant chicks were six times as aggressive as singletons. Although most subordinates consistently lost agonistic encounters during the first 10 days after pairing, the proportion of dominants that won decreased progressively until, by day 6, only about half of dominant chicks were winning. Early social experience has a strong but reversable training effect on both subordinates and dominants. Training as a subordinate showed more persistent effects than training as a dominant, possibly in part because our testing situation perpetuated subordinate training and counteracted dominant training. 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.     

Proximate and ultimate causes of adoption in ring-billed gulls

From 1987 to 1994, the annual frequency of adoption by breeding pairs at a Lake Erie ring-billed gull, Larus delawarensis, colony ranged from 3 to 37% (average 8%/year, N=7 years) and, on average, foster parents raised 0.5 fewer of their own chicks to fledging than pairs that did not adopt. The key evolutionary question is: why do some individuals apparently suffer the costs associated with a behaviour that appears to enhance the fitness of others? From 1992 to 1995, I investigated the proximate and ultimate causes of adoption in ring-billed gulls from the perspectives of both the foster parents and adopted chicks, and tested predictions that differentiated between various competing adaptive and nonadaptive hypotheses that have been proposed to explain it. While I was able to demonstrate a breeding cost, I failed to identify any benefits to foster parents. Thus, the adaptive hypotheses that rely on the foster parents benefiting were not supported (e.g. kin selection, reciprocal altruism, acquisition of parenting experience). From the foster parent's perspective, adoption was mediated through errors in parent-offspring recognition. Under natural conditions, most fostering pairs were tending small chicks (<6 days old) at the time of adoptions; in chick-transfer experiments, resident parents did not discriminate against foreign chicks until their own chicks were 7-9 days old. Chicks (N=25) that subsequently abandoned their natal nests were lighter, and grew at a slower rate, than chicks that survived to fledging in their home broods. Thus, departing chicks were at a survival disadvantage in their home broods. Chicks that gained acceptance into foreign broods where they were older/larger than the resident chicks realized high survival at the expense of their foster siblings and parents. Based upon individual growth rates and the corresponding survival probabilities, disadvantaged chicks approximately doubled their survival chances through foster care. Why has selection not eliminated adoption? I argue that adoption is an evolutionary arms race between the two principle actor groups; disadvantaged chicks, which benefit through foster care, and host parents, which avoid providing foster care (e.g. infanticide). In ring-billed gulls, selection has failed to eliminate adoption because the long-term reproductive cost (estimated at 4%, this study) of an occasional adoption is probably offset by the relatively higher costs associated with stricter kin discrimination mechanisms (e.g. parental infanticide). (c) 1998 The Association for the Study of Animal Behaviour.     

Song learning in brood-parasitic indigobirds Vidua chalybeata: song mimicry of the host species

Brood-parasitic village indigobirds, Vidua chalybeata, were bred in captivity and foster-reared by their normal host, red-billed firefinch, Lagonosticta senegala, or by an experimental foster species, Bengalese finch, Lonchura striata. Male indigobirds reared by Bengalese finches developed the songs of Bengalese finches, and males reared by firefinches developed songs of firefinches. Males copied their foster father only when they had lived with him long after independence (45 days post-fledging), while males separated normally at independence (22-24 days post-fledging) copied songs of other individuals and not songs of their foster father. Males reared by Bengalese finches showed no preference to learn firefinch song over songs of the experimental foster species or other control finch species even when they had lived with firefinches as companions from the time of fledging to independence. Males copied several song themes, acquired the same number of mimicry songs, and acquired their songs at the same age, whether reared by Bengalese finches or by firefinches. When they lived with other indigobirds, the male indigobirds copied mimicry songs of male indigobirds that mimicked the same foster species. We predicted mimicry-song specificity and repertoire size in experimental indigobirds from a hypothesis of an early developmental period when young indigobirds focus their attention on their foster parents, and a later period when they direct their attention to other birds with similar songs. The predictions, based on field observations of wild birds, were that (1) males reared by a novel foster species other than the normal host would learn the song of that foster species, and (2) males that left their foster parents at the normal time of independence would copy the songs of other individuals, including other adult indigobirds that mimicked the same foster species. Begging calls of young indigobirds did not mimic the calls of young firefinches. Indigobirds reared alone, or with young of the normal host or of the experimental foster species, all developed begging calls in adult song that resembled their own begging as nestlings and fledglings, and only males that heard other adult indigobirds with firefinch-mimicry begging developed firefinch begging in their song. The incorporation of the innate begging calls as well as the learned begging calls into adult song, and the modification of the song themes of their individual song models, suggest that song development involves processes in addition to copying the songs of their own foster species and of older adult male indigobirds with songs like their own foster parents. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Individual variation in male vocal traits and female mating preferences in Bufo americanus

We investigated the amount of variation in mating behaviour between and within individual male and female American toads, because both sources of trait variation can influence the course of sexual selection. Males varied in all four call parameters investigated (dominant call frequency, pulse rate, call rate and call duration). Individual males lowered the dominant frequency of their call when they interacted vocally with nearby males. Dominant call frequency was more highly correlated with body size in vocally interacting males than in non-interacting males. Pulse rate of calls primarily varied with water temperature. Call rate and call duration showed the most variation of the four call properties, but this variation was unrelated to male morphology or social interactions. Females varied in three aspects of mating behaviour: two measures of pair formation and their preference for dominant frequency of male calls. The body size of paired males varied between females both in pairings initiated by either sex and in pairings initiated only by females. Males chosen by females were usually larger than average, although age and prior breeding experience of females did not affect mate choice. Playback experiments indicated that female preference for calls of low dominant frequency depended on the temporal patterning of alternative calls presented. Each of the four male vocal properties showed significant repeatability, but only one of the three aspects of female mating behaviour was repeatable. We discuss how different degrees of repeatability in sexual traits of males and females may influence the action and detection of sexual selection in this and other species. 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.     

Parental behaviour is unrelated to experimentally manipulated great tit brood sex ratio

Parental investment may be biased with respect to parental sex or offspring sex or there may be an interaction between parental and offspring sex. We investigated whether any of these types of bias occurred in great tits, Parus major. By sexing chicks using random amplified polymorphic DNA (RAPD) markers and subsequently moving chicks between broods, we were able to manipulate broods early in the nestling period to give all-male, mixed-sex and all-female broods. Provisioning behaviour (total feeding rate, proportion of feeding visits by the male, prey size, visit duration and proportion of visits in which a faecal sac was removed) was measured for broods aged 8-9 and 11-12 days. Nest defence behaviour was measured for 15-day-old broods. Parental weight, the occurrence of second broods and overwinter survival of the parents were also analysed. There were some differences in parental care between the parents: males made the majority of feeding visits and were more vigorous in nest defence. However, there was no evidence that parental care varied in relation to brood sex ratio or that there was an interaction in parental care between parental sex and brood sex ratio. Copyright 1998 The Association for the Study of Animal Behaviour     

The island posterior calf fasciocutaneous flap: an alternative to the gastrocnemius muscle for cover of knee and tibial defects

By repeatedly presenting an alien scent to territory-owning beavers, Castor canadensis, we tested two competing hypotheses about the function of scent marking: scent fence and scent matching. The scent-fence hypothesis predicts that territory owners should respond increasingly strongly over time towards a recurrent alien scent because of the ineffectiveness of previous responses. The scent-matching hypothesis predicts that the intensity of response should be the same or decrease because, without the presence of the intruding signaller coupled with the chemical signal, the presence of the scent itself does not advertise the ownership of a territory. The response level of resident beaver families was stable to strangers' anal gland secretions (AGSs) and decreased to strangers' castoreum during a period of 6 days. These results support the scent-matching hypothesis but not the scent-fence hypothesis. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Brood parasitism in the sand martin, Riparia riparia: evidence for two parasitic strategies in a colonial passerine

Sand martin parentage was studied at a large breeding colony in central Scotland. Multilocus DNA fingerprinting was used during the 3-year study to exclude some social parents as true parents, and thereby determine the frequency of monogamy, quasiparasitism (QP), intraspecific brood parasitism (ISBP) and extrapair fertilization (EPF) amongst 45 broods and 167 nestlings. Monogamous parentage characterized the majority of broods (60%), so most chicks were the offspring of their social parents (81%). QP (involving a male's extrapair mate laying in his nest) was found in 9% of broods and 2.4% of chicks and ISBP (or 'egg dumping') in 4% of broods and 1.8% of chicks. A substantial proportion of offspring arose from EPFs, affecting 36% of broods and 14% of chicks. On present evidence, the relatively high frequency of QP found in sand martins is unusual. We propose that its observed frequency is unlikely to be due to chance events and may represent a female-driven strategy. (c)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.     

How mothers influence the development of litter-mate preferences in Belding's ground squirrels

We performed three experiments to examine the role of mothers in the development of litter-mate preferences in captive juvenile Belding's ground squirrels, Spermophilus beldingi. First, when observed in the absence of mothers, juveniles did not play preferentially with litter-mates, which suggests that mothers somehow influence the ontogeny of litter-mate preferences. Second, when mothers were present but unable to intervene in social interactions, juveniles displayed litter-mate preferences, which suggests that mothers do not influence their offsprings' social development by directly intervening in social interactions. In another group, mothers were removed daily, a few hours before nocturnal immergence, and returned the following morning. Juveniles in this group did not display litter-mate preferences and at night they occupied burrows with many more non-litter-mates than litter-mates. These results suggest that associating with non-litter-mates can compromise the development of litter-mate preferences, and implies that mothers indirectly influence social development by affecting the identities of sleeping partners. Third, newly emergent juveniles that interacted only with litter-mates for 3 days in the absence of mothers subsequently preferred litter-mates over non-litter-mates as play partners. This result demonstrates that once litter-mate preferences are instilled, due in part to social experiences during juveniles' initial days above-ground, the preferences are expressed even in the absence of mothers. Collectively, the results demonstrate that the presence of S. beldingi mothers is important to juvenile social development, but that mothers do not actively direct the ontogeny of their offsprings' social relationships. 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.     

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.     

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.     

The onset of incubation in birds: can females control hatching patterns?

We investigated intraspecific variation in incubation behaviour of wild Eurasian kestrels, Falco tinnunculus, in Finland and tested whether patterns of hatching asynchrony could be predicted from patterns of incubation. The timing of the onset of incubation varied considerably for 17 female kestrels. Eggs generally hatched in the order they were laid, and both total hatching span of the clutch and the pattern of eggs hatching on certain days corresponded well with incubation behaviour. This result was consistent with the idea that females have much control over hatching patterns. In the majority (65%) of cases, the proportion of daily incubation increased monotonically with the laying sequence, a pattern described previously in other birds. Unusual patterns of incubation (35%) were most common in females with poor body condition during incubation and may be the result of energy constraints during laying.Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Juvenile Richardson's ground squirrels, Spermophilus richardsonii, discriminate among individual alarm callers

Richardson's ground squirrels, Spermophilus richardsonii, issue vocal alarm responses to avian and terrestrial predators. Recipients of those calls presumably benefit from enhanced detection and subsequent avoidance of predators. If receivers of alarm calls differentiate among callers, they could use that information to tailor their behavioural response to the perceived level of threat. A neighbour's call may indicate more imminent danger than that of a non-neighbour; with individual recognition, recipients could adjust their response according to the reliability of the caller. I elicited and recorded alarm calls of juvenile Richardson's ground squirrels using an avian predator model. Series of five calls were then played back to focal juveniles in the field. Within each series, playbacks involved an initial 'habituation series' of four calls of either a neighbour or a non-neighbour. In 'control' series, the fifth call was from the same individual but differed from the four preceding it. In 'experimental' series, the fifth call was from a different individual than those played earlier. Juveniles showed greater vigilance in response to playbacks of neighbours' calls relative to non-neighbours' calls, but habituated rapidly to call playbacks, showing a significant decline in vigilance by the second call. In control series, a different call from the same individual did not significantly increase vigilance. In experimental series, a call from a different individual restored vigilance to a level similar to that recorded prior to habituation. These results suggest that juvenile Richardson's ground squirrels discriminate among callers and use that ability to respond differentially to alarm calls issued by neighbours and non-neighbours. Copyright 1998 The Association for the Study of Animal Behaviour.     

The energetic cost of begging behaviour in nestling house wrens

This study presents data relevant to the hypothesis that the energy expenditure associated with begging influences the signalling of need by nestling birds. We used open-circuit respirometry to measure the energy costs of resting, begging and non-begging activities in nestling house wrens, Troglodytes aedon, ranging in age from 1 to 11 days post-hatching. Across all ages, begging caused a 27% increase in metabolism above resting rates. The metabolic rate during begging was not related to begging vigour. However, more vigorous begs were longer and so required a greater total energy expenditure. We analysed videotapes of broods for nestling behavioural time budgets which were combined with the metabolic data and data on growth at different ages to generate daily energy budgets. Over a 24-h period, the cumulative energy allocated to begging was slight, ranging from 0.02% of the energy budget in younger nestlings (3 days old) to 0.22% in older ones (10 days old). In contrast, non-begging movements accounted for 2 and 9% of the daily energy budget of younger and older nestlings, respectively. Relative to daily growth, the energy allocated to begging was equivalent to 0.05% (younger nestlings) and 2.3% (older nestlings) of the energy sequestered in new tissue, whereas the values for non-begging activities were 5.1 and 96.8%, respectively. These results suggest that the energetic cost of begging is not likely to have a substantial role in influencing communication of need by nestlings. Copyright 1998 The Association for the Study of Animal Behaviour. 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.     

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.