The role of male vs male interactions in maintaining population dialect structure

Summary Nonmigratory populations of Whitecrowned Sparrows in coastal California exhibit dialects in territorial male songs that are stable in space and time. By field playback experiments, we tested a prediction from the hypothesis that male aggressive interactions prohibit mixing of song dialects. Playback of the home dialect Clear song to territorial males singing the Clear dialect resulted in less response than that given to playback of the neighboring Buzzy dialect. Response to both Buzzy and Clear dialect songs by target Clear males, however, was greater than that given to the Bodega dialect recorded 55 km away (Figs. 2 and 3). We conclude that these results are consistent with the hypothesis that male-male aggressive interactions play an important role in reducing dialect mixing.     

Reproductive effort in relation to maternal social rank in reindeer (<Emphasis Type="Italic">Rangifer tarandus</Emphasis>)

In polygynous mammals, high-quality females may increase their fitness by providing superior care to their offspring. Based on the agonistic interactions of female reindeer in an experimental herd during two consecutive years (1997 and 1998), we tested whether maternal social rank influenced: (1) winter body-mass change of females, (2) preparturition reproductive effort (measured as fecundity, the birth mass and the birth date of their calves), (3) preweaning maternal effort (measured as calves preweaning mortality, early preweaning and late preweaning growth rate and September body mass of calves), and (4) postweaning maternal effort (measured as calves body-mass change during their first winter). In the models, we included September females body mass as a covariate to separate the effects of maternal rank and body mass. We also tested whether the effect of social rank on maternal efforts was dependent on offspring sex. High-ranked females gained body mass whereas low-ranked females lost weight during the winter. Fecundity was higher and date of birth was earlier in high-ranked females than in subordinates, whereas no effect of females rank on birth mass of calves was found. Early preweaning growth rate and September body mass of calves increased with increasing females social rank, whereas late preweaning daily growth rate of calves was not influenced by females rank. Calves preweaning mortality was only influenced by year, which also explained most of the variance in the winter body-mass change of calves. The effects of females rank on the reproductive-efforts parameters studied were not specific to offspring sex. These findings suggest that females rank influences reproductive effort during the preparturition, as well as the preweaning, period, the effect being sex independent.Communicated by R. Gibson     

Song as an attractant for male and female European starlings,and the influence of song complexity on their response

Summary We tested the hypothesis that song attracts females and repels males in the European starling. We broadcast recorded song from speakers attached to nestboxes, while paired boxes with silent speakers served as controls. As predicted, females were attracted to the song boxes. Contrary to prediction, males were also attracted to the `song' boxes. Singing by male starlings may be costly because it attracts competitors for limited nesting sites, but the cost cannot be avoided due to the need to attract a mate. In a second experiment simple song (composed of 20 different phrase types) and complex song (40 phrase types) were played simultaneously. More males were captured at boxes where simple song was played. Song complexity may function as an indicator of male quality and be used by male starlings to assess potential competitors.     

On the evolution of male workers in the Hymenoptera

Summary The effects of brood sex-ratio (investment ratio) and the presence of laying workers on relatedness in the Hymenoptera are analyzed. It is shown that the conditions of brood composition that generate degrees of relatedness favorable to the evolution of eusocial type helping behavior among females will select against such helping behavior among males, and vice versa (see Fig. 1). Thus, societies in the Hymenoptera can be expected to have male workers or female workers, but not both. It is argued that the conditions leading to degrees of relatedness favorable to male helping are quite restrictive and unlikely to be met in haplodiploid species.The presence of laying workers is shown to lead to biasses in relatedness such that females may be selected to be workers even when the sex-ratio is male-biassed. This result sheds new light on a possible pathway to eusociality in the Hymenoptera. It is argued that offspring parasitism of the natal nest may have been important in the evolution of eusociality.     

Nutritional phagostimulants function as male courtship pheromone in the German cockroach, <Emphasis Type="Italic">Blattella germanica</Emphasis>

Summary. Males of the German cockroach, Blattella germanica, secrete a pheromonal substance from the abdominal tergal glands, which elicits a feeding response in females during the sequential courtship behavior. The nuptial secretion consists predominantly of a synergistic mixture of sugars and phospholipids. Cholesterol and a series of amino acids, which are also components of the males glandular secretion, significantly enhanced the phagostimulant activity of the sugar components. The nuptial feeding behavior of the female cockroach is therefore elicited by a complex assortment of nutritive components in the male tergal secretion, including sugars, phospholipids, cholesterol, and amino acids. These results indicate that a mixture of primary metabolites, and not of specific secondary metabolites, serves as a pheromonal cue that appeals to the females gustatory sense and effectively brings her to the precopulatory position. Although the male secretion consists of nutrients, we suggest that these compounds probably do not represent a significant nutrient investment in females and their progeny but rather function as a signal in the mating sequence of B. germanica.     

The evolution of cheating and selfish behavior

Summary We examine the necessary conditions for the spread of genes that determine selfish and cheating behaviors and the rate of spread of these genes through structured populations, in order to address the question of the invadability of altruistic systems by anti-social mutations. We find that, although cheaters always have a higher relative fitness than altruists within groups, population structures which permit the evolution of altruism also preclude invasion by anti-social mutations. These results are related to a discussion by Hamilton (1971) concerning the limits to the evolution of altruistic and selfish behaviors.     

Extra-pair paternity and intraspecific brood parasitism in wild zebra finches Taeniopygia guttata,revealed by DNA fingerprinting

Summary The frequency of extra-pair parentage in a wild population of zebra finches Taeniopygia guttata was examined by DNA fingerprinting. A total of 25 families, comprising 16 pairs of parents and 92 offspring (in broods of 1 to 6) were examined. Ten cases of extra-pair parentage, presumed to constitute intraspecific brood parasitism, were detected (10.9% of offspring or 36% of broods), including one possible instance of quasi-parasitism (parasitism by a female fertilized by the male nest owner). The average number of parasitic eggs per clutch detected by fingerprinting was 1.10±0.32 SD, very similar to the one egg difference in average clutch size between parasitised (6.0±0.82) and unparasitised nests (5.0±0.95). Two cases of extra-pair paternity (EPP) were detected among 82 offspring whose maternity was confirmed: 2.4% of offspring, or 8% of broods. In both cases EPP accounted for only a single offspring within a brood. Behavioural observations show that EPP occurs through extra-pair copulation rather than rapid mate switching. The results are discussed in the light of what is known about the fertile period and sperm precedence patterns in this species. Offprint requests to: T.R. Birkhead     

Baboon loud calls advertise male quality: acoustic features and their relation to rank,age, and exhaustion

Free-ranging adult male baboons give loud two-syllable wahoo calls during dawn choruses, interactions between groups, when chasing females, and in aggressive interactions with other males. Previous research has shown that the rate and duration of these contest wahoos are correlated with a males competitive ability: high-ranking males call more often, call at faster rates, and call for longer bouts than do low-ranking males. Here we report that acoustic features of wahoos also reveal information about male competitive ability. High-ranking males give wahoos with higher fundamental frequencies (F0) and longer hoo syllables. Within-subject analyses revealed that, as males fall in rank, the hoo syllables tend to shorten within a period of months. As males age and continue to fall in rank, F0 declines, hoo syllables shorten, and formant dispersion decreases. Independent of age and rank, within bouts of calling F0 declines and hoo syllables become shorter. Because wahoos are often given while males are running or leaping through trees, variation in these acoustic features may function as an indicator of a males stamina. The acoustic features of contest wahoos thus potentially allow listeners to assess a males competitive ability.Communicated by C. Nunn     

Male mating history and female fecundity in the Lepidoptera: do male virgins make better partners?

In insects, large ejaculate and associated materials, including spermatophores, appear to have evolved via sexual selection acting on males to either delay female remating or to increase the rate of egg-laying. It is also possible, however, that females use nutrients transferred during mating to increase their lifetime fecundity. If so, male ejaculate size may also have evolved under natural selection as a form of paternal investment. In Lepidoptera, males with a greater number of prior matings tend to produce smaller spermatophores. However, the reported effects of male mating history on female fecundity vary widely among species. We therefore performed a meta-analysis using data from 29 studies of 25 species. Overall, the reproductive output of females mated to virgin males was significantly higher than that of females mated to sexually experienced males (Hedges d=0.33, P<0.01). A sample size of around 145 females per male mating type is required to detect an effect of this size with 80% statistical power at =0.05 (two-tailed). There was no difference in mean effect size between butterflies/skippers and moths. After controlling for any effect of taxonomic group, however, the mean effect size for polyandrous species was significantly greater than that for monandrous species (Hedges d=0.45 vs 0.25, P=0.01). We then discuss possible reasons why male mating history, presumably acting through its effect on spermatophore size, might have a stronger effect in polyandrous than monandrous species.Communicated by A. Cockburn     

No evidence for acoustic mate-guarding in duetting buff-breasted wrens (Thryothorus leucotis)

There are few empirical tests of the acoustic mate-guarding hypothesis for the function of duetting in birds. This hypothesis states that when females are fertile, males initiate many songs or answer most of their mates solo songs to form duets and repel rival males seeking extra-pair copulations. We tested the hypothesis by comparing song initiation and answer rates of males and females in socially monogamous buff-breasted wrens (Throthorus leucotis) during pre-fertile and fertile periods. During pre-fertile periods, males often sang for short periods before being answered by their mates, yet first duets were formed earlier relative to dawn and more duets were given during the dawn chorus on pre-fertile than fertile mornings. Males initiated more songs during pre-fertile than fertile periods, whereas there was no difference between stages in female song initiation rates. The proportion of songs answered by individuals of both sexes did not differ between breeding stages. Other mate-guarding behaviours, such as frequent copulation and maintaining close proximity to mates when fertile, did not appear to be important in this species, as no copulations were observed and there was no difference in the time pairs spent in close proximity when females were fertile or not. Parentage analysis revealed that only 3% of 31 broods had young that were likely the result of extra-pair paternity. These findings do not support the acoustic mate-guarding hypothesis, and suggest that the low rate of extra-pair paternity in buff-breasted wrens was maintained without the use of acoustic or traditional paternity guards.Communicated by R. Gibson     

Divorce in common murres (Uria aalge): relationship to parental quality

Behavioral precursors of 12 divorces were examined in 30 color-banded pairs of common murres (Uria aalge) over six breeding seasons. Common murres are long-lived seabirds that typically return each year to the same mate and nest site in dense colonies. At least one parent is present continuously from egg lay to chick fledging. Murres, therefore, have considerable opportunities to compare their mates parental behavior with that of several familiar neighbors. Previous reproductive success was lower for divorcing birds than for reuniting pairs. As predicted by the better option hypothesis, there were clear choosers (seven females and five males) that initiated divorce by moving to a new birds site or by courting a new partner at their current site. Choosers improved their reproductive success after the divorce, whereas their previous partners, the victims did not. Yearly divorce rates (average 8.2% per year) were significantly correlated with yearly mortality rates. Divorces appear to be opportunistic: pairs divorced after varying numbers of reproductive failures with the immediate precursor usually being the disappearance (death) of a murre from a successful neighboring site. In contrast to the delays experienced by victims, choosers formed new pairs quickly and laid their eggs no later than reuniting pairs. Prior to the divorce, victims fed their chicks less often than choosers, and some engaged in other behaviors that compromised egg or chick survival. These observations suggest that deficiencies in parental behavior were precursors to the divorce. This report is one of the first cases where reproductive failure of divorcing pairs has been linked to deficits in the parental behavior of the subsequent divorce victim.Communicated by C. Brown     

Comparisons of the feeding activity and diets of male and female cunners Tautogolabrus adspersus (Pisces: Labridae)

The diel distribution of feeding activity during the spawning season was compared for territorial male and female cunners Tautogolabrus adspersus in Conception Bay, Newfoundland, Canada between June and August, 1978. Territorial males feed significantly less often than females and concentrate their feeding activities in the morning, whereas females feed as frequently in the afternoon as in the morning. Based on the contents of alimentary tracts, territorial males, non-territorial males, and females have different diets. Since these three groups share the same habitat, the observed dietary differences probably reflect differences in their foraging behaviour. The relevance of these findings to the concept of time minimizer and energy maximizer is discussed.     

The erect ‘penis’ is a flag of submission in a female-dominated society: greetings in Serengeti spotted hyenas

In East Africa, spotted hyenas live in large clans in a highly structured society dominated by females. A clan is a fission-fusion society where members are often solitary or in small groups. Spotted hyenas have a ritualized greeting during which two individuals stand parallel and face in opposite directions. Both individuals usually lift their hind leg and sniff or lick the anogenital region of the other. The unique aspect of greetings between individuals is the prominent role of the erect penis in animals of both sex. Female spotted hyenas have fused outer labiae and a pseudo-penis formed by the clitoris which closely resembles the male penis and can be erected. During greetings subordinates signalled submission with gestures which were not necessarily reciprocated by the dominant participant. Asymmetries were most pronounced in greetings between adult females where the probability of asymmetries increased with the divergence in rank between partners. Greetings between adult females and males were uncommon and restricted to males above median rank, principally the alpha male. Models of primate affiliative behavior assume that benefits derived from social relationships with different individuals are not equal and that individuals are selected to maximize the benefits they receive from social relationships with others. The observed distribution of greetings between partners of different rank matched the predictions of these models. An examination of non-adaptive hypotheses on the evolution of the pseudo-penis demonstrated that the conventional scenario linking (initial) virilization of female genitalia with selection for female dominance does not explain either the initial virilization, nor the evolution of the pseudo-penis to its current form and use. We sketch a new scenario that links (1) initial virilization to the occurrence of neonatal siblicide amongst members of a twin litter, and (2) costs of maintenance, pseudo-penile control over copulation and male submission. Our analysis confirms previous adaptive hypotheses on the function of the pseudo-penis in greetings and suggests new hypotheses to account for hitherto unexplained features. Correspondence to: M.L. East     

Sexual dimorphisms in radula of<Emphasis Type="Italic"> Conomurex persicus</Emphasis> (Gastropoda: Strombidae) in the Mediterranean Sea

Dentition characters of Conomurex persicus found along the Mediterranean coasts of Turkey were analyzed. For the analyses of radula, 289 individuals (34 adult males, 140 adult females and the remainder juveniles) were examined. Male and female individuals of the species had different numbers of radular cusps. The radula of the taenioglossate type was made up of two marginal teeth, one lateral and one central (rhachidian) tooth, each being delicate and with different numbers of cusps. The central and lateral teeth had seven cusps and five cusps, respectively, in both males and females. Outer and inner marginal teeth of males had two and one cusps, while those of females had five and six cusps, respectively. The females radula is yellow-whitish. The males radula is reddish dark brown.Communicated by O. Kinne, Oldendorf/Luhe     

Aggregation and foraging behavior of whirligig beetles (Gyrinidae)

Summary Whirligig beetles aggregate in the daytime into dense single-and multispecies groups (rafts) of hundreds or thousands of individuals. On the 22km shoreline of Lake Itasca in northern Minnesota, these aggregations were on the average 0.8 km apart, and they were usually found day after day in the same ocations.Most beetles apparently do not home to the aggregation of their origin after dispersing at night because (a) the species composition of some aggregations changed greatly, and (b) paint-marked beetles (Dineutus horni) moved overnight from one aggregation as far as 4km, joining 11 of the 14 large (>300 beetles) D. horni groups on the lake.Throughout the night, the largest concentrations of beetles remained within 100m of the diurnal aggregation sites. Beetles reconvened into the compact rafts before daybreak, in part by following each other in sometimes long single files or trains. Their forward motion stopped after they joined large number of other beetles. We infer that following behavior enables those individuals that have dispersed from their original aggregations (during their nocturnal foraging) to find and join other aggregations before daylight.Naive fish ate the beetles despite their noxious secretions. However, fish living near rafting sites and feeding on insects on the water surface in daylight should soon learn to avoid the beetles. The rafting sites would then become safe places. We observed fish attacking only those beetles that had been either dispersed from their rafts or released into open water away from raft sites in the daytime. We speculate that the evolutionary significance of the aggregation behavior is related to predator (fish) avoidance.     

Aluminium and fluoride concentrations of three tea varieties growing at Lantau Island,Hong Kong

The present project aims to investigate aluminium (Al) and fluoride (F) contents in teas (Camellia sinensis (L.) O. Kuntze). Three different commercial tea varieties: Assam variety and two China sub-varieties, a large leafed variety and small leafed variety, were collected in two tea gardens of Lantau Island tea plantation of Hong Kong. In general, high concentrations of Al and F were accumulated in the mature leaves (15.3 and of 2.07 g kg^–1 respectively). Among the three varieties, the small leafed variety exhibited the highest Al and F contents followed by the large leafed variety whereas the Assam variety had the lowest Al and F concentrations in its tea bushes. Tea products from a plantation were also analysed and it was noted that black tea had higher Al and F concentrations than green tea. The amount of Al and F released into tea liquor was also tested and the results showed that higher concentrations of Al and F were released into tea liquor under repeated infusion method than continuous infusion method.     

Dynamics of space use and male vigour amongst wood mice,Apodemus sylvaticus,in the cereal ecosystem

The spatial organisation of male and female wood mice,Apodemus sylvaticus, was investigated in a large-scale radio-tracking study on arable farmland near Oxford, United Kingdom, during the breeding season. Both sexes had significantly larger home ranges in the breeding season than at other times, and the breeding season home ranges of male (X = 1.44 ha) were significantly larger than those of females (X = 0.49 ha). Home range overlap was significantly greater between males, and between males and females, than it was between females. Overlap between males tended to be greatest in heavily utilised areas. Except during sexual consortship, there was minimal evidence of dynamic interaction among individuals. Home range sizes of breeding males varied widely, as did their body weights. There was no relationship between male body weight and home range size or any other movement parameter. However, males with the largest home ranges had the highest scores on all other movement parameters, indicating that they expended more energy in movement. These more vigorous males had access to the home ranges of more females than did males with small home ranges.     

Copulation behavior and paternity in the chaffinch

Summary We investigated two aspects of sperm competition in a wild population of chaffinches Fringilla coelebs: copulation behavior and genetic parentage determined by DNA fingerprinting. Pairs copulated at a high rate before laying, peaking at 4.4 copulation attempts per hour on day –3 relative to laying, with an average of 207 copulation attempts (83 behaviorally successful) per clutch. Extra-pair copulation attempts (n = 20) made up 7.8% of all copulation attempts that females were involved in. The rate at which pairs copulated was lower during egg-laying, but there was no evidence that this was due to the male of the pair timing copulations to coincide with an insemination window; it was more likely due to the fact that females solicited copulations at a lower rate. Both sexes solicited copulations but males solicited mainly extra-pair copulations. DNA fingerprinting showed that 17.0% of chicks (n = 47) in 23% of broods (n = 13) were fathered by a male other than the one paired to their mother. There was no evidence of intraspecific brood parasitism. In three cases where we were able to identify the father of extra-pair offspring it proved to be a neighboring male.Correspondence to: B.C. Sheldon     

Are communal pukeko caught in the prisoner's dilemma?

Summary The prisoner's dilemma of game theory provides a possible explanation for communal breeding in the pukeko (Porphyrio porphyrio, Aves) where group breeding birds are at a reproductive disavantag compared to pairs. Territorial defence is largely the realm of males. A male who defect on neighbours by taking in an extra male defender and so becoming communal stands to gain territorial area and possibly higher reproductive success. Neighbours are forced to follow suit if additional males are available or lose their territory and therefore their breeding opportunities. If neighbours also admit an extra defender, the initial defector loses his advantages and all males end up with the lower breeding success of communal groups. Such defection to a communal habit appears to be the only stable solution.     

Female defence polygyny in the bumblebee wolf,Philanthus bicinctus (Hymenoptera: Sphecidae)

Summary In the digger wasp Philanthus bicinctus the first adult males emerge about a week before the first females. The sex ratio of emerging wasps is near unity. Females appear to mate once and do so when they first start to nest, not when they first emerge.Males defend mating territories in a large area of female ground nests. Territoriality begins when females first start to nest and throughout the season coincides with the digging activities of females initiating rests. During the day territoriality occurs only when females are engaged in digging activities.Males compete for certain territory sites within the resting area; the most frequently occupied male territories are in areas where the density of nests is highest. About half of the males are excluded from nesting area territories. Some of these males defend areas among the flowers of snakeweed where females occasionally forage; this appears to be a loser tactic of males unable to obtain nesting area territories.Although there was no significant difference in the sizes of males on nesting area and snakeweed territories, within the nesting area larger males usually occupy territories with the higher nest densities.