Showing papers in "Behavioral Ecology and Sociobiology in 1979"

Reconciliation and consolation among chimpanzees

Abstract: 1. After agonistic interactions among chimpanzees, former opponents often come into non-violent body contact. The present paper gives a quantitative description of such contacts among the chimpanzees of a large semi-free-living colony at the Arnhem Zoo, in order to establish whether these post-conflict contacts are of a specific nature. 2. Our data indicate that former opponents preferentially make body contact with each other rather than with third partners. They tend to contact each other shortly after the conflict and show special behaviour patterns during these first contacts. Data on contacts of the aggressed party with third animals indicate that such contacts are characterized by the same special behaviour patterns as first interopponent contacts. These patterns are: ‘kiss’, ‘embrace’, ‘hold-out-hand’, ‘submissive vocalization’ and ‘touch’. 3. Such interactions apparently serve an important socially homeostatic function and we termed them ‘reconciliation’ (i.e. contact between former opponents) and ‘consolation’ (i.e. contact of the aggressed party with a third animal). According to our data, ‘kissing’ is characteristic of reconciliation and ‘embracing’ of consolation.

Mating patterns and reproductive strategies in a community of wild chimpanzees (Pan troglodytes schweinfurthii)

Abstract: 1. The sexual behaviour of a chimpanzee community in the Gombe National Park, Tanzania, was studied intensively for 16 months. Additional information came from 15 years of demographic and behavioural data accumulated by Jane Goodall and members of the Gombe Stream Research Centre. 2. The mating system of the Gombe chimpanzees is flexible and comprises three distinct mating patterns: (a) opportunistic, non-competitive mating, when an oestrous female may be mated by all the community males; (b) possessiveness, when a male forms a special short-term relationship with an oestrous female and may prevent lower-ranking males from copulating with her; and (c) consortships, when a male and a female leave the group and remain alone, actively avoiding other chimpanzees. While males took the initiative in possessive behaviour and consortships, females had to cooperate for a successful relationship to develop. 3. Data from 14 conceptions indicated that the majority of females (9) became pregnant while participating in the restrictive mating patterns, possessiveness and consorting. It could be established definitely that seven of these females were consorting during the cycle in which they conceived. As 73% of the 1137 observed copulations occurred during opportunistic mating, 25% during possessiveness, and only 2% during consortships, there was no correlation between copulation frequency and reproductive success. 4. Adult males showed differential frequencies of participation in the restrictive mating patterns. Male age, dominance rank, and the amount of agonistic behaviour directed to females showed no correlation with participation in the restrictive mating patterns. The following male characteristics did show significant, positive correlations with involvement in the restrictive mating patterns: (a) the amount of time spent in the same group as oestrous females, (b) the proportion of that time spent grooming oestrous females in groups, and (c) the frequency with which males shared food with females. While dominance ranks of the adult males showed no consistent correlation with involvement in the restrictive mating patterns, it was clear that the most dominant male did gain an advantage. He was the only male able to monopolise oestrous females by showing possessive behaviour. 5. Consortships appeared to be the optimal reproductive strategy for males (with the exception of the most dominant) and females, as they gave males the highest probability of reproductive success, and allowed females to exercise choice. However, there appeared to be disadvantages associated with consort formation; the greatest of these was the increased risk of intercommunity encounters. While all individuals have the potential to practice each mating pattern, the strategy actually used at any moment will be determined by variables both within the individual, e.g. age, physical condition, dominance position; and by social factors in the group, e.g. general stability of male dominance relationships, presence of a strong alpha male, existence of special male-female relationships.

Analysis of Two Genetic Models for the Innate Components of Colony Odor in Social Hymenoptera

Abstract: We propose two models for the inheritance of the innate components of colony odor in social Hymenoptera. Under the Individualistic model, individuals are hostile unless they share at least one allele at all colony-odor loci. Under the Gestalt model, colony-odor pheromones are transferred between individuals, resulting in a ‘gestalt’ colony odor; colonies will not fuse unless they have the same genetic mix of workers. We analyze these models for the case of colonies founded by single, once-mated queens. The Gestalt model seems generally favored for most species, although some evidence suggests the Individualistic model may operate in some primitive ants. A single colony-odor locus is possible in the Gestalt model, but seems improbable in the Individualistic case. We propose a general inbreeding test to estimate the number of loci involved in colony odor.

Territoriality: The relation of ranging pattern and home range size to defendability, with an analysis of territoriality among primate species

Abstract: 1. Existing theory suggests that territoriality will evolve when resources are limited and defendable, but defendability has seldom been analyzed quantitatively. 2. Here we argue that defendability depends on the ability of an animal to monitor the boundaries of its range in order to detect potential intruders and introduce an index of defendability (D) which is the ratio of observed daily path length (d) to an area equal to the diameter (d′) of a circle with area equal to home range area of the animal. This index is sensitive only to extreme deviation from circular shape. 3. Review of the literature on primate ranging reveals that all territorial groups for which data are available have an index of 1.0 or greater, and that few nonterritorial species have an index of 1.0 or greater. 4. Regression analysis of the relationship of daily path length to feeding group weight and foliage in the diet reveals that both feeding group weight and foliage in the diet account for a large proportion of the variance in daily path length, and that territorial and nonterritorial groups do not differ in day range for a given group weight and diet.

Social behavior of the little brown bat, Myotis lucifugus

Abstract: 1. As part of an overall study of the social behavior of the little brown bat, Myotis lucifugus, we compiled the vocal repertoire of this gregarious species in its natural habitat. Ten vocalizations were identified and associated with certain behavioral contexts. 2. Echolocation pulses, although primarily used for or entation, are also available as interindividual communication signals and modified forms are used in several situations such as during near-collisions in flight and the first flights of newly volant young. 3. Nonecholocation calls are used in three main contexts. Agonistic vocalizations appear to take the place of physical aggression and may be used to protect an individual's position within a roost. Two vocalizations emitted in maternal-infant situations appear to contain vocal signatures which are important for individual recognition. During mating, a distinct copulation call given by males likely conveys a male's sexual motivation to a female in the absence of precopulatory displays. 4. The size of the vocal repertoire is comparable to those of some solitary mammals. Behavioral observations indicate that despite the gregarious nature of the species, a simple social system exists and the small repertoire is therefore not surprising.

Parental care and mating system of the prairie vole, Microtus ochrogaster

Abstract: 1. The mating system of prairie voles (Microtus ochrogaster) was investigated by experimentally manipulating the sexual composition of vole societies, thereby providing each vole with a variety of mating choices. 2. In male-female pairs, both parents appeared to contribute equally to the care of young, with the exception of lactation. Paternal activities included nest and runway construction, food caching, and grooming, retrieving, and brooding the young. 3. Voles in 26 of 27 societies mated monogamously; those in the other group mated polygynously. 4. Nonreproductive voles in the experimental societies generally lived in communal groups. Communal groups are known to occur in field populations of prairie voles, but it is not known if they exist during periods of reproductive activity. 5. We address the questions of the adaptive significance of voles living communally and we consider the relationship between communal voles and dispersing voles in nature. The results of this study were interpreted relative to four mating systems that may be associated with paternal care in mammals. We conclude that M. ochrogaster is basically monogamous; a verbal model is presented for the evolution of monogamy in this species.

The flexible social system of the golden jackal, Canis aureus

Abstract: 1. The study provides information on the intra-specific variation in social behaviour found within carnivores in terms of food supply. Jackals were chosen for study because they live in a variety of habitats, in several of which they had already been studied by others. 2. An area was selected where at least a section of the jackal population obtained 92% of its food from one feeding site of only 10 m2 area (based on analysis of 2,120 faeces). The jackals were observed by day and by night (with infra-red equipment) and many of them could be individually recognised. Other data were gathered by detailed field tracking. Examples of the jackals' behaviour and the interactions both within and between groups are described. 3. Some of the jackals of this area were organised into two groups (numbering about 20 and 10 individuals respectively); these two groups had a stable composition and occupied neighbouring ranges which, for one of them, could be termed a territory. The limit of this territory was delineated by faeces arranged in piles or middens. Food marking experiments and subsequent faecal analysis confirmed that these middens marked a genuine territorial boundary. 4. These findings are compared with those of other authors and it is clear that the flexibility of carnivore social systems in general, and that of jackals in particular, is considerable. The limits to the flexibility of social systems differ for various carnivore species. The description of selection pressures which have fashioned inter-specific differences in the possibilities for intra-specific variation within carnivore communities is an important task for the future.

Patterns of group splitting within matrilineal kinship groups

Abstract: 1. When social groups of free-ranging rhesus monkeys on Cayo Santiago, Puerto Rico, undergo fission, they usually divide between genealogies. 2. If a genealogy divides, it is usually between an eldest daughter with her family and the rest of the genealogy. 3. The separation of the eldest daughter from her genealogy is the extreme case of peripheralization of low-ranking females among rhesus monkeys. 4. The founders of new groups that disperse from the former home range are likely to be subordinate individuals in the parent group, as predicted by Christian (1970). 5. The dispersal of families as units is likely to lead to ‘lineal effects’ (Neel and Salzano, 1967) in the genetical substructure of the population.

Insect disturbance stridulation: Its Defensive role

Abstract: 1. Many insects stridulate when they are handled or attacked. It has been suggested that this disturbance stridulation acts to deter predators. This hypothesis was investigated in a series of experiments. Predators were given insects which had been silenced by disruption of their sound-producing mechanism or else had been sham operated but retained their normal ability to stridulate. 2. Three types of insects (mutillid wasps, Dasymutilla spp.; water scavenger beetles, Tropisternus spp.; and round sand beetles, Omophron labiatus) were given to wolf spiders (Lycosa ceratiola and Geolycosa ornatipes) at night in the field under natural conditions. When attacking silenced insects, spiders displayed greater persistence than when attacking phonic insects (Table 1). In addition, mortality was greater among silenced insects. 3. Spiders (L. ceratiola) were also given an artificial ‘insect’—a vibrating probe whose vibration mimicked that of the cuticle of a stridulating insect. As with real insects, spiders persisted longer in their attack on the probe when it was silent than when it was ‘stridulating”. 4. Female mutillid wasps were given to wild-caught mice (Peromyscus floridanus) in the laboratory. Unsilenced mutillids survived the encounter more often than their silenced counterparts. In another experiment, the stings of mutillid wasps were removed before testing. Mice killed nearly all these ‘unprotected’ mutillids. However, it took mice significantly longer to attack unsilenced mutillids and longer to kill them after initiating the assault (Table 2). 5. These results support the view that insect disturbance stridulation deters predators. Two modes of action by which these sounds may have their effect are discussed: they may serve to startle the attacker or they may alert it to the potential harmfulness of the insect and as such may qualify as an example of acoustic aposematism.

Games spiders play: II. Resource assessment strategies

Abstract: 1. The predictions of game theory concerning the use of resource assessment strategies by animals in conflict situations were tested through study of the agonistic behavior of the funnel-web spider, Ageleropsis aperta, in disputes over web sites and associated territories. Specifically, contest cost was considered relative to resource value (i.e., the quality and availability of territories). 2. The contest methodology was similar to that described in Riechert (1978a) with weight controlled to eliminate size bias. In addition, relative contest costs were converted to joules using resting metabolism under field conditions as a reference. Estimates of territory quality and availability were made through the application of a model of spider reproductive success to the results of discriminant analyses of site characteristics. 3. The immediate and ultimate benefits of ownership of specific territories accounts for a significant amount of the within-population variability in dispute cost-the greater the benefit, the greater the total cost of the dispute. The territory owner is shown to determine the level of escalation reached in these contests, while the intruder merely adjusts its behavior to that of its opponent. 4. Contest behavior is also shown to vary according to the relative availability of territories: more energy is expended in maintaining and winning territories in a habitat near saturation (desert grassland) than where territories are in ready supply (desert riparian). 5. A greater range of benefits was available to spiders occupying specific sites in the desert grassland study area than to the riparian population. This was emphasized by the greater variability in contest cost, richness, and in the total number of acts exhibited in the sequences involving desert grassland spiders. Prey availability and ultimately reproductive success were found to be correlated with web-site quality in the desert grassland habitat, whereas differential utilization of specific habitat types by the riparian spiders corresponded not to reproductive potential but to the ease of web placement. 6. The correspondance existing between within-population contest cost and site quality reflects active resource assessment on the part of the territory owner, while population differences observed in the level of escalation achieved in disputes over territories is attributed to selection pressure for evolved differences in level of aggression. These findings are discussed in terms of optimization and relative to the predictions of game theory.

Queen Substance Dispersal by Messenger Workers in Honeybee Colonies

Abstract: 1. Worker honeybees contacting a queen can transport the queen's inhibitory signal, queen substance, to other workers unable to contact the queen. Airborne dispersal of queen substance is at most a minor mechanism for queen substance transmission. 2. This worker transport of queen substance is an important supplement to queen substance dispersal by direct queen-worker contacts. For although colonies lose their inhibition against queen rearing within 10 h of queen loss, a queen contacts only approximately 35% of the broodnest workers in 10 h. 3. The queen facilitates queen substance dispersal by frequently standing stationary, at which times workers can thoroughly contact her, and by occasionally making a major shift in her position within the nest. 4. Queen attendance by workers is strongly age-dependent, with 3–9 days being the age range for intense contact with the queen. 5. Workers that have made extensive (>30s) queen contact appear to behave as ‘messengers’ dispersing queen substance. They walk more rapidly, antennate nestmates and receive inspections more frequently, and perform fewer labor acts in the 30 min following queen contact than do randomly chosen broodnest workers of the same age (control bees). 6. The following observations support the surface transport model over the food exchange model for queen substance transmission by workers: (1) the higher frequency of antennations with nestmates and of inspections by nestmates for messenger bees relative to control bees, (2) the close correlation (r=0.76) for messenger bees between duration of queen contact and number of inspections by nestmates, and (3) the low frequency of food donations (x=1.8) compared with nestmate antennations (x=56.4) by messenger bees in the 30 min following queen contact. 7. There are no messenger bee specialists cycling rapidly between contacts with the queen and workers. 8. Messenger bees were analyzed by gas chromatography for (E)-9-oxodec-2-enoic acid. As little as 0.1 ng (=3.3x1011 molecules) of the acid per messenger bee could have been detected, but none was found. 9. The evolution of messenger behavior by workers and the significance of the findings to understanding the timing of colony reproduction are discussed.

Costs and benefits of male-male competition in the orb weaving spider, Nephila clavipes

Abstract: 1. The reproductive benefits and predatory costs of male-male competition were studied in the orb weaver, Nephila clavipes. During the breeding season adult males search for females, and congregate on their orbs. 2. Males compete for hub position proximal to the female, with the largest male assuming hub status. Smaller males move about the periphery of the orb. 3. Hub males gained the advantage of almost exclusive mating, and a potential advantage of feeding on prey captured by the female. Peripheral males pursued various alternatives, but rarely mated. 4. Females, the larger sex, occasionally preyed on males. The cost to males from female predation was no greater for hub than peripheral males.

Age cohorts as paternal sibships

Abstract: Characteristics of a populations's reproductive system affect the degree of relatedness within the age cohorts and maternal sibships of that population. Two consequences of a small litter size, particularly of size one, a relatively polygynous mating system at any one time period, and frequent replacement of reproductively active males over successive periods, are that (1) the set of offspring that each female produces (a maternal sibship) will usually consist of halfsiblings, and (2) within a social group the members of each age cohort will be closely related, either all forming one paternal sibship (half-siblings) if there is only one reproductively active male at a time, or in the case of several reproductively active males, a set of individuals whose mean relatedness is some-what ower than in the one-father case. In the present paper, degree of relatedness within each of these two subgroups is calculated on the basis of a simple model. I then examine effects of the various reproductive parameters on this relatedness and compare maternal sibships and age cohorts in the relative degree of relatedness within them. Age cohorts will often be identifiable, closely related units, paternal sibships in the extreme case. Age cohorts may be important in the evolution of family altruism. They differ from maternal sibships in interesting ways that may affect the kinds of behaviors that are likely to evolve.

Goal-Oriented and Compass-Oriented Movements of Displaced Homing Pigeons After Confinement in Differentially Shielded Aviaries

Abstract: Young pigeons were kept in an aviary from the time of weaning until the time of displacement 3–5 months later. The two compartments of the aviary were differentially shielded by surrounding walls, and birds of both compartments were released simultaneously. During six years, seven types of shieldings were used (Fig. 1). Releases were conducted at four sites in the cardinal directions (distances about 100 and 30 km, respectively). Initial bearings and distributions of recoveries led to the following conclusions (Figs. 3 and 4): 1. Visual shielding of the environment up to about 10° above the horizontal plane does not influence long-distance orientation, provided that the shielding does not also impair the airflow through the aviary. 2. Homeward orientation is drastically reduced if the aviary is surrounded by walls made of glass. 3. Homeward orientation from all four directions persists if the pigeons lived in corridors between two solid walls permitting airflow either along the N-S axis or along the E-W axis. 4. The preferred compass direction (PCD) of pigeons which lived in this aviary in unscreened conditions is SSW. In the initial bearings, this PCD is more pronounced than the tendency toward home. 5. The PCD is reversed to NNE in pigeons which lived in a corridor open at east and west (but is unaffected by a N-S corridor). 6. The results obtained with the corridor aviaries do not support the olfactory navigation hypothesis as it stands so far (cf. Papi, 1976).

Spatial and temporal multi-species nesting aggregations in birds as anti-parasite and anti-predator defenses

Abstract: 1. The purpose of this study was to determine whether the yellow warbler (Dendroica petechia) derives any benefits from nesting in close proximity to its own and other species in reducing predator pressure or the incidence of brood parasitism by the brown-headed cowbird (Molothrus ater). 2. Yellow warblers nesting synchronously with their own and with neighbouring species resulted in a proportionate reduction in the number of nests preyed upon, suggesting a ‘swamping effect’ of the local predators. A significantly lower incidence of predation occurred at yellow warbler nests which were inside a gray catbird (Dumetella carolinensis) response range. This was thought to be the result of yellow warblers taking advantage of the catbird's nest-guarding behaviour and aggressive responses to predators. 3. Yellow warblers nesting synchronously with other yellow warblers were subject to a proportionately lower incidence of brood parasitism than asynchronous nests, suggesting a ‘swamping effect’ on the cowbird. A significantly lower incidence of brood parasitism occurred at yellow warbler nests which were in a red-winged blackbird (Agelaius phoeniceus) response range. The yellow warbler was thought to be taking advantage of the aggressive response of red-winged blackbirds to cowbirds. 4. Overall, yellow warblers which nested within the response range of red-winged blackbirds or gray catbirds had significantly higher nest success than other yellow warblers. This suggests that selection for defence against predators and cowbirds may lead to multi-species aggregations.

Vocal regulation of use of space by groups of titi monkeys Callicebus moloch

Abstract: The daily movements and the resulting activity and calling fields are described for three groups of titi monkeys Callicebus moloch. Groups move to the periphery of their home range in the early morning and then call. Playback experiments confirmed that both proximity and location of calling by neighboring animals affect the group's response. Subsequent countercalling often regulates the approach of neighboring groups to a boundary. After encountering adjacent groups, animals return to areas near the home range center. Movements, calling behavior, and the response to neighboring groups all increase the probability of intergroup encounters in the early morning. Encounters define and reinforce the conventional location of boundaries. Boundaries decrease the probability of intergroup encounters at other times and allow exclusive use of space.

Adaptive significance of postcopulatory guarding of mates and nonmates by male Calopteryx maculata (Odonata)

Abstract: 1. The postcopulatory behavior of the damselfly Calopteryx maculata (De Beauvois) (Odonata: Calopterygidae) was studied in field populations to determine the adaptive significance of guarding of ovipositing females by males. Of particular interest was an explanation for the guarding of ovipositing nonmates by males. A promiscuous mating system and the large variation in mating success (Table 1) among territorial males indicated that sexual selection may have been a significant factor in the evolution of C. maculata postcopulatory behavior. 2. Territorial males defend ovipositing mates by chasing and displaying toward conspecific males attempting takeovers. Guarded mates averaged 12–15 min of undisturbed oviposition while unguarded females averaged only 1–2 min of oviposition prior to disturbance by males. Postcopulatory guarding is advantageous to both sexes because it allows undisturbed oviposition. 3. During mating, 88%–100% of the sperm stored by a female from a previous mating was removed by a male before he transferred his own sperm to her storage organs. Given this potential for sperm displacement, postcopulatory guarding is advantageous to the guarding male since it assures him of fertilizing a substantial number of eggs prior to a subsequent mating by his mate. 4. The duration of guarding (interval between matings) for males was 10–15 min. It did not differ significantly between two populations in on year. Guarding duration did not significantly change with (a) time of day, (b) time devoted to defensive behavior, (c) female arrival rate, and (d) presence of absence of an ovipositing female (Table 2). 5. Males frequently guarded females with which they did not mate. Nonmates were guarded only when the male was simultaneously guarding a mate or had recently mated. These nonmates deposited eggs fertilized by rival males. Their presence did not significantly increase the time and energy expended by guarding males but did attract additional females (Table 3). However, these additional females did not lead to an increase in mating frequency for the guarding male. 6. Three factors appeared to limit the ability of guarding males to exclude or attempt matings with arriving nonmates: (a) a lack of individual recognition, (b) a risk of losing a previous mate while failing to copulate with an arriving female, and (c) a probable physiologic limit to mating frequency. These limitations in male postcopulatory behavior were exploited by females. 7. Some males were not territorial. While appearing less effective at obtaining mates, they devoted no time and energy to defending territories or mates. Because of sperm displacement, their reproductive success depended upon the ability of their mates to exploit the limitations in guarding behavior of territorial males.

Orientation by jumping spiders of the genus Phidippus (Araneae: Salticidae) during the pursuit of prey

Abstract: 1. Jumping spiders of the genus Phidippus tend to occupy waiting positions on plants during the day. From such reconnaissance positions, the spiders often utilize an indirect route of access (detour) to attain a position from which sighted prey (the primary objective of pursuit) can be captured. 2. Selection of an appropriate route of access is based upon movement toward a visually determined secondary objective (part of a plant) which may provide access to the prey position (Fig. 2, Table 1). 3. During pursuit, the spider retains a memory of the relative position of the prey at all times. This memory of prey position is frequently expressed in the form of a reorientation turn to face the expected position of the prey (Fig. 1). Each reorientation can be considered to initiate a new segment of the pursuit. 4. Phidippus employ the immediate direction (or route) of pursuit as a reference direction, for the determination of prey position (Figs. 3 and 4). The spider compensates for its own movement in determining the direction of the prey from a new position (Fig. 5). 5. The spider retains a memory of the prey direction with reference to gravity (Fig. 6); this memory of the inclination of prey direction can take precedence over conflicting information based upon the use of the route as a reference direction (Figs. 7 and 8). 6. Visual cues provided by both the background and the immediate plant configuration can be used by the spider to determine a (radial) direction in the plane perpendicular to the route of pursuit (Fig. 9, Table 2). 7. The jumping spider must employ at least two independent reference systems (route direction, gravity, visual cues) in concert to determine the position of the prey in space (Fig. 10 and Table 3, Fig. 11). 8. Apart from the context of predatory pursuit, the indirect pursuit of visually determined objectives is a general feature of the movement of salticid spiders upon vegetation.

Philopatric and nonphilopatric foundress associations in the social wasp Polistes fuscatus

Abstract: 1. Overwintering females of the paper wasp, Polistes fuscatus, were marked on their home colonies in 1977 and identified in the spring of 1978. Most females which joined foundress associations in 1978 did so with former nestmates, which are close relatives. The probability that any two associating females were nestmates ranges between 0.77 and 0.93. 2. Philopatric females — those which nested at the site where they emerged — enjoyed a higher probability that an associate would be a nestmate (0.90–1.00) than did nonphilopatric females (0.50–0.79). 3. Philopatric females formed associations of 2–7 wasps. Nonphilopatric females which did not found singly almost always formed associations of only two foundresses. The bias to two-foundress colonies in nonphilopatric females might be explained by a hypothesis of ‘selfish joining’.

Kinship, promiscuity, and communal breeding in the acorn woodpecker

Abstract: 1. Acorn woodpeckers typically live in permanent social groups in which most adults help to incubate and feed the young of a single nest. The selective basis of communal breeding in this species is examined. 2. At the study area in New Mexico, most juveniles did not remain on their natal territories during subsequent breeding seasons. There was also a high rate of turnover among adults within each group. The groups were not composed entirely of extended families, and unrelated adults fed young. Kin selection alone does not appear to be adequate to explain all instances of communal breeding. 3. Immigrants that joined groups before courtship in the spring participated in all phases of reproduction in their new groups. However, immigrants that joined groups after eggs were laid did not incubate or feed the young. This, combined with the high rate of turnover within groups, indicates that hypotheses based upon individual benefits through increased production of young and/or reciprocity are also not sufficient for this species. 4. An examination of the reproductive behavior within groups suggests that the mating system may be promiscuous. It was not possible to identify which individuals were the parents of the young, and all group members normally participated in every phase of reproduction. A promiscuous mating system means that each group member could make a genetic contribution to the young and that all would help to raise the young to protect their genetic investment. 5. Larger groups successfully fledged more young than did smaller groups, and promiscuity may be an individual strategy to insure that all individuals remain within the group and participate in reproduction.

Prey catching with and without echolocation in the Indian false vampire ( Megaderma lyra )

Abstract: 1. Under laboratory conditions echolocation sounds were recorded from four Megaderma lyra catching a mouse in complete darkness from an experimental table. Flight paths and sequences of sound emission were synchronously recorded by stroboscopic photography and high-speed tape-recording (Figs. 1 and 2). 2. During approach toward a live mouse in 54% of 35 completely recorded flights, the bat emitted ultrasounds, but only up to five sounds could be recorded during a complete approach (Fig. 1a). During the other 46% of the 35 flights, the bat did not emit a sound, yet successfully caught the prey (Fig. 1 b). 3. When a dead mouse was offered, only one bat successfully echolocated the dead mouse and emitted a specific double sound sequence of intense ultrasounds. The other three bats did not take off for an approach. When mouse noises were substituted for the live mouse, the approach flight of two of the bats was immediately triggered as if a live mouse were offered. Only a few echolocation sounds were emitted in both cases. 4. It is concluded that M. lyra can locate the noise of live prey in complete darkness, without the use of echolocation.

Intra-colony demography and reproductive rate of the Africanized honeybee in South America

Abstract: 1. Demography and growth patterns of Africanized honeybee colonies in South America are described, and the influence of worker survivorship, rate of worker production, age structure, and colony growth patterns on their reproductive rate (swarm production) is discussed. 2. During a reproductive cycle, a colony passes through four phases: pre-emergence, post-emergence, pre-swarming, and post-swarming. Growth in the worker population approximates a sigmoid curve, but swarming occurs before high growth rates peak. Colonies swarm at a small size, with sufficient workers to produce viable prime swarms and afterswarms, as well as to continue the parent colony. 3. The timing of adult worker emergence influences the number of afterswarms, as well as the number of adults maintained in the original colony when swarming is completed. 4. Patterns of survivorship for both brood and adult workers shift during swarming cycles, with high brood mortality and reduced adult longevity early in the cycle, in contrast with lower brood mortality and increased longevity of adults as colonies mature. 5. Survivorship appears to be related to the age structure of colonies, with high mortality at points in the swarming cycle at which there is a high mean worker age and a low proportion of young workers. The age structure of colonies also shifts during swarming cycles with a progressive increase in the proportion of young workers. A consequence of this shift is that swarms are populated predominantly by young workers. Patterns of survivorship and age structure influence colony growth rates, and thus partly determine the rate of swarm production.

Reproduction of the weakly electric fish Eigenmannia virescens (Rhamphichtyidae, Teleostei) in captivity

Abstract: 1. The paper describes the effect of four environmental factors, conductivity, pH, water level, and rain, on gonadal recrudescence and regression in the tropical gymnotoid fish Eigenmannia virescens. The developmental state of the gonads was either assessed quantitatively (maturity coefficient, MC) or judged by visual inspection in the transparent fish (Fig. 1). Spawning indicates that fish are mature. 2. Decreasing conductivity and pH, increasing water level, and imitation of rain (‘rainy season’) led to gonadal recrudescence (Figs. 2, 4, and 5) in fish which had entirely regressed gonads at the beginning of the experiment. Increase of conductivity and pH and missing rain, when increase in water level continued (‘dry season’), provoked gonadal regression (Figs. 2, 4, and 5). 3. When the four exogenous factors were held constant for 102 days (Fig. 6), this had no effect on ovary weight; they remained regressed. In males, an increase to full maturity after 62 days was found. 4. Eigenmannia, imported from South America, reached maturity in the laboratory, but did not spawn at all or only very irregularly, whereas fishes which were born and raised in captivity spawned very regularly when mature (Table 1), under optimal conditions every third to fourth day (Fig. 7). Females about 15-cm long spawned 100–200 eggs each time. 5. Over a period of one year, ovary recrudescence could be induced four times and regression three times with a group of three females and four males (Fig. 8). Neither Eigenmannia females nor males showed post-breeding refractoriness. Ovarian recrudescence and regression could be stopped experimentally at apparently any level; maturation was always possible afterwards (Figs. 9 d and 10 d). 6. Experiments were designed to test the significance of the four factors as ‘zeitgebers.’ Gonad maturation occurred at decreasing, increasing, variable, and at constant pH values (Fig. 9); pH apparently is not a zeitgeber. Conductivity, water level, and rain are presumably all zeitgebers which together induce ovary maturation and spawning (Fig. 10e). Decreasing conductivity alone (Fig. 10a), rain plus rising water level (Fig. 10b), decreasing conductivity plus rain (Fig. 10c), and decreasing conductivity plus rising water level (Fig. 10d) provoked ovary growth, but did not lead to mature gonads. Decreasing conductivity alone and rain plus rising water level led to mature testes, but maturation seemed to be less complete as judged from the number of spermatozoa present compaired with the result of the experiment where all three effective factors acted together (Fig. 2). 7. Decreasing conductivity was one of the exogenous factors which induced gonad maturation. The fish also reached maturity when, at decreasing conductivity, the concentration of some of the ions (carbonate and total hardness) increased (Fig. 11). 8. Regression of ovaries could be provoked by continuous increase of conductivity alone (Fig. 7). 9. Mature fish no longer required the variation of the environmental factors, which had earlier provoked gonadal recrudescence, in order to continue spawning (Fig. 12). 10. A ‘rainy season’ which was interrupted by a very short ‘dry season’ (sudden, large increase of conductivity) led to irregular spawnings (Fig. 13) for two months in fish which were previously spawning regularly.

Genetic structure of nests in the ant Formica sanguinea

Abstract: 1. Polymorphism at an enzyme locus encoding for malate dehydrogenase was studied in 92 nests of the ant Formica sanguinea, mainly in Finland. Four alleles segregated at the locus. In seven nests all workers were homozygous for a single allele. In all other nests heterozygotes were observed. Of the nests, 75% were two-genotype nests having mainly one homozygous and one heterozygous worker genotype. 2. Each single nest could be explained as the offspring of one gyne, but this interpretation does not agree with the expectations at the population level. The distribution of different nest types was compared with the results obtained by various computer-simulated reproductive strategies. The observations were best explained by several related, single-mated gynes per nest, and by one gyne possibly dominating the egg-laying. This agrees with earlier field observations and is also supported by the level of genetic relatedness among nestmates. 3. In two successive years, the average coefficients of relatedness (b±SE) among workers of a single nest in one population were 0.420±0.098 and 0.311±0.124. As the coefficient of relatedness of the female brood to the workers of the same nest was 0.378±0.173, the brood that the workers care for is less closely related to them than their own offspring would be. The relatedness of the male brood to the workers was b=0.616±0.402. Worker ants of neighbouring nests were related to one another, b=0.248±0.093, presumably due to existence of sister nests.

Habitat variation in the social organization of a communal gallinule, the pukeko, Porphyrio porphyrio melanotus

Abstract: 1. The social organization and dispersal of pukeko or swamphen, Porphyrio porphyrio melanotus, was studied in two different habitats in the Manawatu, New Zealand. 2. A non-territorial flock formed each summer in the swamp-lake habitat complex and fed in the pasture of breeding territories. Flocks had a high proportion of males and young. Most dispersed prior to the breeding season although some birds remained, set up territories, and attempted to breed. Such flocks did not form in the stream-pasture habitat complex. 3. The remaining birds in both areas held territories for at least the breeding season with the number of individuals in a territory varying from two to six. Pairs were common in the stream-pasture habitat whereas groups predominated in the other swamp-lake habitat. The number of birds in a territory related to the length of the defended boundary and its stability. Within each group, pair with young, and flock a linear hierarchy was found with status related to age, sex and prior residence. 4. Pukeko satisfy many of the criteria suggested by Brown (1974) which lead to communality. The number of birds in a group appears to relate to the costs of territorial defence which is in turn linked to habitat structure. Variations in the spatial organization are related to theories of a continuum of social organization regulating access to resources.

Behavioral ecology of alpine yellow-bellied marmots

Abstract: 1. An investigation of the behavior and ecology of several contiguous harems of yellow-bellied marmots (Marmota flaviventris) was conducted in an alpine area of North Pole Basin, Gunnison County, Colorado. At an elevation of 3,400 m, the study site differed from those of previous marmot studies in that no forest restricted interharem movement or social contact. 2. Meadow vegetation was patchily distributed and covered half the study area; clumps of willow comprised most of the remaining vegetation. Eighty-two marmot burrows within the study area (most of which were unoccupied) were randomly distributed. The 26 most frequently occupied burrows (hibernacula and summer residences) also had a random spatial distribution. 3. Two or more marmots commonly occupied the same hibernacula and summer residence burrows, resulting in a highly clumped spatial distribution of marmots. 4. Ecological densities of adult and yearling residents in North Pole Basin were usually higher than densities at East River Valley study sites in the same region (Table 9). 5. In contrast to annual reproduction commonly observed at lower elevations, no alpine female marmot was observed to produce young in consecutive years. 6. Burrowmates were generally much more closely related than nonburrowmate members of the same harem (Table 4). 7. The intensity of foraging activity varied throughout the active season, being low in May, June, and September and very high in July and August (Fig. 1). Forage ranges of individuals varied in size from 0.1 to 2.2 ha (Table 5), and were larger in the year of low food availability. The average degrees of forage range exclusivity for each level of social organization were: individuals, 10%; burrow groups, 41%; and harem groups, 88%. 8. Rates of social interactions changed throughout the active season; agonistic and sexual rates of interactions generally decreased and the amicable interaction rate generally rose between early June and late August (Fig. 6). 9. Among burrowmates, social interactions were predominantly amicable. But between nonburrowmate members of the same harem and between members of different harems, agonistic interactions predominated. 10. Yearling offspring that remained resident in their natal harem throughout the summer had predominantly amicable social interactions with their parents. Social interactions of these yearlings with nonparent adults were primarily agonistic ones in which the yearlings were subordinant. 11. Environmental parameters, population dynamics, resource utilization patterns, and social dynamics were evaluated in terms of their relationships to population density, intraspecific competition, parent—offspring relations, and male territoriality.

Conspecifics as cues: A mechanism for habitat selection in the Panamanian grass anole (Anolis auratus)

Abstract: In an experimental choice situation, individuals of both sexes of the lizard Anolis auratus choose to associate with a conspecific individual regardless of its sex. Further, individuals of both sexes associate with an individual of A. tropidogaster, a related species. Given the choice between the two species, they choose their own. Given the choice between a conspecific and a small patch of natural habitat, they do not choose one or the other consistently. These experiments indicate that conspecific association does not function just as a mate selection mechanism as has been previously proposed. The initial association may, in addition, serve a habitat selection function. Conspecifics can thus be seen as cues indicating the presence of suitable habitat as well as being important biological factors in themselves.

Foraging flocks of spiders

Abstract: 1. The prey capture efficiency of each individual in a Cyrtophora citricola colony is dependent on time (Fig. 1), total colony size (Fig. 1), and the spider's position within the colony (Fig. 2). 2. Aggressive approaches by orbless individuals within the colony appear to concentrate on the positions within the matrix of webs that have the highest capture efficiency (compare Figs. 2 and 5). 3. The incidence of avian attempts at predation and/or cleptoparasitism increases directly with colony size (Fig. 4), which indicates that the conspicuousness of the colonies is a disadvantage to the spiders. 4. Resource division is evident in the one mixed-species aggregation observed. Sticky-orb spiders (Leucauge spp.) take the same size prey as C. citricola (Fig. 3), but forage during the day when C. citricola is least active. Tangle-web spiders (Argyrodes spp.) capture prey in significantly smaller size classes than C. citricola capture (Fig. 3).

Electric and Motor Responses of the Weakly Electric Fish, Gnathonemus petersii (Mormyridae), to Play-back of Social Signals

Abstract: 1. Seven isolated G. petersii resting in their daytime hiding-places were stimulated via a dipole model (Fig. 1a) with previously tape-recorded electric organ discharge (EOD) patterns in an attempt to determine whether G. petersii distinguishes two different intraspecific EOD patterns, rest and attack. 2. Rest pattern A was characterized by a broad distribution of EOD intervals, a low mean discharge rate (8 Hz, Fig. 3), and a long period of significantly positive autocorrelation (2 s, Fig. 4a). Accordingly, the spectrum of EOD rate fluctuations showed a low frequency range (0.005 to 0.12 Hz, Fig. 5a). Attack pattern B was a considerably different EOD interval distribution of high mean discharge rate (25 Hz, Fig. 3), showing a short period of significantly positive autocorrelation (0.8 s, Fig. 4b), only. Here, the spectrum of EOD rate fluctuations was at a considerably higher frequency range (0.09 to 0.47 Hz, Fig. 5b). 3. Play-back of attack pattern B elicited significantly more bodily startle responses from the experimental fish (Fig. 6) than did the rest pattern A (Table 1). Also the number of attacks directed at the dipolemodel was significantly greater during stimulation with attack pattern B (Table 2, Fig. 6). 4. The EOD responses of the experimental fish differed in several respects depending on which stimulation pattern was used. The modes of the pulse rate histograms as well as their spans were lower during play-back of rest pattern A than during stimulation with attack pattern B (average 12.3 vs 16.2 Hz, and average 47 vs 56 Hz, respectively; Fig. 11). Shortterm (0.2 s) EOD rate correlations were stronger when the fish were stimulated with rest pattern A than when they were stimulated with attack pattern B (average correlations 0.67 and 0.61, respectively; Figs. 10 and 11). Significant positive correlations were maintained for longer periods of time during rest pattern stimulation than during attack pattern stimulation (average 1.94 and 1.24 s, respectively; Figs. 10 and 11). The spectra of EOD rate fluctuations of the stimulated fish were at lower frequency ranges during rest pattern stimulation than during attack pattern stimulation (average amplitude-spectrum peak frequencies 0.02 and 0.07 Hz, respectively; Figs. 12 and 13). 5. Although maximal cross-correlations from the EOD rates to the stimulus pulse rates were weaker during rest pattern stimulation (average 0.2) than during attack pattern stimulation (average 0.33), significant cross-correlations were maintained for longer periods of time during rest pattern stimulation than during attack pattern stimulation (average 1.78 and 0.92 s, respectively). The lags of maximal cross-correlations were greater during rest pattern stimulation than during attack pattern stimulation (average 2.6 and 0.8 s, respectively; Figs. 14 and 15). 6. The results clearly showed that at least two specific EOD time patterns encode different ‘messages’ in the intraspecific communication system of G. petersii.