Showing papers in "Behaviour in 1990"

Family planning in the kestrel (Falco tinnunculus): the ultimate control of covariation of laying date and clutch size

Abstract: The time in spring when a male kestrel rapidly increases his daily hunting time and his hunting yield, and thereby the amount of food delivered to the female, determines the date when she lays the first egg. Food experiments in free-living and captive kestrels gave a significant advance in laying date. Clutch size, which decreases with progressive laying date, did not change independent of date in response to food manipulation. These effects are in agreement with most other feeding experiments. Photoperiod experiments in kestrels advanced the reproductive cycle in constant long days, and a similar seasonal decline in clutch size was found. It seems that there is an internally preprogrammed decrease in clutch size within an annual "reproductive window". A proximate control model for the seasonal decline of clutch size is proposed, modified from an earlier model by HAFTORN (1985). This incorporates an increasing tendency to incubate the first eggs with progression of the season, an egg contact-incubation positive feedback loop, and the resorption of further follicles in the ovary when the laying female incubates 50% of the time. This follicle resorption fixes the clutch size ca. four days before the last egg is laid. the 50% incubation level is reached earlier in late females and consequently resorption starts earlier and the resulting clutch is smaller than in early females. Experiments in kestrels with removal and addition of eggs, in combination with measurements of incubation behaviour are discussed in relation to the model. Plasma prolactin data of female kestrels show that this hormone is a serious candidate for a physiological component relaying time of year in our model for clutch size regulation.

The evolution of monogamy in large primates: a new hypothesis and some crucial tests

Abstract: Monogamy among the large primates is not accompanied by high levels of male care for infants. The selective pressures that have led to its evolution in this case are far from clear. In this paper, we evaluate and test four different hypotheses. Monogamy in these species did not evolve because males are unable to defend access to more than one female. Hence, it must be related to behavioural services provided by the male which substantially increase the female's reproductive output. Existing data argue against the suggestion that these services involve protection against predators or defence of an exclusive feeding area. We propose that the male's service consists primarily in protecting the female against infanticide by other males. Tests that would differentiate this hypothesis unequivocally from other hypotheses are suggested. To the extent that these predictions can be tested with the data currently available, the evidence supports the infanticide hypothesis. We speculate that infanticide avoidance is also responsible for the near-universal occurrence among primates of male-female bonds.

Behavioural changes at adolescence in chimpanzees

Abstract: Male chimpanzees experience puberty (marked testicular growth and ejaculation) when they are about 9 years old and just over half adult weight. They reach adult weight at 14-15 years. Females start small sexual swellings at about 8 years, mate with adult males when they are about 10.5 years and have their first infants when they are about 12 years. Males reduce their constant association with their mothers when they reach puberty and associate more with adult males and cycling females. Some males form strong, long-lasting associations with particular adult males. Females remain with their mothers until first oestrus,and then associate with adult males either in their natal community or a new community during oestrus. The decline in association with the mother is more closely correlated with pubertal stage than with chronological age in both sexes. Immatures of all ages spend 3-13% of their time in social grooming, but grooming partners change during adolescence. Juveniles of both sexes groom their mothers and siblings most, but males groom individuals outside their maternal unit more than do females. Juveniles receive over 90% of their grooming from mothers and siblings. Adolescent males groom less with their mothers and more with cycling females and adult males. While early adolescent males start to be groomed by females only late adolescent males receive any grooming from adult males. Adolescent females without mothers groom little except with adult males when they are in oestrus. Social play is most frequent with individuals aged 2-9 years and individuals play most with others of their age. Time spent playing by both sexes declines markedly during adolescence. Juveniles and early adolescents of both sexes have friendly interactions with infants, but late adolescents rarely interact with infants. Males show frequent sexual behaviour with oestrous females from an early age. Males spend more time with oestrous females as they get older but frequency of copulation declines gradually through adolescence. Early adolescent males try to take females on consort, but only late adolescent males succeed. One female rejected the sexual advances of a male once he reached puberty. Rates of interference in copulations by males decline during adolescence and males become more cautious of copulating in the presence of adult males. Females show little sexual behaviour until they start getting large oestrus swellings. Males receive increased aggression from adult males during adolescence. They become tense in the presence of adult males and even late adolescents are peripheral to grooming clusters of adult males. Males start to challenge adult females in adolescence but are often attacked, and are not able to dominate them all until late adolescence. Male juveniles perform elements of charging displays without hair erection more frequently than females. The freqency of this declines in adolescence while the frequency of charging displays with hair erection by males increases in adolescence and displays become increasingly more adult-like in length and form. Males show the shoulder hunch for the first time in early adolescence. Males pant hoot more than females and rates of pant-hooting increase with age in both sexes.

Routine Formation and Flexibility in Social and Non-Social Behaviour of Aggressive and Non-Aggressive Male Mice

Abstract: To investigate the relationship between aggression and routine-like behaviour the response of male mice of bidirectionally selected lines for attack latency to a change in the social and non-social environment has been measured. In a non-social situation the extent of routine-like behaviour was measured in a Y-maze in which only one of the two arms gave access to the food compartments. The number of errors made in response to reversal of the arm that was blocked was taken as indicator for the degree of routine formation. Males of the short attack latency (SAL) line made significantly more errors, and hence were more routine-like in their performance, than mice of the long attack latency (LAL) line. Males of the LAL line that nevertheless had short attack latencies (i. e. aggressive LAL mice) turned out to be flexible in their behaviour; their response was similar to that of the non-aggressive LAL males. In a social situation SAL and aggressive LAL mice were used to investigate routine formation in attacking behaviour. The males were given different amounts of experience with male opponents after which their own female was introduced as opponent. The more extended the experience with male intruders was, the more SAL males subsequently attacked their female. In contrast, LAL mice appropriately changed their behaviour towards the female opponent. Thus, the attacking behaviour of SAL mice gets routine-like, whereas that of LAL males remains flexible. It is concluded that selection for attack latency generally coincides with selection for routine-like behaviour, suggesting that these two factors are influenced by many of the same genes. Regarding the fact that aggressive males of the LAL line show flexible behaviour, it may be proposed that with the phenotypic selection for attack latency there has in fact been selected for a mechanism that determines the organization (routine-like vs flexible) of behaviour.

Territoriality in a terrestrial salamander: the influence of resource quality and body size

Abstract: Intraspecific interference competition associated with territoriality has been documented in laboratory studies of the red-backed salamander, Plethodon cinereus. I used laboratory and field experiments to study the effect of resource quality and body size on such competition. In an experiment in southwestern Virginia, cover objects (e.g., logs) from which the resident salamanders were removed were invaded significantly more often than cover objects from which the resident salamander was not removed. These data provide the first direct test of territoriality for a salamander in a natural habitat. Newly invading salamanders were significantly smaller than the original territorial residents. Therefore, large body size is an advantage in territorial encounters. Because cover objects are important resources for terrestrial salamanders, characteristics of the cover object may contribute to territory quality. In an experiment conducted during warm summer weather at the Virginia site, soil temperatures under large cover objects were significantly cooler than those under small cover objects or under the leaf litter. Large cover objects may therefore benefit the salamanders by providing a buffer zone between the salamander and extreme environmental temperatures on the forest floor. In both laboratory and field experiments, when salamanders were offered a choice between large and small cover objects, both large and small salamanders exhibited a significant preference for large cover objects. Also I censused cover objects in a natural mixed hardwood forest habitat during courting and noncourting seasons and, for both seasons, I found a significant positive correlation between the body size of the salamander and the size of the cover object that it occupied. I conclude that, in this natural forest habitat, there is intraspecific competition for high quality cover objects and larger individuals are more successful competitors than smaller individuals.

Reproductive Tactics of Male Savanna Baboons

Abstract: The strongly related parameters rank, age and period-of-residence determine which reproductive tactics a savanna baboon male will use primarily. Baboon males go through the following phases with respect to the use of mating tactics, as they are longer in the group and thus grow older and, as a rule, drop in rank: Phase 1. Peripheral, relatively little social contact, low mating success, building up of a social bond with a few females. Phase 2. High mating success, based on individual fighting ability, social bonds mainly with females that are, or will soon be, sexually attractive. Phase 3, variant a. (Males that were very successful in Phase 2). Considerable time devoted to guarding infants conceived in phase 2 and to the mothers of those infants. Mating activity drops sharply compared to Phase 2. Phase 3, variant b. (Males that did not go through a very successful Phase 2). Low mating success through whatever tactic, relatively peripheral. Phase 4. Relatively high mating success, partly through collaboration with other males. Considerable time is invested in the care for potential offspring and their mothers. Phase 5. Diminishing share in the total mating activity in the group. The support for infants is spread over a relatively large class of infants conceived after immigration. Social contact with a large number of females. The data did not show the relation between agonistic rank and mating success predicted by ALTMANN'S priority-of-access model. A modification of the model is presented, which allows for coalition formation among males that are too low in rank to be successful on their own. This model could not fully explain, however, the exceptional success of some middle ranking males. The theory of Coalition games can give insight in the processes that lead to distributions of mating success that depart from the modified priority-of-acces model. The lack of agreement between the data and the original priority-of-access model cannot be explained by higher selectivity of the high ranking males. The only qualitative parameter of consorts obtained, according to which high ranking males had an advantage, is the time of the day on which mating activity takes place. This is a direct result of the way in which males obtain their consorts. Consorts are often formed in the sleeping trees during the night or in the early morning. In that situation single, strong males have an advantage in conflicts against coalitions of lower ranking males. Lower ranking males have a relative advantage later in the day, when conflicts are fought out on the ground.

Risk Sensitive Courtship in the Guppy (Poecilia Reticulata)

Abstract: This study investigated population differences in the courtship behaviour of male guppies, Poecilia reticulata, in the presence and absence of predators. Two Trinidad populations were compared: the Lower Aripo where guppies occur sympatrically with a range of piscivores and the Upper Aripo where levels of fish predation are low. Upper Aripo males displayed risk-reckless courtship behaviour and did not reduce their sigmoid display rate or otherwise modify their courtship behaviour when threatened by two Astyanax bimaculatus. The courtship behaviour of the Lower Aripo males was, by contrast, risk sensitive. These fish performed a lower proportion of sigmoid displays and increased their level of sneaky mating attempts in the presence of predators. Although males from the two populations used both sneaky and conventional courtship behaviours there were individual differences in the use of the reproductive tactics.

Adaptive Superparasitism and Patch Time Allocation in Solitary Parasitoids: the Influence of the Number of Parasitoids Depleting a Patch

Abstract: An ESS model that predicts more superparasitism and longer patch times with an increasing number of searching parasitoids in a patch, was tested in experiments with Leptopilina heterotoma, a solitary larval parasitoid of Drosophila. The observed egg distributions and patch times were in quantitative agreement with the predictions of the model; oviposition and patch time decisions are clearly influenced by the number of conspecifics in the patch. Both in the model and in the experiment patch quality was kept constant (the number of hosts and the patch area per parasitoid were kept constant). The model predicted and the experiments showed that parasitoids gain less offspring per unit of time when searching a patch together: superparasitism leads to mutual interference. No self-superparasitism should have occurred when parasitoids searched alone. This prediction was only met with females that had been kept in isolation in the days before the experiment; when stored in groups of four, self-superparasitism did occur. This indicates an ability of the parasitoids to assess the probability of future superparasitism by conspecifics.

An Experimental Comparison of Male and Female Spawning Territoriality in a Pacific Salmon

Abstract: The spawning territoriality of male and female non-anadromous sockeye salmon, Oncorhynchus nerka, was examined experimentally by comparing the resources sought after, the behaviours used in intrasexual competition, and the correlates of success in intrasexual competition for each sex. Females expressed territorial behaviour both in the presence and absence of males, defending specific, repeatedly selected, spawning sites. In contrast, males exhibited clear territorial behaviour only in the presence of females, defending access to specific females and positions over time. Size was a factor in determining which females established territories within preferred areas, but this advantage was largely negated by prior residency. Size was a major factor in determining which males gained closest access to individual females, with smaller males adopting subordinate, sneak, positions. Prior residence was also a significant factor in determining the outcome of contests for access to females, with the weight of this factor dependent on the relative sizes of competing males. The behavioural differences between sexes appear to arise from differences both in the resources defended and the relative costs of potential losses for each sex.

The Behavioral Ecology of Maternal Effort in Fur Seals and Sea Lions

Abstract: Otariid seals form a group of similar species distributed from subpolar to tropical seas. Many species were recently studied under conditions of low and high food abundance during major oceanographic disturbances. Evidence for the phenotypic flexibility of and constraints on the rearing strategy of these species derives from inter- and intra-specific comparisons and experimental measurements. I review how changes in food abundance influence foraging behavior and energetics of mothers, pup growth rates, milk composition, weaning age, and the fertility cost of pup rearing. Eared seal females rear young by alternating between lactation ashore and foraging at sea. Subpolar fur seals always wean pups at four month of age, a trait which seems to be genetically fixed and adaptive in their highly seasonal environment. Temperate and tropical fur seals and sea lions can respond to changes in food abundnace by increasing or decreasing time to weaning. During pup rearing, mothers regulate body mass to different absolute values when abundance of food resources changes. This seems to be a constraint caused by reduced foraging efficiency at low food availability. Most species feed exclusively during the night, but sea lions (Zalophus californianus) and Northern fur seals (Callorhinus ursinus) also forage during the day by diving deeper. Females of some species increase the rate of at-sea energy expenditure at low food abundance while keeping the duration of foraging trips constant. Females of other species stay at sea longer working at the same rate. The latter species may be food specialist with a narrower time window for efficient foraging. Pups grow slower when mothers increase time at sea, and at very low food abundance pups may starve. Pups have little influence on the duration of maternal foraging trips, but may diminish the mothers' time ashore by increasing the rate of milk extraction and prolonged non-nutritive sucking. The impact of long maternal at-sea times is reduced by increasing milk fat content as time at sea increases. This mechanism does not fully compensate pup energy intake rate for longer trip durations. Non-migratory species can partly compensate for reduced pup growth rates by lengthening the lactation period. In the Galapagos fur seal (A. galapagoensis), this entails a considerable cost to the mother by reducing her future fertility. Lactation reduces the probability of a successful simultaneous pregnancy and, if pregnancy succeeds, sibling competition for maternal milk ensues. Competition is usually won by the older sibling leading in many cases to the death of the newborn. The rate of energy transfer to pups is high in food-rich years and low in scarce ones. Because pups are more likely to be weaned as yearlings when juvenile growth rate is high than when it is low, high energy transfer to the pup in year "a" reduces the cost of reproduction incurred in year "a+1". The flexibility of the rearing strategy of temperate and tropical species permits mothers to adjust phenotypically to variance in food availability thus partly masking the theoretically expected trade-offs in the life history of these species.

Comparative Fine Structure of Action: Rules of Form and Sequence in the Grooming Patterns of Six Rodent Species

Abstract: The phylogenetic constancy of a set of syntactic patterning rules for grooming was examined in six rodent species: guinea pig, Belding's ground squirrel, gerbil, hamster, rat, mouse. Species were chosen to allow comparisons of separate suborders of Rodentia (Hystricomorpha, Sciuromorpha, Myomorpha) and of separate families within suborders (Cricetidae and Muridae). Each species was examined for possession of the syntactic patterns of chaining, transition reciprocity, sequential stereotypy, and hierarchical clustering. These syntactic patterns were detected and quantified using videoanalysis, graphic notation, and a variety of computer-assisted action coding and analysis techniques. Each syntactic pattern or sequencing rule mentioned above was found to obtain in all six of the species tested. The wide applicability of these rules suggests that they reflect a fundamental feature of neurobehavioral organization, which was established relatively early in rodent evolution. Syntactic organization appears to be a basic property of action production by mammalian brains. The techniques used in this study also allowed a quantitative comparison to be made across species of syntactic pattern strength, form, stereotypy, and timing parameters. This comparison showed that many differences in behavioral patterns among species could be explained by one of two principles. The first explanatory principle was phylogenetic relationship: the behavioral traits of species from within a single family tended to be more similar than were traits of species from separate families, and species from a single suborder tended to be more similar than species from separate suborders. The second principle, which applied especially to temporal parameters, was programmed allometric control by physical size. The timing of patterns (for example, the cycle duration of certain highly stereotyped forepaw strokes performed on the face) was related to the average size of the species by an allometric power function. The nature of these syntactic patterns and of the rules that generate them, the nature of their neural substrates, and the origin of parameters differences between species, is discussed.

Mating behavior of horseshoe crabs, limulus polyphemus

Abstract: Horseshoe crabs have an explosive breeding system not unlike that of some frogs and toads. They synchronize nesting to only a few hours each day at the time of the spring new and full-moon high tides. Males search for females as they come to the breeding beaches, grasp them with specially modified claws and cling to them, sometimes for weeks. Females lay several clutches of eggs in the sand and the male fertilizes them externally, the only extant arthropod with such a reproductive system. Unattached males cluster around the nesting couple, pushing on and occasionally displacing attached males. An experimental manipulation demonstrated that satellite males are capable of fertilizing eggs which suggests that sperm competition is the primary explanation for the presence of unattached males on the beach. Like other explosively breeding species, male Limulus search for females, often grabbing inappropriate objects, and satellite males compete for access to females. There is little assortative mating and attached and unattached males do not differ in size. In extreme explosively breeding species like Limulus, selection favors those males that are best able to locate and remain attached to females, and there is little opportunity for female choice or male-male competition.

Family Planning in the Great Tit (Parus Major): Optimal Clutch Size as Integration of Parent and Offspring Fitness

Abstract: Fitness variations due to natural variation in the size of the first clutch and its laying date were estimated using Fisher's reproductive value for both the clutch (Vc) and the parent (Vp) in a population of great tits. In order to test the hypothesis that individual birds maximize their reproductive value by the choice of clutch size, artificial variation in brood size was introduced and the consequences in terms of reproductive value estimated. Maximal Vc, computed on the basis of natural variation in clutch size, occurred at a clutch size of 15.2, and increased slightly with laying date. Vp increased with natural variation in clutch size and decreased with date. The total reproductive value V (= Vc+Vp) was maximal at a clutch size of 15.4, substantially higher than the population mean clutch size (9.2). The components of the reproductive value of the clutch (Vc) that were negatively affected by manipulation were the survival of the nestlings and the recruitment rate. The reproductive value of the parent (Vp) was negatively affected only through the probability of having a second clutch. Maximal Vc computed on basis of artificial variation in clutch size, occurred at a clutch size of 10.0, and also increased with date. Vp decreased with artificial variation in clutch size causing the clutch size maximising reproductive value V to shift to a value of 9.4, very close to the population mean clutch size (9.2). It is concluded that the majority of great tits produces the number of eggs (9-10) that maximizes their individual fitness, even though those individual birds laying 15 eggs have the highest reproductive value in the population. The fact that birds laying very large clutches have the highest reproductive value points in the direction of a selection pressure towards larger clutches. Yet, over the last 30 years clutch sizes have not increased in the study population. This apparent contradiction is discussed. Either no genetic variation in clutch size is involved, or a complex polymorphism exists.

Matrilineal signatures in the recruitment screams of pigtail macaques, Macaca nemestrina

Abstract: In macaques and baboons, scream vocalizations play a major role in the recruitment of allies against agonistic opponents. Pigtail macaques make use of 4 acoustically distinct scream types, with each associated with a particular agonistic context (defined in terms of the opponent's relative dominance rank and the intensity of the aggression). Information about caller identity must also be encoded in recruitment screams if spatially distant allies are to make decisions about intervention. In this study, the agonistic screams of pigtail macaques were analyzed for evidence of vocal signatures that may serve to identify matrilineal kin groups. Maternal genealogical relationships were known for all individuals in the 56 member study group. Direct discriminant analysis was used to classify calls of individuals on the basis of their acoustic structure to one of 3 groups defined by matrilineal relatedness (two homogeneous groups, or matrilines, and one heterogeneous control group). Two scream types associated with higher-ranking opponents were analyzed separately: contact aggression screams and noncontact screams. A highly significant proportion of calls was classified to the correct matrilineal group for both scream classes. The acoustic basis for matrilineal vocal signatures in these calls apparently exists. Efficient vocal communication may require monkeys to classify group members at different levels, depending upon the degree of specificity needed.

Determinants of Male Mating Success in the Temperate Crayfish Orconectes Rusticus: Chela Size and Sperm Competition

Abstract: The large chelipeds of male Orconectes rusticus have an adaptive function related to inter-male competition for mates. Large clawed males dominate over smaller clawed, but otherwise physically similar, competitors. Additionally, males with large chela are better able to secure, and more quickly orient, females into the copulatory position. Large clawed males also copulate for longer periods than smaller clawed competitors. The significance of copulation duration is unclear, but is likely related to mate guarding. Sexual selection for increased cheliped size in 0. rusticus has been more intense on males than females. Sperm of the second male to inseminate a dually mated female takes precedence over that of the previous male. The paternity attributable to the second male was determined as approximately 92 % .

The development of a behavior system: dustbathing in the burmese red junglefowl i. the influence of the rearing environment on the organization of dustbathing

Abstract: The purpose of this study was to determine the role played by functional experience in the development of the dustbathing behavior system in junglefowl. Small groups of birds were raised either in a rich environment with sand and earth, or in a poor environment with a wire mesh floor. Dustbathing and other behaviors were recorded at intervals between 2 and 9 months of age. The results showed that the form of the individual behavior patterns as well as the organization of extended bouts of dustbathing developed normally in chicks raised in a dustless environment. Further, the frequency of occurrence of dustbathing and the diurnal rhythm did not differ between groups raised in the two environments. Functional experience was necessary for the development of dust recognition, but some stimuli came to be recognized as "dust" more easily than others.

Variation in the Mating System and Associated Parental Behaviour of Captive and Free-Living Cichlasoma Nigrofasciatum (Pisces, Cichlidae)

Abstract: C. nigrofasciatum typically breed in monogamous pairs with biparental care of the young for up to 6 weeks. In experimental ponds in southern Canada and streams in north-western Costa Rica two variations on this system were studied: male desertion followed by maternal care, and simultaneous bigamy by males. In the ponds, with a female-biased sex ratio, males deserted or became bigamous when their broods were at all stages from eggs to advanced, free-swimming fry. These departures from monogamy did not consistently influence brood survival, except that broods deserted by their father shortly after spawning did not survive, whereas those deserted when they were at least one week into the fry stage survived to independence with only their mother as guardian. Both in the ponds and at the field sites females with monogamous partners spent more time away from their broods than did deserted females, but only in the ponds did this correspond with reduced feeding by the deserted females. In nature all parental females foraged less often than did non-parental females, and this reduction was not strongly influenced by mate desertion. Brood defense behaviour by adults in monogamous pairs provided some evidence of division of parental labour. In the ponds guarding females attacked sub-adult juveniles more than males did, whereas in the field guarding females attacked non-cichlid fishes (mainly characins and poeciliids) and conspecific females and juveniles more than males did. Both in the ponds and the field guarding males attacked conspecific adult males more than females did. Most deserted, brood-guarding females seen in Costa Rican streams had young that were relatively large, mobile fry, approaching independence. This may reflect the need for both parents to guard their young during the first few days of free-swimming. They are probably highly vulnerable to predators at this stage and paternal desertion may be more costly than later, when they are stronger swimmers and better able to escape from predators.

Copying the Mate Choice of Others? Observations On Female Black Grouse

Abstract: It has been suggested that the non-random mating often observed in lekking species is a consequence of either male-male competition or active female mate choice. Here we show that the highly skewed mating distributions observed in a black grouse lek in three years were indeed different from random expectations. We suggest that females copying the mate choice of others enhance this skew. Observations in favour of copying are: females pay multiple visits to the lek during several days; females arrive and move in bands which makes it possible to observe the visits to male territories and matings of other females; in the main lek in the study area, males often mated in sequence indicating that by being visited by many females and by mating the attractiveness of males increased. However, this last effect was only evident in one of the years of the study, and only on the largest lek which had exceptionally many female visits this year. In leks with a smaller number of visiting females, copying, even if present, is difficult to detect without experiments since almost all females tend to copulate with the top-male.

Parasites And Male Ornaments In Free-Ranging And Captive Red Jungle Fowl

Abstract: The morphology and parasite burdens of culled free-ranging red jungle fowl (Gallus gallus) from the San Diego Zoo were compared with those of captive roosters used previously in sexual selection experiments, to determine if results obtained with the captive birds were relevant to more natural situations. Zoo roosters had three helminth gut parasites: Ascaridia galli, tapeworms, and Heterakis. Parasite distribution was generally over-dispersed, with most individuals having none or few worms and some having heavy parasite burdens. These levels were comparable to those artificially induced in test roosters. The appearance of the zoo birds was similar to test roosters as well. Higher parasite burdens in the zoo birds was negatively related to hackle feather redness, comb length, and especially testis volume. The latter finding is discussed in light of information about the relationship between testosterone levels, sexual selection, and the immune system. A new analysis of female choice of uninfected controls versus experimentally infected roosters suggests that females prefer a multivariate array of traits perceived as a continuous, rather than categorical, variable.

Estimating the Frequency of Constrained Sex Allocation in Field Populations of Hymenoptera

Abstract: 1) Sex ratio theory has assumed that females can produce offspring of both sexes. It has been suggested that some females in haplodiploid populations are only able to produce sons (constrained sex allocation), for example because they are virgin. The presence of such females influences the optimal sex ratio of unconstrained females. The relevance of these ideas to field sex ratios is largely untested. 2) The frequencies of constrained oviposition in three Drosophila parasitoid species are estimated. Constrained, ovipositing females were distinguished by the absence of sperm in the spermatheca. Constrained females were absent or rare in these species. 3) We review data from the literature that allow an estimate of the frequency of constrained females. 4) We conclude that the available evidence suggests that while constrained oviposition is uncommon, there are some species in which constrained females are sufficiently common to select for an observable sex ratio bias by unconstrained females.

Co-Operative Breeding in Riflemen (Acanthissitta Chloris) Benefits To Parents, Offspring and Helpers

Abstract: Two types of helpers were observed feeding young of the New Zealand rifleman (Acanthisitta chloris): "regulars" and "casuals". The former contributed significantly to feeding young from only one nest while the latter contributed a trivial amount to young from a number of nests. Regulars were usually unpaired adult males some of which acquired a mate from the brood they helped. While some casuals were unpaired adult males, most were current season offspring helping with their parents' second clutch. The relative contributions of parents and helpers in raising broods were measured to establish the benefits of co-operative breeding to offspring and feeders. Whether or not helpers were present while feeding young, the breeding female's contribution was the same. By contrast, the work load of the breeding male was significantly reduced when helpers were present, but even then he usually contributed more than this mate. That male parents benefited most from helpers feeding young was probably related to their being responsible for most of the feeding in the absence of helpers. A helper's presence did not improve productivity or the male parent's chance of survival. However, female parents of nests with regular helpers survived better than those without. Offspring fed by helpers were not heavier upon fledging nor were their chances of survival improved. The interval between fledging first clutch broods and laying second clutches was the same whether helpers were present or not.

Instability of harems of feral horses in relation to season and presence of subordinate stallions

Abstract: Male horses (Equus caballus) defend harems of females (bands) year-round and throughout their lifetimes. A male's lifetime reproductive success depends upon the number of females in his harem. Although harems have previously been reported as remaining stable over many years, during the two years of this study 30 % of the adult females in an island population of feral horses changed harems during late winter. The seasonal differences in harem stability resulted from seasonal differences in the abundance and distribution of food. The spacing between band members was greater and the frequency of social interactions between them was lower in winter than in summer. In addition, the amount of time devoted to grazing increased in winter. These differences are attributed to the lower availability of suitable vegetation duirng winter. Harem stability did not depend on the age of females, the size of the harem, nor the age of the harem stallion, but did depend on the presence of subordinate stallions attached to the band. All of the females that changed bands left single-male bands; multi-male bands were stable throughout the study.

Social Tension in Familiar and Unfamiliar Pairs of Long-Tailed Macaques

Abstract: The behavioural responses of monkeys to the pairing with familiar and unfamiliar individuals were analysed in order to test whether differences in social tension were related to different patterns of affiliation. Social tension was derived from the frequency of displacement activities. Ten familiar pairs (the F group) and 20 unfamiliar pairs (the UF group) of adult female long-tailed macaques (Macaca fascicularis) were observed in a two-hour test. The UF group was divided into two subgroups on the basis of the establishment of clearcut dominance relations within the pairs (as revealed by bared-teeth displays). Unfamiliar pairs showing clearcut dominance relations (the UFa subgroup) did not differ from the F group in terms of grooming exchanged and displacement activities. Unfamiliar pairs without clearcut dominance relations (the UFb subgroup) showed less grooming and more displacement activities. A delay in the onset of allogrooming due to unresolved dominance relations was responsible for the differences in social tension between the different monkey pairs. The results of this study suggest that unfamiliarity between the monkeys is not a good predictor of social tension if the patterns of behavioural interactions between the individuals are not taken into account.

Greeting Behaviour in Male Baboons, I: Communication, Reciprocity and Symmetry

Abstract: Matrilineal structures are typical of many species of Old World monkeys including the savanna baboon. Both isosexual dyads of females and heterosexual dyads frequently reach the stage of greatest social compatibility, i.e. grooming. Male dyads, in contrast, very rarely reach such stage, they show instead marked mutual intolerance and overt aggressive competition. Grooming and other forms of physical contact are fairly frequent between adult males in the patrilineal society of chimpanzees. In the hamadryas baboon, also with patrilineal organization, adult males do not groom with each other but they frequently exchange greeting interactions, particularly in contexts of excitement provoked by social tension. Species-specific differences (savanna versus desert baboons) in the morphology of greeting interactions have also been reported. The objective of this study was to examine the nature and function of this category of non-agonistic interactions recorded over a period of 9 years between 20 males members of a well-established colony of baboons, Papio hamadryas, P. cynocephaus and their hybrids, housed in a large, open enclosure in the Madrid Zoo. Greetings were conceptualized as interactions, i.e. in which each participant's action is examined in relation to that of the other interacting partner. A description and qualitative analysis were provided of the morphology (i.e. facial, vocal, manipulatory and contact, postural and orientation, and locomotory patterns) and properties (i.e. reciprocity/non-reciprocity, and symmetry/asymmetry) of greeting interactions. The most significant feature of greeting interactions was the three-stage pattern of performance observed, corresponding with the phases of approximation, proximity, and retreat. In each phase, characteristic behavioural patterns were displayed, some were quite stereotyped but others seemed to be rather influenced by the identity of, and social relationship of, the interacting males, and also by the immediate social context of the interaction. A quantitative analysis of 1583 greeting interactions and 1039 aggressive episodes between the 20 study males was then carried out. Individual males were assigned to one of the following classes of reproductive status: subadult (SA), follower (FW), new leader (NL), prime leader (PL), old leader (OL), and old follower (OFW). It was found a correlation between a male's status class and the frequency with which he played several different roles in greeting and aggressive interactions. Greeting interactions were typical of mature males (FWs, NLs, PLs, OLs, and OFWs), but very especially of reproductive males (NLs, PLs, and OLs). Their rate of participation (both as initiator and recipient) was positively related both to the size of their harem (e.g. prime leaders) and to the potentiality to increase the harem size by taking over new females (e.g. prime and new leaders). Males at its prime reproductive period (i.e. PLs) showed the highest rates of involvement in symmetrical greetings, and the males who were reaching that stage (i.e. NLs) were the ones who most frequently refused to reciprocate a greeting approach. As males approached the stages of higher reproductive potential their rates of symmetrical, i.e. non-contact and notifying, greetings increased. In contrast, the contact patterns observed during asymmetrical greetings were mostly displayed in interactions in which at least one of the participants was either an immature or a young nonreproductive (i.e. follower) male. Reproductive males, i.e. prime and new leaders, were the most frequent initiators and recipients of both greeting and aggression. Examination of the morphology of greeting interactions, particularly of the symmetrical and unreciprocated greetings, i.e. the approach/retreat non-contact pattern, that were typical of prime and new leader males, and of the contexts in which both aggression and many greeting episodes took place, i.e. agonistic conflicts and competition over resources, suggested that these two categories of behaviour might share some causal factors and that they might be regarded as two alternative strategies to deal with a similar problem, namely, the resolution of conflicts. In many cases, greeting may be regarded as a quasi-aggressive behaviour aimed at testing a potential or actual rival's tendencies in a competition situation rather than as a category of affiliative or friendly behaviour. Greeting in baboons is a nice example of a non-stereotyped behaviour in a higher animal, in which relational and interactional properties can be studied, and in which, as discussed in the paper, all the traditional ethological issues of causation, development, function, and evolution can be addressed.

The Calls of the Red Squirrel: a Contextual Analysis of Function

Abstract: I examined the context of occurrence of five calls used by adult red squirrels (Tamiasciurus hudsonicus) in the field, in an attempt to 1) determine whether rattles and screeches function as threat displays in the context of territorial defence; and 2) identify the possible function of those calls not involved in territorial defence. Focal squirrels were much more likely to approach aggressively, attack, or chase their opponents, and the latter much more likely to retreat, after the focal squirrels had screeched than when they did not screech. I interpret the screech as a threat call that honestly signals a territory owner's intention to chase out an intruder. The rattle, which SMITH (1978) considered to function in territorial defence, was not associated with aggression from the caller when used independently of the screech. It was significantly associated with courting approaches by males towards females during the mating season. In addition, the rattle occurred in association with screeches more often than expected, and the screech almost never occurred without rattles, suggesting that the functions of the two calls are linked. I discuss the evidence that the rattle is a self-advertisement signal, or "signature". On the other hand, squirrels were less likely to be aggressive when they rattled and screeched if they also barked than if they did not; and recipients were concomitantly less likely to retreat, but not more likely to show aggression. I suggest that callers emitted barks after rattles and screeches in response to the other squirrel's not leaving after being threatened, rather than to signal a lower probability of aggression. Barks not accompanied by rattles or screeches had no predictable effect on either the caller's or the recipient's subsequent behaviour. I tentatively interpret the call as a signal emitted in motivational conflict situations, to elicit a change in the recipient's behaviour that would help the caller decide what to do next (HINDE, 1981). The growl was a defensive threat call that accompanied close-range aggression by the caller, but that was not followed by the immediate retreat of the opponent. Finally, the buzz was associated with non-aggressive approaches by the caller. I discuss the function of the screech in the light of the theory of animal conflicts, and suggest that it may convey information contingent upon the recipient's response (WILEY, 1983), rather than unconditional information.

Optimistic and pessimistic fruit flies: evaluating fitness consequences of estimation errors.

Abstract: I began with an observation that there exists consistent variation among fruit-parasitic female flies (Rhagoletis pomonella) with regard to search time allocation. In essence, populations appear to be composed of flies that are "optimistic" and "pessimistic" about their chances of locating other higher quality patches. I posed the question "how can such variation be maintaned over time?". To answer this question I developed stochastic, dynamic, state-variable model that considered patch emigration decisions by individuals as a function of: (1) current patch quality, (2) average patch quality, (3) density of patches, (4) time of day, and, (5) egg load. The model was then altered to allow for optimistic and pessimistic estimates of patch availability. The optimal behaviour for such flies was then solved. Results obtained showed that optimists move more often within trees and pessimists move more frequently among trees. Further, calculation of daily reproductive output showed that both optimists and pessimists performed nearly as well as flies with errorless estimates of patch availability so long as over and under-estimates were moderate. This is because of the interaction between egg limitation, host availability and time limitation. When patch estimate errors were large (e.g. 90%), however, pessimists performed less well than optimists. These results allowed me to derive fitness curves for optimists and pessimists. These curves were then used to predict the distribution of search allocation by flies in the field. Predictions as to the shape of the distribution were consistent with field data (i.e. optimists are over-represented in samples).

Interventions in a Herd of Semi-Captive Plains Zebras

Abstract: In a herd of semi-captive plains zebras interventions, which occurred within the harems, were investigated in order to answer the question why zebras interfered. These interventions are of interest because they regulate the contacts between companions and because, as corrective and preventive measures, they reveal the normative principles underlying the behaviours by which animals structure their social environment. An attempt was made to deduce 1) the internal norms of the interferer; 2) his short term aims; 3) his tactis and 4) his perception of the social environment. The analysis revealed that in the case of an affiliative interaction foals, yearlings and adult mares started to interfere if a friend had an affiliative contact with another zebra. In view of the interferer's behaviours it was concluded that their aim was to break off the ongoing interaction and that zebras tended to protect friendship bonds. Foals and yearlings further interfered if their mother was being threatened, attacked or sexually approached by a stallion. In view of the interferer's behaviours its aim was to prevent iminent interactions or to break off ongoing interactions. This suggests that these interventions were of a protective nature. The interferer's behaviours in both contexts ware very much alike. Mares tended to interfere if their foal/yearling or adult daughter was threathened or aggressed or if a mare friend was being sexually approached by a stallion. This type of intervention was of a protective nature. Stallions in a multi male harem showed a high tendency to interfere in courtship interactions. From the resemblance between interventions in courtship and in aggressive interactions it is concluded that, at leat in a number of cases, the individuals have perceived courtship behaviour by the stallion as a threat towards the mare involved.

Avoidance of Male Giant Water Striders By Females

Abstract: Shifts in behaviour and microhabitat preference were exhibited by female giant water striders (G. remigis) when males were experimentally introduced into and removed from wading pools containing females. In the presence of males, females became significantly less active, interacted with one another less, spent less time in open water, and spent more time out of the water away from females. Furthermore, they resumed their original behaviours once males were removed. It is potentially advantageous for females to avoid male harassment due to costs associated with such interactions.

Ontogeny of Fish Capture and Ingestion in Four Species of Garter Snakes (Thamnophis)

Abstract: The feeding behaviour of four species of garter snakes (Thamnophis butleri, T melanogaster, T. radix, and T sirtalis) was observed in an attempt to determine differences across species and among age groups with respect to capturing, handling and swallowing large and small fish. Although belonging to the same genus, the four species differ widely in habitat and prey preferences (T. butieri being recognized as an earthworm specialist, T melanogaster as an aquatic specialist, and the other two species as generalists). Overall, feeding patterns were quite similar across species following a general sequence of capturing fish, maneuvering the jaws to either the head or tail of the fish (the head being "chosen" more often), and swallowing it. Head-first ingestion was related to prey size: the larger the fish the greater the probability the snake would ingest it head first. When this behaviour was analysed more closely, species and age differences emerged. Adults were more efficient at capturing and ingesting fish head-first and took less time to handle and swallow their prey than did juveniles. This difference was not as marked in the two specialist species as in the two generalist species. Considering differences within species and age classes with respect to their handling behaviour of either a large or a small fish, T melanogaster handled both sizes of prey in a time period that was not significantly different, T. butleri took significantly more time to handle a large fish whereas T radix and T. sirtalis took considerably more time to handle a large fish as newborns but not as adults. These results support field observations that T. melanogaster is an aquatic specialist, T. butleri, an earthworm specialist, and the other two species, generalists. In spite of the similarities between the two generalist species, similarities were also found between T. butleri and T. radix which are believed to the taxonomically related.