Showing papers in "Ethology Ecology & Evolution in 1991"

Queen number, mode of colony founding, and queen reproductive success in ants (Hymenoptera Formicidae)

Abstract: In ants, there are two main strategies of colony founding: young queens can start colonies without the help of workers (independent mode), or young queens need the help of workers (dependent mode). Independent founding is generally assumed to be the common manner of colony founding in ants, whereas dependent founding is thought to be a derived character typical of polygyne (i.e., several queens per colony) species with unicolonial nests. A comparative study of 24 European ant species showed that dependent colony founding is not restricted to unicolonial polygyne species but that a significant proportion of all polygyne species utilize this mode of reproduction. Twelve (92%) of 13 monogyne (i.e., a single queen per colony) species were independent founding species, and only one (8%) employed budding. In contrast, only three (27%) of the 11 polygyne species always used independent founding, two (18%) were either independent or dependent founding species, five (45%) of them employed only budding and one (9%)...

Predator avoidance and antipredator mechanisms : distinct pathways to survival

Abstract: Prey may respond evolutionarily to predator pressure either by removing themselves from the foraging microhabitat of the predators (predator avoidance mechanisms) or by reducing the probability of successful predation when they are within the perceptual field of the predators (antipredator mechanisms). These two categories of survival mechanisms are under different selective regimes and the evolution of one type of prey survival mechanism reduces selection on the other.

Individual recognition of male Tawny owls (Strix aluco) using spectrograms of their territorial calls

Abstract: Faced with the problem of mapping accurately the Tawny owl's territories, we used spectrographic analyses of the recorded territorial calls to distinguish the different individual males. From November 1986 to August 1988 we collected about 2000 hootings from different Tawny owls. The visual analysis of the spectrograms revealed a high degree of inter-individual variation and a certain amount of intra-individual variation in the song, so that we have submitted a sample of 140 calls of 17 identified individuals to univariate and multivariate analyses, in order to reach objective conclusions. Seven temporal parameters of the song were selected and measured. The coefficient of variation for each parameter and the test of homogeneity of variances between two series of calls of the same owl showed a stability over time of the selected parameters. On the other hand, the ANOVA test indicated that all the parameters of song varied significantly within the population and discriminant analysis provided a correct cla...

Interspecific interference competition in three European raptor species

Abstract: (1) These analyses were based on 366 territory-years in Common Buzzards, 134 territory-years in Goshawks and 105 territory-years in Honey Buzzards. All sets of data which could have been biased by factors other than interference competition were previously omitted. (2) Common Buzzards and Goshawks defended territories against con- and interspecifics throughout the year in the study area. The migratory Honey Buzzards also defended their territories during the breeding season. Goshawks took over several nesting territories of Common Buzzards, and have also taken young of Honey and Common Buzzards. After Goshawks settled in territories of Common Buzzards, the Buzzard pairs disappeared from these areas. This seemed to be the most important evidence for competition for territories between species and had effects on local Buzzard density. (3) Interspecific spacing of all three species was highly regular, indicating a competition for space. Spacing between conspecifics was also regular. (4) Due to interference b...

Ultrastructural organization of the exocrine glands in ants

Abstract: Ants, and social insects in general, are characterized by their very well developed exocrine system. According to their cellular arrangement, the numerous glands either belong to the epithelial type, or are composed of bicellular units, each comprising a secretory cell and a duct cell. The ultrastructural organization with regard to the uptake, biosynthesis and discharge of the secretory products is very similar in both types, and generally involves surface increasing foldings of the plasmalemma. The cuticle, that forms part of each glandular cell, is mostly provided with pore canals. Pheromone producing glands are characterized by numerous mitochondria, a well developed Golgi apparatus and an extensive smooth endoplasmic reticulum in their secretory cells. The often abundant multilamellar inclusions may correspond with secretory material. Glands producing venomous substances or performing digestive functions, on the other hand, are characterized by their well developed granular endoplasmic reticulum.

Filial cannibalism in sticklebacks: a reproductive management strategy?

Abstract: We studied filial cannibalism (cannibalism of kin) in male threespine (Gasterosteus aculeatus) and black-spotted sticklebacks (G. wheatlandi). G. aculeatus were studied in the laboratory by establishing a population of males defending eggs of different ages. Males of both species were also collected in the field throughout the breeding seasons of 1988 and 1989. To distinguish filial cannibalism from heterocannibalism, we compared territorial males tending eggs to those without eggs. Parental males should be more cannibalistic than non-parental males if filial cannibalism is important. Filial cannibalism was relatively common in laboratory breeding G. aculeatus and in field-breeding G. aculeatus and G. wheatlandi. We also examined the possible adaptive significance of filial cannibalism by testing ROHWER'S (1978) hypothesis that males consume some of their eggs to remain in good physical condition for subsequent breeding cycles. Surprisingly, filial cannibalism by male G. aculeatus was unrelated to food ra...

Activity patterns of Emys orbicularis L. (Chelonia emydidae) in central Italy

Abstract: A total of 102 specimens of Emys orbicularis were collected, marked and repeatedly located in a study area in southern Tuscany (Italy) during 3 consecutive years. Most of turtles inhabit a canal where they remain throughout the whole activity season (March to October) and where they overwinter as well. A few movements occurred to and from nearby temporary pools. In both sexes activity peaks in May and at the end of September. Males intensively use longer segments of the canal than females. Home ranges show inter-individual overlapping but fighting between males is frequent. Spatial distribution seems to be affected by aquatic vegetation which offers shelter and food. Basking on canal banks is a critical factor in the spatial strategy of this population and repeated use of the same basking site during the year is common. Both males and females show a definite fidelity to a constant segment of the canal during the year and from year to year.

Coordinated visual displays and vocal duetting in different ecological situations among Western Palearctic non-passerine birds

Abstract: The biological significance of mutual behaviours, like duet singing and visual displays, is not entirely clear. The main hypotheses (pair bonding and territorial defence) come from studies of tropical bird species. The aim of this work is to identify some behavioural-ecological parameters that characterize the birds of the temperate area showing duets and coordinated-visual displays (CVD). To this end we performed a multivariate statistical analysis considering 122 non-passerine of the Western Palearctic, 46 of which make coordinated displays. Five main groups have been obtained, two of which are pure vocal duetters (owls/woodpeckers and swifts/shearwaters), and the other three consisting of birds where vocalisations are accompanied by CVD (some marine colonial species, Anatidae and divers). In agreement with previous studies of tropical birds, vocal duetting is typical of monogamous, monomorphic and territorial species. CVD is present in species living in open habitat with nidifugous offspring and migrat...

Ballooning in spiders: results of wind tunnel experiments

Abstract: Ballooning refers to the aerial displacement of spiders made possible by friction between rising air and strands of silk. The phenomenon is widespread in the order Araneae and is thought to be the primary means by which spiders disperse over long distances. Only recently have attempts been made to understand the aerodynamic constraints under which ballooning spiders must operate. The current study was stimulated by the cogent theoretical work of HUMPHREY (1987), and provides the first empirical data on the physical forces acting on spiders about to become airborne and on those that are already airborne. The data indicate (1) that both the silk and the spider's body provide the drag necessary for ballooning, (2) that fluid dynamic models overestimate the difficulty of becoming and remaining airborne, (3) that the spider has both postural and silk length control over drag development, (4) and that only very small spiders can rely on ballooning for dispersal over long distances.

Unpalatability in anuran larvae as a defense against natural salamander predators

Abstract: Throughout the animal kingdom, there is a general correlation between conspicuousness and qualities that are aversive to predators. The larvae of certain species of anuran amphibians form extremely large, conspicuous, aggregations composed of thousands of individuals. Members of these aggregations are not overtly attacked or eaten by vertebrate predators. The larvae of other anuran species are cryptic, form small aggregations, disperse rapidly from and are readily eaten by vertebrate predators. In conjunction with forming large, conspicuous groups, unpalatability may be one means by which larvae in conspicuous groups avoid predation. Therefore, in the laboratory, we used natural salamanders as predators to investigate relative payabilities of the larvae of three species of anurans that differ in their mode of aggregation. The larvae of the western toad (Bufo boreas) form large conspicuous aggregations and are not conspicuously attacked by most vertebrate predators. The larvae of the Cascades frog (Rana ca...

Interaction between periodic socio-sexual cues and light-dark cycles in controlling the phasing of activity rhythms in golden hamsters

Abstract: Most of the previous work on the effects of social stimuli on circadian rhythms has involved the use of constant environmental conditions. In the present experiments, male golden hamsters were maintained in a light-dark cycle and exposed to females daily for 1-hr intervals. Periodic exposure to female hamsters in estrous condition resulted in advances of the males' activity onsets on subsequent days when females were not introduced (probe days). Periodic exposure to female hamsters without regard to the stage of their estrous cycle produced similar but smaller effects. With repeated exposure to female hamsters, there were decreases in the wheel-running induced during the hour when females were present (pulse hour), perhaps reflecting habituation to socio-sexual cues. These results suggest that exposure to an arousing stimulus during the normal resting time of hamsters can result in phase shifts of their endogenous circadian activity rhythms. Non-photic events may have effects on the phasing of biological ...

Alternative reproductive strategies in Formica lugubris Zett. (Hymenoptera Formicidae)

Abstract: A long term study on the reproductive strategies of Formica lugubris (Formica rufa group) has revealed many new important facts. Within a supercolony the sex-ratio is strongly female biased. Some of the sexuals mate on the nest surface, whereas others fly from the nest. Those sexuals participating in flights aggregate in particular meadow sites (mating places). On these places females attract males by releasing a sex pheromone.

The influence of body size and prior residency on the outcome of male-male interactions of Marpissa marina, a New Zealand jumping spider (Araneae salticidae)

Abstract: In experiments, body size and prior residency at nests are shown to be factors that influence the outcome of male-male aggressive interactions of Marpissa marina, a New Zealand jumping spider. Away from nests, larger males tend to win, but at nests the occupant tends to win. Possible reasons for M. marina male-male conflict being settled by these rules are discussed. The larger question of why salticid males are aggressive is also discussed.

Caste differentiation in Isoptera: basic features, role of pheromones

Abstract: The polymorphism of termites, essentially phenotypic, results from alternative orientations during individual development, triggered by hormones and neurohormones. The hormonal equilibrium is itself modulated by several influences, both from the outer world and the society. Among the latter, the primer pheromones seem especially important in the regulation (either by stimulation or inhibition) of the separate castes.

Illegitimate exploitation of sexual signalling systems and the origin of species

Abstract: The sexual signals passed between conspecific males and females in the context of mate attraction and stimulation also are available for exploitation by predators and parasites. These «illegitimate» receivers have profoundly influenced the evolution of sexual signalling systems within populations, as briefly reviewed in this paper. I then extend this concept to groups of conspecific populations exposed to different communities of exploiters. I hypothesize that selection in the form of arms-races among «exploited» and «exploiter» species may cause divergence of sexual signalling systems in the former (in both traits and preferences). This divergence may be sufficient to generate sexual isolation among populations, permitting further population differentiation and, perhaps, the origin of new species. Results of recent research on the ethology and ecology of male sexual signals and female preferences in the guppy Poecilia reticulata are used to test this hypothesis.

Landmark orientation in natural situations in the red wood ant Formica lugubris Zett. (Hymenoptera Formicidae)

Abstract: Terrestrial landmark orientation was studied in Formica lugubris by investigating the effects of two natural phenomena on homing. First, the influence of a thick layer of snow on site recognition was studied in early spring, and second, the orientation of workers passively displaced by a stream at various distances from their nest was examined. The results show that ants associate the location of their nest with the position of the trees which have the highest apparent size above the horizon. Since for most parts of the foraging area this always involves the trees standing close to the nest, ants only need to follow this simple rule to readily go back to their nest. The significance of this orientation behavior for individual ants as well as for the organization of the foraging of the colony is discussed.

Habitat use in a central Italy population of Testudo hermanni Gmelin (Reptilia Testudinidae)

Abstract: Extensive radiotracking of adult Testudo hermanni for 1 year, and regular inspections for 5 years, in a coastal area of central Italy, allowed us to assess the seasonal variation in mobility and home range size of both sexes, and their use of the different parts of home range. Males are more mobile than the females but, due to a different long-term movement pattern, they have a generally smaller home range. Both sexes show a marked seasonal variation in home range size, but no seasonal migrations. Wild rabbits burrows, and simple pallets under dense vegetation are repeatedly used as shelters by the same individual. The animals show a certain preference for specific basking areas in the midst of dense shrubbery. They feed mainly on vegetation common throughout the study area but special displacements in order to forage also occur. Mating encounters are based on home range overlapping between mates and high male mobility. Our findings and those of other authors on different populations of the same species s...

Female song in European starlings: the case of non-competitive song-matching

Abstract: This paper concerns the occurrence of female song in European starlings Stumus vulgaris and aims to identify the elements of song that are similar to that of male starling song. Testosterone-implanted females produced a song very close in structure to male song (whistles and warbling) but most of the typical male species-specific elements were missing. The female repertoire was only slightly smaller than most male repertoires. Sonographic structure of the songs of the members of a polygynous trio (a male and two females) were strikingly similar. All whistle types were shared by the females and all but one were the same as their mate's whistle types (especially mimicries of other species' songs). Most of the females' songs, although rarely heard, were produced during female-female or male-female song-matching bouts during nonagonistic situations.

Search behavior and foraging ecology of the ant Formica schaufussi: colony-level and individual patterns

Abstract: Records of resource loads carried to the nest showed that foragers of the ant Formica schaufussi collect carbohydrate secretions and retrieve dead arthropods (chiefly insects) as the major components of the mixed diet feeding habit of this species. The foraging paths of workers collecting these resources were mapped in the field by marking the spatial coordinates (fixes) of an individual's position at 20-sec intervals. The frequency distribution of the azimuth of the fixes was significantly different from random, indicating that foraging activity is concentrated in certain directions around the nest. Ninety percent of all fixes were located within a radius of 5 m from the nest, a distance which is apparently equal to one-half the average nearest neighbor distance in a population of F. schaufussi colonies. Of the total number of foragers observed, a small proportion traveled with a high degree of linearity in one sector away from the nest; these workers were apparently involved in the collection of homopte...

Order of eclosion and reproductive differentiation in a social allodapine bee

Abstract: The majority of naturally occuring nests of Exoneura bicolor are occupied by more than one adult female. During overwintering periods inseminated females with large ovaries inhibit ovarian enlargement of their female nestmates. In this study we examine ovarian development among nestmates as a function of body size and order of adult eclosion. We show that order of eclosion is a more important determinant of ovarian rank than body size and that the period of time separating first and later eclosion events does not appear to influence relative ovary size in early stages of reproductive differentiation. Although first and later eclosion events may be separated by a few days or less, reproductive hierarchies are maintained for at least 3 months and probably longer, suggesting that reproductive ranks are stable. We discuss four possible factors that may contribute to the stability of reproductive hierarchies in E. bicolor and then consider why hierarchies are based on order of eclosion, rather than age or body...

Honey from honeybees and other insects

Abstract: Honey can be stored without risk of spoilage, by social insects that produce it from the nectar or honeydew they collect from living plants. The insects include all Apis spp. (Apinae), almost all Meliponinae, all Bombus (Bombinae), honey wasps in the Polistinae, and honey ants in the Formicinae and Dolichoderinae. The production of honey involves the activity of secreted invertase and glucose oxidase, and a table indicates enzyme activities in 14 of the honey-producing species or genera.

Social behavior and space-use of young of ground-dwelling squirrel species with different levels of sociality

Abstract: Comparisons among young of ground-dwelling squirrel species with different adult sociality indicate patterns of interaction during development that may influence the evolution of complex sociality. Social behavior and spatial overlap of weaned young with their mothers, littermates, non-littermate young, and adult conspecifics were compared among Gunnison's prairie dogs (Cynomys gunnisoni), yellow-bellied marmots (Marmota flaviventris), Columbian ground squirrels (Spermophilus columbianus), and thirteen-lined ground squirrels (S. tridecemlineatus). The adult social organization of these species differs markedly: Gunnison's prairie dogs are highly social, yellow-bellied marmots and Columbian ground squirrels are relatively less social, and thirteen-lined ground squirrels are asocial. In young Gunnison's prairie dogs, social cohesion and spatial overlap were high not only with the mother and littermates, but with all members of the harem. In yellow-bellied marmots, social cohesion occurred with all members o...

Twofold path integration during hoarding in the golden hamster

Abstract: Golden hamsters which hoard food in darkness return from food source to their nest by relying on internal signals generated during the preceding outward journey to the food location. The question arises whether the animals are also capable of reorientating to the last food finding site on the basis of path integration. This possibility would allow the animals to exploit a profitable food source without acquiring and storing long term information about the itinerary between the nest and the last food finding site through a learning process. In each experimental trial, the subject was led at first from its centrally located nest to a (new) food source near the periphery of the experimental arena. Thereafter, the hamster returned by itself to the nest and then performed a second, unguided hoarding excursion during which it could find the food at the same location. The experiments took place in different conditions, with or without an asymmetrical nest exit or the availability of optical cues. Even when teste...

Methods for collecting data on natural mortality in bee

Abstract: To evaluate natural bee mortality a comparison was made between Gary traps (which are normally used for this purpose) and a new type of trap called «underbasket». The results obtained with the latt...

Flexible responses to predators in a marine fish

Abstract: The effect of predators on the behavior of signal blennies, Emblemaria hypacanthus (Pisces Chaenopsidae), was examined by comparing populations from two sites in the central Gulf of California that differed significantly in the abundance of predatory fishes. At the low-risk site the sexes differed in habitat use with males and females spending most of their time in shelters and in the open, respectively. At the high-risk site both sexes spent most of their time in shelters and also moved less and retreated into shelters more frequently than they did at the low-risk site. Both sexes fed at similar rates at the two sites, but their feeding efficiency was not measured. Males at the high-risk site courted females less vigorously and exhibited less intense courtship coloration than did males at the low-risk site. Although this difference in coloration was evident in the field over 3 consecutive years, males from both sites exhibited full courtship coloration in aquaria lacking predators. This implies that the ...

Mule deer density and pattern distribution in the pine-oak forest at the Sierra de La Laguna in Baja California Sur, Mexico

Abstract: The study of the mule deer (Odocoileus hemionus peninsulae) population was carried out in the relict pine-oak forest of the Sierra de La Laguna in Baja California Sur, Mexico, from July 1987 to March 1989, in order to evaluate the population density with pellet group surveys done in six permanent transects, in July and November 1987, March, June and November 1988, and March 1989. It was found that the distribution of pellet groups is aggregated with a negative binomial pattern (Chi-squared goodness of fit test were not significant P>0.05) and k values varied from 0.96 (July 1987) to 0.22 (November 1988). This pattern is probably due to social factors as well as habitat preference (habitat heterogeneity). There were no differences in pellet-group counts between transects (F=1.25, P>0.05), although there were significant differences between seasons (F = 5.4, P<0.01). The density average estimated was 0.37 ±0.05 deer/ha. The mule deer population seems stable, but the fragility of this habitat, that is consid...

Preliminary observations of the clustering behaviour of the tropical hermit crab, Clibanarius laevimanus

Abstract: The habit of clustering was studied within a semilunar tide cycle in the man-grove-dwelling hermit crab Clibanarius laevimanus Notwithstanding the stability with time of aggregation size, shape, spatial position and shell-size composition together with the relatively strong site-attachment showed by these hermits, one individual's probability of changing cluster was high Some hypotheses are set forth to explain the adaptive meaning of this behaviour

Pesticides in Ferrara Province: two years' monitoring with honey bees (1987–1988)

Abstract: During the 1st year 20 strategic sites evenly distributed in this area, have been chosen. Each station consisted of two hives equipped with Gary cages to evaluate the weekly mortality. The data (presented as bee-risk maps) pointed out a situation of medium-high risk for honey bee and this was re-confirmed during the 2nd year of study with 26 stations. The most frequently detected active ingredients in these 2 years were: Dithiocarbamates (97% of 46 analyzed dead-bee samples) which are nonlethal to them, Azinphos-methyl (57%) and Dimethoate (55%) in 1987; and the same active ingredients, in the same order or importance but at different percentages (83.3%, 66.7% and 46.7% respectively) were detected on 30 dead-bee samples analyzed in 1988. These active ingredients are the most widely sold chemicals throughout the Ferrara Province.

Sex ratio and asymmetry between the sexes in the production of replacement reproductives in the termite, Neotermes papua (Desneux)

Abstract: Sex ratio data were collected and orphaning experiments carried out in the New Guinea giant cocoa termite, Neotermes papua. The sex ratio of the alates tends to be slightly female-biased, whereas males represent on average about 60% of the pseudergates and soldiers. This might represent a rudimentary form of sex specialization in the production of working individuals. Male neotenics readily appear in orphan cultures. By contrast, only imaginai replacement females were obtained. Neither a higher fecundity nor a quicker differentiation seem able to account for the evolutionary change from neotenic replacement females to imaginai ones. Another explanation is proposed, based on the potential advantages of channelling a maximum proportion of female nymphs into dispersing alates.

Male rubbing behaviour and the hypothesis of pheromonal release in polistine wasps (Hymenoptera Vespidae)

Abstract: In polistine wasps male flight activity is typically centred on a set of habitual perches. We review the co-occurrence of perching behaviour, rubbing activity and exocrine glands probably involved in a pheromonal release.