Male-Female Interactions in Hairy-footed Gerbils (Genus Gerbillurus)

Staged 10-min encounters between male and female gerbils of the same species were characterized by high levels of exploratory and solitary behaviour, variable levels of agonistic behaviour, and little contact-promoting behaviour. Female Gerbillurus paeba paeba, G. p. exilis and G. tytonis dominated males of these species, while male and female G. setzeri and G. vallinus were equally aggressive. Results of this study indicate that G. p. paeba, G. p. exilis and G. tytonis are aggressively solitary and that females behave aggressively towards unfamiliar males, while G. setzeri and G. vallinus are more tolerant. This is in partial agreement with findings for other gerbil species.     

Ultrasonic Vocalizations of Six Taxa of Southern African Gerbils (Rodentia: Gerbillinae)

Ultrasonic calling during male-female encounters between individuals of the same species was investigated in six taxa of southern African gerbils, namely Tatera brantsii, Gerbillurus paeba paeba, G. p. cxilis, G. tytonis, G. setzeri, and G. vallinus. Vocalizations were detected by means of a bat detector utilizing a superheterodyne signal converter and a countdown circuit. Signals were recorded at audible frequencies and analysed with a sonograph. All taxa vocalized at ultrasonic frequencies by means of strongly modulated frequency “sweep” calls, which differed among taxa in duration, maximum and minimum frequency. “Clicks” were emitted by G. p. paeba and G. p. exilis, and G. tytonis emitted a “stutter” vocalization which consisted of a series of clicks. Long modulated “whistles” were identified from G. vallinus and T. brantsii at lower frequencies than “sweep” calls. Only one call type, a “sweep” call which differed in duration and frequency from all other taxa, was identified in G. setzeri. Cluster analysis was applied to the data using 7 acoustic characters. G. p. paeba and G. p. exilis displayed the highest similarity level between taxa and differed only in frequency of “sweep” vocalizations. G. paeba, G. tytonis and G. setzeri formed one cluster, while G. vallinus and T. brantsii formed a separate cluster. Numbers of calls in interspecific encounters were non-significantly less than in intraspecific encounters in all taxa except G. p. paeba, in which more vocalizations were recorded in inter- than intraspecific encounters. It is not clear whether species discrimination, measured by numbers of vocalizations in interspecific encounters, occurs.     

A Comparative Study of the Behaviour of Six Taxa of Male and Female Gerbils (Rodentia) in Intra- and Interspecific Encounters

Frequencies and sequences of visually-identifiable acts were investigated in male-female combinations of gerbils of the taxa Tatera brantsii, Gerbillurus paeba paeba, G. p. exilis, G. tytonis, G. setzeri, and G. vallinus. Sexual dimorphism of behaviour was most apparent in T. brantsii, G. setzeri, and G. vallinus, in which following, anogenital sniffing, and mounting were significantly more frequently performed by males than females. Females of all taxa presented and darted, while males did not perform these acts. Analysis of first-order transitions of acts in intraspecific encounters revealed remarkable similarity among species in the sequences identified as most significantly deviating from expected frequency. Species-specific patterns of behaviour were detected by discriminant analysis. G. p. paeba, G. p. exilis and G. vallinus were not clearly distinguished by discriminant analysis, and presented a behaviour pattern characterized by low levels of aggression and high levels of huddling behaviour. G. tytonis, G. setzeri and T. brantsii were characterized by low levels of huddling, G. tytonis performed the largest number of upright postures of all taxa, G. setzeri watched more than other taxa, and T. brantsii nasal sniffed less frequently than Gerbillurus taxa. Differences among taxa were more apparent in males than in females. Interspecific encounters were staged between G. p. paeba and G. p. exilis, G. p. paeba and G. tytonis, G. setzeri and G. vallinus. Males showed more evidence of changed behaviour in interspecific encounters than females. More sexual and less agonistic behaviour was detected in intraspecific encounters than in interspecific encounters, but this was statistically significant in only 5 of 12 combinations. Visual, tactile and olfactory communication during physical contact with another individual may complement auditory communication in promoting conspecific recognition in southern African gerbils.     

Behaviour Associated with Ultrasonic Vocalizations in Six Gerbilline Rodent Species

Encounters were staged between male and oestrus-induced females of the same or different taxa of the species/subspecies Gerbillurus paeba paeba, G. p. exilis, G. tytonis, G. setzeri, G. vallinus and Tatera brantsii. Each encounter lasted 20 min; converted ultrasonic emissions were recorded on videotape simultaneously with visual images. Videotapes were transcribed and sequences of acts and vocalizations were recorded. The frequency of acts was compared separately with the number of ultrasonic vocalizations during and after acts by χ² contingency table analysis, followed by partitioned χ² to identify individual acts which contributed significantly to the overall χ² value. Vocalizations occurred significantly more frequently than expected during sexual and/or huddling behaviour in all species-groups; and significantly less frequently than expected during exploratory, watching and/or submissive behaviour. Vocalizations were uncommon during investigative behaviour in all taxa, and aggressive behaviour in Gerbillurus taxa, but occurred significantly more frequently than expected after these behaviour categories in all taxa. Analysis of vocalizations immediately following acts verified the interpretations of function of vocalizations during acts. Ultrasonic vocalizations clearly play an important role in the communication of six taxa of southern African gerbils.     

Observations on the reproductive biology of the land tortoises Geochelone emys and Geochelone yniphora in the Honolulu Zoo

Captive reproduction of the Burmese brown tortoise (Geochelone emys) has occurred repeatedly over a five-year period in the Honolulu Zoo. Maximum clutch size (51 eggs) exceeds that reported for other members of the Testudinidae. Nesting behavior in G emys includes construction of a large leaf-litter mound. Collection of nest-building material is accomplished by “back-sweeping” of ground litter within a distance of up to 4 m from the nest site. The nesting female assumes a “nest-guarding” behavior for a period of 2–3 days following egg laying. Eggs incubated artificially hatched in 63–84 days, with egg fertility at 78–84%. One hundred and three G emys were successfully hatched and reared during the period 1978–82. A colony of endangered Madagascar angulated tortoises (Geochelone yniphora) have been maintained at the Honolulu Zoo since 1971. Courtship and mating behavior is similar to that described for the consubgeneric G radiata. Distinctive male “hooking” behavior during courtship in G yniphora is related to the exaggerated epiplastron development in this species. Egg laying has occurred repeatedly in the G yniphora colony since 1979 (mean clutch size = 4.2; N = 6) although no eggs have yet proved fertile.     

Inter-specific competitors reduce inter-gender competition in Negev Desert gerbils

We examined gender-dependent competitive interactions between two nocturnal desert gerbil species, Gerbillus andersoni allenbyi and G. pyramidum, by a field manipulation experiment. The study was done in two 1-ha enclosed plots and included allopatric (only G. a. allenbyi) and sympatric (both species together) treatments. Seed trays and thermal imaging cameras were used to observe the gerbils foraging activities and aggressive interactions. We found that the negative effect of the competitively dominant species, G. pyramidum, on time spent in seed trays, and ability to control these artificial food patches, was stronger on male than on female G. a. allenbyi. Consequently, the aggression of male G. a. allenbyi towards female G. a. allenbyi was markedly reduced, indicating that the dominant species mediated competition between the genders of the subordinate species. Furthermore, this interference-mediated indirect effect was associated with a decrease in the body mass of male G. a. allenbyi and an increase in the survival of female G. a. allenbyi. We suggest that both the reduction in intra-specific aggression and the positive effect on female survival can potentially stabilize competitive interactions and promote coexistence in this small mammal community.     

Information on Resource Quality Mediates Aggression between Male Madagascar Hissing Cockroaches, Gromphadorhina portentosa (Dictyoptera: Blaberidae)

Male Madagascar hissing cockroaches, Gromphadorhina portentosa Schaum (Dictyoptera: Blaberidae) have a well‐defined dominance hierarchy that has been assumed to explain the outcome of most competitive interactions. We studied whether males of this species would alter their level of aggression towards unfamiliar rivals as a function of changing resource availability and value – two factors that are key to aggression levels in non‐hierarchical species. We quantified male aggression as three variables (aggressive state – behaviours measured by their duration; aggressive act – behaviours measured by their frequency of occurrence; aggressive latency – the latency to first aggressive behaviour, either state or act) and tested for any context‐specific variation within each by manipulating both territorial status (males were either residents or intruders) and access to mates (female present or absent). Both the presence of a female and territorial status affected male aggression towards rivals as measured by duration of aggressive state. Highest levels of aggression were displayed by residents when a female was present. These results show that inter‐male aggression in G. portentosa is tuned to the immediate expected payoff from fighting, and not exclusively aimed at establishing dominance relationships (which can affect future payoffs).     

Grouping and Inhibition of Oogenesis in Two Strains of Acanthoscelides obtectus Say (Coleoptera Bruchidae) of Different Geographical Origin-Specificity of This Inhibitory Effect

Summary

Reproduction of A. obtectus females originating from Rubona (Rwanda) was inhibited after grouping (2 females, or 1 male—1 female). Only a few females produced mature oocytes; vitellogenin was synthesized, released into the haemolymph, but not incorporated into the oocytes. When females produced mature oocytes, their ovarian production was lower than in isolated virgin females. After pairing of a male and a female, 38% of the females mated, but mating under these conditions did not stimulate oogenesis.

Oogenesis of females originating from Tours (France) was only slightly inhibited by the presence of males or females of the same origin. “France” males and females inhibited the reproduction of “Rwanda” females under grouping conditions. However, “France” females showed only a slight sensitivity to grouping with “Rwanda” bruchids. In the presence of Phaseolus vulgaris seeds, grouping had no effect and all females, whatever their origin, produced mature oocytes. Inhibition weis relatively specific as cohabitation with bruchids of other genera (Callosobruchus maculatus-Zabrotes subfasciatus) had no effect. Cohabitation with two species of the same genus (Acanthoscelides obvelatus—A. argilaceus) inhibited oogenesis of A. obtectus “Rwanda” strain. The significance of this regulation and its importance in the maintenance of populations in nature are also analyzed.     

Virgin females compete for mates in the male lekking species Ceratitis capitata

Abstract. Aggressive behaviour occurring in intrasexual competition is an important trait for animal fitness. Although female intrasexual aggression is reported in several insect species, little is known about female competition and aggressive interactions in polygynous male lekking species. The interactions of female Mediterranean fruit flies, Ceratitis capitata (a male lekking species), with other females and mating pairs under laboratory conditions are investigated. Mature, unmated (virgin) females are aggressive against each other and against mating pairs, whereas immature females are not. Female aggression against other females decreases dramatically after mating; however, mated females maintain aggression against mating pairs. In addition, higher intrasexual aggression rates are observed for mature, virgin females than for virgin males of the same age. The results show that female aggressiveness is virginity related, suggesting female competition for mates. These findings have important implications for understanding the physiological aspects of a complex social behaviour such as aggression and should stimulate further research on female agonistic behaviour in male lekking mating systems.     

Behavioural Divergence in Allopatric and Sympatric Gerbil Species (Rodentia: Gerbillinae)

Southern African gerbils comprise 3 genera, each genus represented by morphologically- and ecologically-similar species. All species are monomorphic, with social systems varying from asocial (Desmodillus auricularis) to colonial (Tatera species). This study compares the behaviour patterns of an allopatric species, T. afra, 2 sympatric species, T. leucogaster and T. brantsii, and a species of a different genus, D. auricularis which is sympatric with T. leucogaster and T. brantsii. Interactions between males and females of the same species were staged and quantified in terms of the frequencies of each of 23 behavioural acts. D. auricularis performed 2 acts, namely “sidle” and “fight” which have not been identified in Gerbillurus or Tatera interactions. Sequences of behaviour were similar in all species, and involved females moving away from males, which followed, sniffed the anogenital region and attempted to mount the females. Females responded by presenting, if receptive, or agonistic behaviour such as aggressive or upright postures. Exploration of the terrarium accounted for a large proportion of the behaviour during the 20 min encounter, and watching the opponent also occurred frequently. Discriminant function analysis successfully separated all 4 species on the basis of behaviour frequencies. Individuals were assigned to the correct species with an accuracy of 80%, indicating that each species exhibits species-specific patterns of behaviour. D. auricularis displayed more agonistic and sexual behaviour and less huddling behaviour than any of the Tatera species. The sympatric species-pair, T. leucogaster and T. brantsii, exhibited more significant difference in behaviour than either of the allopatric species-pairs, T. afra and T. brantsii, and T. afra and T. leucogaster. Divergence in behaviour patterns has occurred in allopatric species, but divergence is more marked in species which are sympatric. It is not known whether divergence between T. leucogaster and T. brantsii occurred during a period of allopatry, or whether divergence has occurred due to selection against hybrids in sympatry.     

A Comparative Study of Social Behaviour of Two Sympatric Ground Squirrels (Spermophilus spilosoma,S. mexicanus)

During the reproductive period, intraspecific dyadic encounters were staged within and between S. spilosoma and S. mexicanus individuals under controlled conditions. Video recordings were used to describe and quantify behaviour of males and females of these two sympatric ground squirrels. To compare dyads within and between species two indices (an Agonistic index and a Tolerance index) were designed from measures of behavioural frequencies. During intrasexual encounters, S. mexicanns males and females appear to be more aggressive than male and female S. spilosoma. In both species, encounters between males were more aggressive than between females, which were very tolerant to each other in S. spilosoma. In most cases encounters between male and female conspecifics exhibit an intermediate level of agonistic behaviour and tolerance. The null hypothesis of similarity of the social behaviour of S. spilosoma and S. mexicanus is falsified. Some alternative hypotheses are proposed. First, the tolerance of S. spilosoma is an adaptation to the difficult environmental conditions. Thus differences between the two species reflect differences in behavioural evolution in allopatric populations. Second, S. spilosoma tolerance is a behavioural response to S. mexicanus' recent arrival.     

Biology of <Emphasis Type="Italic">Lasioglossum</Emphasis> (<Emphasis Type="Italic">L.</Emphasis>) <Emphasis Type="Italic">majus</Emphasis> (Hymenoptera: Halictidae), a largely solitary sweat bee with behavioural adaptations to communality

Within the bee family Halictidae there have been three origins of sociality. Although detection of origins and reversal from sociality requires phylogenetic studies, at a behavioural level a predisposition to sociality can be detected by analysis of intra-specific interactions. We studied aspects of nesting biology and behavioural interactions in Lasioglossum (Lasioglossum) majus, a poorly known halictine inhabiting temperate regions of Europe, which is suspected to be solitary. Nests were found to be largely used by one female, but some were shared by more than one individual. These few nests, whose entrances were very close to each other, were found to be connected underground. A few individuals were observed to enter in a nest where a female was waiting, behaving as a guard and allowing the incoming bee to enter the nest. By use of circle-tube experiments, the behavioural repertoire exhibited by females during encounters was assessed. Levels of withdrawal and cooperative events were comparable with those observed in other solitary nesting species, but aggressive events were very rare, as in several observed communal species. We conclude that L. (L.) majus females, despite general solitary nesting, possess behavioural components enabling them to adopt, probably in high nest-density areas, nest-sharing strategies. A similar kind of local social polymorphism has been observed in two other species of the subgenus Lasioglossum, but these are the first data available on a European species and the first record of subterranean connections among nests of halictid bees.     

Social polymorphism in the sweat bee <Emphasis Type="Italic">Lasioglossum (Evylaeus) baleicum</Emphasis> (Cockerell) (Hymenoptera,Halictidae) in Hokkaido,northern Japan

Summary The life cycle and social behaviour of the sweat bee Lasioglossum (Evylaeus) baleicum (Cockerell) was investigated in two geographically separate populations in Hokkaido, northern Japan. Colonies were excavated throughout the brood rearing season from an aggregation in Nishioka forest park, Sapporo, and near Kawakita in eastern Hokkaido during 2000 and 2001. The Nishioka population produced two discrete broods during the year and was weakly eusocial; 57% of workers were mated and 28% exhibited some ovarian development, 12–16% of the first brood was male, and workers were on average 4.5% smaller than their respective queen. In contrast, the population at Kawakita was solitary, and produced a single brood per year with an unbiased sex ratio. In addition however, there were some solitary colonies in the Nishioka population and evidence of a partial second brood in some colonies at Kawakita, suggesting differences between the populations are not fixed and that this species is truly socially polymorphic. L. (E.) baleicum is a member of the fulvicorne species group, which includes other examples of social polymorphic species as well as solitary and eusocial species, though this is the only species of this group so far known to exhibit a solitary/non-delayed eusocial polymorphism. Recent studies suggest that social polymorphism has both genetic and environmental influences, raising questions as to the relative import of each.     

Mate location in the green capsid bug, Lygocoris pabulinus

Headspace extracts from female Lygocoris pabulinus (L.) (Heteroptera: Miridae) as well as female leg extracts attracted male L. pabulinus in Y‐track olfactometer bioassays. In contrast, only female leg extracts were active in the vibration bioassay. Male extracts had no activity at all in either bioassay. When the female leg extract was analysed by coupled gas chromatography‐electroantennography (Z)‐9‐pentacosene and (Z)‐7‐pentacosene were EAD‐active. (Z)‐9‐Pentacosene and sometimes (Z)‐7‐pentacosene were also observed in female headspace extracts. EAG responses could be obtained for (Z)‐9‐pentacosene. A mixture of (Z)‐9‐pentacosene and (Z)‐7‐pentacosene in the ratio 5 : 1 elicited vibration behaviour in males. The results indicate that these alkenes are important cues for male L. pabulinus in mate location behaviour.     

THE STABILITY OF THE SYMBIOSIS BETWEEN DIOECIOUS FIGS AND THEIR POLLINATORS: A STUDY OF FICUS CARICA L. AND BLASTOPHAGA PSENES L.

Each Ficus species depends on a specific mutualistic wasp for pollination. The wasp breeds on the fig, each larva destroying a female flower. It is, however, not known why the wasps have not evolved the ability to use all female flowers. In “dioecious” figs, the wasp can only breed in the female flowers of the “male” trees, so that pollination of a female tree is always lethal. The wasps should therefore be selected to avoid female trees. Field data is presented showing that the fruiting phenology of the dioecious fig Ficus carica is such that this selection does not occur: syconia are not receptive at the same time on “male” and female trees. Most wasps are forced to emerge from the syconia of “male” trees at a time when they will not be able to reproduce, whether they avoid female trees or not. This aspect of the life cycle of the wasp, although noticed, has been obscured in most previous studies. It is shown that the fruiting phenology of Ficus carica, which stabilizes the symbiosis, is the result of short-term selective pressures on the male function of the trees. Such selective pressures suggest a possible pathway from monoecy to dioecy in Ficus under seasonal climates.     

Beobachtungen zum Paarungs- und Aufzuchtverhalten der Wasserspitzmaus Neomys fodiens (Soricidae)

Five European Water Shrews (Neomys fodiens) were kept in an indoor enclosure of 2.7 m² where one couple mated regularly. Multiple copulations appeared over a period of about 12 hours. Ten litters with 56 offspring were born and 33 survived. The female gave birth to her latest litter at an age of about 20 month, 2 month later as the end of the reported lifespan in nature. The period of fertility lasted 336 days and is comparable to those of Crocidura. At the end of this period three times signs of pseudopregnancy were detected: After copulating the female started building her nest and intensified this behaviour after about three weeks, at the end of the expected “gestation” swollen nipples could also be noticed, but no offspring inside the nest. The female died at an age of about 38 month.After successful copulations a copulatory lock was achieved and the female could track her mate. The mating behaviour can be classified as follows: a) male entering female's territory, b) precopulatory chasing, c) approaching of the mates, d) mounting and repeated copulations attempts, e) successful copulation, male slipping down from female's back, f) copulatory lock and resting, g) cleaning sexual organs, h) continuing chasing and further copulations or i) displacing the male and finishing sexual behaviour. Driving off the male from female's territory could last some time. No special calls were uttered in the close context of copulatory behaviour, only the known ones while chasing, some low contact calls inside the nest and aggressive calls while driving off the male.     

Female aggression and the maintenance of monogamy: female behaviour predicts male mating status in European starlings

Any reduction in the fitness of a breeding female induced by the settlement of additional females with her mate creates a conflict between the sexes over mating system. In birds, females are often aggressive towards other females but few studies have been able to quantify the importance of female-female aggression for the maintenance of monogamy. This study of the European starling, Sturnus vulgaris, quantifies male and female behaviour towards a potential prospecting female, presented in a cage during the pre-laying period, and relates it to the subsequent mating status of the male. A solitary breeding male was given the opportunity to attract an additional mate, which almost half of the males did. No biometric characters of the male or female were related to the subsequent mating status. Males demonstrated mate-attraction behaviour towards the caged female but the behaviour of the male did not predict the likelihood to attract an additional female. However, the proportion of time that the female spent near the potential settler was related to mating status, indicating that females that reacted more strongly towards a potential female competitor maintained their monogamous status. These results suggest that female behaviour may play an important role in shaping the mating system of facultatively polygynous species.     

Male aggression and female mate choice in the threespine stickleback,Gasterosteus aculeatus L.*

A laboratory study of female G. aculeatus revealed no conclusive evidence of active female mate choice on the basis of male aggression levels. However, highly aggressive males failed in 95% of all choice tests. The less aggressive ‘chosen’ males were generally successful again in subsequent trials with the same female, and certain males were consistently successful with different females. Females exhibited an increased readiness to spawn at the end of the reproductive season, although the same males were usually selected again.     

CELL SIZE DIFFERENTIATION IN THE BLOOM-FORMING DINOFLAGELLATE GYMNODINIUM CF. NAGASAKIENSE1

Two subpopulations differing essentially by their mean cell size were observed regularly in cultures and natural samples of the naked dinoflagellate Gymnodinium cf. nagasakiense Takayama et Adachi (currently known as Gyrodinium aureolum Hulburt), a species which frequently forms red tides in North European seas. “Large” cells represented the typical forms; they were morphologically similar to cells of the closely related Japanese species G. nagasakiense, which did not form any subpopulation of reduced size. “Small” and “large” cells of G. cf. nagasakiense had the same DNA content, but the nucleus of the former appeared to be much more condensed during interphase. Each cell type was able to divide and had its own growth dynamics; therefore, any intermediary between pure populations of “small” and of “large” cells were observed in culture. The “large” form generated a “small” cell by an atypical budding-like division, whereas the “small” form gave back a “large” form, once it ceased to divide, by simple enlargement of its cell body. Factory inducing cell size differentiation are yet unclear. Neither nitrogen nor phosphorus starvation induced a significant increase in the relative proportion of “small” and budding cells. Although cell size differentiation is associated with the formation of gametes in a variety of dinoflagellates, we demonstrated that “small” cells of G. cf. nagasakiense are able to divide asexually, in contrast to gametes of most other species. The high proliferative power of “small” cells as compared with normal cells suggests that they could play a significant role during red tides of G. cf. nagasakiense; in contrast, cells of the Japanese species G. Nagasakiense could sustain high growth rates with larger cell size because this species generally blooms in waters much warmer than those found in northern Europe.     

Reproductive behaviour and sexual production in the first‐generation hybrids of roach Rutilus rutilus L. × common bream Abramis brama L

The aim of this study was to further test the viability of the roach Rutilus rutilus × common bream Abramis brama hybrid in terms of reproductive behaviour and sexual production. Egg release, mating and aggressive acts in reproductive behaviour, as well as absolute fecundity and sperm density in milt for sexual production were examined in the first generation of these hybrids at their first sexual maturity. The F2 and backcrosses of hybrids were also studied. The results revealed that these hybrids expressed a normal and typical mating behaviour, producing viable gametes. Under experimental reproduction between hybrids (hybrid reproduction), the number of egg‐release acts (range, 21–66) was nearer (χ² test, P > 0.05) the number of mating acts (11–65). Moreover, hybrid males exhibited territorial and aggressive behaviours. However, in experimental reproduction of female and male hybrids mixed with parental males (mixed reproduction), the egg‐release act and the mating act were inhibited by the intense territorial and aggressive activities of the common bream male. Absolute fecundity values (median, <2.2 × 10³ eggs) and sperm density (<7 × 10⁹ spermatozoa ml^?1) of hybrids showed a greater decrease (U test, P < 0.05) than in parental species (median, >6.0 × 10³ eggs and >14 × 10⁹ spermatozoa ml^?1, respectively). Nevertheless, these hybrids were fertile. F2 and backcross generations were produced, although with a significantly lower viable hatching rate (FEP test, P < 0.05) in F2 individuals from the female and its corresponding hybrid male (<6%), indicating a very low chance of survival in rivers.