Long copulations and post-copulatory ‘escort’ behaviour in the locust leaf miner,Odontota dorsalis (Coleoptera: Chrysomelidae)

The adult behaviour of Odontota dorsalis on its host plant Robinia pseudo-acacia was studied by following marked individuals in nature. Copulations often lasted several hours, and were characteristically followed by long escort phases in which males remain mounted atop females. Pairing lasted as long as several days. Most pairs broke up around the time of day when most females were ovipositing. Females normally laid a small cluster of eggs once per day. Both sexes mated repeatedly, and females did not resist copulations.

Long pairings in O. dorsalis may have evolved because the encounter rate between the sexes is high and costs to the female low. It is suggested that escort behaviour will be found in many other species with similar ecology and in which males remain mounted on females while copulating.     

Use of space by the marsupials Gracilinanus microtarsus (Gardner and Creighton, 1989) and Marmosops incanus (Lund, 1840) in an Atlantic Forest of southeastern Brazil

The use of space by animals is determined by environmental conditions, biological and ecological adaptations and interactions and mostly by resource availability. We sampled two species of Neotropical mammals to investigate their use of different strata in Atlantic Forest habitat in Brazil, as well as the home range sizes and movements of both sexes of each species. We found no difference in home ranges and movements between the sexes and species, but we found differences in the use of strata, with Gracilinanus microtarsus mostly using the canopy and Marmosops incanus using the ground. Gracilinanus microtarsus males mostly use the understorey in the wet season and the canopy in the dry season. We believe that these patterns of strata use reflect intrinsic characteristics of the species; and the shifts in resources and interspecific competition, which are lower in the dry season, seem to be responsible for the shifts in space use observed for G. microtarsus males. We recommend studies with spool-and-line techniques or radio tracking to further test refined hypotheses regarding the use of space, including the role of territoriality in females.     

Dietary variation and overlap in D’Orbigny’s slider turtles Trachemys dorbigni (Duméril and Bibron 1835) (Testudines: Emydidae)

Although D’Orbigny’s slider (Trachemys dorbigni) is the most abundant freshwater chelonian species in southern Brazil, little is known about its feeding habits. Our goal was therefore to evaluate this species’ dietary composition and niche variation there. For this, we collected road-killed animals (n = 73) on a federal highway (BR 392) between 2002 and 2003, and analysed their gut contents. We identified 26 different dietary items, and our results indicated that D’Orbigny’s slider is omnivorous in this area. Total food volume, as well as the degree of herbivory and carnivory, were similar between males and females. However dietary composition of plants was different: although both males and females fed on underwater plant matter, only females consumed surface macrophytes. This finding suggested differential microhabitat usage between males and females throughout the swamps.     

Behavioural and morphological dimorphism of the sexes: an account of two primitively eusocial wasps

In social Hymenoptera, foraging, nest building, brood care and all other colony maintenance functions are carried out by the females while males function solely as reproductives. This asymmetry in social roles of the two sexes has led social insect researchers to focus almost exclusively on the females whereas males have remained relatively neglected. We studied two sympatric, primitively eusocial wasps, Ropalidia marginata and Ropalidia cyathiformis, and compared the morphological and behavioural profiles of males and females. Males of both species are smaller in size and weigh less compared to females. Males of the two species live in the nest for different durations. Borrowing from the ecological literature we use novel methods to compute and compare behavioural diversity and behavioural richness and show that females of both species are behaviourally richer and more diverse than the males.     

The scramble competition mating system of the sphecid wasp Palmodes praestans (Kohl)

Males of the wasp Palmodes praestans engage in non‐territorial patrolling behaviour within a scramble competition mating system, showing great fidelity to their wide‐ranging patrolling routes without attempting to monopolize the areas covered. Scramble competition appears adaptive given that mating opportunities are not spatially aggregated in this species, whose females build isolated, single‐celled nests. Because of the female distribution pattern, a male's reproductive success in P. praestans probably depends upon the ability to find highly scattered, unmated females. The females of some close relatives of this sphecid wasp form fairly dense nesting aggregations. As mating system theory predicts, the males of some (but not all) of these species focus their searching at these concentrated nesting/emergence sites where potential mates are clustered spatially.     

A morphological study of Phyllotreta tetrastigma (Coleoptera: Chrysomelidae: Alticinae) including two colour forms

P. tetrastigma is a chrysomelid beetle with two colour forms, and has populations feeding on two different host plants. Morphological variation was studied within both males and females of six populations of P. tetrastigma. Morphological difference was detected between the sexes and between populations from different localities but not between the colour forms. It is not clear whether host plant influences morphology.     

The genus Grammostola Simon 1892 (Araneae: Theraphosidae): a new species from western Argentina,new synonymy and distributional data

Explosive breeding is a common reproductive strategy, especially in anurans. In some cases of explosive breeding in anurans, intense aggressive interactions occur among males attempting to gain access to females, and for terrestrial species that mate in water, females may die by drowning during long mating struggles. Such occurrences are obviously detrimental to females, and may also cause a decrease in the reproductive success of males through depletion of energy without obtaining access to a live female. However, the males of the small Amazonian frog Rhinella proboscidea can promote the ejection of oocytes from the abdominal cavities of dead females and fertilize them. This behaviour can minimize losses to both partners during explosive reproduction events. The existence of such a “functional necrophile strategy” shows that there may be possible selection in favour of stronger and more persistent males in explosive breeders.     

Acoustic ecology of an anuran assemblage in the arid Caatinga of northeastern Brazil

Differences in advertisement calls and calling sites are important mechanisms that regulate interactions in anuran assemblages. Individuals might have preferences for ranges of acoustic parameters and calling sites that reduce overlap and ensure coexistence. Herein, acoustic and ecological data were used to investigate the relationships among 12 anurans that co-occur in temporary ponds in the Caatinga, Cabaceiras municipality, Paraíba state, Brazil. Anurans exhibited calling activity correlated with rainfall, but were also spatially dispersed. High overlap levels in calling microhabitats and acoustic parameters were observed, especially among pairs of closely related species. Analysis of null models showed a lack of structure in the spatial and acoustic niche, indicating the lack of detected competition. Results suggest that the calling activity of the species is strongly influenced by rainfall, moreover, the temporal partition appears to ensure coexistence. Finally, strong historical effects were detected in Leiuperinae, Leptodactylidae and in the partition Hylidae–Leptodactyliformes.     

Resource defence mating system in two flies from Sulawesi: Gymnonerius fuscus Wiedemann and Telostylinus sp. near duplicatus Wiedemann (Diptera: Neriidae)

Gymnonerius fuscus and Telostylinus sp. near duplicatus are two neriid flies which breed in rot-holes (often beetle larval borings) in fallen trees in tropical forests. Males of both species attempt to establish territories beside rot-holes likely to attract females for egg-laying purposes. Monopolization of incoming females and paternity of any eggs laid are therefore assured. Aggression between males of the larger species G. fuscus is largely through ritualized intimidatory signalling, i.e. wing-flicks. Actual physical aggression only occurs when opponents are evenly matched. By contrast, lengthy and hectic wrestling matches on stilted legs is the normal method of establishing site-ownership in the smaller species T. near duplicatus. Males only seek to exclude conspecific males, such that both species may establish simultaneous ownership of a single rot-hole without interacting. Males of G. fuscus who ‘sneak’ matings away from the territories of larger males, or who manage to mate within a territory, gain little or no reproductive benefit. This is because the territory-owner prevents all females, other than his own current mate, from laying eggs within his territory and females seem reluctant to utilize non-territorial rot-holes for oviposition.     

Ranging behaviour of the invasive crayfish,Procambarus clarkii (Girard)

The spreading of the invasive crayfish Procambarus clarkii throughout the world is attributed to human introductions; however, the rapid and widespread diffusion of the species following its establishment is the result of its dispersal capabilities. This study aimed to provide further information for the comprehension of the invasive potential of this crayfish by underlining some aspects of its behavioural flexibility. Radio-telemetry was used to analyse locomotion, home-range faithfulness and dispersal of the species in an Italian irrigation ditch system. Space was used differently by the two sexes, females being more nomadic in their ranging behaviour probably due to their reproductive phase. In addition, an inter-individual variability was found in both speed of locomotion and dispersal pattern. By applying a simulation model, it was shown that (1) both sexes disperse, and (2) ranging behaviour is not the result of a passive dispersion, but that the occupancy of burrows may affect the rate of dispersion. Finally, an intra-individual variability is related to the occurrence of two spatial strategies within the same population.     

An imperfect imago? Post-mating loss of iridescent scales in Cheimas butterflies may change female from attractive to cryptic (Lepidoptera: Nymphalidae: Satyrinae)

Adults of both sexes of Cheimas opalinus (Staudinger), a Satyrinae butterfly occurring in the cloud forests of the Venezuelan Cordillera de Mérida, have simple wing colour patterns, dark brown dorsa marked by one conspicuous element, large greenish-blue patches in the discal area of the hind wing. It was observed that in young, freshly emerged females these patches are frequently absent. They fade away and eventually disappear during mating and nuptial flights when brushed out by lateral movements of the male’s hind wing put between folded female hind wings. The falling off of the scales is made easy because they do not adhere to the wing as firmly as brown background scales due to their particular folded extremities. We speculate that this process is related to the fitness of the females. Prior to mating, blue-green patches are advantageous because they attract the attention of the opposite sex and enhance the chances of successful mating. After mating they lose their sexual role. Females without the blue-green patches become cryptic. Thus, they are less apparent not only for the males, which helps them avoid sexual harassment, but also for potential bird predators. Additionally, the loss of blue reflecting scales may speed up the warming up of the abdomen and egg maturation. In the males, positive role of the patches (signalling), and negative (bird attraction), is balanced during their entire life span, and they fade gradually due to regular usage of wings scaling in flight. Our hypothesis is supported by morphological, optical, experimental and statistical analysis in which we used 509 individuals of both sexes. A similar ratio of young (with undamaged wing) females with or without blue patch was recorded, whereas in the males no individuals without any trace of blue patch were reported, and a correlation of age (wing damage) and gradual fading off of the patch was demonstrated. Such an adaptation involving an active change of the appearance of adults, i.e. colour patterns related to sexual selection, has not been reported previously in Lepidoptera.     

Body size, organ size, and sex ratios in adult and yearling Belding ground squirrels

A five - year study of Belding ground squirrels was conducted at high altitude in the Sierra Nevada. Body weight and body length varied seasonally depending upon the fat depletion - deposition cycle, age, and sex. Adult males tended to be heavier and longer than adult females, particularly in the last half of the active season. A similar pattern was present in yearlings. Yearling squirrels were often distinguishable from adults on the basis of body size. Mean body weights were greater in adults throughout the season, and mean body lengths were greater in adults through the first half of the season. Adults also had larger internal organs than yearlings at the beginning of the season. In liver and heart this difference was sustained. Sex ratios in adults and in yearlings were 1:1 but there was considerable spatial and temporal asymmetry in distribution of the sexes. Males tended to live in areas peripheral to lush meadows occupied by females and young.       

Microhabitat use and feeding habits of Crossodactylus bokermanni Caramaschi and Sazima, 1985 (Anura,Hylodidae) at a site in south‐eastern Brazil

We studied a population of Crossodactylus bokermanni in a stream at the Reserva Particular do Patrimônio Natural, Santuário do Caraça, south‐eastern Brazil, with respect to microhabitat use and diet. We characterized microhabitats based on substrate, distance to water and exposure level of the occupying individual (exposed or sheltered), and adjacent aquatic microhabitats (evaluated as potential nesting sites based on observed nests), according to water current (absent, slow or fast), substrate and depth. Calling males, silent males, ovigerous females, non‐ovigerous females and juveniles showed spatial niche overlap higher than that expected by chance, with calling males showing the strongest preference for microhabitats close to potential nesting sites (with intermediate depths, fast current and sandy bottom). Only 14 males out of 48 individuals examined for stomach contents had prey in their stomachs. The food items with the highest electivity values were Coleoptera and Diptera, but preys with both high and low mobility were exploited.     

Anuran assemblage composition and distribution at a modified environment in Três Marias reservoir,south-eastern Brazil

We assessed the influence of environmental features on anuran species distribution in Pirapitinga, an island formed by the filling of a reservoir in south-eastern Brazil. We investigated whether the species exhibited preferences towards certain habitat types and the existence of niche partitioning. We recorded 474 individuals from seven species. Although considered as generalists, these species were not distributed randomly, but according to specific habitat preferences that happened to be fulfilled by the shores of the reservoir. Niche overlaps were higher than expected by chance during the wet season, when most species were active, but not different from random during the dry season. Environmental variables seemed to be important and promote aggregation of several anuran species at the same habitats. Interspecific signals may be used for this purpose, and competition is probably small or less important than the benefits provided by choosing the most suitable habitats in this impacted environment.     

Diurnal colour change in a sexually dimorphic trait in the Andean lizard Anolis heterodermus (Squamata: Dactyloidae)

Sexual dimorphism in body size, shape and colour is widespread in lizards as well as in other taxa. In the context of sexual selection, these sex differences are commonly manifested as exaggerated male traits, which are selected by females to assess the quality of males. However, differences in sex by environment interactions can also lead to sexual dimorphism. The genus of Anolis lizards is particularly well known for sharp sexual dimorphism in dewlap colour and size; however, this is not the case in all anole species. Using digital image analyses, I assessed the existence of sexual differences in the diurnal change in colour and size of a conspicuous patch on the tail of the lizard Anolis heterodermus Duméril 1851. Results showed that the tail patch of both males and females changed in colour, but not size, from red to blue throughout the day in a similar fashion. This process took almost half a day to complete and occurred in the absence of conspecifics, suggesting that the change itself may not have an active role in social communication. However, the colour patches of males were consistently larger. The cause of the substantial variation in colour and size of the tail patch of A. heterodermus is still unknown and deserves more research. This study highlights the importance of continuous wildlife observations to identify life history traits that may be important in animal behaviour but are challenging to observe in nature.     

Age-related body weight,fecundity and population change in a south Dorset sika population (Cervus nippon); 1985–1993

Density-related changes in performance have been documented for a number of different ungulate species, with recorded decline in body weight, fecundity and both juvenile and adult survival as population densities increase. While density-dependent responses of this kind have been explored in some detail in red, roe and fallow deer, little published information is available on demographic responses to density in European populations of sika deer (Cervus nippon). This paper offers an analysis of the dynamics of two populations of sika from the south of England from 1985–1993. Data on age-related body weights for males and females and pregnancy rates of females are taken from analysis of cull records of 321 males and 534 females culled during that 8-year period. We describe trends in body mass of adult and juvenile sika of both sexes, and consider changes in pregnancy rates of both mature and yearling females in relation to changes in relative abundance. Despite steadily increasing population density between 1985 and 1991/1992, no consistent decline was recorded in body weight or condition (as measured by % cover of kidney fat) for calves or yearlings of either sex, or for mature females. A decline in recorded body weight of adult males was not significantly correlated to ranked relative abundance. Fecundity was high (with > 90% of mature females sampled found pregnant). Most mature females found pregnant were also lactating. The proportion of animals that conceived as yearlings (72%) was lower than that recorded for more mature hinds; however there is some indication that the difference recorded may simply reflect the fact that yearlings may conceive later in the season than older animals. No significant differences were apparent in the proportion of either adult or yearling females found pregnant in different years.     

Home range behaviour in male and female poison frogs in Amazonian Peru (Dendrobatidae: Ranitomeya reticulata)

The poison frog Ranitomeya reticulata was studied for 3 months while mark–recapture surveys were performed. Ranitomeya species deposit terrestrial clutches and carry tadpoles to phytotelmata with few taxa performing biparental brood care including larval feeding. Home range size and spatial affinity to phytotelmata in the genus are linked to mating systems. In R. reticulata, individual home range size and overlap were similar in both sexes, indicating equal levels of site fidelity. Although territory defence was never observed, strong intrasexual intolerance within individuals' core areas was found. The large intersexual home range overlap for breeding pairs indicated that mate fidelity occurs. Individuals' home ranges were not overlapping, suggesting that R. reticulata lacks pair-bonding or strongly cooperative behaviour in parental duties. The number of ground bromeliads containing phytotelmata and home range size of males were positively correlated. Our findings suggest that females do not perform egg-feeding and male-only parental care is likely.     

Natural history and behaviour of the primitively eusocial wasp Ropalidia marginata (Hymenoptera: Vespidae): a comparison of the two sexes

We report the natural history and behaviour of the primitively eusocial wasp Ropalidia marginata with a special reference to the males. We found that just as nests of this species are found throughout the year, so are the males. Females spend all their life in their nests but males stay in their natal nests only for 1–12 days and leave to lead a nomadic life. Males maintained in the laboratory can live for up to 140 days. Like all eusocial hymenopteran males, R. marginata males also do not perform any colony maintenance activities. We found that males did not forage or feed larvae. Compared with females, males showed fewer dominance and subordinate behaviours and being solicited behaviour and more feeding self and soliciting behaviours. By comparing males with young females, we found similar differences, except that the males showed similar rates of feeding self and higher rates of subordinate behaviour.     

Den and relocation site characteristics and home ranges of Peromyscus truei in the White Mountains of California

We used ratio telemetry to describe nighttime movements and daytime den sites of pinyon mice ( Peromyscus truei ) in the White Mountains of California, 1991-1993. Characteristics of nighttime relocations and den sites for mice concurred with previously reported habitat-use information for the species and supported the claim that pinyon mice use multiple daytime sites. However, males and females were associated with different habitat characteristics at den sites, indicating differential microhabitat selection by the sexes, perhaps related to reproductive constraints on females. Pinyon mice also exhibited high variability in den site habitat use in the summer, but low variability in the fall and winter. The dens of male mice were farther apart than those of females, and home range areas averaged 2.9 ha ( s = 4.27 ha) for 8 males , and 0.8 ha ( s = 0.76 ha) for 7 females (overall ￣ x = 1.7 + 2.97 ha). These areas were larger than those reported for other species of Peromyscus . The combined effects of drought and reduced food availability may have contributed to the larger areas used.