Hostplant-habitat structure and the evolution of butterfly mate-locating behaviour

A hostplant-habitat model is described which explains fundamental differences in mate-locating behaviour between butterfly species, based on a sequence of spatially distinctive activities (habitual patrolling, localized perching, territoriality, lek assembly). It gives equal weight to phylogeny and ecology and is consistent with models for the evolution of territoriality and population structure. Perching repeatedly at characteristic sites, territoriality and lek assembly evolve when resources become associated with distinctive hostplant-habitat structures in which topographic features provide predictable vantage points for acquiring mates. Habitual patrolling is an ancestral behaviour which is suited to widespread and unpredictable resource distributions and to species whose individual apparency detracts from the use of topographic vantage points. Hostplants (emergence sites), nectar and thermoregulation sites typically provide resources and act as precursors to localized perching, territoriality and lek assemblages. But these behaviours fail to evolve in species whose habitats do not include obvious topographic landmarks which provide clear vantage points for males awaiting females and focal points for females searching for males. Where these landmarks occur they result in an increase in receptive female density at those locations compared to the remainder of the habitat.     

Lek behaviour of Drosophila cnecopleura in Hawaii

ABSTRACT.

• 1 Male spacing, aggression, and female visitation are described for a lek of Drosophila cnecopleura Hardy within a Hawaiian rainforest. The lek was located at a single tree of Pisonia umbellifera, and the males present defended individual leaves as mating territories. Observations were made in October 1986 and April 1987.
• 2 Approximately twice as many males were present at the lek in October than in April. At both times, males generally perched on the lowest leaves in the lek. Individuals did not remain on particular leaves for long periods of time but frequently moved among different territories.
• 3 Males engaged in two types of aggressive encounters, face-offs and chases, and in all encounters the resident displaced the intruder.
• 4 Females were sighted at the lek 0.69 times/h in October and 0.23 times/h in April. Most of the leaves visited by females were among the lowest in the lek.

     

Agonistic behaviour and control of access to hiding places in two intertidal blennies, Lipophrys pholis and Coryphoblennius galerita (Pisces: Blenniidae)

In this study we investigated the relationships between dominance rank and access to shelters in captive groups of Lipophrys pholis and Coryphoblennius galerita, as well as the effects of group size and shelter availability. Dominance rank was strongly correlated with size in juvenile L. pholis and with sex and size in adult C. galerita, males being dominant over females of similar size. Access to shelters was significantly correlated with dominance rank. For both species, most interactions occurred out of shelters. Direct disputes over shelters were always initiated by the dominant fish and the initiator was always the winner. The rate of aggression per fish per unit time decreased with an increase in the number of fish in L. pholis but not in C. galerita. No significant differences were found in groups differing in the number of shelters. C. galerita showed a higher rate of agonistic interactions and a higher proportion of overt aggression than L. pholis. It is suggested that one of the functions of agonistic interactions in these fishes is the control of a set of shelters, in the network of pathways used by each individual within its home range, minimising the time required to hide in case of danger. Received in revised form: 29 January 2001 Electronic Publication     

Movements,status, access to nectar,and spatial organisation of the tui

Abstract

Movements of tui (Prosthetnadera novaeseelandiae) breeding on Tiritiri Matangi Island were followed and related to changes in nectar access. The island has limited nectar sources and birds must move to gain access to nectar year round. All tui leave the island, although the extent and timing of movement varies for different individuals. Tui return for breeding but again the timing of the return varies for individuals. Nectar sources were typically concentrated in both time and space, and access was related to individual asymmetries such as sex, residential status and age. These same asymmetries also relate to the timing of individuals movements, and where individuals nest relative to nectar sources. At concentrated food sources, access was determined by an absolute social hierarchy. Although tui defend exclusive feeding territories, breeding territories are not exclusive and access to nectar is determined by distance to nest site. Such variability in spatial organisation is related to a continuum concept of social organisation.     

Observations on the breeding biology of the Writhed-billed Hornbill (Aceros waldeni) in the Philippines

Summary We report on some aspects of the breeding biology of the critically endangered Writhed-billed Hornbill (Aceros waldeni) on the island of Panay, Philippines. Observations were made at three nests during 1995–1997. Walling-in of the females commenced in the first week of March. One female remained incarcerated for 77 days, two of three broods completed fledging around May 20 (1995, 1997). Details on fledging of the female and her brood and postfledging care by both parents are reported.The food of the males at two nests was ca. 98% fruits and 2% invertebrates. The plants exploited comprised at least 14 species. Over a third of the fruits delivered were figs of a small number of species.Two males had average feeding rates of 0.56 and 0.88 times per hour respectively, and fed 1 to 66 (median 8) items per feeding visit at the nest. The hourly feeding rate increased after hatching, but the composition of the diet did not change noticeably. As a rule, food items were delivered singly and, during one visit, in runs of one, or rarely up to 3, species.In the three weeks following vacation of the nest, the male appeared to be the sole food provider while the female stayed continually with the 3 young (as sentinel?) in the vicinity of the nest.The nest environs were defended by the male against Tarictic Hornbills (Penelopides panini panini). Six vocalisations of the parents are mentioned. One was used in territorial skirmishes with Tarictic Hornbills.With perhaps less than 30 pairs of the Writhed-bill surviving, the future for the species looks bleak. Only drastic conservation measures can prevent the species' demise. Some have been started by the PESCP.This paper is publication No. 11 of the Philippine Endemic Species Conservation Project (PESCP) of the Frankfurt Zoological Society.     

Territoriality and associated behaviour in three species of the genus Cephalopholis (Pisces: Serranidae) in the Gulf of Aqaba, Red Sea

Social structure and behavioural mechanisms enabling sympatry in three species of predatory fish in the Gulf of Aqaba ( Cephalopholis miniata (Forsskål), Cephalopholis argus Bloch and Schneider, and Cephalopholis henistiktos (Rüppell)) were examined in this study. C. miniata and C. argus formed compound interspecific territories in which they occurred in haremic groups consisting of a dominant male and two to 12 females. C. miniata and C. argus groups occupied territories of up to 475 m², and 2000 m² respectively, subdivided into secondary territories, each inhabited by an individual female. Observations of tagged fish disclosed behaviour patterns of patrolling by males, visiting the females, and antiparallel swimming of sexes. C. hemistiktos , in contrast, was monogamous and each pair jointly defended a common territory of up to 62 m². Among the three species the dominance hierarchy was C. argus > C. miniata > C. hemistiktos .     

Size-related differences in behaviour and spatial distribution of juvenile Atlantic salmon in a novel environment

Within a month of first feeding sibling juvenile salmon had developed not only large differences in size (up to fivefold in weight), but also significant differences in behaviour. Large fish remained in refuges (overhead cover) significantly longer after having been frightened. On leaving the shelters most small fish established individual territories on the bottom and. downstream of the shelters. The greater aggressiveness of small fish in a novel environment (from holding tank to experimental stream) was related to this apparent territoriality. The increased shelter residence time and delayed establishment of individual territories might be interpreted as greater caution in large fish, which are able to avoid risky situations due to their higher energy reserves. In contrast, smaller fish need to leave refuges more quickly and to establish individual territories in a novel environment.     

The food and feeding habits of blackspot snapper, Lutjanus fulviflamma (Pisces: Lutjanidae) in shallow waters of Mafia Island, Tanzania

Natural diet and feeding habits of blackspot snapper, Lutjanus fulviflamma (Forsskål 1775) were investigated in Mafia Island Marine Park (MIMP) and intensively fished areas (IFA) between May 1999 and April 2001. An index of relative importance (IRI) was used to assess the food preference for L. fulviflamma. Feeding habits were studied with respect to sex and size of the predator, seasons and feeding periodicity. Of 4642 L. fulviflamma specimens sampled, 46% had empty stomachs. Brachyurans were the main prey of L. fulviflamma accounting for 48% IRI. Benthic invertebrates dominated by other crustaceans, gastropods, bivalves, cephalopods and polychaetes and demersal teleosts made up the remainder of the diet. Female and male L. fulviflamma were not effectively segregated by trophic dimension in the study areas. Specimens in the 90–120 mm total length (TL) fed exclusively on crustaceans, with shrimps accounting for 40% IRI. Lutjanus fulviflamma in the 270–300 mm TL preferred fish prey accounting for 50% IRI. The diet of fish species showed clear spatial differences, which were dependent on size distributions. Lutjanus fulviflamma fed mostly but not exclusively at night peaking at dusk and dawn. The results clearly demonstrate that L. fulviflamma is an opportunistic forager, which exhibits both diel and ontogenetic feeding habits.     

From population structure to individual behaviour: genetic analysis of social structure in the European wild rabbit (Oryctolagus cuniculus)

The European wild rabbit (Oryctolagus cuniculus) lives in stable, territorial breeding groups, with male-biased natal dispersal, female philopatry, and a polygynous mating system. It was introduced into Britain in the 11 th century and kept in captive warrens as a food and fur resource. Populations expanded in the wild in the 18th century. Microsatellite markers were employed to examine the genetic structure of wild rabbit populations on three spatial scales: macrogeographic structure of 17 populations in East Anglia, microgeographic structure of a tagged population in the grounds of the University of East Anglia over four consecutive years, and pairwise kinships and individual movement within this tagged population. Populations across East Anglia were found to be genetically distinct, and heterozygote deficits were observed at all loci indicating sub-division within sampled populations. Analysis of the tagged population confirmed that rabbit populations are genetically sub-divided among social groups. Studying this population over four consecutive years revealed that as the population size increased, the number of social groups increased. Analysis of individual pairwise relatedness of females indicated that individuals did not necessarily group with kin, and behavioural data indicate that an optimum group size may exist which maximizes reproductive success.     

Selection,structure and the heritability of behaviour

Characters which are closely linked to fitness often have low heritabilities (V_A/V_P). Low heritabilities could be because of low additive genetic variation (V_A), that had been depleted by directional selection. Alternatively, low heritabilities may be caused by large residual variation (V_R=V_P – V_A) compounded at a disproportionately higher rate than V_A across integrated characters. Both hypotheses assume that each component of quantitative variation has an independent effect on heritability. However, V_A and V_R may also covary, in which case differences in heritability cannot be fully explained by the independent effects of elimination‐selection or compounded residual variation. We compared the central tendency of published behavioural heritabilities (mean=0.31, median=0.23) with morphological and life history data collected by 26 ). Average behavioural heritability was not significantly different from average life history heritability, but both were smaller than average morphological heritability. We cross‐classified behavioural traits to test whether variation in heritability was related to selection (dominance, domestic/wild) or variance compounding (integration level). There was a significant three‐way interaction between indices of selection and variance compounding, related to the absence of either effect at the highest integration level. At lower integration levels, high dominance variance indicated effects of selection. It was also indicated by the low CV_A of domestic species. At the same time CV_R increased disproportionately faster than CV_A across integration levels, demonstrating variance compounding. However, neither CV_R nor CV_A had a predominant effect on heritability. The partial regression coefficients of CV_R and CV_A on heritability were similar and a path analysis indicated that their (positive) correlation was also necessary to explain variation in heritability. These results suggest that relationships between additive genetic and residual components of quantitative genetic variation can constrain their independent direct effects on behavioural heritability.     

Sexual and seasonal variation in the diet and foraging behaviour of a sexually dimorphic carnivore, the honey badger (Mellivora capensis)

The honey badger, or ratel, Mellivora capensis has not been well studied despite its extensive distribution. As part of the first detailed study, visual observations of nine habituated free-living individuals (five females, four males) were used to investigate seasonal, annual and sexual differences in diet and foraging behaviour. Theory predicts that generalist predators 'switch' between alternative prey species depending on which prey species are currently most abundant, and diet breadth expands in response to decreased availability of preferred food types. There were significant seasonal differences in the consumption of eight prey categories related to changes in prey availability but no seasonal differences in food intake per kg of body mass. As predicted, the cold-dry season diet was characterized by low species richness and low foraging yield but high dietary diversity, while the reverse was true in the hot-dry and hot-wet seasons. In accordance with these predictions, results suggest that the honey badger maintains its intake level by food switching and by varying dietary breadth. Despite marked sexual size dimorphism, male and female honey badgers showed no intersexual differences in prey size, digging success, daily food intake per unit body weight or foraging behaviour. Results do not support the hypothesis that size dimorphism is primarily an adaptation to reduce intersexual competition for food.     

Changes in food selection by workers of the pharaoh's ant, Monomorium pharaonis

The results from simple choice test experiments with laboratory and field colonies of pharaoh's ants have revealed two behavioural traits that influence the way in which foraging worker ants respond to foods. Initially, worker ants from laboratory colonies showed a distinct preference for certain foods (e.g. honey and peanut butter). However, when given only these 'preferred' foods continuously for several weeks, workers showed a marked preference for other foods when offered a choice. This 'satiation' response occurred even though the initial diet was originally highly attractive to foraging workers. In addition, workers show a marked tendency to alternate between carbohydrate foods and protein foods. Thus, workers from colonies fed predominantly on proteins, subsequently showed a marked preference for carbohydrates, and vice versa. The 'satiation' and 'alternation' responses to foods ensure that colonies receive a diet that is both varied and balanced. In addition, these aspects of feeding behaviour have important consequences for the use of food-based baits in control measures against Monomorium pharaonis (L.).     

Habitat structure and animal movement: the behaviour of bumble bees in uniform and random spatial resource distributions

Foraging organisms (like bumble bees) move between resource points (like flowers) whose natural distributions vary enormously: from hyperdispersed to random to clumped. These differences in habitat structure may significantly influence the fitness of both plant and pollinator. To examine the effect of habitat structure on pollinator movement and fitness, we observed captive worker bumble bees collecting nectar from artificial flowers containing equal volumes of reward and arranged in two spatial configurations: a hexagonal array with constant distances between flowers (“constant”), and an “exploded hexagonal” array, with variable distances between flowers (“variable”). The mean nearest-neighbour distance was the same in both arrays, as was the general hexagonal appearance. The experiment therefore compares how resource dispersion, independent of nearest-neighbour distance, influences bee behaviour. Bees in the variable array showed decreased directionality, higher revisitation frequencies, and greater inter-flower flight distances than shown in the constant array. As a consequence, bees in the variable array had a 19% lower gross rate of nectar collection. Our results suggest that wild-foraging bees should prefer regularly spaced flowers (when all else, including mean nearest-neighbour distance, is equal), and that plants can decrease self-pollination by regular spacing between flowers, inflorescences, or individuals. Received: 16 January 1996 / Accepted: 30 June 1997