Site fidelity of male Galápagos sea lions: a lifetime perspective

Knowledge about the distribution of resources can lead to the development of spatial preferences and long-term site fidelity. Individuals are expected to choose sites that best suit their needs. However, dominant individuals restrict movements of less competitive ones. Accordingly, one may expect spatial preferences to differ with regard to individual characteristics and to change over time. We investigated lifetime changes of site fidelity patterns with regard to reproductive success in male Galápagos sea lions (Zalophus wollebaeki). Showing a high degree of natal philopatry in the first 2 years of life, non-territorial males pass through a stage of fidelity to their natal colony where they develop preferences for areas outside prime breeding areas. Variation in the degree of spatial preferences was not associated with age or size, characteristics linked to an individual’s dominance status. For non-territorial males, roaming proved to be an adequate strategy to gain reproductive success. Only the most competitive males established territories in areas preferentially visited by females. They had a high probability to return to breeding areas where they successfully reproduced in previous seasons. Overall, the results reveal lifetime changes in site fidelity with regard to male status. The degree of site fidelity observed within the colony suggests familiarity and thus a high degree of tolerance among individuals using the same areas. This seems to facilitate attendance in the colony and thus the possibility to prospect for oestrus females.     

Transatlantic migration by post-breeding puffins: a strategy to exploit a temporarily abundant food resource?

The distribution of Atlantic puffins (Fratercula arctica) from Skellig Michael, south-west Ireland, was investigated using geolocation loggers between the 2010 and 2011 breeding seasons. All tracked birds travelled rapidly west into the North Atlantic at the end of the breeding season in August, with the majority undertaking transatlantic trips from Ireland to the Newfoundland-Labrador shelf. The furthest distance from the colony reached by each bird was not influenced by body mass or sex and was achieved in approximately 20 days. By October, all birds had moved back to the mid Atlantic where they remained resident until returning to the breeding colony. The most parsimonious explanation for the rapid, directed long-distance migration is that birds exploit the seasonally high abundance of prey [e.g., fish species such as capelin (Mallotus villosus) and sandlance (Ammodytes spp.)] off the Canadian coast, which is also utilised by large populations of North American seabirds at this time. Once the availability of this short-term prey resource has diminished, the tracked puffins moved back towards the north-east Atlantic. A relationship between relative abundance of puffins and zooplankton was found in all winter months, but after correcting for spatial autocorrelation, was only significant in November and January. Nevertheless, these results suggest a potential switch in diet from mainly fish during the breeding and early post-breeding periods to zooplankton over the remaining winter period. This study suggests that puffins from south-west Ireland have a long-distance migration strategy that is rare in breeding puffins from the UK and identifies a key non-breeding destination for puffins from Ireland. This has implications for the susceptibility of different breeding populations to the effects of possible climatic or oceanographic change.     

Localized defecation by pike: a response to labelling by cyprinid alarm pheromone?

Fathead minnows (Pimephales promelas) that have never encountered a predatory pike (Esox lucius), are able to detect conspecific alarm pheromone in a pike's diet if the pike has recently consumed minnows. It remains unclear how this minnow alarm pheromone is secreted by pike and if a pike is able to avoid being labelled as a potential predator by localizing these cues away from its foraging range. The first experiment determined that minnow alarm pheromone is present in pike feces when pike are fed minnows. Individual fathead minnows exhibited a fright response to a stimulus of pike feces if the pike had been fed minnows, but not if the pike had been fed swordtails, which lack alarm pheromone. Individual minnows also exhibited a fright reaction to alarm pheromone in the water (which contained no feces) housing pike which had been fed minnows, suggesting that alarm pheromone is also released in urine, mucous secretions and/or via respiration. The second experiment determined that test pike spent a significantly greater proportion of time in the home area of the test tanks (i.e. where they were fed) but the majority of feces were deposited in the opposite end of the test tank. By localizing their defecation away from the home or foraging area, pike may be able to counter the effects of being labelled as a predator by the alarm pheromone of the prey species.     

How do larvae attach to a solid in a laminar flow?

A hydrodynamic model explaining the mechanism of contact of marine larvae in vertical flows is presented. Two hydrodynamic factors—flow vorticity and larval self-propulsion—are the key components in the mathematical model. It is shown that flow vorticity causes a larva to rotate and change the direction of self-thrust, thus leading to its migration across the mean flow. The latter motion is of an oscillatory nature. Contact will be enabled only for sufficiently large amplitudes of oscillations. Simple expressions for the probability of initial contact are obtained for two-dimensional Couette and Poiseuille flows. The three-dimensional motion of a larva in a tube is studied using the Monte-Carlo simulations. It is shown that contact probability depends mainly on the ratio of the characteristic flow velocity and the larva’s swimming speed. The theoretical results compare favorably with available experimental data. Possible applications of the method and results presented here to the classical problem of larval attachment to bodies of general geometry are briefly discussed in the concluding section.     

Trading rules and the environment: Does equal treatment lead to a cleaner world?

In this paper, we consider a three-stage game in the context of a competing exporters model to compare and contrast the effects of discriminatory and uniform (Most Favored Nation, MFN) tariffs on countries’ choice over environmental standards for varying degrees of pollution spillovers. Because of the presence of punishment effects and stronger own and cross-tariff effects, we find that discrimination yields higher standards than MFN (and free trade) independently of the extent of pollution spillovers. When pollution is local and incentives to free ride on other countries’ abatement efforts are weak, we show, however, that welfare is larger under MFN than under discrimination. In a dynamic setting, we consider the impact of symmetric and asymmetric treatments on the sustainability of an international environmental agreement (IEA) and obtain that multilateral cooperation is easier to sustain under discrimination than under MFN (or free trade).     

Reproduction versus work in queenless ants: when to join a hierarchy of hopeful reproductives?

Many animal societies contain few breeders and many helpers. In some species, individuals can become either helpers or breeders, and breeding is often restricted to high rankers in a dominance hierarchy. In social Hymenoptera with no morphological queen caste, all females have the potential to become dominant and reproduce. In our model, females involved in the hierarchy do not work and gain direct fitness if they become alpha following death of the current alpha, while females not in the hierarchy gain indirect fitness by working. Using an inclusive-fitness model combined with models of alpha replacement in slightly different types of near-linear hierarchies, we determined the critical rank (i.e., optimal hierarchy length) for which the gain in fitness by entering the hierarchy as a hopeful reproductive equals the cost caused by a reduced worker force. High relatedness decreases the hierarchy length by lowering the potential benefit of entering the hierarchy. In contrast, large colony size increases the hierarchy length because the cost of each non-working high ranker is relatively lower. The model predicts a hierarchy of five workers in the queenless ant Dinoponera quadriceps, close to empirical data which show that in a colony of about 100 females, the top 5 carry out 72.8% of the aggressive interactions. The model is also used to make several testable predictions about the effect on hierarchy length of (1) variation in colony size and (2) variation in worker reproductive options between species of the queenless ants genus Diacamma. Received: 16 March 1999 / Received in revised form: 30 June 1999 / Accepted: 11 July 1999     

Maternal transfer of mercury to the developing embryo/fetus: is there a safe level?

Mercury (Hg) exposure is ubiquitous in modern society via vaccines, fish/crustacea, dental amalgam, food, water, and the atmosphere. This article examines Hg exposure in the context of primary exposure to pregnant women and secondary exposure experienced by their unborn babies. Babies in utero are particularly at risk of higher Hg exposure than adults (on a dose/weight basis through maternal Hg transfer via the placenta), and are more susceptible to adverse effects from mercury and its biologically active compounds. It is, therefore, critical that regulatory advisories around maximum safe Hg exposures account for pregnant women and secondary exposure that children in utero experience. This study focused on standardized embryonic and fetal Hg exposures via primary exposure to the pregnant mother of two common Hg sources (dietary fish and parenteral vaccines). Data demonstrated that Hg exposures, particularly during the first trimester of pregnancy, at well-established dose/weight ratios produced severe damage to humans including death. In light of research suggestive of a mercuric risk factor for childhood conditions such as tic disorders, cerebral palsy, and autism, it is essential that Hg advisories account for secondary prenatal human exposures.     

Hypoxia increases the behavioural activity of schooling herring: a response to physiological stress or respiratory distress?

Atlantic herring, Clupea harengus, increase their swimming speed during low O₂ (hypoxia) and it has been hypothesised that the behavioural response is modulated by the degree of “respiratory distress” (i.e. a rise in anaerobic metabolism and severe physiological stress). To test directly whether a deviation in physiological homeostasis is associated with any change in behavioural activity, we exposed C. harengus in a school to a progressive stepwise decline in water oxygen pressure and measured fish swimming speed and valid indicators of primary and secondary stress (i.e. blood cortisol, lactate, glucose and osmolality). Herring in hypoxia increased their swimming speed by 11–39% but only when was <8.5 kPa and in an unsteady (i.e. declining) state. In parallel with the shift in behaviour, plasma cortisol also exhibited an increase with plasma osmolality was subject to a transient rise at 8.5 kPa and plasma glucose was generally reduced at However, without any rise in anaerobically derived lactate levels, there was no evidence of respiratory distress at any set We show that a shift in physiological homeostasis is indeed linked with an increase in the swimming speed of herring but the physiological response reflects a hypoxia-induced shift in metabolic fuel-use rather than respiratory distress per se. The significance of this behavioural–physiological reaction is discussed in terms of behavioural-energetic trade-offs, schooling dynamics and the hypoxia tolerance of herring.     

Connectivity in solitary ascidians: Is a 24-h propagule duration sufficient to maintain large-scale genetic homogeneity?

Ascidians are considered to have lower dispersal potential than most other sessile marine invertebrates with planktonic propagules by virtue of a very brief propagule duration. The larvae of colonial forms remain in the water column for only a few minutes, whereas most solitary forms settle in less than 24 h. This difference in propagule duration has been used to explain why allozyme data from colonial ascidians on the Australian east coast were genetically distinct at different sampling sites, whereas a solitary species exhibited no genetic structure. Spatial homogeneity in solitary species is surprising because genetic structure of species with much higher dispersal potential can be characterised by isolation by geographic distance, suggesting that these disperse by means of a stepping-stone pattern of dispersal. I reassessed the dispersal potential of solitary ascidians using DNA sequence data from the mitochondrial cytochrome oxidase subunit 1 gene and the intron of the nuclear adenine nucleotide transporter gene of a common south-eastern Australian solitary ascidian, Pyura praeputialis, using samples that span the species’ distribution range. Congruent with earlier findings, there was no evidence for stepping-stone dispersal, but it must be conceded that these results could be strongly affected by frequent adult dispersal, particularly by means of anthropogenic vectors, as well as insufficient marker resolution.     

Nanotechnology in cosmetics: a boon or bane?

Recent advances in the field of nanotechnology enabled the manufacturing of elaborated nanometer-sized particles for various biomedical applications. The cosmetic industry is one of the most enthusiastic early adopters of nanotechnology which routinely uses nano-scale ingredients. However, in the absence of mandatory product labeling, it is difficult to estimate the number of cosmetics, sunscreens and personal care products containing nanoparticles that are now commercially available. The increased capacity of nanoparticles to penetrate skin and gain access to human cells is a double-edged sword as it may be useful for medical purposes, but might also result in far greater uptake of substances that exert adverse health effects. Since nanomaterials represent a large group of structurally, physically, and chemically variable substances, specific toxicological studies are required for each product prior to commercialization. This review aims to delineate the most investigated applications, risk and safety considerations, and regulation of nanotechnology in the field of cosmetics.     

Deconstructing an assemblage of “turtle” barnacles: species assignments and fickle fidelity in Chelonibia

Barnacles in the genus Chelonibia are commensal with a variety of motile marine animals including sea turtles, crustaceans, and sirenians. We conducted a worldwide molecular phylogenetic survey of Chelonibia collected from nearly all known hosts to assess species relationships, host-fidelity, and phylogeographic structure. Using DNA sequences from a protein-coding mitochondrial gene (COI), a mitochondrial rRNA gene (12S), and one nuclear rRNA gene (28S), we found that of four species, three (C. testudinaria, C. patula, and C. manati) are genetically indistinguishable. In addition, we show each utilizes a rare androdioecious mode of reproduction involving complemental males. In contrast, the fourth species (C. caretta), which is hermaphroditic and specializes on turtles, is genetically distinct—leading to the conclusion that the three former taxa are morphotypes of the same species and should be synonymized under C. testudinaria. Phylogenetic analysis resulted in three geographic clades (Atlantic, Indian Ocean/western Pacific, and eastern Pacific) with haplotype parsimony networks revealing no shared haplotypes among geographic regions. Analysis of molecular variance detected significant differences among sequences by region (p < 0.005); conversely, there were no significant differences among sequences when grouped by host or taxonomic designation. Average pairwise genetic distances were lower between the eastern Pacific and Atlantic clades (0.053 ± 0.006) than between the eastern Pacific and Indian Ocean/western Pacific clades (0.073 ± 0.008), suggesting Atlantic and eastern Pacific populations were connected more recently, perhaps until the rise of the Isthmus of Panama. Host use by Chelonibia morphotypes is discussed along with speculation on possible ancestral hosts and support for a “turtle-first” hypothesis.     

Sensitivity of a coupled physical–biological model to turbulence: high-frequency simulations in a northern Adriatic station

This paper investigates the impacts of different turbulence models on the biological state at an ocean station in the northern Adriatic sea, named S3, comparing them with other uncertainties inherent to coupled physical–biological simulations. The numerical tool is a 1-D model resulting from the coupling of two advanced numerical models. The hydrodynamic part is modelled using the General Ocean Turbulence Model (www.gotm.net), in a version adopting state-of-the-art second-moment Turbulence Closure Models (TCMs). Marine biogeochemistry is parameterized with the Biogeochemical Flux Model (http://www.bo.ingv.it/bfm), which is a direct descendant of ERSEM (European Regional Sea Ecosystem Model). Results, obtained by forcing the model with hourly wind and solar radiation data and assimilating salinity casts, are compared against monthly observations made at the station during 2000–2001. Provided that modern second-moment TCMs are employed, the comparisons indicate that both the physical and the biological dynamics are relatively insensitive to the choice of the particular scheme adopted, suggesting that TCMs have finally ‘converged’ in recent years. As a further example, the choice of the nutrient boundary conditions has an impact on the system evolution that is more significant than the choice of the specific TCM, therefore representing a possible limitation of the 1-D model applied to stations located in a Region of Freshwater Influence. The 1-D model simulates the onset and intensity of the spring–summer bloom quite well, although the duration of the bloom is not as prolonged as in the data. Since local dynamics appears unable to sustain the bloom conditions well into summer, phytoplankton at the station was most likely influenced by river input or advection processes, an aspect that was not found when the S3 behaviour was adequately modelled using climatological forcings. When the focus is in predicting high-frequency dynamics, it is more likely that lateral advection cannot be neglected. While the physical state can be satisfactorily estimated at these short time scales, the accurate estimation of the biological state in coastal regions still appears as rather elusive.     

Ectomised conductors in the golden orb-web spider, Nephila plumipes (Araneoidea): a male adaptation to sexual conflict?

Male genitalia may facilitate sperm protection by acting as a plug that prevents or hinders future matings. The pedipalps (intromittant organs) of males of the orb-web spider, Nephila plumipes, have a conductor with a peculiarly curved ending and a triangular process near the terminal end. The tip of the conductor, including the process, breaks during most matings and remains inside the female genital tract. We explored the possible function of the conductor as a mating plug using the double-mating sterile-male technique. Our data are not consistent with a plug function because males use only one pedipalp in each mating, thus leaving an unobstructed insemination duct available for future matings; conductors of males mating with virgin females are not more likely to break than those of males mating with mated females, and second males show no preference for used or unused spermathecae. In addition, males that inserted their palp in the insemination duct that contained a tip of the conductor from a previous male obtained a share in the paternity of the female's clutch of eggs. Interestingly, the conductor is more likely to break if it is inserted in an unused spermatheca. We argue that several lines of evidence suggest that the conductor breaks as a result of intersexual conflict over the duration of copulation.     

Kelp gulls attack Southern right whales: a conservation concern?

Kelp gulls (Larus dominicanus) feed on pieces of skin and blubber they rip from Southern right whales’ (Eubalaena australis) backs in their breeding areas at Península Valdés, Argentina, producing injuries. This behavior has increased since the first record in 1972, and some authors have suggested that constant gull harassment could have a negative effect on right whale population. The main goal of this study is to assess the variables that most affect the gull attacks. We analyzed 5359 whale-watching sightings made during trips from Puerto Pirámides (42o34′S, 64o16′W) along the whale breeding seasons (June–December) 2005 to 2007. The most important factors affecting the attacks include the presence of a mother–calf pair, the time within the season, the distance to the coast and the wind velocity. There is also concern of possible transmission of infectious diseases in the attacks since increasing number of whales with different patterns of skin lesions have been observed.     

Guppies as heterospecific facilitators: a precursor of exploratory behavior?

Behavior can explain population-level processes such as dispersal, yet connecting a specific behavioral phenomenon with a larger ecological pattern is often speculative rather than supported by experimental studies. We investigate how exploratory behavior may develop in the killifish, Rivulus hartii through association with another taxon, the guppy, Poecilia reticulata. We hypothesize that exploratory behavior is enhanced by nearby guppies, which embolden Rivulus to move along the river edge, through zones of high predation risk. We tested individual boldness in the presence of both guppies and conspecifics. We also tested for the effect of prior experience with guppies, comparing boldness in Rivulus from locations in which it was either allopatric to or sympatric with guppies. Guppies increased boldness in Rivulus, equivalent to the effect of conspecifics, and prior experience with guppies also increased boldness over that of inexperienced Rivulus. Sympatric Rivulus were shy compared with the allopatric ones when each was tested alone, but this relationship reversed when guppies were present, showing that boldness is a plastic trait that can be influenced by the population of origin. An experimental field-stream test showed that guppies increased movement of Rivulus under predation threat, supporting links in a conceptual framework that connects a behavioral phenomenon, exploratory boldness, with a larger ecological pattern, selection of favorable habitats that, in turn, can lead to increased reproduction and fitness relative to non-dispersers.     

Do honey bees average directions in the waggle dance to determine a flight direction?

The waggle dance of the honey bee is a recruitment behavior used to communicate the location of a resource to a nest mate. There is, however, significant imprecision communicating the direction across waggle runs in a single dance. In this study, we ask whether honey bee recruits determine the direction of their flight based on an average of many waggle runs, or on a single waggle run. We show that the distribution of recruit flight directions is narrower than the distribution of directions indicated in the dance. We also show that there is a better fit between observed flight directions and the prediction of a multiple-waggle-run-averaging model than a last-waggle-run or other single-waggle-run models. These findings substantially weaken hypotheses about the adaptive nature of imprecision in honey bee recruitment.     

Recognising one’s enemies: a functional approach to risk assessment by prey

Little has been done to compare the relative importance of various mechanisms through which prey assess the potential risk from natural enemies. We used predator-naive spider mites (Tetranychus urticae, Tetranychidae) to (1) compare the responses of prey to chemical cues from enemy and non-enemy species and (2) investigate the source of these cues. In the laboratory, we observed the distribution of T. urticae in response to cues from nine mite species, including (1) predators of spider mites, (2) predators/parasites of other animals, and (3) fungivores/pollen-feeders. When given a choice over 24 h, spider mites foraged and oviposited in fewer numbers on leaf discs that were previously exposed to predatory or parasitic mites (including species incapable of attacking spider mites) than on clean leaf discs (unexposed to mites). Interestingly, previous exposure of leaf arenas to fungivores and pollen-feeders had no significant effect on spider mite distribution. We then observed the response of T. urticae to cues from two species of predator that had been reared on a diet of either spider mites or pollen. T. urticae showed stronger avoidance of leaf discs that were previously exposed to spider-mite-fed predators than of discs exposed to pollen-fed predators. Nevertheless, for one predator species (Amblyseius andersoni), T. urticae still preferred to forage and oviposit on clean (unexposed) discs than on discs exposed to pollen-fed predators. Protein-derived metabolic wastes of predatory or parasitic mites may provide a general cue about potential predation risk for T. urticae. However, T. urticae also avoided areas exposed to pollen-fed predators, suggesting there may be other sources of enemy recognition by the spider mites. We discuss the ecological and evolutionary mechanisms that may influence the scope of information through which animals assess predation risk. Received: 11 January 1999 / Received in revised form: 25 October 1999 / Accepted: 20 November 1999