Maternal effects on begging behaviour: an experimental demonstration of the effects of laying sequence, hatch order, nestling sex and brood size

Differential resource allocation by females across the laying sequence has been hypothesised as a mechanism through which females could either compensate nestlings that hatch last in asynchronous broods or promote brood reduction. In this study we artificially incubated eggs and cross-fostered offspring to manipulate nestlings’ position in the hatching order, to identify whether the competitive ability of nestlings is dependent on position in the laying sequence. In both control and experimentally reversed broods, first hatched chicks had a higher survival than last hatched siblings. Yet, nestlings that hatched from eggs laid in the second half of a clutch begged with a greater intensity than nestlings hatched from eggs laid in the first half of a clutch. In natural broods, the greater begging competitiveness of nestlings from later-laid eggs led to a moderation of sibling competition and these nestlings achieved the same body size and weight as nestlings from eggs laid in the first half of the clutch. The lack of a substantial difference in the size and condition of surviving nestlings in respect to laying order suggests that differential resource allocation across the egg-laying sequence partially compensates for hatching last in asynchronous broods and reduces the negative effects of the nestling size hierarchy. The effect of laying order, brood size and experimental treatment also differed for male and female nestlings. Our study highlights the need to be aware of the complex and subtle effects of nestling sex and laying sequence when investigating genetic and environmental influences on individual fitness.     

A curvilinear effect of height on reproductive success in human males

Human male height is associated with mate choice and intra-sexual competition, and therefore potentially with reproductive success. A literature review (n = 18) on the relationship between male height and reproductive success revealed a variety of relationships ranging from negative to curvilinear to positive. Some of the variation in results may stem from methodological issues, such as low power, including men in the sample who have not yet ended their reproductive career, or not controlling for important potential confounders (e.g. education and income). We investigated the associations between height, education, income and the number of surviving children in a large longitudinal sample of men (n = 3,578; Wisconsin Longitudinal Study), who likely had ended their reproductive careers (e.g. > 64 years). There was a curvilinear association between height and number of children, with men of average height attaining the highest reproductive success. This curvilinear relationship remained after controlling for education and income, which were associated with both reproductive success and height. Average height men also married at a younger age than shorter and taller men, and the effect of height diminished after controlling for this association. Thus, average height men partly achieved higher reproductive success by marrying at a younger age. On the basis of our literature review and our data, we conclude that men of average height most likely have higher reproductive success than either short or tall men.     

Effects of time since fire on birds: how informative are generalized fire response curves for conservation management?

Fire is both a widespread natural disturbance that affects the distribution of species and a tool that can be used to manage habitats for species. Knowledge of temporal changes in the occurrence of species after fire is essential for conservation management in fire-prone environments. Two key issues are: whether postfire responses of species are idiosyncratic or if multiple species show a limited number of similar responses; and whether such responses to time since fire can predict the occurrence of species across broad spatial scales. We examined the response of bird species to time since fire in semiarid shrubland in southeastern Australia using data from surveys at 499 sites representing a 100-year chronosequence. We used nonlinear regression to model the probability of occurrence of 30 species with time since fire in two vegetation types, and compared species' responses with generalized response shapes from the literature. The occurrence of 16 species was significantly influenced by time since fire: they displayed six main responses consistent with generalized response shapes. Of these 16 species, 15 occurred more frequently in mid- or later-successional vegetation (> 20 years since fire), and only one species occurred more often in early succession (< 5 years since fire). The models had reasonable predictive ability for eight species, some predictive ability for seven species, and were little better than random for one species. Bird species displayed a limited range of responses to time since fire; thus a small set of fire ages should allow the provision of habitat for most species. Postfire successional changes extend for decades and management of the age class distribution of vegetation will need to reflect this timescale. Response curves revealed important seral stages for species and highlighted the importance of mid- to late-successional vegetation (> 20 years). Although time since fire clearly influences the distribution of numerous bird species, predictive models of the spatial distribution of species in fire-prone landscapes need to incorporate other factors in addition to time since fire.     

Structural confirmation of the sea ice biomarker IP25 found in Arctic marine sediments

IP₂₅ is a highly branched isoprenoid and an organic geochemical biomarker that is produced by some Arctic sea ice diatoms. IP₂₅ has previously been used in Arctic palaeo sea ice reconstruction studies and as a tracer for studying Arctic food webs. Here, the molecular structure of IP₂₅ has been confirmed by ¹H and ¹³C NMR spectroscopy following large-scale extraction from marine sediments obtained from the Canadian Arctic and purification using a combination of open-column and HPLC chromatographic methods. The structure of IP₂₅ was consistent between the three different sampling locations and was identical to that found previously for this biomarker following synthesis from a closely related highly branched isoprenoid diene. Since this study represents the first structural characterisation of IP₂₅ in sediments, future analysis of sedimentary IP₂₅ for palaeo Arctic sea ice reconstructions can be carried out with much greater confidence.     

Peregrine falcon egg pollutants

The role of the peregrine falcon (Falco peregrinus) as a bioindicator for the accumulation of organohalogen compounds and other persistent organic pollutants has been established in field studies. Biometric indices for damage caused by pollutants such as the shell thickness and the shell index were determined and the egg contents were analyzed for various pollutants by gas chromatography/mass spectrometry. A wide range of chemically activated luciferase expression (CALUX®) bioassays were performed on subsamples of the eggs.

The following organohalogen compounds were found in the eggs of 2009: dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethane, heptachlor epoxide, hexachlorobenzene, dieldrin, hexachlorocyclohexane, polychlorobiphenyls and polychlorodibenzodioxins and polychlorodibenzofurans, polybromodiphenyl ethers, hexabromocyclododecane, tetrabromobisphenyl A, perfluoro compounds, and mercury. The DDT metabolite, dichlorodiphenyldichloroethene (DDE) (11,800 ng/g dry matter), was found to be the most highly concentrated egg contaminant followed by 2,2′,4,4′,5,5′-hexachlorobiphenyl (3800 ng/g). After a past general drop in pollution level, most egg contaminants presently plateau at levels that may still exceed limit values in foods of animal origin (DDE) or even toxicological thresholds (polychlorobiphenyls + polychlorodibenzodioxins, polybromodiphenyl ethers, perfluorooctanesulfonate, methylmercury).

Accumulation of DDE could be shown in peregrine falcon eggs from the uplands of Southwest Germany with elevations up to 1500 m, presumably due to its global distribution and its cold condensation in higher altitudes. In contrast, the concentration of polychlorobiphenyls in falcon eggs decreases with elevation, indicating that these pollutants originate mainly from conurbations and local industrial sites.

Significant negative correlations were found between both shell index and thickness and the concentration of Hg. A deleterious effect is also evident from a no-observed-adverse-effect level of 120 ng MeHg per gram egg determined by other authors in chronic feeding studies with ibises, which resulted in decreased egg productivity and male homosexual nesting and courtship behavior. The average Hg concentration in the peregrine falcon eggs from 2009 is almost four times higher than this level. MeHg accounted for 82.5% of the Hg present in the eggs of 2009 and 2010.

The cell test DR CALUX® for screening of dioxin-like activities can be used to detect not only the 29 regulated dioxin-like substances but also many other persistent organic pollutants with dioxin-like potencies, such as mixed halogenated dioxins/biphenyls. In our case, the results of bioanalytical screening methods showed no additional effect of other compounds with dioxin-like activity.

Ninety-three out of 177 analytes sought could be detected in the eggs. Chlorinated paraffins, organotin compounds, some pesticides that are still in use, and phthalic esters with the exception of traces of diethylhexyl phthalate could be excluded. All pollutants found in the eggs belong to substance classes banned by the Stockholm and Minamata Conventions.     

Symbiont shuffling during thermal bleaching and recovery in the sea anemone Entacmaea quadricolor

The sea anemone Entacmaea quadricolor simultaneously harbours multiple symbiont types from the genus Symbiodinium, while providing essential habitat for anemonefish. This anemone lives close to its upper thermal threshold and experiences bleaching under elevated temperature and light stress. Here, we determine whether E. quadricolor experienced a shuffling in the abundance of two genetically distinct symbiont types (Symbiodinium C25 and C3.25) during bleaching and recovery. Anemones were exposed to control (22.9 °C) or elevated temperature (28.5 °C) for 42 days, whereas for the following 75 days, all anemones were exposed to 22.9 °C. By day 47, a more pronounced bleaching occurred via symbiont expulsion in the elevated temperature treatment than the control, and the proportion of C25 to C25 + C3.25 increased by 6.2 and 13.2 % in the control and bleached anemones, respectively. The increased relative abundance of C25 to C3.25 after exposure to thermal stress may indicate that C3.25 performs poorly when temperature is elevated. Although no significant recovery in symbiont density was detected, a revival of the C3.25 genotype was found at day 117, which may indicate that it is either more competitive or has qualities that are beneficial to the symbiosis when thermal stress is no longer apparent. This work demonstrates the potential for this anemone species to shuffle its symbiont types in response to environmental change and could provide resilience during times of stress.     

The spatial ecology of juvenile loggerhead turtles (Caretta caretta) in the Indian Ocean sheds light on the “lost years” mystery

While our understanding of the early oceanic developmental stage of sea turtles has improved markedly over recent decades, the spatial context for this life history stage remains unknown for Indian Ocean loggerhead turtle populations. To address this gap in our knowledge, 18 juvenile loggerheads were satellite tracked from Reunion Island (21.2°S, 55.3°E) between 2007 and 2011. Nine turtles swam north toward Oman (20.5°N, 58.8°E), where one of the world’s largest rookeries of loggerheads is located. Three individuals traveled south toward South Africa and Madagascar, countries that also host loggerhead nesting grounds. Fourteen of the transmitters relayed diving profiles. A dichotomy between diurnal and nocturnal diving behavior was observed with a larger number of shorter dives occurring during the day. Diving behavior also differed according to movement behavior as individuals spent more time in subsurface waters (between 10 and 20 m) during transit phases. The study provides an understanding of the oceanic movement behavior of juvenile loggerheads in the Indian Ocean that suggests the existence of an atypical trans-equatorial developmental cycle for the species at the ocean basin scale in the Indian Ocean. These results address a significant gap in the understanding of loggerhead oceanic movements and may help with the conservation of the species.     

Chemical communication in green and golden bell frogs: do tadpoles respond to chemical cues from dead conspecifics?

Captive bred animals often lack the ability of predator recognition and predation is one of the strongest causes of failure of breed and release projects. Several tadpole and fish species respond defensively to chemical cues from injured or dead conspecifics, often referred to as alarm pheromones. In natural conditions and in species that school, the association of chemical cues from predators to alarm pheromones released by attacked conspecifics may lead to the learning of the predator-related danger without experiencing an attack. In the laboratory, this chemical communication can also be used in associative learning techniques to teach naïve tadpoles to avoid specific predators and improve survivorship of released animals. In our experimental trials, tadpoles of the threatened green and golden bell frog (Litoria aurea) did not avoid or decrease their activity when exposed to solutions of conspecific macerate, suggesting that the chemicals released into the water by dead/injured conspecifics do not function as an alarm pheromone. This non-avoidance of dead conspecific chemicals may explain why green and golden bell frog tadpoles have seemingly not developed any avoidance behaviour to the presence of introduced mosquito fish, and may render attempts to teach naïve tadpoles to avoid this novel predator more difficult.     

Modeling regional impacts of climate teleconnections using functional data analysis

Teleconnections are quasi-periodic changes in atmospheric circulation that oscillate over long periods of time and impact climate over large regions. These patterns are often linked to long-term variations in climate and extreme weather events and may explain regional differences in climate vulnerability. We apply methods of functional data analysis to examine regional impacts of teleconnections on climate in British Columbia, Canada, between 1951 and 2000. We focus on monthly mean temperature as an overall determinant of crop growth and apply functional principal components analysis (FPCA) to study variations in the impacts of four major teleconnection indices affecting the Northern Hemisphere (the Southern Oscillation Index, the Pacific North American (PNA), Pacific Decadal Oscillation, and the North American Oscillation indices). Two challenges we consider are that the impacts of teleconnections cannot be observed directly and that fine scale data required to study regional variations may come from different sources with highly varied records. We first fit thin-plate regression splines to the raw data to construct complete series of pseudo-data at fixed grid points. Regression models incorporating Bayesian P-splines were then fit to the pseudo-data to estimate the impacts of the four teleconnections over time. Finally, FPCA was then applied to study regional variations in these effects. Our analysis identified strong variations in mean temperature associated with the PNA. The resulting spatial patterns also reveal areas of increased/decreased temperature variability that may have higher climate risk or be suitable for expansion of agricultural activity.