Why do dolphins form mixed-species associations in the Azores ?

Mixed-species associations are temporary associations between individuals of different species that are often observed in birds, primates and cetaceans. They have been interpreted as a strategy to reduce predation risk, enhance foraging success and/or provide a social advantage. In the archipelago of the Azores, four species of dolphins are commonly involved in mixed-species associations: the common dolphin, Delphinus delphis, the bottlenose dolphin, Tursiops truncatus, the striped dolphin, Stenella coeruleoalba, and the spotted dolphin, Stenella frontalis. In order to understand the reasons why dolphins associate, we analysed field data collected since 1999 by research scientists and trained observers placed onboard fishing vessels. In total, 113 mixed-species groups were observed out of 5720 sightings. The temporal distribution, habitat (water depth, distance to the coast), behaviour (i.e. feeding, travelling, socializing), size and composition of mixed-species groups were compared with those of single-species groups. Results did not support the predation avoidance hypothesis and gave little support to the social advantage hypothesis. The foraging advantage hypothesis was the most convincing. However, the benefits of mixed-species associations appeared to depend on the species. Associations were likely to be opportunistic in the larger bottlenose dolphin, while there seemed to be some evolutionary constraints favouring associations in the rarer striped dolphin. Comparison with previous studies suggests that the formation of mixed-species groups depends on several environmental factors, and therefore may constitute an adaptive response

Combined and single effects of pesticide carbaryl and toxic Microcystis aeruginosa on the life history of Daphnia pulicaria

The combined influence of a pesticide (carbaryl) and a cyanotoxin (microcystin LR) on the life history of Daphnia pulicaria was investigated. At the beginning of the experiments animals were pulse exposed to carbaryl for 24 h and microcystins were delivered bound in Microcystis’ cells at different, sub-lethal concentrations (chronic exposure). In order to determine the actual carbaryl concentrations in the water LC–MS/MS was used. For analyses of the cyanotoxin concentration in Daphnia’s body enzyme-linked immunosorbent assay (ELISA) was used. Individual daphnids were cultured in a flow-through system under constant light (16 h of light: 8 h of dark), temperature (20°C), and food conditions (Scenedesmus obliquus, 1 mg of C l−1). The results showed that in the treatments with carbaryl egg numbers per female did not differ significantly from controls, but the mortality of newborns increased significantly. Increasing microcystin concentrations significantly delayed maturation, reduced size at first reproduction, number of eggs, and newborns. The interaction between carbaryl and Microcystis was highly significant. Animals matured later and at a smaller size than in controls. The number of eggs per female was reduced as well. Moreover, combined stressors caused frequent premature delivery of offspring with body deformations such as dented carapax or an undeveloped heart. This effect is concluded to be synergistic and could not be predicted from the effects of the single stressors.

Seascape Genetics of a Globally Distributed, Highly Mobile Marine Mammal: The Short-Beaked Common Dolphin (Genus Delphinus)

Identifying which factors shape the distribution of intraspecific genetic diversity is central in evolutionary and conservation biology. In the marine realm, the absence of obvious barriers to dispersal can make this task more difficult. Nevertheless, recent studies have provided valuable insights into which factors may be shaping genetic structure in the world's oceans. These studies were, however, generally conducted on marine organisms with larval dispersal. Here, using a seascape genetics approach, we show that marine productivity and sea surface temperature are correlated with genetic structure in a highly mobile, widely distributed marine mammal species, the short-beaked common dolphin. Isolation by distance also appears to influence population divergence over larger geographical scales (i.e. across different ocean basins). We suggest that the relationship between environmental variables and population structure may be caused by prey behaviour, which is believed to determine common dolphins' movement patterns and preferred associations with certain oceanographic conditions. Our study highlights the role of oceanography in shaping genetic structure of a highly mobile and widely distributed top marine predator. Thus, seascape genetic studies can potentially track the biological effects of ongoing climate-change at oceanographic interfaces and also inform marine reserve design in relation to the distribution and genetic connectivity of charismatic and ecologically important megafauna

Predation life history responses to increased temperature variability

The evolution of life history traits is regulated by energy expenditure, which is, in turn, governed by temperature. The forecasted increase in temperature variability is expected to impose greater stress to organisms, in turn influencing the balance of energy expenditure and consequently life history responses. Here we examine how increased temperature variability affects life history responses to predation. Individuals reared under constant temperatures responded to different levels of predation risk as appropriate: namely, by producing greater number of neonates of smaller sizes and reducing the time to first brood. In contrast, we detected no response to predation regime when temperature was more variable. In addition, population growth rate was slowest among individuals reared under variable temperatures. Increased temperature variability also affected the development of inducible defenses. The combined effects of failing to respond to predation risk, slower growth rate and the miss-match development of morphological defenses supports suggestions that increased variability in temperature poses a greater risk for species adaptation than that posed by a mean shift in temperature

The effects of food and temperature regimes on life-history responses to fish kairomones in Daphnia hyalina x galeata

Life-history responses to two concentrations of fish released info-chemicals at two temperature and food regimes were investigated for one clone of Daphnia hyalina x galeata. The presence of fish kairomones had a negative impact on size at maturity, carbon allocation to individual eggs and size of neonates in all treatments. Food concentration and temperature had positive effects on size of adult stages, independent of kairomone treatment. However, kairomone treatment were not found to interact with food or temperature. Age at maturity was positively influenced by increased temperature and food concentrations, whereas no direct kairomone effects were detected for this trait. Clutch size was not directly influenced by kairomone treatment, whereas both food concentration and temperature had strong, positive effects. [KEYWORDS: life-history, trade-offs, kairomones, Daphnia, food, temperature]

Talking green, behaving brown : A study about consumers intention-behavior gap among eco-labels

Title: Talking green, behaving brown - A study about consumers intention-behavior gap among eco-labels Level: Bachelor thesis in Business & Administration   Authors: Emma-Sophie Doksaeter & Julia Nordman   Supervisor: Jonas Kågström   Date: January 2019   Purpose: The purpose of this study is to analyze consumers intention-behavior gap towards eco-labeled products based on Carrington’s et. al. model considering more recent studies regarding different variables such as relations, moral and knowledge.   Method: A quantitative survey design was developed based on variables from Carrington et al. (2010) and variables from more recent studies. Four surveys were made divided into three different countries; Sweden, Norway and Finland. The total number of participating respondents were 540. We used cluster, factor and SEM analysis to interpret our results.   Result & analysis: The result shows that it exists a gap between intention and behavior when speaking of eco-labels among consumers. Variables such as knowledge, actual behavior control have a big impact on implementation intention. Situational context and relations have low significance on implementation intention. Although, by considering all of these variables, it is possible to close the gap. To close the gap, it is also important to consider different consumer groups.     Contribution of the thesis: The study shows that it exists a gap between what consumers say they are going to do, and what they actually do, and that it is possible to close the gap between intentions and behavior when talking about eco-labels.   Suggestions for future research: The study shows cultural differences in intentions and behavior towards eco-labels. It would be possible to study this further. Another study could look at how organizations could increase eco-labels credibility towards consumers.    Keywords: Green marketing, behavior economics, intention-behavior gap, eco-labels, environmental intentio

Contrasting life history responses to fish released infochemicals of two co-occurring Daphnia species that show different migration behaviour

In a previous field study (Flik & Vijverberg 2003) we showed that in an oligotrophic-mesotrophic lake in the Netherlands (L. Maarsseveen) two co-occurring Daphnia species, Daphnia pulicaria and Daphnia galeata × hyalina performed distinct vertical migration behaviour during summer which is induced by a high fish biomass of young perch. During late spring and summer, D. galeata × hyalina exhibits diel vertical migration, whereas D. pulicaria is staying down day and night in the hypolimnion. This difference in migration behaviour results in contrasting predation mortalities caused by fish, low for D. pulicaria and relatively high for D. galeata × hyalina. In the present study, we measured in the laboratory the effects of fish released infochemicals on five life history traits in four genetically distinct D. galeata × hyalina and three genetically distinct D. pulicaria clones collected during summer at day-time from the hypolimnion. We tested the hypothesis that the species which behaviour is providing the best protection against fish predation (i.e. D. pulicaria) is less protected by life history traits induced by fish released infochemicals than the species which by its behaviour is less well protected against fish predation (i.e. D. galeata × hyalina). Our results show that D. galeata × hyalina responded in three out of five traits differently to fish infochemicals than D. pulicaria. In all these three traits D. galeata × hyalina responded significantly to fish-released infochemicals, whereas D. pulicaria did not show any significant response at all. We conclude that in D. pulicaria behavioural defences trade-off against life history defences

Contrasting life history responses to fish released infochemicals of two co-occurring Daphnia species that show different migration behaviour

In a previous field study (Flik & Vijverberg 2003) we showed that in an oligotrophic-mesotrophic lake in the Netherlands (L. Maarsseveen) two co-occurring Daphnia species, Daphnia pulicaria and Daphnia galeata × hyalina performed distinct vertical migration behaviour during summer which is induced by a high fish biomass of young perch. During late spring and summer, D. galeata × hyalina exhibits diel vertical migration, whereas D. pulicaria is staying down day and night in the hypolimnion. This difference in migration behaviour results in contrasting predation mortalities caused by fish, low for D. pulicaria and relatively high for D. galeata × hyalina. In the present study, we measured in the laboratory the effects of fish released infochemicals on five life history traits in four genetically distinct D. galeata × hyalina and three genetically distinct D. pulicaria clones collected during summer at day-time from the hypolimnion. We tested the hypothesis that the species which behaviour is providing the best protection against fish predation (i.e. D. pulicaria) is less protected by life history traits induced by fish released infochemicals than the species which by its behaviour is less well protected against fish predation (i.e. D. galeata × hyalina). Our results show that D. galeata × hyalina responded in three out of five traits differently to fish infochemicals than D. pulicaria. In all these three traits D. galeata × hyalina responded significantly to fish-released infochemicals, whereas D. pulicaria did not show any significant response at all. We conclude that in D. pulicaria behavioural defences trade-off against life history defences.

Predator sound playbacks reveal strong avoidance responses in a fight strategist baleen whale

Anti-predator strategies are often defined as ‘flight’ or ‘fight’, based upon prey anatomical adaptations for size, morphology and weapons, as well as observed behaviours in the presence of predators. The humpback whale Megaptera nova eangliae is considered a ‘fight’ specialist based upon anatomy and observations of grouping behaviour and active defence when attacked by killer whales. However, the early stage of humpback whale anti-predator strategy, when the prey detects the presence of a distant potential predator that may not have perceived it, has never been described. Our aim was to experimentally examine this initial stage of anti-predator responses. Humpbacks are likely to hear well at the frequencies of killer whale vocalisations, thus the perception of killer whale sounds could trigger anti-predator responses. To address this hypothesis, we played mammal-eating killer whale sounds to 8 solitary or paired humpback whales in North Atlantic feeding grounds and monitored their behavioural responses. We found that predator sound playbacks induced a cessation of feeding, a change in the diving pattern and a clear directional and rapid horizontal avoidance away from the speaker. Interestingly, in mothercalf pairs with young calves, the directional horizontal avoidance was atypically alternated by 90 degree turns, which may serve as a mechanism to better track the pre dator or a stealth tactic when more vulnerable animals are present. These results provide experimental evidence that humpback whales can exhibit a strong horizontal avoidance as an initial stage of anti-predator defence, indicating that anti-predator responses may be more graded and mixed than previously recognized.Publisher PDFPublisher PDFPeer reviewe