| 1. |
- Le Vaillant, Maryline, et al.
(författare)
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Individual parameters shape foraging activity in breeding king penguins
- 2016
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 27:1, s. 352-362
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Tidskriftsartikel (refereegranskat)abstract
- The variability in individual fitness within a population is likely to be mediated through individual foraging ability and tactics, themselves linked to age-or experience-related processes, but also to differences in individual quality. Not only age, experience, and quality but also sex-related foraging strategies should particularly play an important role in long-lived central-place foragers that have to cope with strong environmental constraints. We monitored the foraging effort (foraging trip durations and number of trips) of 262 known-age micro-tagged king penguins, Aptenodytes patagonicus, at different breeding stages during one of their breeding cycles. We investigated how their age (4-11 years old), sex, past breeding experience (the number of successful breeding attempts), and breeding quality (the expected breeding success, corresponding to the residual of the linear relationship between the age and on the number of past breeding success divided by the number of breeding attempts) affected foraging over a whole breeding season. During the incubation, younger birds (4 years old) undertook longer foraging trips compared with older ones. During the brooding phase and the second period of the creching phase, more experienced birds performed shorter foraging trip than those with a low breeding experience, whereas, during the first period of the creching phase, individuals with better breeding quality performed shorter foraging trips at sea than low breeding quality individuals. Sex-specific foraging patterns were also observed depending on the period of the breeding cycle. Our study shows, for the first time, how foraging effort can be driven by a complex interplay of several individual parameters according to breeding stage and resource availability and abundance.
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| 2. |
- Le Vaillant, Maryline, et al.
(författare)
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Telomere length reflects individual quality in free-living adult king penguins
- 2015
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Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 0722-4060 .- 1432-2056. ; 38:12, s. 2059-2067
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Tidskriftsartikel (refereegranskat)abstract
- Growing evidence suggests that telomeres, non-coding DNA sequences that shorten with age and stress, are related in an undefined way to individual breeding performances and survival rates in several species. Short telomeres and elevated shortening rates are typically associated with life stress and low health. As such, telomeres could serve as an integrative proxy of individual quality, describing the overall biological state of an individual at a given age. Telomere length could be associated with the decline of an array of physiological traits in age-controlled individuals. Here, we investigated the links between individuals' relative telomere length, breeding performance and various physiological (body condition, natural antibody levels) and life history (age, past breeding success) parameters in a long-lived seabird species, the king penguin Aptenodytes patagonicus. While we observed no link between relative telomere length and age, we found that birds with longer telomeres arrived earlier for breeding at the colony, and had higher breeding performances (i.e. the amount of time adults managed to maintain their chicks alive, and ultimately breeding success) than individuals with shorter telomeres. Further, we observed a positive correlation between telomere length and natural antibody levels. Taken together, our results add to the growing evidence that telomere length is likely to reflect individual quality difference in wild animal.
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| 3. |
- Audusseau, Hélène, et al.
(författare)
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Species range expansion constrains the ecological niches of resident butterflies
- 2017
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 44:1, s. 28-38
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Changes in community composition resulting from environmental changes modify biotic interactions and affect the distribution and density of local populations. Such changes are currently occurring in nettle-feeding butterflies in Sweden where Araschnia levana has recently expanded its range northward and is now likely to interact with resident species (Aglais urticae and Aglais io). Butterfly occurrence data collected over years and across regions enabled us to investigate how a recent range expansion of A. levana may have affected the environmental niche of resident species.Location: We focused on two regions of Sweden (Skane and Norrstrom) where A. levana has and has not established and two time periods (2001-2006 and 2009-2012) during its establishment in Skane.Methods: We performed two distinct analyses in each region using the PCA-env and the framework described in Broennimann etal. (2012). First, we described the main sources of variation in the environment. Second, in each time period and region, we characterized the realized niches of our focal species across topographic and land use gradients. Third, we quantified overlaps and differences in realized niches between and within species over time.Results: In Skane, A. levana has stabilized its distribution over time, while the distribution of the native species has shifted. These shifts depicted a consistent pattern of avoiding overlap between the native species and the environmental space occupied by A. levana, and it was stronger for A. urticae than for A. io. In both regions, we also found evidence of niche partitioning between native species.Main conclusions: Interspecific interactions are likely to affect local species distributions. It appears that the ongoing establishment of A. levana has modified local biotic interactions and induced shifts in resident species distributions. Among the mechanisms that can explain such patterns of niche partitioning, parasitoid-driven apparent competition may play an important role in this community.
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| 4. |
- Elliott, Kyle H., et al.
(författare)
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Age-related variation in energy expenditure in a long-lived bird within the envelope of an energy ceiling
- 2014
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 83:1, s. 136-146
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Tidskriftsartikel (refereegranskat)abstract
- Energy expenditure in wild animals can be limited (i) intrinsically by physiological processes that constrain an animal's capacity to use energy, (ii) extrinsically by energy availability in the environment and/or (iii) strategically based on trade-offs between elevated metabolism and survival. Although these factors apply to all individuals within a population, some individuals expend more or less energy than other individuals. To examine the role of an energy ceiling in a species with a high and individually repeatable metabolic rate, we compared energy expenditure of thick-billed murres (Uria lomvia) with and without handicaps during a period of peak energy demand (chick-rearing, N=16). We also compared energy expenditure of unencumbered birds (N=260) across 8years exhibiting contrasting environmental conditions and correlated energy expenditure with fitness (reproductive success and survival). Murres experienced an energy ceiling mediated through behavioural adjustments. Handicapped birds decreased time spent flying/diving and chick-provisioning rates such that overall daily energy expenditure remained unchanged across the two treatments. The energy ceiling did not reflect energy availability or trade-offs with fitness, as energy expenditure was similar across contrasting foraging conditions and was not associated with reduced survival or increased reproductive success. We found partial support for the trade-off hypothesis as older murres, where prospects for future reproduction would be relatively limited, did overcome an energy ceiling to invest more in offspring following handicapping by reducing their own energy reserves. The ceiling therefore appeared to operate at the level of intake (i.e. digestion) rather than expenditure (i.e. thermal constraint, oxidative stress). A meta-analysis comparing responses of breeding animals to handicapping suggests that our results are typical: animals either reduced investment in themselves or in their offspring to remain below an energy ceiling. Across species, whether a handicapped individual invested in its own energy stores or its offspring's growth was not explained by life history (future vs. current reproductive potential). Many breeding animals apparently experience an intrinsic energy ceiling, and increased energy costs lead to a decline in self-maintenance and/or offspring provisioning.
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| 5. |
- Le Vaillant, Maryline, et al.
(författare)
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Spatial distribution in Norwegian lemming Lemmus lemmus in relation to the phase of the cycle
- 2018
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Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 0722-4060 .- 1432-2056. ; 41:7, s. 1391-1403
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Tidskriftsartikel (refereegranskat)abstract
- Competition between individuals of the same or different species affects spatial distribution of organisms at any given time. Consequently, a species geographical distribution is related to population dynamics through density-dependent processes. Small Arctic rodents are important prey species in many Arctic ecosystems. They commonly show large cyclic fluctuations in abundance offering a potential to investigate how landscape characteristics relates to density-dependent habitat selection. Based on long-term summer trapping data of the Norwegian lemming (Lemmus lemmus) in the Scandinavian Mountain tundra, we applied species distribution modeling to test if the effect of environmental variables on lemming distribution changed in relation to the lemming cycle. Lemmings were less habitat specific during the peak phase, as their distribution was only related to primary productivity. During the increase phase, however, lemming distribution was, in addition, associated with landscape characteristics such as hilly terrain and slopes that are less likely to get flooded. Lemming habitat use varied during the cycle, suggesting density-dependent changes in habitat selection that could be explained by intraspecific competition. We believe that the distribution patterns observed during the increase phase show a stronger ecological signal for habitat preference and that the less specific habitat use during the peak phase is a result of lemmings grazing themselves out of the best habitat as the population grows. Future research on lemming winter distribution would make it possible to investigate the year around strategies of habitat selection in lemmings and a better understanding of a fundamental actor in many Arctic ecosystems.
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| 6. |
- Vigués, Jan, et al.
(författare)
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A beacon of dung : using lemming (Lemmus lemmus) winter nests and DNA analysis of faeces to further understand predator-prey dynamics in Northern Sweden
- 2021
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Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 0722-4060 .- 1432-2056. ; 44:12, s. 2269-2276
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Tidskriftsartikel (refereegranskat)abstract
- The hypothesis that predation is the cause of the regular small rodent population oscillations observed in boreal and Arctic regions has long been debated. Within this hypothesis, it is proposed that the most likely predators to cause these destabilizing effects are sedentary specialists, with small mustelids being possible candidates. One such case would be the highly specialized least weasel (Mustela nivalis) driving the Norwegian lemming (Lemmus lemmus) cycle in Fennoscandia. These predators are often elusive and therefore distribution data can only be based on field signs, which is problematic when various mustelid species are sympatric, such as weasels and stoats (Mustela erminea). Here we present the results of using mustelid faeces in predated winter lemming nests to correctly identify the predator and thus discern which species exerts the strongest predation pressure on lemming winter populations. Samples were obtained during different phases in the lemming cycle, spanning 6 years, to account for different prey densities. Faecal mitochondrial DNA extraction and amplification of a 400-bp fragment was successful in 92/114 samples (81%); the sequencing of these samples proved that most predation occurrences (83%) could be attributed to the least weasel. These findings support the hypothesis that weasels in particular show high specificity in predation and could therefore be candidates to driving the lemming cycle in this area. We conclude that DNA analysis of faecal remains around predated nests can be a useful tool for further investigations concerning predator-prey interactions in the tundra.
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