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Sökning: WFRF:(Sunde Peter)

  • Resultat 11-19 av 19
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  • Persson Sunde, Erik, et al. (författare)
  • The physical state of water in bacterial spores.
  • 2009
  • Ingår i: Proceedings of the National Academy of Sciences. - : National Academy of Sciences. - 1091-6490. ; 106:46, s. 19334-19339
  • Tidskriftsartikel (refereegranskat)abstract
    • The bacterial spore, the hardiest known life form, can survive in a metabolically dormant state for many years and can withstand high temperatures, radiation, and toxic chemicals. The molecular basis of spore dormancy and resistance is not understood, but the physical state of water in the different spore compartments is thought to play a key role. To characterize this water in situ, we recorded the water 2H and 17O spin relaxation rates in D2O-exchanged Bacillus subtilis spores over a wide frequency range. The data indicate high water mobility throughout the spore, comparable with binary protein–water systems at similar hydration levels. Even in the dense core, the average water rotational correlation time is only 50 ps. Spore dormancy therefore cannot be explained by glass-like quenching of molecular diffusion but may be linked to dehydration-induced conformational changes in key enzymes. The data demonstrate that most spore proteins are rotationally immobilized, which may contribute to heat resistance by preventing heat-denatured proteins from aggregating irreversibly. We also find that the water permeability of the inner membrane is at least 2 orders of magnitude lower than for model membranes, consistent with the reported high degree of lipid immobilization in this membrane and with its proposed role in spore resistance to chemicals that damage DNA. The quantitative results reported here on water mobility and transport provide important clues about the mechanism of spore dormancy and resistance, with relevance to food preservation, disease prevention, and astrobiology.
  • Peters, Wibke, et al. (författare)
  • Large herbivore migration plasticity along environmental gradients in Europe : life-history traits modulate forage effects
  • 2018
  • Ingår i: Oikos. - Chichester : Wiley-Blackwell Publishing Inc.. - 0030-1299 .- 1600-0706. ; 128:3, s. 416-429
  • Tidskriftsartikel (refereegranskat)abstract
    • The most common framework under which ungulate migration is studied predicts that it is driven by spatio–temporal variation in plant phenology, yet other hypotheses may explain differences within and between species. To disentangle more complex patterns than those based on single species/ single populations, we quantified migration variability using two sympatric ungulate species differing in their foraging strategy, mating system and physiological constraints due to body size. We related observed variation to a set of hypotheses. We used GPS-collar data from 537 individuals in 10 roe Capreolus capreolus and 12 red deer Cervus elaphus populations spanning environmental gradients across Europe to assess variation in migration propensity, distance and timing. Using time-to-event models, we explored how the probability of migration varied in relation to sex, landscape (e.g. topography, forest cover) and temporally-varying environmental factors (e.g. plant green-up, snow cover). Migration propensity varied across study areas. Red deer were, on average, three times more migratory than roe deer (56% versus 18%). This relationship was mainly driven by red deer males which were twice as migratory as females (82% versus 38%). The probability of roe deer migration was similar between sexes. Roe deer (both sexes) migrated earliest in spring. While territorial male roe deer migrated last in autumn, male and female red deer migrated around the same time in autumn, likely due to their polygynous mating system. Plant productivity determined the onset of spring migration in both species, but if plant productivity on winter ranges was sufficiently high, roe deer were less likely to leave. In autumn, migration coincided with reduced plant productivity for both species. This relationship was stronger for red deer. Our results confirm that ungulate migration is influenced by plant phenology, but in a novel way, that these effects appear to be modulated by species-specific traits, especially mating strategies. © 2018 The Authors. Oikos © 2018 Nordic Society Oikos
  • Sunde, Peter, et al. (författare)
  • A telemetry study of the social organization of a tawny owl (Strix aluco) population
  • 2004
  • Ingår i: Journal of Zoology. - : Wiley-Blackwell. - 0952-8369. ; 263:1, s. 65-76
  • Tidskriftsartikel (refereegranskat)abstract
    • The spatial dispersion and social interactions were studied in I I neighbouring pairs of radio-tagged tawny owls Strix aluco in a deciduous wood in Denmark from 1998-2001. The numbers and shapes of territories were stable throughout the survey and similar to a mapping made 40 years earlier. The home ranges of mates were of equal size and overlapped 82% in summer and 56% in winter. The inter-mate distances were on average 2.7% shorter than expected by chance. The activity distribution of neighbouring pairs overlapped 9% (95% CI: 2-15%) on average. Males and females did not differ in overlap with neighbours, and there was a similar overlap between neighbours of the same and opposite sex. Both sexes vocalized more often in the peripheries than in the centres of their territory. The vocal activity during May-September varied extensively among years and months in accordance with variation in the density of juvenile floaters. Males and females vocalized equally often and were involved in disputes with neighbours at similar rates. Usually, neighbouring disputes involved either one individual from each pair or all four. Disputes involving all four owls more often involved chasing and fighting than those involving one owl only from each pair. The dispute rate between neighbouring pairs correlated positively with home-range overlap. The total annual mortality was 21% (95% CI: 6-33%). Dead owners were usually replaced within 1 2 months. Two out of four cases of radio-tagged owls disappearing from their territory because of natural causes was due to take-overs by invading owls, suggesting that the risk of losing fitness resulting from eviction was important. The apparent co-operative territorial behaviour of tawny owl pairs is probably due to improved resource holding potential of pair coalitions compared to single individuals.
  • Sunde, Peter, et al. (författare)
  • Combining information from range use and habitat selection: sex-specific spatial responses to habitat fragmentation in tawny owls Strix aluco
  • 2006
  • Ingår i: Ecography. - : Wiley-Blackwell. - 1600-0587. ; 29:2, s. 152-158
  • Tidskriftsartikel (refereegranskat)abstract
    • How individuals respond to habitat heterogeneity is usually measured as variation in range size and by ranking the relative importance of habitat types (habitat selection). The combined effect of how individuals incorporate different habitat types in their home ranges and allocate their time budget between them is rarely derived. Additionally, when home range size varies between individuals, habitat selection analyses might be flawed if foraging decisions are based on variation in absolute rather than proportional availability. We investigated the suitability of standard analytical approaches by measuring the spatial responses of tawny owls to habitat fragmentation. These owls inhabited woodland of various sizes, representing a fragmentation gradient from open farmland with small, isolated woodland patches, to continuous woodland within their home ranges. In 17 territories within open farmland, the available area covered by woodland increased with the square root of the area of open land embraced in the home range. The owls did not display functional response in habitat selection, but females selected woodland more strongly than males. Females utilised woodland 10 times more intensively in farmland than in continuous woods, whereas males utilised farmland woods 3.2 times more intensively. Moreover, females in farmland exploited woodland 3.2 times as intensively as males, apparently because of higher travel costs in open areas. Since the extensive variation in intensity of use as a function of total availability was not indicated from the analysis of habitat selection, we suggest that information about intensity of use be more widely used as a supplementary measure of habitat use patterns than appears to be the practice at present.
  • Sunde, Peter, et al. (författare)
  • Diurnal exposure as a risk sensitive behaviour in tawny owls Strix aluco?
  • 2003
  • Ingår i: Journal of Avian Biology. - : Blackwell. - 0908-8857. ; 34:4, s. 409-418
  • Tidskriftsartikel (refereegranskat)abstract
    • Tawny owls Strix aluco generally roost in cryptic locations during the day. To test the hypothesis that this cryptic behaviour is an effort to avoid mobbers or avian predators, we measured diurnal behaviour and cause-specific mortality of radio-tagged birds. Non-breeding adults (assumed to be well fed individuals, optimising their own survival) roosted in less exposed locations than adults with young and newly independent juveniles. Parents roosted in the most exposed sites when their young were immature and vulnerable to depredation, probably to guard offspring. Newly independent juveniles apparently selected roosting sites in exposed places to get access to food, as this behaviour was associated with lower perching heights and higher prey abundance beneath their roosting sites. They also perched in more exposed sites, closer to the ground, in summers with low prey abundance compared to summers with high prey abundance. After previous encounters with goshawks Accipiter gentilis, dependent juveniles roosted in less exposed places compared to other young. The increased risk of being mobbed was highly significant with increasing roosting exposure. Once an owl was mobbed, the intensity of the mobbing correlated positively with the mass of the mobbers, but mobbing birds never killed any owls. In contrast, diurnal raptors caused 73% of natural owl deaths (n = 15) and the depredation rate by raptors was 3.8 times higher in population classes that generally roosted in more exposed locations than did non-breeding adults. We therefore suggest that depredation by diurnal raptors is the main factor shaping the diurnal behaviour of tawny owls.
  • Sunde, Peter (författare)
  • Effects of backpack radio tags on tawny owls
  • 2006
  • Ingår i: Journal of Wildlife Management. - : The Wildlife Society. - 0022-541X. ; 70:2, s. 594-599
  • Tidskriftsartikel (övrigt vetenskapligt)
  • Sunde, Peter (författare)
  • Predators control post-fledging mortality in tawny owls, Strix aluco
  • 2005
  • Ingår i: Oikos. - : Wiley-Blackwell. - 1600-0706. ; 110:3, s. 461-472
  • Tidskriftsartikel (refereegranskat)abstract
    • Despite its recognition as an important source of variation in recruitment probability, the ecological processes leading to mortality between fledging and independence are poorly studied. Accordingly, the proximate and ultimate impact of bottom-up (food limitation) and top-down factors (predators, pathogens) for individual survival as well as population productivity is largely unknown in most terrestrial birds. Survival and behaviour of 131 radio-tagged tawny owls (Strix aluco) during the post-fledging dependency period were studied for each of three years with high food abundance and three years of poor food supply in Danish deciduous woods. To identify the effects of food limitation, 32 young received extra food 2-3 weeks prior to fledging, as opposed to 99 young that were fed by their parents only. Thirty-six percent of the young from control broods died between fledging and independence, primarily due to predation from raptors and mammals (predominantly foxes Vulpes vulpes). Predation by mammals occurred within the first few days after fledging, with young leaving the nest at an early age being at particularly high risk. Young that had received extra food as nestlings were also at higher risk of being preyed upon by mammals, possibly because they were easier to locate on their smell. Total mortality risk (control broods) increased with fledging date from 14% in April to > 58% in June due to an increasing raptor predation risk. Individual attributes such as sex, condition, immunocompetence or prevalence of blood parasites did not predict total or cause-specific mortality risk. Survival during the post-fledging dependency period was therefore primarily a function of variation in predation pressures, particularly from raptors. Increasing raptor predation of late broods appears to be an important selective agent for early breeding in the tawny owl.
  • Sunde, Peter, et al. (författare)
  • Reversed sexual dimorphism in tawny owls, Strix aluco, correlates with duty division in breeding effort
  • 2003
  • Ingår i: Oikos. - : Wiley-Blackwell. - 1600-0706. ; 101:2, s. 265-278
  • Tidskriftsartikel (refereegranskat)abstract
    • Even though most bird species with a raptorial feeding habit express varying extents of reversed sexual dimorphism (RSD: females bigger than males), the evolutionary basis for its maintenance, as well as its possible secondary consequences for the ecological adaptations of the different sexes, is debated. We studied pairs of tawny owls, Strix aluco (females 20% heavier than males), throughout the year by telemetry to test whether any inter-sexual differences in movement patterns, resource partitioning and breeding effort correlated with RSD. Females were larger than males in all body size measures and were 16% heavier than would be expected from the difference in wing length alone. In accordance with predictions from flight economics, males moved longer distances per time unit than females, in particular during the post-fledging season, when they also fed chicks more often than the females. Males had larger home ranges than females during the post-fledging period, whereas the sexes had home ranges of equal size during the non-breeding season. Until 10 days after fledging, females foraged much closer to the offspring than males, apparently balancing their distance to offspring between the needs of offspring guarding and foraging. In males, the parent-offspring distance only increased with decreasing brood condition. The sexes did not differ in habitat use or feeding habits, rendering no indications of food niche partitioning. The study provides further evidence that selection for males to be light and energetically efficient foragers is the main evolutionary force behind RSD in raptorial birds, even when the prey base is confined by territoriality.
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