Publications by authors named "Hans C Pedersen"

9 Publications

  • Page 1 of 1

Impacts of predator-mediated interactions along a climatic gradient on the population dynamics of an alpine bird.

Proc Biol Sci 2020 12 23;287(1941):20202653. Epub 2020 Dec 23.

Department of Terrestrial Biodiversity, Norwegian Institute for Nature Research, P.O. 5685 Torgarden, 7485 Trondheim, Norway.

According to classic theory, species' population dynamics and distributions are less influenced by species interactions under harsh climatic conditions compared to under more benign climatic conditions. In alpine and boreal ecosystems in Fennoscandia, the cyclic dynamics of rodents strongly affect many other species, including ground-nesting birds such as ptarmigan. According to the 'alternative prey hypothesis' (APH), the densities of ground-nesting birds and rodents are positively associated due to predator-prey dynamics and prey-switching. However, it remains unclear how the strength of these predator-mediated interactions change along a climatic harshness gradient in comparison with the effects of climatic variation. We built a hierarchical Bayesian model to estimate the sensitivity of ptarmigan populations to interannual variation in climate and rodent occurrence across Norway during 2007-2017. Ptarmigan abundance was positively linked with rodent occurrence, consistent with the APH. Moreover, we found that the link between ptarmigan abundance and rodent dynamics was strongest in colder regions. Our study highlights how species interactions play an important role in population dynamics of species at high latitudes and suggests that they can become even more important in the most climatically harsh regions.
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http://dx.doi.org/10.1098/rspb.2020.2653DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7779518PMC
December 2020

Effect of tower base painting on willow ptarmigan collision rates with wind turbines.

Ecol Evol 2020 Jun 29;10(12):5670-5679. Epub 2020 Apr 29.

Norwegian Institute for Nature Research (NINA) Trondheim Norway.

Birds colliding with turbine rotor blades is a well-known negative consequence of wind-power plants. However, there has been far less attention to the risk of birds colliding with the turbine towers, and how to mitigate this risk.Based on data from the Smøla wind-power plant in Central Norway, it seems highly likely that willow ptarmigan (the only gallinaceous species found on the island) is prone to collide with turbine towers. By employing a BACI-approach, we tested if painting the lower parts of turbine towers black would reduce the collision risk.Overall, there was a 48% reduction in the number of recorded ptarmigan carcasses per search at painted turbines relative to neighboring control (unpainted) ones, with significant variation both within and between years.Using contrast painting to the turbine towers resulted in significantly reduced number of ptarmigan carcasses found, emphasizing the effectiveness of such a relatively simple mitigation measure.
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http://dx.doi.org/10.1002/ece3.6307DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7319111PMC
June 2020

Impact of screening and risk factors for local recurrence and survival after conservative surgery and radiotherapy for early breast cancer: results from a large series with long-term follow-up.

Int J Radiat Oncol Biol Phys 2012 Jul 22;83(3):829-38. Epub 2011 Dec 22.

Edinburgh Cancer Centre, Western General Hospital, Edinburgh, United Kingdom.

Purpose: To investigate conventional prognostic factors for ipsilateral breast tumor recurrence (IBTR), distant metastasis (DM), and survival after breast-conserving therapy (BCT) in screen-detected and symptomatic cases on surveillance up to 25 years.

Patients And Methods: A total of 1812 consecutive patients in three cohorts (1981-1989, 1990-1992, and 1993-1998) with T12N01M0 invasive breast cancer were treated with BCT (median follow-up, 14 years). Tumor type and grade were reviewed by a single pathologist. Hormone receptor status was measured by immunohistochemistry on tissue microarrays. A Cox proportional hazards model was used to assess independent prognostic variables for relapse and survival.

Results: A total of 205 IBTR occurred, with 5-, 10-, 15-, and 20-year actuarial relapse rates of 4.5% (95% confidence interval [CI] 3.35-5.5%), 8.4% (95% CI 7.1-9.8%), 14.1% (95% CI 12.0-16%), and 17.4% (95% CI 14.5-20.2%). Number of nodes, young age, pathologic tumor size, and multifocality were significant factors for IBTR. Three hundred seventy-eight patients developed DM. The actuarial metastatic rate was 12% at 5 years and 17.9% at 10 years. Young age, number of positive nodes, pathologic tumor size, and tumor grade were significant factors for DM relapse. When conventional prognostic indices were taken into account screen-detected cancers showed no improvement in overall relapse or survival rate compared with symptomatic cases but did show a reduced risk of DM after IBTR. After 10 years IBTR relapse continued at a constant rate of 0.87% per annum.

Conclusions: The Edinburgh BCT series has shown that screen-detected invasive breast cancers do not have significantly different clinical outcomes compared with symptomatic cases when pathologic risk factors are taken into account. This suggests that these patients be managed in a similar way.
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http://dx.doi.org/10.1016/j.ijrobp.2011.08.018DOI Listing
July 2012

Predicting the potential demographic impact of predators on their prey: a comparative analysis of two carnivore-ungulate systems in Scandinavia.

J Anim Ecol 2012 Mar 11;81(2):443-54. Epub 2011 Nov 11.

Norwegian Institute for Nature Research, PO Box 5685, Sluppen, NO-7485 Trondheim, Norway.

1. Understanding the role of predation in shaping the dynamics of animal communities is a fundamental issue in ecological research. Nevertheless, the complex nature of predator-prey interactions often prevents researchers from modelling them explicitly. 2. By using periodic Leslie-Usher matrices and a simulation approach together with parameters obtained from long-term field projects, we reconstructed the underlying mechanisms of predator-prey demographic interactions and compared the dynamics of the roe deer-red fox-Eurasian lynx-human harvest system with those of the moose-brown bear-gray wolf-human harvest system in the boreal forest ecosystem of the southern Scandinavian Peninsula. 3. The functional relationship of both roe deer and moose λ to changes in predation rates from the four predators was remarkably different. Lynx had the strongest impact among the four predators, whereas predation rates by wolves, red foxes, or brown bears generated minor variations in prey population λ. Elasticity values of lynx, wolf, fox and bear predation rates were -0·157, -0·056, -0·031 and -0·006, respectively, but varied with both predator and prey densities. 4. Differences in predation impact were only partially related to differences in kill or predation rates, but were rather a result of different distribution of predation events among prey age classes. Therefore, the age composition of killed individuals emerged as the main underlying factor determining the overall per capita impact of predation. 5. Our results confirm the complex nature of predator-prey interactions in large terrestrial mammals, by showing that different carnivores preying on the same prey species can exert a dramatically different demographic impact, even in the same ecological context, as a direct consequence of their predation patterns. Similar applications of this analytical framework in other geographical and ecological contexts are needed, but a more general evaluation of the subject is also required, aimed to assess, on a broader systematic and ecological range, what specific traits of a carnivore are most related to its potential impact on prey species.
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http://dx.doi.org/10.1111/j.1365-2656.2011.01928.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3440569PMC
March 2012

Is hunting mortality additive or compensatory to natural mortality? Effects of experimental harvest on the survival and cause-specific mortality of willow ptarmigan.

J Anim Ecol 2011 Jan 4;80(1):244-58. Epub 2010 Nov 4.

Division of Biology, Kansas State University, Manhattan, KS 66506, USA.

1. The effects of harvest on the annual and seasonal survival of willow ptarmigan Lagopus lagopus L. were tested in a large-scale harvest experiment. Management units were randomly assigned to one of three experimental treatments: 0%, 15% or 30% harvest. Seasonal quotas were based on the experimental treatment and estimates of bird density before the hunting season. Survival rates and hazard functions for radio-marked ptarmigan were then estimated under the competing risks of harvest and natural mortality. 2. The partially compensatory mortality hypothesis was supported: annual survival of ptarmigan was 0·54 ± 0·08 SE under 0% harvest, 0·47 ± 0·06 under 15% harvest, and was reduced to 0·30 ± 0·05 under 30% harvest. Harvest mortality increased linearly from 0·08 ± 0·05, 0·27 ± 0·05 and 0·42 ± 0·06 from 0% to 30% harvest, whereas natural mortality was 0·38 ± 0·08, 0·25 ± 0·05 and 0·28 ± 0·06 under the same treatments. 3. Realized risk of harvest mortality was 0·08-0·12 points higher than our set harvest treatments of 0-30% because birds were exposed to risk if they moved out of protected areas. The superadditive hypothesis was supported because birds in the 30% harvest treatment had higher natural mortality during winter after the hunting season. 4. Natural mortality was mainly because of raptor predation, with two seasonal peaks in fall and spring. Natural and harvest mortality coincided during early autumn with little potential for compensation during winter months. Peak risk of harvest mortality was 5× higher than natural mortality. Low natural mortality during winter suggests that most late season harvest would be additive mortality. 5. Environmental correlates of natural mortality of ptarmigan included seasonal changes in snow cover, onset of juvenile dispersal, and periods of territorial activity. Natural mortality of ptarmigan was highest during autumn movements and nesting by gyrfalcons Falco rusticolus L. Mortality was low when gyrfalcons had departed for coastal wintering sites, and during summer when ptarmigan were attending nests and broods. 6. Our experimental results have important implications for harvest management of upland gamebirds. Seasonal quotas based on proportional harvest were effective and should be set at ≤ 15% of August populations for regional management plans. Under threshold harvest of a reproductive surplus, 15% harvest would be sustainable at productivity rates ≥ 2·5 young per pair. Impacts of winter harvest could be minimized by closing the hunting season in early November or by reducing late season quotas.
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http://dx.doi.org/10.1111/j.1365-2656.2010.01769.xDOI Listing
January 2011

Habitat differentiation within the large-carnivore community of Norway's multiple-use landscapes.

J Appl Ecol 2008 Oct;45(5):1382-1391

The re-establishment of large carnivores in Norway has led to increased conflicts and the adoption of regional zoning for these predators. When planning the future distribution of large carnivores, it is important to consider details of their potential habitat tolerances and strength of inter-specific differentiation. We studied differentiation in habitat and kill sites within the large-carnivore community of south-eastern Norway.We compared habitat selection of the brown bear Ursus arctos L., Eurasian lynx Lynx lynx L., wolf Canis lupus L. and wolverine Gulo gulo L., based on radio-tracking data. Differences in kill site locations were explored using locations of documented predator-killed sheep Ovis aries L. We modelled each species' selection for, and differentiation in, habitat and kill sites on a landscape scale using resource selection functions and multinomial logistic regression. Based on projected probability of occurrence maps, we estimated continuous patches of habitat within the study area.Although bears, lynx, wolves and wolverines had overlapping distributions, we found a clear differentiation for all four species in both habitat and kill sites. The presence of bears, wolves and lynx was generally associated with rugged, forested areas at lower elevations, whereas wolverines selected rugged terrain at higher elevations. Some degree of sympatry was possible in over 40% of the study area, although only 1.5% could hold all four large carnivores together.Synthesis and applications. A geographically differentiated management policy has been adopted in Norway, aimed at conserving viable populations of large carnivores while minimizing the potential for conflicts. Sympatry of all four carnivores will be most successful if regional zones are established of adequate size spanning an elevational gradient. High prey densities, low carnivore densities, low dietary overlap and scavenging opportunities have most probably led to reduced competitive exclusion. Although regional sympatry enhances the conservation of an intact guild of large carnivores, it may well increase conflict levels and resistance to carnivore conservation locally.
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http://dx.doi.org/10.1111/j.1365-2664.2008.01527.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658717PMC
October 2008

Summer kill rates and predation pattern in a wolf-moose system: can we rely on winter estimates?

Oecologia 2008 May 13;156(1):53-64. Epub 2008 Feb 13.

Grimsö Wildlife Research Station, Department of Ecology, Swedish University of Agricultural Sciences, 73091 Riddarhyttan, Sweden.

So far the vast majority of studies on large carnivore predation, including kill rates and consumption, have been based on winter studies. Because large carnivores relying on ungulates as prey often show a preference for juveniles, kill rates may be both higher and more variable during the summer season than during the rest of the year leading to serious underestimates of the total annual predation rate. This study is the first to present detailed empirical data on kill rates and prey selection in a wolf-moose system during summer (June-September) as obtained by applying modern Global Positioning System-collar techniques on individual wolves (Canis lupus) in Scandinavia. Moose (Alces alces) was the dominant prey species both by number (74.4%) and biomass (95.6%); 89.9% of all moose killed were juveniles, representing 76.0% of the biomass consumed by wolves. Kill rate in terms of the kilogram biomass/kilogram wolf per day averaged 0.20 (range: 0.07-0.32) among wolf territories and was above, or well above, the daily minimum food requirements in most territories. The average number of days between moose kills across wolf territories and study periods was 1.71 days, but increased with time and size of growing moose calves during summer. Over the entire summer (June-September, 122 days), a group (from two to nine) of wolves killed a total of 66 (confidence interval 95%; 56-81) moose. Incorporation of body growth functions of moose calves and yearlings and wolf pups over the summer period showed that wolves adjusted their kill rate on moose, so the amount of biomass/kilogram wolf was relatively constant or increased. The kill rate was much higher (94-116%) than estimated from the winter period. As a consequence, projecting winter kill rates to obtain annual estimates of predation in similar predator-prey systems may result in a significant underestimation of the total number of prey killed.
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http://dx.doi.org/10.1007/s00442-008-0969-2DOI Listing
May 2008

Nuclear export inhibitors and kinase inhibitors identified using a MAPK-activated protein kinase 2 redistribution screen.

Assay Drug Dev Technol 2004 Feb;2(1):7-20

BioImage A/S, Søborg, Denmark.

Redistribution (BioImage) A/S, Søborg, Denmark) is a novel high-throughput screening technology that monitors translocation of specific protein components of intracellular signaling pathways within intact mammalian cells, using green fluorescent protein as a tag. A single Redistribution assay can be used to identify multiple classes of compounds that act at, or upstream of, the level of the protein target used in the primary screening assay. Such compounds may include both conventional and allosteric enzyme inhibitors, as well as protein-protein interaction modulators. We have developed a series of Redistribution assays to discover and characterize compounds that inhibit tumor necrosis factor-alpha biosynthesis via modulation of the p38 mitogen-activated protein kinase (MAPK) pathway. A primary assay was designed to identify low-molecular-weight compounds that inhibit the activation-dependent nuclear export of the p38 kinase substrate MAPK-activated protein kinase 2 (MK2). Hits from the primary screen were categorized, using secondary assays, either as direct inhibitors of MK2 nuclear export, or as inhibitors of the upstream p38 MAPK pathway. Activity profiles are presented for a nuclear export inhibitor, and a compound that structurally and functionally resembles a known p38 kinase inhibitor. These results demonstrate the utility of Redistribution technology as a pathway screening method for the identification of diverse and novel compounds that are active within therapeutically important signaling pathways.
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http://dx.doi.org/10.1089/154065804322966270DOI Listing
February 2004

Characterization of two novel nuclear BTB/POZ domain zinc finger isoforms. Association with differentiation of hippocampal neurons, cerebellar granule cells, and macroglia.

J Biol Chem 2002 Mar 13;277(9):7598-609. Epub 2001 Dec 13.

Laboratory of Mammalian Molecular Genetics, The Panum Institute 6.5, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N.

BTB/POZ (broad complex tramtrack bric-a-brac/poxvirus and zinc finger) zinc finger factors are a class of nuclear DNA-binding proteins involved in development, chromatin remodeling, and cancer. However, BTB/POZ domain zinc finger factors linked to development of the mammalian cerebral cortex, cerebellum, and macroglia have not been described previously. We report here the isolation and characterization of two novel nuclear BTB/POZ domain zinc finger isoforms, designated HOF(L) and HOF(S), that are specifically expressed in early hippocampal neurons, cerebellar granule cells, and gliogenic progenitors as well as in differentiated glia. During embryonic development of the murine cerebral cortex, HOF expression is restricted to the hippocampal subdivision. Expression coincides with early differentiation of presumptive CA1 and CA3 pyramidal neurons and dentate gyrus granule cells, with a sharp decline in expression at the CA1/subicular border. By using bromodeoxyuridine labeling and immunohistochemistry, we show that HOF expression coincides with immature non-dividing cells and is down-regulated in differentiated cells, suggesting a role for HOF in hippocampal neurogenesis. Consistent with the postulated role of the POZ domain as a site for protein-protein interactions, both HOF isoforms are able to dimerize. The HOF zinc fingers bind specifically to the binding site for the related promyelocytic leukemia zinc finger protein as well as to a newly identified DNA sequence.
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http://dx.doi.org/10.1074/jbc.M110023200DOI Listing
March 2002