Hans Christian Pedersen

Shoot, shovel and shut up: cryptic poaching slows restoration of a large carnivore in Europe

Poaching is a widespread and well-appreciated problem for the conservation of many threatened species. Because poaching is illegal, there is strong incentive for poachers to conceal their activities, and consequently, little data on the effects of poaching on population dynamics are available. Quantifying poaching mortality should be a required knowledge when developing conservation plans for endangered species but is hampered by methodological challenges. We show that rigorous estimates of the effects of poaching relative to other sources of mortality can be obtained with a hierarchical state–space model combined with multiple sources of data. Using the Scandinavian wolf (Canis lupus) population as an illustrative example, we show that poaching accounted for approximately half of total mortality and more than two-thirds of total poaching remained undetected by conventional methods, a source of mortality we term as ‘cryptic poaching’. Our simulations suggest that without poaching during the past decade, the population would have been almost four times as large in 2009. Such a severe impact of poaching on population recovery may be widespread among large carnivores. We believe that conservation strategies for large carnivores considering only observed data may not be adequate and should be revised by including and quantifying cryptic poaching.

Activity patterns of predator and prey: a simultaneous study of GPS-collared wolves and moose

This is the postprint version of the article published in Animal behaviour. You can find the published article here: http://dx.doi.org/doi:10.1016/j.anbehav.2010.11.011

Grouse Hunting Regulations and Hunter Typologies in Norway

Sustainable game management relies on satisfied hunters. Satisfaction determinants are seldom uniform across all hunters and may therefore be difficult to accommodate. Latent class analysis (LCA) is a probabilistic model-based approach to categorizing hunter typologies (by, e.g., their attitudes and preferences). We applied LCA to large-scale survey data relating to grouse hunting regulations in Norway (3,293 respondents). We identified three typologies with regard to importance of bag size (“The Experience Seeker” 43%, “The Bag Oriented” 32% and “The Northern Traditionalist” 25%) and crowding tolerance (“The Semi-tolerant Mainstream” 85%, “The Laissez Faire” 11%, and “The Passionate Crowd-avoiding” 4%). We could not find a single set of typologies that conformed to both aspects, which suggests that studies of this kind are more likely to be successful if target-specific. We conclude that knowledge of typologies is valuable for tailoring local hunting regulations, provided their actual distribution is identified at the appropriate scale.

Large-scale climate variability and rodent abundance modulates recruitment rates in Willow Ptarmigan (Lagopus lagopus)

AbstractRecruitment of juveniles is important for the size of the next year’s breeding population in many bird species. Climate variability and predation may affect recruitment rates, and when these factors are spatially correlated, recruitment rates in spatially separated populations of a species may be synchronized. We used production data from an extensive survey of Willow Ptarmigan from 2000 to 2011 to investigate spatial synchrony in recruitment of juveniles within and among mountain region populations. In addition, we assessed the effects of predation and large—as well as local—scale climate on recruitment of juveniles. Recruitment was synchronized both within and among mountain regions, but the mean spatial correlation was strongest among mountain regions. This may be caused by small-scale factors such as predation or habitat structure, or be a result of sampling variation, which may be large at small spatial scales. The strong synchrony suggests that populations are subject to similar environmental forces. We used mixed effect models at the survey area and mountain region scales to assess the effect of rodent abundance (a proxy for predation rates) and local and regional climate during the breeding season on the recruitment of juvenile birds. Model selection based on AICc revealed that the most parsimonious models at both spatial scales included positive effects of rodent abundance and the North Atlantic oscillation during May, June and July (NAOMJJ). The NAOMJJ index was positively related to temperature and precipitation during the pre-incubation period; temperature during the incubation period and positive NAOMJJ values accelerate plant growth. A comparison of the relative effects of NAOMJJ and rodent abundance showed that variation in NAOMJJ had greatest impact on the recruitment of juveniles. This suggests that the climate effect was stronger than the effect of rodent abundance in our study populations. This is in contrast to previous studies on Willow Ptarmigan, but may be explained by the collapse in rodent cycles since the 1990s. If Willow Ptarmigan dynamics in the past were linked to the rodent cycle through a shared predator regime, this link may have been weakened when rodent cycles became more irregular, resulting in a more pronounced effect of environmental perturbation on the dynamics of ptarmigan.ZusammenfassungGroßräumige klimatische Schwankungen und Abundanz von Nagetieren bestimmen die Rekrutierungsraten von Moorschneehühnern Lagopus lagopus Die Rekrutierung von Juvenilen ist von großer Bedeutung für die Größe der Brutpopulation vieler Vogelarten im folgenden Jahr. Klimaschwankungen und Prädation können Rekrutierungsraten beeinflussen. Wenn solche Faktoren räumlich korreliert sind, können Rekrutierungsraten in räumlich getrennten Populationen synchronisiert sein. Wir nutzten Brutdaten einer umfangreichen Bestandsaufnahme von Moorschneehühnern aus den Jahren 2000–2011 zur Untersuchung räumlicher Synchronie in der Rekrutierung von Juvenilen innerhalb und zwischen Populationen in Bergregionen. Darüber hinaus schätzten wir die Effekte von Prädation und groß- wie kleinräumigem Klima auf die Rekrutierung von Juvenilen ein. Die Rekrutierung war sowohl innerhalb als auch zwischen Bergregionen synchronisiert, wobei die durchschnittliche räumliche Korrelation am stärksten zwischen den Bergregionen war. Die könnte durch kleinskalige Faktoren wie Prädation oder Habitatstruktur begründet sein oder aber durch unterschiedliche Stichproben, die größer sein können bei kleinen Maßstäben. Die starke Synchronie deutet darauf hin, dass die Populationen ähnlichen Umwelteinflüssen ausgesetzt sind. Wir wendeten Gemischte Modelle auf Untersuchungsgebiet und Bergregion an, um den Einfluss der Nagerabundanz (Parameter für Prädationsraten) sowie lokales und regionales Klima während der Brutsaison auf die Rekrutierung juveniler Vögel zu berechnen. Die Modellauswahl basierend auf AICs zeigte, dass die minimalsten Modelle auf beiden räumlichen Skalen positive Effekte auf die Nagerdichte und die nordatlantische Oszillation im Mai, Juni und Juli (NAOMJJ) beinhalten. Der NAOMJJ Index war positiv verbunden mit der Temperatur und Niederschlag in der Vorbrutzeit. Temperatur während der Bebrütungsphase und positive NAOMJJ Werte überstiegen das Pflanzenwachstum. Ein Vergleich der relativen Effekte von NAOMJJ und Nagerdiche zeigten, dass Schwankungen des NAOMJJ den größten Einfluss auf die Rekrutierung von Juvenilen haben. Das deutet darauf hin, dass klimatische Effekte stärker wirkten auf die untersuchten Populationen als die Nagerabundanz. Dies steht im Gegensatz zu vorherigen Untersuchungen an Moorschneehühnern, könnte aber erklärt werden durch den Zusammenbruch der Nagerzyklen seit den 1990er Jahren. Wenn die Dynamik von Moorschneehuhn Populationen in der Vergangenheit gekoppelt war mit den Nagerzyklen durch ein gemeinsames Prädatorenregime, dann kann diese Beziehung geschwächt worden sein, als die Nagerzyklen unregelmäßiger wurden. Dies resultiert in einem stärker ausgeprägten Einfluss von störenden Umwelteinflüssen auf die Dynamik von Moorschneehühnern.

Nest-predator prevalence along a mountain birch–alpine tundra ecotone

Dette er postprint versjonen av en artikkel publisert i Wildlife Research. Den publiserte versjonen av artikkelen kan finnes her: http://www.publish.csiro.au/paper/WR11031

Quantifying suitable late summer brood habitats for willow ptarmigan in Norway

BackgroundHabitat models provide information about which habitat management should target to avoid species extinctions or range contractions. The willow ptarmigan inhabits alpine- and arctic tundra habitats in the northern hemisphere and is listed as near threatened (NT) in the Norwegian red list due to declining population size. Habitat alteration is one of several factors affecting willow ptarmigan populations, but there is a lack of studies quantifying and describing habitat selection in willow ptarmigan. We used data from an extensive line transect survey program from 2014 to 2017 to develop resource selection functions (RSF) for willow ptarmigan in Norway. The selection coefficients for the RSF were estimated using a mixed-effects logistic regression model fitted with random intercepts for each area. We predicted relative probability of selection across Norway and quantile-binned the predictions in 10 RSF bins ranging from low-(1) to high-(10) relative probability of selection.ResultsRandom cross-validation suggest that our models were highly predictive, but validation based spatial blocking revealed that the predictability was better in southern parts of Norway compared to the northernmost region. Willow ptarmigan selected for herb-rich meadows and avoided lichen rich heathlands. There was generally stronger selection for vegetation types with dense field layer and for rich bogs and avoidance of vegetation types with sparse field layer cover and for lowland forest. Further, willow ptarmigan selected for areas around the timberline and for intermediate slopes. Mapping of the RSF showed that 60% of Norway is in the lowest ranked RSF bin and only 2% in the highest ranked RSF bin.ConclusionsWillow ptarmigan selected for vegetation types with dense field layer and bogs at intermediate slopes around the timberline. Selection coincides with previous habitat selection studies on willow ptarmigan. This is the first attempt to assess and quantify habitat selection for willow ptarmigan at a large scale using data from line transect distance sampling surveys. Spatial variation in predictability suggests that habitat selection in late summer might vary from north to south. The resource selection map can be a useful tool when planning harvest quotas and habitat interventions in alpine areas.