Using empirical data to quantify implementation uncertainty in small game harvest management

Sustainable resource management requires that managers are able to control the harvest offtake. This is challenging in systems with multiple objectives and great uncertainties, which is often the case in small game harvest management. The difference between the strategies implemented by management and the actual harvest bag size (i.e. implementation uncertainty) may be substantial, but few studies have so far explored this. In this study I investigated how different management strategies and system parameters affected actual offtake in willow ptarmigan (Lagopus lagopus L.) harvest, using empirical data and simulating performance of strategies and risk of harvest above selected harvest rate thresholds under varying population states. I used data from nine independently managed state owned hunting areas in Central and South Norway. Two paths were explored; analysing harvest directly (as bagged birds per km2) and indirectly by combining models for hunting pressure (hunting days per km2) and hunter efficiency (bagged birds per hunting day). My results show that the best model explaining bagged birds per km2 included total allowable catch per km2 (TAC) set by managers and willow ptarmigan density, where number of bagged birds at high TAC and low density was comparable to the number at lower TAC and higher density. Hunting pressure was best explained by number of sold permits per km2 and type of quota, while the best hunter efficiency model only included density. The results strongly suggested that hunters were relatively more effective at low densities and removed a higher proportion of birds from the area when densities were low. The simulations with alternative harvest management scenarios revealed that this effect was present for all strategies, whether managers used a constant harvest strategy (TAC or effort) or had adapted their strategy to the density estimates. High risks at lower densities of harvest rates above the levels associated with sustainability, indicate the need for knowledge of population state before hunting permits are sold, and urges the use of threshold strategies to balance the competing objectives of hunting opportunities and sustainability. Quantified risks of harvest rates over a range of densities enable informed manager decisions of trade-offs between competing objectives. This study is one of the first approaches to quantifying implementation uncertainty in small game harvest, and shows how estimates from empirical analyses may be used as elements of a full management strategy evaluation (MSE) framework

Quantifying risk of overharvest when implementation is uncertain

1. Sustainable harvest management implies an ability to control harvest rates. This is challenging in systems that have limited control of resources and resource users, which is often the case in small game harvest management. The difference between management strategies and actual harvest bag size (i.e. implementation uncertainty) may be substantial, but few studies have explored this. 2. We investigated how different management strategies and ecosystem variables affected realised harvest of willow ptarmigan (Lagopus lagopus L.) among nine independently managed, state-owned hunting areas in Central and South Norway during 2008–2015. First, we focused our empirical analysis around three response variables of interest: hunting bag (scaled by area), hunting effort (number of hunting days scaled by area) and hunter efficiency (shot birds per hunting day). Akaike information criteria (AIC) guided model selection among candidate GLMMs. Then, we used model-averaged parameter estimating from the statistical models in numerical simulations to explore risk of overharvest due to implementation uncertainty. 3. The most parsimonious model explaining hunting bag included total allowable catch (TAC) and willow ptarmigan density. Hunting effort was explained by number of permits sold and type of quota (daily vs. weekly quota). The most parsimonious model describing hunter efficiency only included the effect of willow ptarmigan density. 4. Our results show that managers have only partial control over harvest rates in this system, and that hunters were relatively more efficient and harvest rates higher at low densities. This effect was present for all management strategy scenarios, including when managers adjusted TAC according to population estimates from monitoring programmes. 5. Synthesis and applications. Quantifying risk of unsustainable harvest rates under different scenarios enables managers to make informed decisions, when dealing with competing objectives of harvest opportunities and sustainability. The substantial risk of high harvest rates at low densities reported here should encourage frequent use of threshold strategies. This study is one of the first approaches for quantifying implementation uncertainty in small game harvest, and shows how estimates from empirical analyses could be used to quantify risk of overharvest.publishedVersionPaid Open Acces

Climatic forcing and individual heterogeneity in a resident mountain bird : legacy data reveal effects on reproductive strategies

Optimization of clutch size and timing of reproduction have substantial effects on lifetime reproductive success in vertebrates, and both individual quality and environmental variation may impact life history strategies. We tested hypotheses related to maternal investment and timing of reproduction, using 17 years (1978–1994) of individual-based life history data on willow ptarmigan (Lagopus l. lagopus, n = 290 breeding females with n = 319 breeding attempts) in central Norway. We analysed whether climatic variation and individual state variables (age and body mass) affected the number of offspring and timing of reproduction, and individual repeatability in strategies. The results suggest that willow ptarmigan share a common optimal clutch size that is largely independent of measured individual states. While we found no clear direct weather effects on clutch size, higher spring temperatures advanced onset of breeding, and early breeding was followed by an increased number of offspring. Warmer springs were positively related to maternal mass, and mass interacted with clutch size in production of hatchlings. Finally, clutch size and timing of reproduction were highly repeatable within individuals, indicating that individual quality guided trade-offs in reproductive effort. Our results demonstrate how climatic forcing and individual heterogeneity in combination influenced life history traits in a resident montane keystone species. trade-offs, state-dependent, clutch size, breeding time, repeatabilitypublishedVersio

Driftsplan småvilt for Åfjord fjellstyre

Småviltet i Åfjord statsallmenning er en ressurs vi både skal ta vare på for fremtiden og nyttiggjøre oss når forholdene tilsier det. Fokuset på småviltet kan deles i to hovedmomenter: Småviltets plass i økosystemet, og betydningen småviltet har for oss i form av jaktutbytte, økonomisk ressurs og verdi i naturopplevelser. For å kunne nyttiggjøre oss av ressursen kreves det at vår bruk er bærekraftig.VRI Trøndelags program forskningsassistent-student, Åfjord kommune, Sør-Trøndelag fylkeskommune, Åfjord fjellstyre og Høgskolen i Nord-Trøndelag (HiNT

Drivers and consequences of partial migration in an alpine bird species

1. Partial migration, where a portion of the population migrates between win-ter and summer (breeding) areas and the rest remain year- round resident, is a common phenomenon across several taxonomic groups. Several hypotheses have been put forward to explain why some individuals migrate while others stay resident, as well as the fitness consequences of the different strategies. Yet, the drivers and consequences of the decision to migrate or not are poorly understood.2. We used data from radio- tagged female (n= 73) willow ptarmiganLagopus lago-pus in an alpine study area in Central Norway to test if (i) the decision to migrate was dependent on individual state variables (age and body weight), (ii) individu-als repeated migratory decisions between seasons, and (iii) the choice of migra-tory strategy was related to reproductive success.3. Partially supporting our prediction that migratory strategy depends on in-dividual state, we found that juvenile birds with small body sizes were more likely to migrate, whereas large juveniles remained resident. For adult females, we found no relationship between the decision to migrate or stay resident and body weight. We found evidence for high individual repeatability of migratory decision between seasons. Migratory strategy did not explain variation in clutch size or nest fate among individuals, suggesting no direct influence of the chosen strategy on reproductive success.4. Our results indicate that partial migration in willow ptarmigan is related to juve-nile body weight, and that migratory behavior becomes a part of the individual life history as a fixed strategy. Nesting success was not affected by migratory strategy in our study population, but future studies should assess other traits to further test potential fitness consequences. alpine wildlife, eco-evolution, Lagopus lagopus, migrationpublishedVersio

Evaluation of Spatio-Temporal Patterns of Predation Risk to Forest Grouse Nests in the Central European Mountain Regions

We evaluated the spatiotemporal patterns of predation risk on black grouse nests using artificial nests that were monitored by camera traps in mountain areas with a small extant (Ore Mts.) and already extinct (Jeseníky Mts.) black grouse population. The overall predation rate of artificial nests was 56% and we found significant differences in survival rate courses over time between both study areas (68% Ore Mts. vs. 41%, Jeseníky Mts.). Within the time required for successful egg incubation (25 days), nest survival probability was 0.32 in the Ore Mts. and 0.59 in Jeseníky Mts. The stone marten (Martes foina) was the primary nest predator in both study areas (39% in total), followed by common raven (Corvus corax, 25%) and red fox (Vulpes vulpes, 22%). The proportion of depredated nests did not differ between habitat types (i.e., open forest interior, clearing, forest edge), but we recorded the effect of interaction of study area and habitat. In Ore Mts., the main nest predator was common raven with seven records (37%). The Eurasian jay (Garrulus glandarius) was responsible for most predation attempts in Jeseníky Mts. (five records, i.e., 83%), while in the Ore Mts., most predation attempts were done by red fox (six records, i.e., 38%publishedVersio

Revidert forvaltningsplan for lirype i Åfjord statsallmenning

Etter flere år med datainnsamling og erfaringer med praktisk bruk av den første driftsplanen for småvilt i Åfjord (2014), er det nå utarbeidet en revidert plan. Dette dokumentet er i større grad en ren forvaltningsplan og fokuserer kun på lirype. Rapporten er ment å stå som faglig bakgrunn for fjellstyrets avgjørelser omkring jaktuttak og andre beslutninger knyttet til lirypeforvaltningen

Evaluering av prosjektet Jakt i Værnesregionen : økt jakt på smårovvilt

Nord universitet har hatt samarbeid med fjellstyrene i Stjørdal siden 2007 og prosjektet Jakt i Stjørdal - økt jakt på smårovvilt siden opprettelsen i 2011. Prosjektet ble opprinnelig startet som et rent forvaltningstiltak, ikke som et forskningsprosjekt. Bakgrunnen for tiltaket var blant annet lav produksjon av hønsefugler og et ønske om å øke jakttrykket på smårovvilt uten bruk av skuddpremier. I historisk perspektiv er ikke felling av smårovvilt som eksempelvis rødrev, mår og kråker, ofte omtalt som predatorkontroll, noe nytt tiltak for å forsøke å øke mengden av matnyttig småvilt. Tidligere studier viser at predatorkontroll kan ha en effekt, forutsatt at innsatsen er effektiv, langvarig og foregår over større områder

Using empirical data to quantify implementation uncertainty in small game harvest management

Sustainable resource management requires that managers are able to control the harvest offtake. This is challenging in systems with multiple objectives and great uncertainties, which is often the case in small game harvest management. The difference between the strategies implemented by management and the actual harvest bag size (i.e. implementation uncertainty) may be substantial, but few studies have so far explored this. In this study I investigated how different management strategies and system parameters affected actual offtake in willow ptarmigan (Lagopus lagopus L.) harvest, using empirical data and simulating performance of strategies and risk of harvest above selected harvest rate thresholds under varying population states. I used data from nine independently managed state owned hunting areas in Central and South Norway. Two paths were explored; analysing harvest directly (as bagged birds per km2) and indirectly by combining models for hunting pressure (hunting days per km2) and hunter efficiency (bagged birds per hunting day). My results show that the best model explaining bagged birds per km2 included total allowable catch per km2 (TAC) set by managers and willow ptarmigan density, where number of bagged birds at high TAC and low density was comparable to the number at lower TAC and higher density. Hunting pressure was best explained by number of sold permits per km2 and type of quota, while the best hunter efficiency model only included density. The results strongly suggested that hunters were relatively more effective at low densities and removed a higher proportion of birds from the area when densities were low. The simulations with alternative harvest management scenarios revealed that this effect was present for all strategies, whether managers used a constant harvest strategy (TAC or effort) or had adapted their strategy to the density estimates. High risks at lower densities of harvest rates above the levels associated with sustainability, indicate the need for knowledge of population state before hunting permits are sold, and urges the use of threshold strategies to balance the competing objectives of hunting opportunities and sustainability. Quantified risks of harvest rates over a range of densities enable informed manager decisions of trade-offs between competing objectives. This study is one of the first approaches to quantifying implementation uncertainty in small game harvest, and shows how estimates from empirical analyses may be used as elements of a full management strategy evaluation (MSE) framework