The present study investigates the determinants of chick survival in willow ptarmigan Lagopus l. lagopus. Chick survival was negatively associated with genetic relatedness of mates. This may imply that more chicks die when genetic relatedness of mates is high, i.e. low chick heterozygosity at hatching. Hence, newly hatched chicks with low heterozygosity may have reduced viability and, therefore, might suffer higher mortality due to biotic/abiotic conditions. However, there was no association between the proportion of chicks with low heterozygosity and ambient temperature, but a highly significant association with predation pressure was found. Because newly hatched chicks are unable to maintain their body temperature even at normal ambient temperatures and because willow ptarmigan chicks start chirping when they get cold, it is suggested that chicks with low genetic variation may become more exposed to predation. It is proposed that genetic variation significantly affects viability of ptarmigan chicks, but that predation is the proximate cause of death. Consistent with several earlier studies, predation was related both to nesting females and to survival of the chicks. However, the present study extends these findings by suggesting a relationship between predation on one side and genetic constitution on the other, and that predation on nesting females, by reducing genetic variation among chicks at hatching, enhance chick mortality.

Willow ptarmigan Lagopus l. lagopus is a popular game bird which fluctuates in abundance. The causes of these fluctuations, however, remain controversial, but several studies have emphasised the effect of predation. Predation not only reduces the number of breeding birds, but does it in such a way that genetic variation among chicks at hatching becomes reduced, causing reduced viability and increased mortality among chicks. We present an extended predation hypothesis in which the multiannually fluctuating population dynamics of the willow ptarmigan are better explained by a model including both predation and genetic variation of territorial nesting females than by predation alone. A simple model including the heterozygosity of nesting territorial females and the percentage of females suffering egg predation explained 95% of the observed fluctuations in chick production on an inland study area during five years, whereas predation alone only explained 72%. The data may suggest a non-additive relationship between predation and genetic variation of nesting females which enhance the effect of predation. Observed and calculated chick production per two adults deviated on average by only 0.38 chicks. In another inland population, showing multiannual fluctuations for almost 20 years, observed and calculated chick production deviated on average by 0.58 chicks, and the model explained 61% of observed fluctuations in chick production, whereas predation alone only explained 28%. In an island population, however, the full model explained 45% of observed fluctuations in chick production. This was about the same as predation alone (44%). It is discussed whether the better fit of the full model than the model including predation alone between observed and calculated chick production obtained in the two inland populations in contrast to the island population, may be caused by the different predator communities.

Two feeding trials on hand-reared grey partridges Perdix perdix were performed to study the effect of a change from a commercial to a natural diet on body mass, food consumption, metabolised energy coefficient, gut morphology and some blood metabolites. We simulated the abrupt change in the diet which takes place when hand-reared birds are released into the wild. In the test group body mass decreased significantly after the change in diet. However, within one week body mass started to increase again, but it stabilised at a lower level than in control birds. Birds in the test group consumed more food (fresh weight) during the feeding trial and even produced more excreta during the second, fourth and fifth week of the feeding trial. Gross energy intake, amount of metabolised energy and metabolised energy coefficient decreased and excretory energy content increased during the feeding trial. No differences were seen in the analysed blood metabolites. Gizzards of the test birds were heavier than gizzards of the control birds. We conclude that the abrupt change from a commercial to a natural diet with the following difference in diet composition affects the partridge's ability to utilise nutrients from food available in the wild. According to our study, a period of six weeks may be inadequate for partridges to get totally adapted to a new diet.

An epizootic of sarcoptic mange among red foxes Vulpes vulpes reached central Norway in 1976, and by 1986 it had spread to the whole country, resulting in a severe decline in the red fox population. We analyse the change in the hunting bags of the predator species red fox and pine marten Martes martes, and the prey species capercaillie Tetrao urogallus, black grouse Tetrao tetrix, mountain hare Lepus timidus and willow grouse Lagopus I. lagopus from the period prior to and during the mange epizootic. The data are gathered from publications by Statistics Norway and are based on answers from more than 5,000 hunters yearly. On the national level, the hunting bags of capercaillie, black grouse, mountain hare and pine marten were significantly negatively correlated with that of the red fox. When the time series at the national level were detrended, there were positive correlations between the hunting bags of all species without time lag, except that of pine marten, which lagged one year behind the other species. At the local level there were negative correlations between the hunting bag of red fox and those of the small game species except for willow grouse. The study confirms that the red fox is a keystone predator in Scandinavia.

Following over-harvest in the early decades of the 20th century, the arctic fox Alopex lagopus has declined and failed to recover in Norway. Competition with the red fox Vulpes vulpes has frequently been suggested as a possible factor hindering arctic fox recovery. Between 1988 and 1997, a total of 213 former arctic fox dens in four alpine regions of Norway, i.e. Hardangervidda, Dovrefjell, Børgefjell and Dividalen, were checked at least once for occupation by red or arctic foxes. Of these 213 former arctic fox dens, 138 were unoccupied, and 32 and 43 were occupied by arctic and red foxes, respectively. In general, red foxes occupied dens situated at significantly lower altitudes than those occupied by arctic foxes, which supports present ideas of red fox/arctic fox coexistence. As arctic foxes tended to avoid dens at the lowest altitudes, it is possible that arctic foxes to some degree avoid the areas where red foxes are most abundant. This may have disproportionate effects, as the probability of reproduction in arctic fox dens was highest in dens at lower altitudes. Despite this, the large number of unoccupied dens indicates that dens are unlikely to be in limited supply. Therefore, neither our data, nor a review of published data and trapping records, support the hypothesis that inter-specific competition with the red fox is currently preventing arctic fox recovery in the Norwegian alpine environment.

The accuracy of hunter observations (moose seen per hunter day) as a source for various population parameters in moose Alces alces L was evaluated. We found an overall positive correlation between density and observation index. The strength of the relationship was similar in all of the three counties studied. The observation index levelled off with increasing density (>1.0 moose/km²). Sightability of moose differed significantly among two of the three counties studied which makes comparisons between the regions difficult. However, adjusting the regional observation index by independent estimates of population size enables comparisons over larger areas. We found a probability of 0.81 that a change in observation index also reflects the direction of a change in population size. The reproductive rate calculated from hunter observations (Σcalves)/(Σfemales) was correlated with the observed mean recorded reproductive rate among radio-collared moose in a county. Furthermore, moose reproduction as estimated from hunter observations was positively correlated among counties in northern Sweden indicating large-scale synchrony. Our findings indicate that hunter observations of moose reflect moose population size and reproductive rate reasonably well, and can be used to monitor population fluctuations. If calibrated, one may use observation indices for estimates of population size in local moose management as an alternative or supplement to more costly monitoring methods. If not calibrated, observational data may be misleading if they are used as a density indicator.

We used hunting dogs and man to simulate the searching for nests and broods of forest grouse, i.e. capercaillie Tetrao urogallus and black grouse Tetrao tetrix, by mammalian predators. Our aim was to find out if and how forest fragmentation affects the searching efficiency of predators. In total, we found 73 capercaillie and 35 black grouse nests and 20 young capercaillie broods. We calculated that a mammalian predator will detect a capercaillie nest if closer than 1.6 m (95% C.I.: 0.7 - 2.2), a black grouse nest if closer than 1.1 m (95% C.I.: 0.8 - 1.6), and a capercaillie brood if closer than 39 m (95% C.I.: 17 - 89). Nests were distributed in all habitat types, whereas broods were restricted to specific brood habitats. Due to this and the difference in the detection radius between nests and broods, we estimated that the predator gain of searching for broods in brood habitat is about 80 times higher than the gain of searching for nests which are situated in all habitat types in our study area. As young broods concentrate in highly restricted habitats, the predator gain of searching for broods increases exponentially with the loss of brood habitat, whereas it decreases linearly with increasing nest predation. We discuss this mechanism as a possible process explaining the observed decline in capercaillie populations in fragmented forests and consider its implications for grouse management.