Olav Hjeljord

Ecological Correlates of Regional Variation in Life History of the Moose Alces Alces

The food limitation hypothesis of population regulation states that a stable equilibrium will exist between a population and its food resources due to a density-depen- dent decrease in fecundity and/or increase in mortality. This hypothesis was tested for the moose (Alces alces) by comparing regional variation in life history characteristics in four Norwegian study areas, chosen to represent a gradient both in summer and winter range conditions. The rate of body growth was most rapid in the northern study area with the best summer ranges. Lowest body growth occurred in the population living under the poorest winter conditions. After snow-free winters the rate of body growth increased substantially, leading to large annual variations in yearling body masses. These differences in growth lead to significant age-specific differences between populations in female carcass masses in autumn. Probability of maturing as a yearling increased with body mass in the three southern populations. In contrast, in the northern study area no such relationship was found, leading to a delayed age at maturity in the population with the largest females. This shows that the relationship between age at maturity and body mass differs regionally, suggesting different selective regimes. The peak timing of ovulation of old females in the autumn showed a latitudinal delay. Females in the alpine population, with the poorest winter conditions, had significantly later mean calving dates and produced fewest calves per year. Gestation length appears to be dependent on nutritional condition of females during pregnancy. Mortality was highest in the northern study area where most of the deaths occurred during the summer. Very few calves died during the winter. These results suggest that a stable high-density equilibrium between moose and their food resources as expected from the food limitation hypothesis is unlikely. The decrease in fecundity and the increase in mortality under poor nutritional conditions during the winter has only a small effect on the population growth rate and is therefore unlikely to have a strong regulatory effect. In the absence of large predators, this will lead to large fluctuations in population size that will overshoot the carrying capacity.

Range-body mass interactions of a northern ungulate - a test of hypothesis

Abstract Summer diet, summer temperature, length of the growth season and animal density appeared to best explain annual and regional differences in calf and yearling body mass in moose from southeastern Norway. In general animals inhabiting steep, alpine landscapes had less body mass than animals using flat, low-altitude habitats. Autumn body mass of calves and yearlings decreased with increasing snow depth during the preceding winter and spring. However, calf body mass was more influenced by the summer range and less by the winter range than was body mass of yearlings. There was no indication that the effect of snow depth on autumn body mass was greater in moose living on poor than on good summer ranges. Body mass decreased with increasing competition for summer forage, while the winter range mainly had an density-independent effect. Habitat quality, expressed as regression lines between calf and yearling body mass and animal density (hunting yield), differed between regions. On ranges of medium and high altitude where birch (Betula spp.) rowan (Sorbus aucuparia) and bilberry (Vaccinium myrtillus) dominated moose summer diet, body mass decreased at a rapid rate with increasing animal density. Body mass decreased at a slower rate at low-altitude ranges and at high-altitude ranges where willow (Salix spp.) and forbs dominated the diet. Body mass of lactating cows decreased with increasing animal density, but animal density did not affect body mass of non-lactating cows. There was no indication that the decrease in autumn body mass with increasing moose density over the last 25 years has caused a decrease in animal condition (ability to survive the winter). The results are discussed in relation to the effect of summer and winter range on population regulation in moose. It is concluded that a density-dependent effect is apparent on the summer range even at low and intermediate population densities. On the winter range, on the other hand, density-dependence is likely to occur only at high levels of population density.

Moose summer and winter diets along a large scale gradient of forage availability in southern Norway

Studies on dietary functional responses in large herbivores are traditionally conducted by following individual animals. The method is very time-consuming, and hence, typically provides only a narrow array of forage species compositions. Here we use a range level approach to look at moose (Alces alces) selectivity for and utilization of forage species in relation to availability in both summer and winter. We compare 12 Norwegian ranges representing a large scale gradient in plant communities. The most important forage species in the diet were birches (Betula spp., comprising 43% of all trees browsed in summer and 27% in winter), rowan (Sorbus aucuparia, 25% of trees browsed in summer, 37% in winter), and bilberry (Vaccinum myrtillus, 42% of herbaceous epidermal fragments in summer feces). Selectivity for birches was positively related to its availability and negatively related to availability of rowan, Salix spp., and aspen (Populus tremula) together (all more selected for than birches). Multiple regression models including availability of several forage species were thus superior to single-species models in explaining the diet content of main forage plants. Selectivity for birches was also stronger in summer than in winter, while the opposite pattern was found for rowan. The finding is relevant for our evaluation of the quality of summer and winter ranges, and hence, their relative influence on population productivity. Our study underlines the need to incorporate species composition of available forage when quantifying dietary functional responses in selective herbivores such as moose. Furthermore, care should be taken when extrapolating data on moose diet across ranges or seasons.

Glyphosate application in forest—ecological aspects

Vegetation changes caused by glyphosate application or hand cutting were evaluated on five experimental sites. Reactions on Norway spruce (Picea abies L.) were also recorded. Betula spp. and Sorbus aucuparia appeared sensitive to glyphosate and the rate of recoverage of the canopy was related to the extent of control. Vegetative regeneration was stimulated by hand cutting and suppressed by glyphosate. Except for fems, which showed high sensitivity to glyphosate and slow regeneration, the great majority of species in the height level below 1 meter were classified as moderately tolerant. The successional development appeared relatively rapid. Glyphosate application caused an increase in the diversity of the plant community established after application. The release of Norway spruce from competition following glyphosate application caused a more rapid increase in the number of plants higher than 50 cm on glyphosate areas than on reference areas.The mountain hares (Lepus timidus) use of sprayed and unsprayed parts of a forest plantation was studied using pellet counts, radiotracking and a winter feeding site survey. There was a strong reduction in use by L. timidus the first year after spraying. The second year after spraying the difference between sprayed and unsprayed parts was small by comparison. It was concluded that spraying of forest plantations up to at least 10 years after logging mainly affects the spring habitat of L. timidus.

Moose Summer Diet From Feces and Field Surveys: A Comparative Study

Abstract Microhistological analysis of feces is the most applied noninvasive method for assessing diets of wild ungulates. However, the method is complicated by differential digestibility of forage species. To evaluate the efficacy of this method in quantifying browse components in summer diets of moose (Alces alces L.) on Norwegian rangelands, we compared it to parallel field surveys of browsed vegetation on the same range. Although the same principal diet components were identified in the feces and in the field, there were consistent discrepancies between the two methods in estimated proportional diet contents. Birch (Betula spp.) showed the highest field:fecal ratio: 3.3 ± 0.50 compared to 0.9 ± 0.16 for Salix spp., 0.8 ± 0.16 for aspen (Populus tremula L.), and 0.6 ± 0.12 for rowan (Sorbus aucuparia L.). Until in vivo fecal correction factors for differential forage digestibility are available, we caution against broad application of fecal analyses for estimating proportions of browse in moose diet. Although we could not determine the exact amount of discrepancy implicit in each method, previous studies of moose summer diet in the area clearly indicate that fecal analyses gave a less accurate representation of actual moose browse diet than did the field survey. Fecal analyses are nevertheless needed to identify moose diet components other than browse, which are not easily obtained from field surveys.

Seasonal mortality of black grouse Tetra tetrix during a year with little snow

The seasonal mortality of black grouse Tetrao tetrix was studied in southeastern Norway (60°26′N, 10°54′E), in a study area dominated by up to 80% Norway spruce Picea abies. Modem forestry with clear-cuttings has been practised, and 50% of the forest was younger than 30 years. Fourteen males and seven females were captured on a lek in spring 1991 and equipped with radio transmitters. During the following 12 months, 72% of the birds were killed, mostly by predators. No birds died from capture through July. In autumn, predation was higher, with four black grouse being killed. Mortality was highest during winter, with 58% of the birds dying. The goshawk Accipiter gentilis was the most important predator during winter. High predation by goshawks in winter 1991–92 may have been the result of black grouse being more vulnerable to predation because limited snowfall precluded snow roosting, or of an invasion by goshawks. Therefore, snow roosting may be an important antipredator behaviour in black grouse. The effect of increased adult mortality is discussed in relation to chick production.

Does fragmentation by logging reduce grouse reproductive success in boreal forests

In 1999 and 2001, we compared the population characteristics of capercaillie Tetrao urogallus, black grouse T. tetrix and hazel grouse Bonasa bonasia inside the pristine forest reserve State Natural Reserve ‘Pinezhskiy’ in northwestern Russia and in the logged forests surrounding the reserve. We also compared the abundance of mammalian predators and birds of prey. The August density of capercaillie was lower in logged forests than in the reserve (P = 0.05), but black grouse tended to be more abundant in the logged area (P = 0.08). For hazel grouse, no difference in abundance was found between the reserve and the logged area. Reproductive success of all three grouse species was generally higher in the logged area than in the reserve. A winter track survey indicated low abundance (< 1 track/10 km/24 hours) and no difference in density of small and mediumsized mammalian predators between the reserve and the logged area. The only exception was red fox Vulpes vulpes whose tracks were recorded only in the logged area. Buzzards Buteo spp. and goshawk Accipiter gentilis were the most numerous birds of prey. Goshawk tended to be more common in the reserve (P = 0.09), whereas buzzards were seen more often in the logged area (P = 0.1). Tracks of mountain hare Lepus timidus was twice as abundant in the logged forest (P = 0.02), whereas tracks of red squirrel Sciurus vulgaris was almost 10 times more numerous in the reserve (P < 0.001) than in the logged area. Judged by the remains found, the majority (72%) of grouse were killed by birds of prey. Our study suggests that reproduction of all three species of forest grouse in this region remains stable or increases following logging. We hypothesise that this may be due to the type of logging performed and to differences in the composition of predators and of prey other than grouse inside and outside the reserve.

Coping in a human-dominated landscape: trade-off between foraging and keeping away from roads by moose (Alces alces)

Roads fragment moose habitat and cause increased mortality through moose–vehicle collisions. Previous studies have found that moose avoid areas near roads. In late winter, when moose face depleting food resources elsewhere, moose may be more prone to use areas near roads for foraging. However, this presumed trade-off between foraging and keeping away from roads has not previously been investigated. We sampled positions from global positioning system-collared moose in late winter from a high-density moose population in Southern Norway that is heavily influenced by human infrastructure. We combined data on moose positions with detailed field surveys of food abundance at sites that were, respectively, intensively used or sparsely used by moose. The probability that a site was intensively used increased with increasing abundance of high-quality browse and also with increasing distance to the nearest road. This indicates that moose trade-off foraging against keeping away from roads. We also found that spatio-temporal movements in relation to roads were influenced by variation in perceived human-derived risk; moose moved closer to smaller roads (low traffic volume) than to major roads (higher traffic volume) and closer to roads at night than at day. Males moved closer to roads than females. In conclusion, moose clearly exhibited behavioural adaptations to cope with roads and traffic in the study area. Because availability of high-quality forage substantially influenced habitat use, it may be an option to establish artificial feeding sites during winter to keep moose away from the roads.

Spring-summer movements of male capercaillie Tetrao urogallus: a test of the 'landscape mosaic' hypothesis.

The ‘landscape mosaic’ hypothesis predicts that adult male capercaillie Tetrao urogallus track available habitat when making distinct seasonal migrations. We tested this hypothesis by comparing movement from leks to summer range in three geographical regions, viz. northwest Russia (Pechora), southwest Russia (Tver) and southeast Norway (Varaldskogen). All radio-collared males dispersed out of their daytime lek territories to an average distance of 2.3 km (±0.37) from lek centres (N = 52). In Russia, three birds, which were not included in this estimate, moved beyond the 6–7 km detection distance, but returned the following year. Due to large variation among birds at each lek, the only significant difference in movement was found between the birds at the lek in Pechora ( = 1.3 km) and those at one of the two leks in Tver ( = 3.6 km) and at one of the three leks in Norway ( = 3.2 km). At all leks except the one in Tver, the amount of suitable summer habitat, e.g. old Norway spruce Picea abies forest on rich soil, was smaller within a 1–km radius of leks centres than in the outer two 1–km zones. Despite a large proportion of old spruce forest at and near the lek site in Tver, the males at this site moved >2 km from the lek centre in late May/early June. When data were pooled, the dispersal distance did not correlate with the amount of old spruce forest nor with the size of patches (e.g. grain size) with increasing distance from leks. However, at the Norwegian study area, which is highly fragmented with a fine-grained habitat mosaic due to commercial forestry, variation in topography and soil quality, birds tended to move farther away from the leks with increasing patch size and with increasing proportion of old spruce forest. When fitting a second polynomial regression function to the pooled data, there was only a weak relationship between dispersal distance and grain size for leks (P = 0.19). When including all birds, the relationship was highly significant (P = 0.002). The Pechora lek in northwest Russia contributed mainly to the lack of a clear relationship between movement pattern and distribution of old spruce forest. Here large, contiguous bands of old spruce forest were located along the main river courses in a coarse-grained fashion within 2 km of lek sites. Thus, local configuration of preferred summer habitat at the landscape scale probably affects both direction and movement to a larger extent than predicted from the ‘landscape mosaic’ hypothesis.

Moose recruitment in relation to bilberry production and bank vole numbers along a summer temperature gradient in Norway

The plant stress hypothesis states that plant stress factors other than herbivory improve herbivore performance due to changes in the content of nutritive or defensive compounds in the plants. In Norway, the bilberry (Vaccinium myrtillus) is important forage for the bank vole (Myodes glareolus) in winter and for the moose (Alces alces) in summer and autumn. The observed peaks in bank vole numbers after years with high production of bilberries are suggested to be caused by increased winter survival of bank voles due to improved forage quality. High production of bilberries should also lead to higher recruitment rates in moose in the following year. We predict, however, that there is an increasing tendency for a 1-year delay of moose indices relative to vole indices with decreasing summer temperatures, because low temperatures prolong the period needed by plants to recover in the vole peak year, and thus positively affect moose reproduction also in the succeeding year. In eight out of nine counties in south-eastern Norway, there was a positive relationship between the number of calves observed per female moose during hunting and a bilberry seed production index or an autumn bank vole population index. When dividing the study area into regions, there was a negative relationship between a moose-vole time-lag index and the mean summer temperature of the region. These patterns suggest that annual fluctuations in the production of bilberries affect forage quality, but that the effect on moose reproduction also depends on summer temperatures.