Lichen Availability Research Articles

Relative contribution of decreased productivity and survival to recent changes in the demographic trend of the Rivière George Caribou Herd

The Rivière George caribou herd (RGCH) was numerically low during the middle part of the century but apparently erupted in the sixties and the seventies. Puberty was early and pregnancy rate was high among RGCH females from 1973 until the mid-eighties when fecundity decreased significantly, in particular among sub-adults; productivity remained low in 1992. Autumn calf:female ratios reflected this trend in pregnancy, exceeding 50 calves: 100 cows between 1973 and 1983, but dropping thereafter progressively to a low of 24 in 1992. In 1993, this ratio rebounded back to 42. Annual adult survival rate of radio-collared females was high (0.95) at the beginning of the monitoring in 1984, but exhibited a variable but declining trend until 1992. Simulations were conducted to estimate the demographic trend of the RGCH between 1984 and 1992, using annual survival rates of radio-collared animals and annual autumn calffemale ratios to estimate calf production. Age structure played a minor role in estimating the finite rate of increase (Lamda). According to the simulations, the RGCH increased in size until 1987, and showed a slight decrease thereafter. The herd should have decreased by 12-15% between 1988 and 1993, according to the simulations. Productivity first caused a decline in Lamda, but in recent years decreased survival contributed slightly more than productivity to the reduction in Lamda. Estimation of the herd size by means of aerial censuses in 1976, 1984, 1988 and 1993 suggested a similar pattern in demographic trend, differences being statistically meaningless. We speculated on the future of the RGCH, that could have erupted after many decades of unfavourable weather. The herd will exhibit a rapid descent to low numbers if wolves show a numerical response to current caribou abundance, or if lichen availability on the winter range decreases due to competition with the adjacent and increasing Rivière aux Feuilles herd; otherwise it will exhibit dampened oscillations, whose amplitude will depend on the time-lag of vegetation reaction to decrease grazing pressure on the summer range.

Winter forage selection by barren-ground caribou: Effects of fire and snow

Both long- and short-term consequences should be considered when examining the effects of fire on the foraging behavior of caribou. Post-fire increases in protein content, digestibility, and availability of E. vaginatum make burned tussock tundra an attractive feeding area for caribou in late winter. These benefits are likely short-lived, however. Lowered availability of lichens and increased relative frequency of bryophytes will persist for a much longer period.

Effects of lichen biomass on winter diet, body mass and reproduction of semi‐domesticated reindeer Rangifer t. tarandus in Finland

Winter food supply very likely influences the life history of reindeer Rangifer t. tarandus. We therefore examined how lichen biomass affects winter diet composition, body mass and reproduction in 14 herds of semi‐domesticated reindeer in northern Finland. Diet composition was assessed microhistologically on faeces collected from the actual winter feeding sites of reindeer. When lichen was scarce at these sites reindeer included vascular plants and mosses in their diet. Calf dressed weight depended on both ground lichen biomass and the intensity of supplemental feeding, doe dressed weight depended on lichen biomass alone. One explanation for this difference between calves and does is the connection between food supply and calf mortality: low lichen biomass may promote newborn mortality, which, in turn, frees breeding females from investing further in current reproductive investment. Relative offspring weight (calf/female weight ratio) depended on both lichen biomass and supplemental feeding. Low lichen availability appeared to enhance the impact of density‐independent factors on reproduction, because the annual variation in reproductive rate increased with decreasing lichen biomass.

Body mass variation in semidomesticated reindeer

The between-years and within-year variation in mass of semidomesticated reindeer calves and females was studied in four herds in Finnish Lapland. Mass data covered 11–23 years. In two of the herds the intensity of supplemental feeding in mid and late winter increased throughout the sampling period, whilst in two other herds the amount of food available per capita fell drastically as a result of increased density (about 1–4 individuals/km2). Calf mass increased in both supplementally fed herds and female mass in one of them. In herds on natural ranges female mass was density dependent. Both calf mass (three herds) and female mass (one herd) correlated negatively with the number of warm days in midsummer, most likely because of severe insect harassment. The sum of snow depth during the two or three preceding winters influenced body mass inversely in one herd and positively in another herd, where snow depth probably increased the availability of arboreal lichens. The detrimental effect of warm midsummers disappeared with intensification of supplemental feeding and the resultant improvement of female condition in winter. Within-year coefficients of variation (CV) correlated negatively with mean mass for calves in all four herds and for females in one herd. For calves (two herds) and for females (one herd) CV correlated positively with the number of warm days in midsummer. We suggest that late-born calves, and females who lost body reserves in winter, were most sensitive to insect harassment.

Patterns of Distribution and Abundance of Corticolous Lichens and Their Invertebrate Associates on Quercus rubra in Maine

Patterns of Distribution and Abundance of Corticolous Lichens and Their Invertebrate Associates on Quercus rubra in Maine

Relative Abundance of Food in Winter for Newfoundland Caribou

Information on the winter feeding behaviour of caribou Rangifer tarandus Bangs in Newfoundland and the relative abundance of food available to them in winter are presented. Sight and smell were used to locate food beneath the snow. Tall shrubs showing above the snow appeared to increase lichen availability by providing air vents. A comparison of absolute abundance of food, based on percentage of ground surface covered with plants, and the relative abundance of food in winter, based on species composition in feeding craters, indicated that shrubs were consumed more than the absolute abundance suggested. Shrubs and terrestrial lichens were consumed more on a lichen woodland range than on a subalpine range, even though caribou densities were similar. Snow was softer and shrubs taller on the lichen woodland range than the subalpine; these factors probably increased the relative abundance of shrubs and lichens in winter.