Winter condition variability decreases the economic sustainability of reindeer husbandry

Wild and semidomesticated reindeer are one of the key species in Arctic and subarctic areas, and their population dynamics are closely tied to winter conditions. Difficult snow conditions have been found to decrease the calving success and survivability of reindeer, but the economic effects of variation in winter conditions on reindeer husbandry have not been studied. In this study, we combine state-of-the-art economic-ecological modeling with the analysis of annual reindeer management reports from Finland. These contain local knowledge of herding communities. We quantify the occurrence probabilities of different types of winters from annual management reports and analyze the effects of this variation in winter conditions on reindeer husbandry using an age- and sex-structured bioeconomic reindeer-lichen model. Our results show that difficult winters decrease the net revenues of reindeer husbandry. However, they also protect lichen pastures from grazing, thereby increasing future net revenues. Nonetheless, our solutions show that the variability of winter conditions overall decrease the net income of herders compared to constant winter conditions. Low lichen biomass appears to make reindeer management more sensitive to the effects of difficult winter conditions. We also found that it is economically sensible to use supplementary feeding during difficult winters, but the net revenues still decrease compared to average winters because of the high feeding costs. Overall, our analysis suggests that the increasing variability of winter conditions due to climate change will decrease net revenues in reindeer husbandry. This decrease will still occur even if the most extreme effects of climate change do not occur. This study shows that combining a state-of-the-art bioeconomic model and practitioner knowledge can bring compatible insights, ideas, results, and a bottom-up perspective to the discussion.

Soft resilience: moisture-dependent lichen elasticity buffer herbivore trampling in cold alpine-tundra ecosystems

Herbivores may have extensive top-down effects in open grazing ecosystems, generating vegetation changes by grazing and trampling. Trampling effects are understudied, but may be a major ecological factor. In cold alpine-Arctic ecosystems grazing and trampling by wild tundra reindeer (Rangifer tarandus) may be particularly important in lichen-dominated heaths. Dry lichen are crushed by trampling, and it is estimated that volume loss of lichen trampled may be considerably larger than lichen volume eaten by reindeer. Humidity affects lichen pliability and elasticity, and thereby resilience to trampling. Although crucial for estimating lichen vegetation trampling loss, the relationship between humidity and lichen elasticity is not well known. We collected samples of three lichen species in natura and in factorial experiments tested effects of species, levels of humidity (25, 70, 80, 90 and 100% RH) and temperatures (5 and 25 °C), on resilience to trampling (pressure resistance). The humidity:species interaction was the strongest factor increasing pressure resilience with increasing humidity, whereas temperature had small or no effects. Lichen elasticity increased rapidly above 70% RH. Consequently, when estimating lichen resources and potential trampling loss, number of dry days (less than 70% RH) should be estimated. This also has important ramifications for effects of climate change on the sustainability of reindeer populations.

Estimating plant abundance using inflated beta distributions: Applied learnings from a lichen-caribou ecosystem

Quantifying abundance and distribution of plant species can be difficult because data are often inflated with zero values due to rarity or absence from many ecosystems. Terrestrial fruticose lichens (Cladonia and Cetraria spp.) occupy a narrow ecological niche and have been linked to the diets of declining caribou and reindeer populations (Rangifer tarandus) across their global distribution, and conditions related to their abundance and distribution are not well understood. We attempted to measure effects related to the occupancy and abundance of terrestrial fruticose lichens by sampling and simultaneously modeling two discrete conditions: absence and abundance. We sampled the proportion cover of terrestrial lichens at 438 vegetation plots, including 98 plots having zero lichens. A zero‐inflated beta regression model was employed to simultaneously estimate both the absence and the proportion cover of terrestrial fruticose lichens using fine resolution satellite imagery and light detection and ranging (LiDAR) derived covariates. The probability of lichen absence significantly increased with shallower groundwater, taller vegetation, and increased Sphagnum moss cover. Vegetation productivity, Sphagnum moss cover, and seasonal changes in photosynthetic capacity were negatively related to the abundances of terrestrial lichens. Inflated beta regression reliably estimated the abundance of terrestrial lichens (R² = .74) which was interpolated on a map at fine resolution across a caribou range to support ecological conservation and reclamation. Results demonstrate that sampling for and simultaneously estimating both occupancy and abundance offer a powerful approach to improve statistical estimation and expand ecological inference in an applied setting. Learnings are broadly applicable to studying species that are rare, occupy narrow niches, or where the response variable is a proportion value containing zero or one, which is typical of vegetation cover data.

Partial seasonal migration in high-arctic Svalbard reindeer (Rangifer tarandus platyrhynchus)

We examined seasonal range use and calving success in wild Svalbard reindeer ( Rangifer tarandus platyrhynchus Vrolik, 1829) on two contrasting ranges separated by risky barriers (open sea, thin sea ice, and glaciers). One (“poor”) range had a depleted lichen resource and negative reindeer population trend, whereas the neighbouring (“rich”) range was recently occupied with initially high lichen abundance and positive population trend. Winter foraging conditions limit survival and reproduction in this predator-free system and lichens are the preferred winter food by reindeer. Accordingly, marked female reindeer that switched between the ranges (“migrants”) spent most winters on the lichen-rich range, yet most summers on the poor range (possibly owing to fidelity to calving area). While facing high mortality risk along the migration route, migrants spending the winter on the rich range and subsequent summer on the poor range had improved calving success compared with residents on the poor range. The partial seasonal migration pattern diminished as lichens were reduced and reindeer carrying capacity reached on the rich range. Besides this apparent density-dependence in migratory behaviour, spatial strategy seems shaped by past experience and trade-offs between current survival (safe habitat) and future reproduction (food-rich habitat).

Winter grazing of reindeer in woodland lichen pasture. Effect of lichen availability on the condition of reindeer

Winter grazing of semi-domesticated reindeer (Rangifer t. tarandus) was investigated at the woodland lichen pasture (lichen approximately 550kg DMha(-1)) in Kaamanen, northern Finland during the winter 1996-1997. Nine female reindeer mainly dug their food in the snow for 122 days (3 December-4 April) in a fenced area of 36.3ha. Over half of the fenced area was lichen dominated dry pine forest. The amount of lichens in lichen forest inside the fence was estimated before and after grazing. Area of grazed and condition of reindeer as well as snow conditions were monitored. Reindeer grazed over the whole area of lichen forest in early winter but from mid-winter they tended to graze on the areas with the greatest lichen abundancy. The amount of lichens measured decreased in the latter areas by 40% and in the other part of the lichen pasture by 17%, respectively. In both of these areas the residual amounts of lichens left after grazing were similar. Of the dominant lichens, the amount of C. stellaris decreased the most and the amount of Cl. uncialis the least. During the study, the estimated average daily area grazed varied from 4 to 87m(2) per reindeer. It was calculated that individual reindeer obtained 2.6kg of lichen DM per day during the most intensive digging period when the body condition score and weight of reindeer increased. Otherwise, the body condition score and weight decreased. Reindeer finished foraging for ground lichens and started to search for arboreal lichens in mid-March when the snow layer was 70-80cm thick and contained some hard snow layers which lifted reindeer. Both the amount of lichens in the pasture and the snow conditions essentially affect the nutritional status of reindeer in the woodland region during winter. Assuming that a reindeer is able to graze around 30m(2) per day in the snow during mid and late winter, there should be, on the basis of energy demand and grazing behaviour of reindeer as well as the nutritive value of lichen, an estimated 1000kg lichen DMha(-1) available in a good condition woodland lichen pasture.

Reproduction in female reindeer

Reindeer are either wild or kept under very extensive farming systems. They are seasonal breeders, with mating coinciding with the decreasing photoperiod in the autumn, and with calving in the spring. Little is known regarding the factors that influence reproduction in reindeer or of their reproductive physiology. Studies carried out to date have mainly focused on issues related to the population dynamics of wild populations and semi-domestic herds, and to a limited extent on the reproductive physiology of the female. Nor is much known about reproductive disorders and their medical treatment, or of the possibilities to manipulate or control reproduction by the use of hormones. Modern reproductive techniques such as artificial insemination and in vitro fertilisation, maturation and transfer of embryos have so far received scant attention.In the future, it is possible that reindeer under certain conditions might be kept in more intensive production systems. Limited access to high-quality winter pastures and increased demands for productivity have resulted in artificial feeding becoming a common practice in various reindeer herding areas in Scandinavia. In efforts to enhance the productivity of reindeer herds, attention has been focused on factors affecting reproduction in the female and survival of the offspring. Further knowledge on these issues seems necessary when developing strategies for optimalization of meat production in domestic herds and the harvesting of wild populations. This paper puts a broad focus on various aspects of reproduction, including factors influencing the fecundity of reproductively active females. In order to understand these effects it is important also to have a basic understanding of the reproductive physiology of these animals.

Reproduction and productivity of semidomesticated reindeer in northern Finland

The increase in the Finnish semidomesticated reindeer (Rangifer tarandus tarandus) stock and the high level of meat production during the 1980s and the beginning of the 1990s were mainly due to reindeer-management practices. However, the continuing deterioration of winter-range quality has now forced reindeer managers to invest increasingly in supplementary feeding. At the same time, carrying-capacity models for semidomesticated- reindeer ranges have proved difficult to develop. This study deals with reproduction and productivity of the reindeer stock in northern Finland during the period 1987-1995. The results reveal that reproduction and productivity of reindeer in the study area are largely regulated by density-dependent factors related to the quantity and quality of winter ranges. Reindeer densities on total rangeland had the strongest effect on the slaughter body masses of reindeer, which indicates the special importance of summer and autumn pastures for growth and autumn condition of reindeer. Through intensive calf slaughtering, the natural mortality rate was minimised and reproduction rates and reindeer meat production were increased, although winter ranges were heavy grazed. Developing semidomesticated-reindeer husbandry to be more economical in the future by keeping sustainable meat production at a sufficiently high level while maintaining reindeer rangeland in adequate condition and supplementary feeding quite marginal in Finland involves consideration of both ecological and management factors. One way of looking at the economic carrying capacity of Finnish semidomesticated-reindeer ranges is to develop a model based on dependence among the factors presented in this study. Sustainable net incomes from reindeer husbandry could then be optimised by studying and modelling the economy of reindeer management itself with respect to stock density.

Size-related changes in winter condition of female and male reindeer calves

This study investigated how relationships between body size and back-fat depth develop in female and male reindeer (Rangifer tarandus tarandus) calves in winter. Back-fat depths did not differ between male and female calves, but depended more strongly on body size in female calves. Because no sex difference was found in the post-rut sample (October), differences were not attributed to male puberty and consequent sexual activity. Sex differences might be related to the fact that female calves feed more often than males from craters dug in the snow by their mother and that daughters of dominant mothers share feeding craters with their mother most often. In the last sample month, February, the fattest males were medium-sized, but mean back-fat depths did not differ between medium-sized and large calves. The decreasing trend in size dependence of fat reserves of male calves through the winter possibly weakens the link between maternal investment and reproductive success of sons.