Reindeer diet in the wild varies a lot throughout the year. In this article, we will discuss reindeer’s natural diet and its seasonal changes. We also talk about the physiological changes that accomodate the changes in diet. In case you haven’t read the first post in this series, about the basics of reindeer nutrition, check it out here!
What do they eat?
As mentioned before, reindeer experience extreme seasonal changes in their environment. In the late spring and summer food is plentiful, it’s high in protein and energy and proportionally low in fiber. When summer turns to autumn, the fiber content climbs and energy and protein decline. In late autumn and the beginning of winter reindeer sift to lichen. Lichen is high in soluble carbohydrates but very low in protein. It’s also sometimes hard to find due to snow cover, and the reindeer must use energy to dig up their food.
To survive in these different environments, they basically have two different nutritional strategies; one for summer and one for winter. As you remember reindeer is classified as intermediate ruminant. This allows the reindeer to move on the ruminant type spectrum closer to a grazer or browser, depending on the food that is available. Can you already guess which strategy is in place in the winter and in the summer?
Summer & Autumn Diet
During summer in their natural habitat reindeer are exposed to long days with lots of light, which triggers hormonal cascade leading to increased appetite and feed intake. Because the changing light triggers the metabolic changes instead of availability of food, the reindeer can get the most out of the first emerging growth of vegetation that is rich in nutrients and easily soluble. In the summer the reindeer spend more time foraging for food and less time resting and sleeping.
Food items
When food is plentiful and energy and protein demands are high, reindeer sifts towards browser type of ruminant. This means that the reindeer pick the most nutritious plants and plant parts, such as new growth of trees and grasses, shrubs and forbes.
In the summer the reindeer eat leaves, buds, forbes, shrubs and grasses. All of these are readily available and high in energy and protein. Summer and autumn are nutritionally very important, because survival through meager winter and early spring depends on the body reserves. Their energy intake and time spent foraging for food are greater than during winter which facilitate positive energy balance needed to gain weight. In autumn the reindeer often feed on mushrooms too.
Nutrients
In early summer reindeer’s diet is rich in energy and protein and proportionally low in fiber. The summer diet has been reported to contain up to 15 % crude protein and 20 % crude fiber in dry matter. Towards autumn the crude protein level declines and crude fiber content inclines. Also calcium, phosphorus and total ash in dry matter are the highest during summer months and decline towards winter.
Body condition
In autumn the reindeer should be on the heftier side of body condition scoring. They need the body reserves to get through the winter and early spring. This means that the body reserves need to be topped up during summer and autumn. Males can lose weight in autumn in rutting season, but they catch up in weight gain afterwards and can get chunky.
Reindeer have been found to be unable to put on more weight after Christmas. Therefore, getting them to the appropriate body condition during summer and autumn is important. Improper nutrition during summer can’t be made up for during winter, because the reindeers’ appetite and feed intake decrease during winter, no matter how much feed they are offered.
Winter & Spring Diet
During winter there is significantly less light which affects the appetite through hormones and feed intake decreases. This is one of the reasons that makes reindeer difficult to feed in captivity: if the summer diet was incorrect, they haven’t accumulated the body reserves and when they naturally eat less, they lose weight. If there isn’t any weight to lose, you are in trouble.
In the winter when food is spares and the nutritional value is low the reindeer move towards grazing ruminant type. This means that the quantity of food goes over the quality as a strategy to gain enough energy and nutrients. Reindeer also spent more time resting during the winter and less time foraging for food than in the summer.
Food items
In the Nordic countries the semi-wild reindeer are known to feed mainly on Caldonia spp. lichens, especially reindeer mosses of this genus are common food items. The lichen by itself is nutritionally insufficient, so especially females carrying a fetus tend to supplement their diet with dead plants that can be found in the winter.
Early spring is nutritionally most challenging time of the year. Winter has been long and though day length is getting longer, snow cover is still deep, temperatures remain below zero Celsius and nothing is growing yet. Most of winter time pastures can be all used up by now and reindeer herders rely on extra feeding with pellets and sometimes hay too.
Late spring marks the change in diet. Snow covers start to melt and trees, shrubs and forbes start budding. Reindeers migrate from winter pastures to summer pastures. Females that may have arrested the development of unborn calves can start growing the fetuses again. Females also grow antlers and start molting, so they really need protein available in the new growth of plants.
Nutrients
Lichens are high in soluble carbohydrates and low in protein. This is why especially females need to supplement the diet with dead plant parts that are higher in protein content. Although lichen contains lots of sulble energy, they are hard to find under the snow cover and digging them up consumes energy. The winter diet of reindeer has been reported to have less than 5 % crude protein and 25 % of crude fiber in dry matter.
Lichens are also low in many minerals and can even inhibit the up take of some of them by binding them to an insoluble form. See tables below for some chemical compositions found in a study.
Table 1. Carbohydrate compositions of some lichens. Lichenin is a polysaccharide found in some lichens (Podterob 2008).
| Species | Water soluble sugars | Lichenin | Hemicelluloce | Celluloce | Total carbohydrates |
| Cladonia alpetris | 0,3 | 2,4 | 73,8 | 7,3 | 83,8 |
| Cladonia mitis | 0,4 | 1,6 | 73,8 | 6,6 | 80,2 |
| Cladonia deformens | 0,3 | 4,1 | 68,5 | 10,8 | 83,7 |
Table 2. Mean amounts of elements found in lichen in dry matter (DM) basis (Podterob 2008).
| Element | Amount mg/kg DM | Element | Amount mg/kg DM |
| N | 8470 | Cl | 100 |
| P | 770 | Fe | 1050 |
| K | 3330 | Mn | 89 |
| Na | 815 | Zn | 40 |
| Ca | 3600 | Cu | 8,4 |
| Mg | 820 | B | 4 |
| Si | 3770 | Mo | 0,39 |
| S | 870 | Co | 0,48 |
In the winter reindeer rely on urea cycle that provides enough nitrogen for rumen microbiota, which in turn provide microbial protein for the reindeer. All ruminants are capable to recycle urea but in reindeer it’s increased in the winter to survive insufficient nitrogen in diet.
Body condition
By the end of spring the reindeer have gone down in body condition scoring. A decrease of one unit or even a bit over one on a scale of one to five is natural. The decrease depends on the body condition at autumn, the more reserves you have the more you can use during winter. Now the increasing appetite and availability of easily digestable food ensures the regaining of body reservers for next winter.
What’s next?
Now we have covered the two different diets of reindeer in the wild. Most important things to remember are:
- Reindeer have two different feeding strategies, one for winter and one for summer conditions
- In the summer and autumn food is readily available and high in energy and protein -> positive energy balance, body condition inclines
- Winter and spring are meager times when food is hard to find and low in protein -> negative energy balance, body condition declines
- Reindeer’s feed intake is higher during summer and lower during winter
- There’s a natural fluctuation in body condition throughout the year. Take a look at this Body Condition Scoring Resource Center by AZA Nutrition advisory group for BCS information for many domestic and exotic species.
Next we will look at how we can implement this knowledge about reindeer diet to feeding reindeer in captivity. See you there!
P.s. If you have questions or comments don’t be afraid to shoot me a message! Contact me here or email aino [a] feralanimalnutrition.com
References and further reading
Barboza, P. & Parker, K. 2006, Body Protein Stores and Isotopic Indicators of N Balance in Female Reindeer (Rangifer tarandus) during Winter, Physiological and Biochemical Zoology, 79 (3), s. 628-644.
Boertje, R.D. 1990, Diet Quality and Intake Requirements of Adult Female Caribou of the Denali Herd, Alaska, Journal of Applied Ecology, 27 (2), s. 420-434.
Case, R.L. 1997, Adaptations of northern ungulates to seasonal cycles in nitrogen intake., dissertation, University of Alberta.
Clauss, M., Hofmann, R.R., Streich, W.J., Fickel, J. & Hummel, J. 2010, Convergence in the macroscopic anatomy of the reticulum in wild ruminant species of different feeding types and a new resulting hypothesis on reticular function, Journal of Zoology, 281 (1), s. 26-38.
Clauss, M., Hofmann, R.R., Fickel, J., Streich, W.J. & Hummel, J. 2009, The intraruminal papillation gradient in wild ruminants of different feeding types: Implications for rumen physiology, Journal of morphology, 270 (8), s. 929-942.
Danell, K., Utsi, P.M., Palo, R.T. & Eriksson, O. 1994, Food Plant Selection by Reindeer during Winter in Relation to Plant Quality, Ecography, 17 (2), s. 153-158.
Heggberget, T.M., Gaare, E. & Ball, J.P. 2002, Reindeer (Rangifer tarandus) and climate change: Importance of winter forage, Rangifer, 22 (1), s. 13-31.
Heiskari, U. & Nieminen, M. 1992, The effect of the diet on the digestive organ size of reindeer, Rangifer, 12 (3), s. 167-168.
Hofmann, R.R. 2011, Functional and comparative digestive system anatomy of Arctic ungulates, Rangifer, 20 (2-3), s. 71-81.
Hofmann, R.R. 1989, Evolutionary Steps of Ecophysiological Adaptation and Diversification of Ruminants: A Comparative View of Their Digestive System, Oecologia, 78 (4), s. 443-457.
Joly, K., Wasser, S.K. & Booth, R. 2015, Non-invasive assessment of the interrelationships of diet, pregnancy rate, group composition, and physiological and nutritional stress of barren-ground caribou in late winter, PLoS ONE, 10 (6).
Josefsen, T.D., Aagnes, T.H. & Mathiesen, S.D. 1996, Influence of diet on the morphology of the ruminal papillae in reindeer calves (Rangifer tarandus tarandus L.), Rangifer, 16 (3), s. 119-128.
Klein, D.R. 1990, Variation in quality of caribou and reindeer forage plants associated with season, plant part, and phenology, Rangifer, 10 (3), s. 123-130.
Maijala, V., Heiskari, U. & Nieminen, M. 2004, The adaptation of the digestive system of a reindeer to a yearly additional feeding, Finnish Game and Fisheries Research Institute, Helsinki.
Mathiesen, S.D., Vader, M.A., Raedergård, V.B., Sørmo, W., Haga, O.E., Tyler, N.J. & Hofmann, R.R. 2000a, Functional anatomy of the omasum in high Arctic Svalbard reindeer (Rangifer tarandus platyrhynchus) and Norwegian reindeer (Rangifer tarandus tarandus). Acta Vet Scand, 41 (1), s. 25-40.
Mathiesen, S.D., Haga, ØE., Kaino, T. & Tyler, N.J.C. 2000b, Diet composition, rumen papillation and maintenance of carcass mass in female Norwegian reindeer (Rangifer tarandus tarandus) in winter, Journal of Zoology, 251 (1), s. 129-138.
Nieminen, M. 1980, Nutritional and seasonal effects on the haematology and blood chemistry in reindeer (Rangifer tarandus tarandus L.), Comparative Biochemistry and Physiology — Part A: Physiology, 66 (3), s. 399-413.
Nieminen, M. & Heiskari, U. 1989, Diets of freely grazing and captive reindeer during summer and winter, Rangifer, 9 (1), s. 17-34.
Ophof, A.A., Oldeboer, K.W. & Kumpula, J. 2013, Intake and chemical composition of winter and spring forage plants consumed by semi-domesticated reindeer (Rangifer tarandus tarandus) in Northern Finland, Animal Feed Science and Technology, 185 (3-4), s. 190.
Podterob, A. 2008, Chemical composition of lichens and their medical applications, Pharmaceutical Chemistry Journal, 42 (10), s. 582-588.
Pösö, A.R., Heiskari, U., Lindström, M., Nieminen, M. & Soveri, T. 2001, Muscle fibre growth in undernourished reindeer calves (Rangifer tarandus tarandus L.) during winter, Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 129 (2), s. 495-500.
Rankama, T. & Ukkonen, P. 2001, On the early history of the wild reindeer (Rangifer tarandus L.) in Finland 30, Blackwell Publishing Ltd, s. 131-147.
Säkkinen, H., Timisjärvi, J., Eloranta, E., Heiskari, U., Nieminen, M. & Puukka, M. 1999, Nutrition-induced changes in blood chemical parameters of pregnant reindeer hinds (Rangifer tarandus tarandus), Small Ruminant Research, 32 (3), s. 211-221.
Sjaastad, ØV., Hove, K. & Sand, O. 2010, Physiology of domestic animals, 2nd ed. p., Scandinavian Veterinary Press, Oslo.
Sørmo, W. & Mathiesen, S.D. 1993, Bacteria in the small intestine of lichen-fed Norwegian reindeer (Rangifer tarandus tarandus), Letters in Applied Microbiology, 16 (3), s. 170-172.
Soveri, T. & Nieminen, M. 2007, Papillar Morphology of the Rumen of Forest Reindeer (Rangifer tarandus fennicus) and Semidomesticated Reindeer (R. t. tarandus), Anantomia Histologia Embryologia, 36 (5), Blackwell Publishing Ltd, s. 366-370.
Soveri, T., Sankari, S. & Nieminen, M. 1992, Blood chemistry of reindeer calves (Rangifer tarandus) during the winter season, Comparative Biochemistry and Physiology — Part A: Physiology, 102 (1), s. 191-196.
Staaland, H., Jacobsen, E. & White, R.G. 1979, Comparison of the Digestive Tract in Svalbard and Norwegian Reindeer, Arctic and Alpine Research, 11 (4), s. 457-466.
Thompson, D.P. & Barboza, P.S. 2017, Seasonal energy and protein requirements for Siberian reindeer (Rangifer tarandus), Journal of Mammalogy, 98 (6), s. 1558-1567.
Thompson, D.p. & Barboza, P.s. 2013, Responses of caribou and reindeer ( Rangifer tarandus) to acute food shortages in spring, Canadian Journal of Zoology, 91 (9), s. 610-618.
Valtonen, M. 1979, Renal responses of reindeer to high and low protein diet and sodium supplement, University of Helsinki.
Warenberg, K., Dannel, Ö, Gaare, E. & Nieminen, M. 1997, Porolaidunten kasvillisuus, Pohjoismainen Porontutkimuselin (NOR), Landbruksforlaget.
White, R.G. 1983, Foraging Patterns and Their Multiplier Effects on Productivity of Northern Ungulates, Oikos, 40 (3), s. 377-384.
White, R.G., Jacobsen, E. & Staaland, H. 1984, Secretion and absorption of nutrients in the alimentary tract of reindeer fed lichens or concentrates during the winter, Canadian Journal of Zoology, 62 (12), s. 2364-2376.