Abstract
Various aspects of optimal foraging and seasonal diet composition of bulls (bachelor and dominant), cows, subadults, and yearlings of muskoxen Ovibos moschatus were investigated in West Greenland during the following seasons: calving, post-calving, summer, rut and mid-winter. The following hypotheses were tested: (1) muskoxen maximize daily energy intake during spring and summer, (2) dominant bulls monopolizing cows during the rutting season shift from an energy maximizing to a time minimizing foraging strategy in order to maximize the time available for reproductive activities, and (3) muskoxen employ a time minimizing foraging strategy during winter to conserve energy. As forage quality changed throughout the short Arctic growing season, muskoxen responded by changing the proportions of daily time spent feeding on graminoids (Cyperaceae, Poaceae) and dicots (Salix, Betula), respectively. This seasonal variation in the relative proportion of daily feeding time spent ingesting graminoids followed approximately the energy maximization prediction over the periods calving to rut. Neither time minimizing nor random foraging could explain the observed diets in this period, thus confirming hypothesis 1. Dominant bulls did not shift to the time minimizing strategy as predicted by hypothesis 2. However, during the pre-rutting and rutting seasons bulls deviated from the other sex/age classes by failing to obtain the daily maximum energy predicted by the model, as a result of a higher proportion of time allocated to agonistic and sexual behaviour. During winter, none of the sex/age classes employed a time minimizing strategy, so rejecting hypothesis 3. Instead, muskoxen were found to maximize Na intake, indicating that Na is of major importance for winter survival. The results emerging from a linear programming model with constraint settings varying over seasons confirm that the constraint parameters applied are indeed important limiting factors for muskoxen in natural populations.
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References
Altmann J (1974) Observational study of behaviour: sampling methods. Behaviour 49:227–267
Andersen R, Sæther B (1992) Functional response during winter of a herbivore, the moose, in relation to age and size. Ecology 73:542–550
Belmann RE, Dreyfus SE (1962) Applied dynamic programming. Princeton University Press, NJ
Belovsky GE (1978) Diet optimization in a generalist herbivore: the moose. Theor Popul Biol 14: 105–134
Belovsky GE (1981) Optimal activity times and habitat choice of moose. Oecologia 48: 22–30
Belovsky GE (1984a) Snowshoe hare optimal foraging and its implications for population dynamics. Theor Popul Biol 25: 235–264
Belovsky GE (1984b) Herbivore optimal foraging: a comparative test of three models. Am Nat 124: 97–115
Belovsky GE (1986) Optimal foraging and community structure: implications for a guild of generalist herbivores. Oecologia 70: 35–52
Belovsky GE (1991) Insights for caribou/reindeer management using optimal foraging theory. Rangifer [Spec Issuc] 7: 7–23
Belovsky GE, Jordan PA (1981) Sodium dynamics and adaptions of a moose population. J Mammal 62: 613–622
Belovsky GE, Schmitz OJ (1993) Owen-Smith's evaluation of herbivore foraging models: what is constraining? Evol Ecol 7: 525–529
Church DC, Smith GE, Fontenot JP, Ralston AT (1971) Digestive physiology and nutrition of ruminants. Origon State University Book Stores, Oregon
Dunbar RIM, Buckland D, Miller D (1990) Mating strategies of male feral goats: a problem in optimal foraging. Anim Behav 40: 653–667
Forchhammer M (1992) Foraging ecology and population dynamics of muskoxen Ovibos moschatus in Greenland. MSc thesis, University of Aarhus, Denmark
Forchhammer M (1995) Sex, age, and seasonal variation in the foraging dynamics of muskoxen, Ovibos moschatus, in Greenland. Can J Zool (in press)
Frisby K, White RG, Sammons B (1984) Food conversion efficiency and growth rates of hand-reared muskox calves. Biol Pap Univ Alaska Spec Rep 4: 196–202
Gray DR (1973) Social organization and behaviour of muskoxen (Ovibos moschatus) on Bathurst Island, N.W.T. PhD thesis, University of Edmonton, Alberta, Canada
Holleman DF, White RG, Frisby K, Jourdan M, Henrichsen P, Tallas PG (1984) Food passage rates in captive muskoxen as measured with non-absorbed radiolabeled markers. Biol Pap Univ Alaska Spec Rep 4: 188–192
Illius AW, Gordon IJ (1992) Modelling the nutritional ecology of ungulate herbivores: evolution of body size and competitive interactions. Oecologia 89: 428–434
Jingfors K (1980) Habitat relationships and activity patterns of a reintroduced muskox population. MSc thesis, University of Fairbanks, Alaska
Klein DR, Bay C (1990) Foraging dynamics of muskoxen in Peary Land, northern Greenland. Holarct Ecol 13: 269–280
Klein DR, Bay C (1991) Diet selection by vertebrate herbivores in the high arctic of Greenland. Holarct Ecol 14: 152–155
Klein DR, Thing H (1989) Chemical elements in mineral licks and associated muskox feces in Jameson Land, northeast Greenland. Can J Zool 67: 1092–1095
Komers PE, Messier F, Gates CC (1992) Search or relax: the case of bachelor wood bison. Behav Ecol Sociobiol 31: 195–203
Moen AN (1973) Wildlife ecology—an analytic approach. Freeman, San Francisco
Oakes EJ, Harmsen R, Eberl C (1992) Sex, age and seasonal differences in the diets and activity budgets of muskoxen Ovibos moschatus. Can J Zool 70: 605–616
Olesen CR (1987) Activity pattern and budget for muskoxen (Ovibos moschatus wardii) in northeast Greenland (in Danish). MSc thesis, University of Aarhus, Denmark
Olesen CR (1990) Population development and ecology of muskoxen in angujaartorfiup nunaa, west Greenland (in Danish with an English summary). Tech Rep 16: 1–85
Olesen CR, Thing H, Aastrup P (1994) Growth of wild muskoxen under two nutritional regimes. Rangifer 14: 3–10
Owen-Smith N (1993a) Evaluating optimal diet models for an African browsing ruminant, the kudu: how constraining are the assumed constraints. Evol Ecol 7: 499–524
Owen-Smith N (1993b) Assessing the constraints for optimal diets. Evol Ecol 7: 530–531
Prins HHT (1989) Condition changes and choice of social environment in African buffalo bulls. Behaviour 108: 77–87
Ritchie ME (1988) Individual ability of Columbian ground squirrel to select an optimal diet. Evol Ecol 2: 232–252
Schmidt-Nielsen K (1972) Locomotion: energy cost of swimming, flying and running. Science 177: 222–228
Sokal RR, Rohlf FJ (1981) Biometry, 2nd edn. Freeman, San Francisco
Staaland H, Thing H (1991) Distribution of nutrients and minerals in the alimentary tract of muskoxen, Ovibos moschatus. Comp Biochem Physiol 98: 543–549
Thie PI (1988) An introduction to linear programming and game theory, 2nd edn. Wiley, New York
Thing H, Klein DR, Jingfors K, Holt S (1987) Ecology of muskoxen in Jameson Land, northeast Greenland. Holarct Ecol 10: 95–103
Tyler NJC, Blix AS (1990) Survival strategies in arctic ungulates. Rangifer [Spec Issue] 3: 211–230
Vulink JT, Drost HJ (1991) A causal analysis of diet composition in free ranging cattle in reed-dominated vegetation. Oecologia 88: 167–172
Westoby M (1974) An analysis of diet selection by large generalist herbivores. Am Nat 108: 290–304
White RG, Frisby K, Kokjer K (1984a) Energy metabolism in young muskoxen. Biol Pap Univ Alaska Spec Rep 4: 203–204
White RG, Holleman DF, Wheat P, Tallas PG, Jourdan M, Henrichsen P (1984b) Seasonal changes in voluntary intake and digestibility of diets by captive muskoxen. Biol Pap Univ Alaska Spec Rep 4: 193–194
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Forchhammer, M.C., Boomsma, J.J. Foraging strategies and seasonal diet optimization of muskoxen in West Greenland. Oecologia 104, 169–180 (1995). https://doi.org/10.1007/BF00328582
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DOI: https://doi.org/10.1007/BF00328582