Table 1 Predictions for expected patterns in time allocation, state occupancy probabilities and activity scheduling if muskoxen were to follow either of the three proposed strategies according to optimal foraging theory, for the summer and winter season, respectively
Summer season (snow-free) | Winter season (snow-covered) |
|---|---|
Energy intake maximisation strategy: muskoxen aim to maximise energy intake (i.e. time spent foraging and forage quality), only limited by digestive physiological constraints (i.e. time required for rumination) | |
S1INTAKE: time allocation only influenced by forage quality/quantity (e.g. landcover, NDVI) since forage quality/quantity determines time required for rumen fill and rumination | W1INTAKE: time allocation only influenced by forage quality/quantity/accessibility (e.g. landcover, snow depth) since forage quality/quantity/accessibility determines time required for rumen fill and rumination |
S2INTAKE: probability of foraging remains constant independent of changes in environmental conditions (e.g. temperature, wind) | W2INTAKE: probability of foraging/resting remains constant independent of changes in environmental conditions (e.g. temperature, snow depth) |
S3 INTAKE: no specific daily scheduling of activities | W3INTAKE: no specific daily scheduling of activities |
S4INTAKE: no interannual differences in time allocation | W4INTAKE: no interannual differences in time allocation |
Time minimisation strategy: muskoxen only forage the minimum required time to satisfy basic energetic needs, while reducing e.g. risk of predation | |
S1TIME: time allocation/state switching mainly influenced by forage quality/quantity (e.g. landcover, NDVI), time of day and light conditions | W1TIME: time allocation/state switching mainly influenced by forage quality/quantity/accessibility (e.g. landcover, snow depth), time of day and light conditions |
S2TIME: proportion of time spent foraging decreases with increasing forage quality/quantity as same foraging effort yields higher energetic gains | W2TIME: proportion of time spent foraging increases with decreasing forage quality/quantity/accessibility to compensate for reduced energetic gains of foraging effort |
S3TIME: specific daily scheduling of activities indicates avoidance of periods with e.g. higher risk of predation | W3TIME: specific daily scheduling of activities indicates avoidance of periods with e.g. higher risk of predation |
Net energy maximisation strategy: muskoxen aim to maximise energy intake but switch to resting (i.e. energy conservation) as soon as constraints/costs of foraging outweigh gains of foraging effort | |
S1NET: time allocation/state switching mainly influenced by forage quality/quantity and environmental conditions representing constraints | W1NET: time allocation/state switching mainly influenced by forage quality/quantity/accessibility and environmental conditions representing constraints |
S2NET: probability of foraging decreases with environmental conditions causing thermal stress or insect harassment (e.g. high temperature, low wind speed) | W2NET: probability of resting increases with conditions causing heat loss (e.g. low temperature, high wind speed) or increasing energetic costs of movement and forage access (e.g. deep snow) |
S3NET: specific daily scheduling of activities indicates avoidance of daily periods during which constraints peak (e.g. highest temperatures) | W3NET: less pronounced specific daily scheduling of activities because peaks in constraints (e.g. temperature/snow depth) do not necessarily follow regular daily patterns |
S4NET: interannual differences in time allocation depending on interannual differences in the strength of environmental constraints | W4NET: interannual differences in time allocation depending on interannual differences in the strength of environmental constraints |