Table 1.
State variable names, descriptions, values, and units from mechanistic model parameterized with data from the tundra producer–caribou–helminth (Ostertagia) system*
| State variable | Parameter | Description | Value | Ref. |
|---|---|---|---|---|
| Producer resources | r | Intrinsic growth rate | 0.2 kg⋅kg−1⋅d−1 | 106 |
| K | Carrying capacity | 200,000 kg⋅km−2 | 107 | |
| Herbivores | f | Foraging rate | 2 kg⋅d−1 | 108 |
| hA | Half saturation constant | 50,000 kg⋅km−2 | 107 | |
| dH | Herbivore death rate | 0.0003 kg⋅d−1 | 109 | |
| y | Yield of caribou biomass from producer biomass | 0.25 kg⋅kg−1 | — | |
| Parasites | αI | Parasite intensity-dependent effect on host resource intake | Varied, 10−8 to 10−3 | — |
| αS | Parasite intensity-dependent effect on host survival | Varied, 10−8 to 10−3 | — | |
| αF | Parasite intensity-dependent effect on host fecundity | Varied, 10−8 to 10−3 | — | |
| ρ | Production of free-living stages of parasite | 284 eggs⋅adult female parasite−1⋅d−1 | 110 | |
| σ | Infection probability given egg ingestion | 0.3 d−1 | 110 | |
| dP | Death rate of parasite | 0.03 kg⋅d−1 | 110 | |
| dE | Death rate of eggs | 0.1 eggs⋅d−1 | 111 | |
| k | Parasite aggregation factor from negative binomial distribution | 2 | 65, 73, 74 |
*For yield, it is assumed that caribou gain 1 kg body weight for every 4 kg of resources consumed.