Fig. 12.11 already prints these arrows: Grasses → Hare, Grasses → Mouse, Hare → Hawk, Mouse → Fox, Grasshopper → Frog, Grasshopper → Bird, Frog → Owl, Bird → Snake and Snake → Hawk.
The links still missing, which you should add, are:
| Arrow to add | Why |
|---|---|
| Grasses → Grasshopper | The grasshopper is a herbivore; the grass is its producer. |
| Hare → Fox | The fox hunts hares as well as mice. |
| Mouse → Owl | The owl hunts small rodents at night. |
| Mouse → Hawk | The hawk also takes mice from open ground. |
| Frog → Snake | Snakes prey on frogs, not only on birds. |
| Bird → Hawk | The hawk hunts small birds. |
| Snake → Owl | Owls take small snakes too. |