Learning target: I can use population data to decide which kind of interaction explains a decline, support the claim with specific evidence, and use the pattern of that interaction to predict what will happen next and what a manager should do.
Read the scenario and study the preserve's six-year dataset. The warm-up questions walk you through the evidence; do them first. Then write your Claim, Evidence and Reasoning in the boxes. A strong response names specific numbers from the table, says what each piece of evidence rules in or rules out, and uses the interaction patterns you have learned to explain why the evidence points where it does.
You will need: This worksheet, Pencil, Scrap paper for the fingerprint table, Calculator (optional)
Pine Hollow Preserve is a 2,000-hectare area of oak woodland and grassy slopes in the California foothills. It was set aside partly to protect a population of mountain quail, a ground-nesting bird that eats seeds and berries. Six years ago the preserve's biologist, Dr. Okafor, started a yearly survey. In the first year, a few red foxes were seen on the preserve for the first time; red foxes are not native to this part of California and probably came from animals released or escaped decades ago elsewhere in the state. Quail numbers have fallen every year since. The preserve's board wants to know why, and what to do. Three explanations are on the table: (1) the foxes are eating the quail (predation); (2) ground squirrels, which also eat seeds, are taking the quail's food (competition); (3) feather lice, which live on the quail and feed on their skin and feathers, are weakening the birds (parasitism). The dataset below is a teaching dataset invented for this case; the numbers are realistic but were not measured on a real preserve.
| Year | Quail counted | Red foxes (adults on cameras) | Ground squirrels counted | Fall seed supply (kg per hectare) | Quail carrying feather lice (%) |
|---|---|---|---|---|---|
| 1 | 420 | 2 | 600 | 31 | 12 |
| 2 | 400 | 3 | 610 | 29 | 14 |
| 3 | 390 | 8 | 590 | 33 | 11 |
| 4 | 300 | 14 | 620 | 30 | 13 |
| 5 | 210 | 18 | 600 | 32 | 12 |
| 6 | 150 | 20 | 610 | 31 | 14 |
On scrap paper, make three rows labeled predation, competition and parasitism. For each row, write what you would expect to see in the data if that explanation were true: for predation, a predator rising while prey falls and prey remains in the predator's diet; for competition, the competitor rising or the shared resource shrinking; for parasitism, the share of infected quail rising. Then write what the table actually shows next to each expectation. The row where expectation and data match is your claim; the rows where they do not match are evidence against the other explanations.
If foxes depend mostly on quail, the predator-prey pattern says the fox population should crash after the quail crash. But red foxes also eat mice, insects, fruit and garbage. Write a paragraph explaining why a predator with many food sources can keep its numbers high even as one prey species disappears, what that means for the quail if nobody intervenes, and why conservation scientists worry more about this situation than about a specialist predator.