Lecture 21 (higher level)

Why does the lynx–hare dataset appear to support LV, and why does deeper analysis show it doesn’t?

Because cycles match LV patterns superficially, but the drivers include food limitation, multiple predators, trapping dynamics, and stress—none of which LV incorporates. [p.1–2]

Why do ecologists favor multi-hypothesis frameworks over single-cause explanations for population cycles?

Complex systems involve interacting bottom-up, top-down, and behavioral processes that cannot be captured by a single mechanism.

Explain how increased reproductive output in hares is evidence for bottom-up forcing.

More food → higher reproductive output → rising hare density, demonstrating that prey physiology responds strongly to resource availability. [p.4]

Why does predation remain essential in explaining hare declines even when food is not limiting?

Because survival drops during predator peaks, and reproductive output cannot compensate for predator-driven mortality. [p.5]

Describe how chronic stress can create population cycles even without high predator kill rates.

Stress reduces reproduction, immune function, and foraging efficiency, creating system-wide demographic deficits.

Why is predator removal ineffective at eliminating hare cycles?

Other predators increase predation when one is removed, maintaining top-down control. [p.6]

Explain why LV is insufficient for systems with multiple predators consuming the same prey.

LV’s two-species structure cannot account for overlapping predator guilds and compensatory predation.

What makes island prey especially vulnerable to extinction by predators?

Lack of historical exposure to predators means little or no selection for anti-predator behaviors. [p.8]

Explain why eradication programs often become more difficult as predator density decreases.

Remaining individuals tend to be trap-resistant, more cautious, and behaviorally sophisticated.

What does the rebounding of albatross populations after cat removal demonstrate about invasive predators?

Even small populations of invasive predators can exert unsustainable mortality pressure on native prey. [p.9]

Why did seabird restoration fail until managers removed the “worst of the evils”?

Mortality occurred across multiple life stages; removing the leading source of mortality was necessary before recovery could occur. [p.10]

Why is introducing natural predators rarely successful for controlling invasive species on islands?

Introduced predators rarely specialize; they shift to vulnerable native species instead of target prey. [p.10]

Explain why the lynx–hare system reflects complex trophic layering rather than simple predator–prey oscillations.

It involves resource pulses, fear effects, multiple predators, winter scarcity, and community-level interactions.

How does the lecture conclude regarding the relative strength of top-down vs bottom-up drivers in hare cycles?

Both influence dynamics: predators strongly drive declines, while food resources modulate peaks. [p.7]

What broader lesson about ecological complexity can be drawn from the lynx–hare and island predator systems?

Simple models provide intuition, but real ecosystems require integrating trophic complexity, species interactions, and behavioral ecology to accurately predict population outcomes.