Lab 6: Population and Community Dynamics — Owl Pellet Dissection

1. Owls cannot digest bones, fur, or feathers. After consuming prey whole or in large chunks, their digestive system compresses indigestible material into a pellet, which the owl regurgitates. Dissecting a pellet reveals exactly what the owl ate.
2. Barn owls (Tyto alba) are the most common species studied in lab dissections. They are nocturnal, silent hunters that consume primarily voles, shrews, mice, and occasionally small birds or insects. One barn owl may consume 3–4 prey items per night.
3. Predator-prey dynamics: owl populations are linked to rodent populations. When vole populations boom (good rainfall, abundant seeds), owl breeding success rises. When vole populations crash, owls face food scarcity and breed less. This creates oscillating population cycles.
4. Community ecology studies how multiple species interact within an ecosystem. The owl pellet reveals multiple prey species and thus multiple trophic relationships — a small food web exists within a single pellet.
5. Bones are identified using a bone sorting key (included with the kit). Key structures: skull shape (predators vs. prey), jaw structure (carnivore vs. herbivore), femur and tibia proportions, number of vertebrae.
6. Calculating prey per pellet: count the number of skulls — each skull = one prey animal. A single barn owl pellet typically contains 1–3 skulls. Multiplying by nightly pellet count estimates daily consumption.
7. From a population ecology perspective: owls are secondary consumers (they eat primary consumers — rodents that eat seeds and plants). Understanding owl populations helps predict rodent population size and the health of the plant community below.
8. Owl pellet dissection connects to BIO 1120 Outcomes 1 and 2: you apply ecological principles (food web structure, predator-prey dynamics) to real physical evidence through a controlled lab procedure.

Netiquette from the syllabus: address ideas, not people. Complete sentences, correct spelling. Personal matters go to email, never the board.

Ask at home: If you were a scientist with only owl pellets to study and nothing else, what could you figure out about the local ecosystem — and what couldn't you figure out?

En español: Si fueras un científico que solo tuviera egagrópilas para estudiar y nada más, ¿qué podrías descubrir sobre el ecosistema local — y qué no podrías descubrir?