A group of conservation biologists wants to estimate the population size of the violet ground beetle (Carabus violaceus), a fast-moving, nocturnal predator, in a designated woodland conservation area.

Which of the following methods could be reliably used to estimate the population size of this species?

1. Mark-release-recapture using pitfall traps
2. Random quadrat sampling, counting individuals observed within each quadrat
3. Percentage cover estimation using a point quadrat