David W. Macdonald

David W. Macdonald is a researcher in wildlife conservation and animal behaviour. His institutional WildCRU profile identifies David Macdonald with publications using the D. W. Macdonald byline. His research includes the 1992 study of mara communal breeding with Andrew B. Taber.^[ref][ref]

An illuminating result concerned collective vigilance. Larger breeding groups could have more total coverage even though each pair spent less time sitting alert. The group-level readout was whether at least one pair was vigilant, a different variable from the alert fraction of a particular pair.^[ref]

A toy probability model explains how this can happen. If $n$ pairs each have alert probability $p$ at a sampled instant, and their alert states are independent events, thenTwo pairs with $p=0.40$ give $1-0.60^2=0.64$. Six pairs with $p=0.20$ give $1-0.80^6\approx 0.738$. In this constructed model, individual alert probability falls while group coverage increases. These values are not the study's data.

Independence is essential to that calculation. If all pairs became alert in perfect synchrony, group coverage would equal $p$, regardless of how many pairs were present. Field measurements of timing and coordination are therefore needed to choose between such models.

The mara work illustrates how an ecological explanation can connect individual behavior to an emergent group outcome while keeping their measurement definitions distinct.