  Cooperation is the backbone of modern human societies, making it a priority
to understand how successful cooperation-sustaining mechanisms operate. Cyclic
dominance, a non-transitive setup comprising at least three strategies wherein
the first strategy overrules the second which overrules the third which, in
turn, overrules the first strategy, is known to maintain bio-diversity, drive
competition between bacterial strains, and preserve cooperation in social
dilemmas. Here, we present a novel route to cyclic dominance in voluntary
social dilemmas by adding to the traditional mix of cooperators, defectors, and
loners, a fourth player type, risk-averse hedgers, who enact tit-for-tat upon
paying a hedging cost to avoid being exploited. When this cost is sufficiently
small, cooperators, defectors, and hedgers enter a loop of cyclic dominance
that preserves cooperation even under the most adverse conditions. In contrast,
when the hedging cost is large, hedgers disappear, consequently reverting to
the traditional interplay of cooperators, defectors, and loners. In the interim
region of hedging costs, complex evolutionary dynamics ensues, prompting
transitions between states with two, three, or four competing strategies. Our
results thus reveal that voluntary participation is but one pathway to
sustained cooperation via cyclic dominance.
