This netsuke depicts an alert frog sitting on a dried lotus pod, with its leg muscles tensed in readiness to leap away from any danger that might present itself.
This is a moment familiar to any observer of a frog in its daily life, and 'Sentinel' alludes to the wary and watchful nature of these small creatures. But there is more contained within this title.
Frogs are indicators of environmental stress, as their delicate, permeable skins absorb pollutants. In recent decades up to 40% of frog species have become extinct and this presents us with a clear warning of the declining health of our environment.
Frogs also consume vast quantities of insect pests, and the secretions of their skins have provided us with a range of medical treatments for conditions as varied as cancer and AIDS; we cannot afford to lose them.
The task of a sentinel is to keep watch. The small creature shown in this netsuke is vigilant not only for his own immediate future, but for that of mankind too.