The God Siva rides the bull, in Tamil called Nandi.
Nandi means actually giving joy in the sense of the sexual potency of the bull and expresses the cosmic creative energy of Shiva.
The bull was in ancient times an independent deity in the form of the Lord of Joy (Nandikeshvara), a man with a bull's head. Joy, by music and dance, were seen as the fundamental forces of creation, an aspect which was later transferred to Shiva. Later it was said that Nandikeshvara was a wise man who guarded Shiva's door to become divine in this way.
The lady trusted her devotion to Nandi in this peaceful Vedaradha Temple in Thiruvadavur on the countryside at evening fall (18 o'clock).