Why are deer specifically depicted in symbols of the first sermon?

Because the first sermon took place in the 'Isipatana' or Deer Park at Sarnath, where deer roamed freely.

Buddhist Symbols in Art

UPSC Archival Analysis

Q: Which event of Buddha's life is represented by the wheel with deer, in Indian Art?

The wheel with deer represents Buddha's first preaching at Sarnath. The wheel symbolizes his teachings, and the deer represent the park where he delivered the sermon.

Exam Year

2002

Evidence Source

Link

ID: HIS_PHI_2002_74 Ref: Chapter 4: Thinkers, Beliefs and Buildings