Complex sentence: In 1977, the university began the tradition of dressing up a student in a blue and gray bulldog costume, replacing the live bulldog, though several live dogs also periodically joined the costumed mascot during the 1980s and 1990s.
Split into simpler sentences: In 1977, the university began the tradition of dressing up a student in a blue and gray bulldog costume, replacing the live bulldog. Several live dogs also periodically joined the costumed mascot during the 1980s and 1990s.