Complex sentence: When his wife Dorothy Jo died, Barker became an advocate for animal rights and of animal-rights activism, supporting groups such as the United Activists for Animal Rights and the Sea Shepherd Conservation Society.
Split into simpler sentences: When his wife Dorothy Jo died, Barker became an advocate for animal rights. Since then, Barker has been a long-time supporter of animal rights, and of animal-rights activism, including groups such as the United Activists for Animal Rights and the Sea Shepherd Conservation Society.