Geoff Bullock, a crew member aboard the Seamaster the night of the slaying, believes the men probably want to go back to Amapa because that prison is easier to escape from.
"I certainly have no sympathy whatsoever."
A Herald source in Brazil said details about the hunger strike were scarce but it appeared the two men might have been egged-on by other prisoners.
They were being held at the Federal Police Station in Acre rather than in the state prison. Although it was unclear why, they may have been separated from other prisoners for their own safety.
"In this building there are some political prisoners and some time ago they were involved with corruption. It's a kind of gang," said the Herald source.
"The director told me maybe they [Tavares and da Costa] were oriented by these guys to go on a hunger strike because these criminals, some time ago they also tried to go on a hunger strike and maybe it worked."
Acre is so far away it is a different time zone to the bandits' home near Macapa in the state of Amapa.
While Amapa is a violent state, Acre is considered one of the most lawless in Brazil.
Police corruption is rife, with civil police officers linked to numerous murders, including brutal slayings of criminals.
Tavares was the ringleader in the December assault on the Seamaster as it lay moored ready to leave the Amazon.
He was jailed for 36 years for shooting Sir Peter twice in the back, killing him instantly.
Da Costa received 32 years, eight months and the other four robbers received sentences ranging from 32 to 26 years.
All six men are awaiting the result of appeals against their sentences.
Peter Blake, 1948-2001
