I'm going to give a different interpretation from some of the other answers. For this, we need to look at a larger portion of the original text:
"[...] detalle que al Suavo no le pasó desapercibido y que más bien contribuyó a agudizar su timidez [...], sus reservas, su discreción rayana en una quimérica omertà de viejo nazi que huele al lobo."
The text above could be translated into English as:
a detail that Suavo did not miss and that contributed to intensify his shyness, his natural reserve, his discretion bordering a chimeric omertà of an old nazi that smells a wolf
where omertà is "(amongst the Mafia) a code of silence about criminal activity and a refusal to give evidence to the police" and smells a wolf is used figuratively as in "smells danger".
Suavo felt he was being observed and reacted with the utmost discretion.
Oler al lobo (smell a wolf) should not be confused with oler a lobo (smell like a wolf).