Perhaps monkeys were the Sleeper ship's techs. There was a male and a female, kept as pets. The tech went to lunch, forgetting that the launch was at 11:45. The monkeys were left on board for the long trip to Sirius on board the Hispania, then when they saw that the Corsairs were taking off, they go "Lolwut?" then grab their own ship and land on Planet Primus.