Predators include, foxes, rats, some birds, some cats, and even some children. We would advise you to never leave your guinea pigs out at night in a run or hutch.
If your guinea pig is housed indoors, your dog or cat may present a problem. However endearing your guinea pig and you dog or cat look together as you take a photo, remember that given the opportunity most dogs and cats will do what comes naturally: hunt and kill.
Foxes: Guinea pigs are very vulnerable to attack by foxes, especially overnight. Once he knows there is a guinea pig or two to be had, he will be back night after night. He is normally relentless in his quest to capture and kill.
Even if he has visited but not managed to get to his prey, the guinea pigs will often die of a trauma related heart attack. A fox will dig, scratch, jump on top of the hutch, try to chew his way in, push the hutch over (especially 2-tier hutches with an open base) in fact anything he can to get to his prey.
If you leave your hutch on grass, he will either knock it over or dig underneath or through the wood to gain access. The hungrier he is, the worse it gets. He is quite adept in sliding open latches and if he fails, he will be back night after night.
Rats: Rats are experts at gaining access, they can chew through wooden floors and the smallest gaps. They often attack adult guinea pigs, sometimes killing them. They always attack and kill baby guinea pigs.
Birds: We know of a lady that kept her guinea pigs in hutches in an aviary with no roof. One morning, she let them out into the aviary and popped indoors, and when she came back one was missing. It then transpired that a hawk had been around for a few days prior to the attack. Other birds with an interest are magpies and seagulls.
Cats: Most cats will get bored after the initial arrival of guinea pigs brings out the ‘hunter’ in them. The wire gauge on the run should not be big enough for the cats to get their paws through. However, if access is made, the guinea pigs will be in trouble. A cat with the capacity to do it, can capture and kill a rabbit, let alone a guinea pig.
Some children: Young children should be supervised around guinea pigs at all times and not given the option to put guinea pigs’ lives at risk.
You can put locks on the hutch doors to help keep out predators but there are other ways of traumatising a guinea pig which often leads to death. We do not keep any of our animals outside, day or night because of the threat of predators.