How to help your pets get along

Introducing a new cat to an existing cat requires as much caution as bringing in a dog – an adult cat is not likely to welcome a fellow feline. This is as nature intended: all species of wild cat, except the lion but including the ancestors of our own domestic moggy, are solitary creatures. They are also territorial and prize personal space above companionship.

Faced with an intruder, cats can become nervous or aggressive and may spray the house to define their territory. Cats are not naturally social creatures and most will function happily on their own, so don't expect instant harmony.

Neutering is the first essential step – as well as the obvious advantage of preventing unwanted litters, it will help your cat to better socialise with other felines, according to Cats Protection. As with dog-cat friendships, feline harmony is possible so long as you take steps to reduce competition for food and, crucially, space. Consideration and care make for contented cats.

Dogs, by contrast, are highly sociable and love company. 'Being in a stable social group helps reduce anxiety, fear and gives a general feeling of security,' says Dogs Trust training and behaviour adviser Victoria Horsley. But you do need to take into account the individual temperaments, the dogs' previous experiences and how you deal with dogs.

'In general, the best canine pairings are where the dogs are as different as possible,' says Carolyn Menteith, a dog behaviourist and author of Dog Manual. It works because different types of dog don't compete for the same things.

'If you have a wired, obsessive dog, get a breed that is known for being more laid-back,' she advises.

Siblings can be a bad idea, as they'll be such firm friends that they'll be less likely to form a bond with their owner, making them difficult to train and manage. Same-sex dogs are also more likely to squabble than opposite-sex pairings.

Every dog is different, however, and common sense is invaluable when getting more than one. Are you going to carry one of them home from the park because it can't handle as much exercise as the other? Most importantly, think about whether you have the time and space to accommodate the needs of both dogs.

Rabbits and guinea pigs also like company and are ill-suited to solitary confinement. When introducing a rabbit to another rabbit, or a guinea pig to another guinea pig, start by putting them each in their own run or cage, within view of the other. Then allow them to become used to each other’s presence for a few weeks before you formally introduce them face-to-face. Ensure that both animals are neutered before the formal introduction takes place, to minimise the risk of fighting.

Because of their sociable dispositions, some pet owners allow rabbits and guinea pigs to share a hutch, but it's not always a good idea to house different species together – even if they are introduced slowly and carefully, in the way outlined above. 'There's a lot of debate among vets about this,' says Elaine Pendlebury, senior veterinary surgeon at the PDSA. 'I would always err on the side of caution.'

To start with, rabbits and guinea pigs have different dietary requirements. Guinea pigs are unable to make their own vitamin C, and if a rabbit companion eats more than its fair share of fruit and vegetables, the guinea pig will lose vital nutrients.

Also, these two creatures originate from different continents and would never meet naturally in the wild. What’s more, they can't communicate, which can cause confusion and conflict. And rabbits can seriously injure guinea pigs. Peaceable though they are, rabbits have very powerful back legs.