DEAR PDSA Vet: My three-year-old German Shepherd, Sterling, is quiet and well-behaved when he’s off the lead, but barks at other dogs when he’s on the lead. Why is this? Michael

Barking can often be linked to fear or anxiety and, in Sterling’s case, it sounds like he’s worrying about other dogs when he’s on the lead. Barking is a really efficient way of making the thing they fear go away and, as it’s so effective, it can be a behaviour that becomes a habit. Sterling probably feels most vulnerable on the lead because he can’t escape or control how he acts if another dog approaches him. There are lots of effective behavioural and training techniques which can help Sterling overcome his fears or learn to be less vocal. The best chance of success is if you get professional help with this, so call your vet’s for advice or visit www.apbc.org.uk.

Dear PDSA Vet: My two guinea pigs are brothers, but they fight. I separate them to sleep, but they are allowed in the run together and play nicely. Would neutering help them live together? Justine

Guinea pigs like company but can fight and sometimes this can’t be resolved. Many disputes are about territory, with one guinea pig exerting dominance over another, so neutering might not solve the problem. Try giving them time apart then encourage them to be friends again. Continue housing the guinea pigs separately when they sleep and feed them apart, as the more dominant guinea pig can stop a more submissive one from eating. Allow them to play together in the run, but try a new, larger run with more hiding places, such as branches and large stones.

Gradually try increasing their time together if they’re happy.

But if they continue fighting, you may need to consider separating and neutering them, then introducing new female companions for them both.

Dear PDSA Vet: Our cat Tigger has gained weight over the years, so a few months ago I reduced the amount I feed him on the advice of the vet. It hasn’t made much of a difference though. What else can I do? Tamieka

Sudden weight loss can be dangerous for cats and may cause problems so slow, gradual losses are much better. It’s important to follow your vet’s advice and not be tempted to cut back his portions further as this could lead to Tigger not getting enough nutrients. Make sure you weigh Tigger’s food each day and check that nobody in your house or neighbourhood is feeding him extras and that they’re aware of his diet. If you’re really struggling your vet may recommend a prescription weight-loss diet to help. Exercise is another important aspect of weight control, so encourage Tigger to play chasing games with fishing rod-type toys.

Dear PDSA Vet: My two-year-old dog Sadie cries and whines when we’re travelling in the car. Can you help? Karen

Some dogs become vocal because they are excited about where they are going, whereas others vocalise because of anxiety.