I have a little short legged female Jack Russell. She is 12 this year. She has shorter front legs than her back legs. I think they term this traight as being a 'pudding'. I believe it's a form of dwarfism? Anyway she has always been very lively and energetic but of late she seems to have lost her fizz. I understand they do live up to 15 years. She seems well in herself eats her food but just seems to have deteriorated in the last few weeks. Is it just that she is getting on a bit or could it be worth a visit to the vet for a check up?