Dog acting lethargic but still eating/playing

[Andersonx3]

Just that really. I have a 15 month old Jack Russell Cross who is usually a bundle of energy 24/7 however since Saturday he's been quite relaxed, more than happy to just lay and sleep/chill. He's been on walks and is his usual self, and if I pick up a ball he's straight up and wants to play. He's also eating his usual amount. Should I worry about him seeming more lethargic than usual?

If you're worried pop him to the vet however I would wonder if he's just coming out of the puppy phase and calming down a bit?

Has anything changed in his environment or routine, e.g. an extra long walk?

I noticed that my own JRT x seems to have calmed down a bit in 'steps' where he just seems to have become less mental in noticeable chunks. He's still obsessed with his ball though - if he lost interest in that we'd be down the vets immediately!

As ever, if you're worried, take him to the vet, but it may just be the natural process of a JRT becoming a bit less obnoxious (or the doggy equivalent of picking up a bug and feeling a bit rough but not so bad you can't get on with life).

@Girliefriendlikescake @AvocadosBeforeMortgages I think you're both probably right. My husband has said he may just be growing up. We've just nipped out on a walk and he was fine, eager to meet other dogs/people. I think I'll keep my eye on him and if anything changes ie. he doesn't want his ball or to go out then I'll have him seen.

Nothing has changed at home - we have a baby due in 9 weeks but he's been around her things for months and is always excited when he gets to go in the nursery so I can't imagine he's sensing anything?