He's still at the age of having "energy bursts" followed by intense sleep, but that will soon come to an end. He's old enough to start walks with you - say 15 to 20 minutes twice a day. If you're in "snow country" you might want to stick with indoor activities until it's warmer. (See the pinned thread at the top of the forum.)
What breed or mix is your pup? Dogs also need mental exercise as well, and that's very important for certain breeds to avoid frustration-related bad behavior.
Three to six months is also an ideal time to begin obedience training. Their minds are like little sponges and any training you do now will last a lifetime with only a little reinforcing here and there.
i really dont have much to add on this, maybe just contact a vet or do some online research if it is a large or giant breed dog as there are some movements that you should avoid (ie jumping in and out of cars) to help the hips develop fully and reduce the risk of bone and joint problems later in life.
As Jaybay said, the brain needs alot of excercise and it REALLY does make a difference. Not only that but you will have a calmer puppy when the brain as well as body is tiered.
Lots of interaction on your part is needed right now. Teach him how to fetch toys. When he brings them back, teach him the "drop it" command so that he gives you the toy.
Something else you can do is to name his toys, and always use the names when you refer to the toys. He will quickly learn who is who, and you can tell him to bring you a specific one and he'll know exactly which one that is. Kate has "Mr. Frog", "Sheepie", "Lambie", "Lime Lion", "Lemon Lion", "Diva", "Larry Lobster", "Splish Duckworth", and about two dozen others (seriously), and she knows every one by name and will bring the one you ask her for. When you give them the toy for the first time, "introduce" them to the toy using the name you are going to use for it, and make sure you stick with that same name each time you refer to that toy, and the dog soon learns who is who.
Play guessing games with them. Take three plastic cups and set them upside down. Put a treat under one of the cups and then scramble them around, and let your dog guess which cup the treat is under. They love this game because they get a reward (the treat) for choosing the correct cup.
Play Hide and Seek with your dog. You can play this either just you and your dog, or another person can help. If you have another person with you, have them hold your dog and keep them busy while you hide. Then have them let the dog go while you call him and let him come find you. You can also do this when it's just you and the dog, however you'll probably have to wait until the dog falls asleep, and when he does, you go off and find a place to hide, and then call him and let him come find you. Give him clues in a silly voice (you're getting warmer! you're getting colder!) so that he has a sound to follow in the beginning, but as he gets better at it you can later hide and he'll find you with a minimum of clues.
These games are good starter games. After your puppy grows a bit, you can move on to more involved things like making an obstacle course in the yard and having him go through it. Dogs are as much fun to play with as kids are! :D
I got so wrapped up with the "mental exercise" question I forgot all about the original question! LOL
At 3.5 months, a puppy is still very much a baby, and still needs quite a bit of sleep. At that age, their attention span is still very short, as well, so 15 minutes at a time is usually sufficient. They will play on their own until they tire themselves out, but when it comes to supervised exercise, where you are the one calling the shots, 15 minute increments are about all that is necessary at this age. As they grow and mature you will notice their attention span doing the same, so extend your exercise periods accordingly. The puppy will let you know when he's tired. They just conk out like they ran out of gas. I've seen them do it in the middle of chasing something. They'll just stop, lay down, and go to sleep like "OK, that was fun but I'm done for a while!" :)
Ghilly!!! that is amazing... what kind of dog do you have? lol i tried to teach my shepherd mix the name of TWO different toys when she was younger... this went on for like 3 weeks before i gave up and just accepted that she's beautiful.... but not that smart =P
Katie is a 6 year old rough collie. She'll be 7 in May. I talk to her like she's a child instead of a dog, and I truly believe that she THINKS she's a child and not a dog. LOL
She gets a new toy for every birthday and, of course, each year for Christmas, and then with me being a claw machine addict, every time I go somewhere that has a claw machine, if I'm lucky enough to get something out of it, it becomes her new "baby". She also gets whatever new arrivals are in the toy aisle of H.E.B. when I go food shopping, as well. One of the reasons she has so many toys is that she actually takes care of them, she has never destroyed anything that belongs to her (or me, come to think of it). One of her toys, Diva, is this silly little doll that I won in a claw machine when she was about five months old, and she still has her! The only way in which Diva is any the worse for wear is that she USED to have a single strand of yellow yarn going across the top of her head that was her "hair", and over the last 5+ years the hair has gotten pulled off and lost. But she's even holding a little purse that is sewn to one of her hands with a single stitch, and the purse is still there and going strong.
Katie always takes one of her toys along when we go for our walks every day. It's almost always someone different than it was on the previous walk, it's like she wants everyone to have a turn. She also has her own little purse that she takes with her sometimes, we put a few cookies in it so she has a snack with her while we're walking. Naturally she can't undo the zipper, I have to do that for her, but when we stop and sit down, she'll have a cookie from her purse, I zip it up, and we continue on.
My dog, my daughter, it's all the same thing. I wasn't ever blessed with human kids, so Katie and our kitties are the next best thing. That's her picture in my avatar. :D
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