Don't fret too much. I'm sure the baby is okay. A ferret's weight fluctuates a lot. Especially seasonally. They typically loose weight for the summer and gain it for the winter. However, many of our neutered, pet store ferrets have their seasons mixed up. So that's not always the case and its hard to predict these weight changes in them. Also note that in the last two weeks, the time of sunset has changed drastically. It was daylight here until 9pm in July here. But now its daylight only until 8pm, if that. Birds and small animals sense this change right away and experience hormonal changes. Possibly something was triggered in your furry one. A ferret's weight can also fluctuate very quickly. Ferrets can loose weight in a matter of a couple of days believe it or not. They can "crash" and become skin and bones in what seems like over night. So it's very important to handle your ferret, monitor him, look inside his mouth, and examine him (by running your hands over him while playing with him) every day. That way these things don't sneak up on you. However, you don't seem to be at risk for this! You seem to be very in tune with your baby. Very cool. We'd need to know where/how your ferret is gaining size. Is your ferret picking up "weight" or changing size in a specific area? That's an important thing to note. Increase in general body size is usually normal. Even if it seems like only the bulk of the body (rib cage down) increases and nothing else, its usually normal. What wouldn't be normal is if the ferret "changes shape". Such as only the bottom part of the stomach gets puffy (so it has a major pear shape to the body) or if the area seems asymmetrical. Bottom line is you know your ferret better than anyone. So do listen to your gut. If it alarms you and it would help you sleep at night, sure, take him to the vet. If you are new to ferrets, this can be a very difficult thing to decide. I wish I could help more, but without knowing any details about your pet, pictures, etc, I can't tell you much more. Also know that I'm just a ferret lover, not an expert. [Posted in FML 7164]