About a year ago I had to put down my 10 year male boxer mix. I also have another 5 year old male boxer mix that has known the elder since he was a little pup. The older one always used to get very nervous during thunderstorms as I have read this is not uncommon with dogs. But, the younger one always seems to not care or they did not bother him at all. This changed once I had to put down the older dog. Soon after the other seemed to pick up the same behaviors (panting\shaking\not eating etc) during the storms. I have also noticed other subtle changes in his behavior that reflect the older dog. Is this normal? And what causes it? I also got another pup about a month after I put him down last year if that might have anything to do with it?