Adult unaltered male dog humping unaltered male puppy

So this maybe a strange question, but I have a male dog who has suddenly started humping one of our male 6 month old puppies. He is whining, and following him around. The puppy doesn't seem to mind at all and is chasing our older dog around and jumping at him. Is this normal behavior? The reason I am so worried about it, even though it just started about 30 minutes ago is because on Sunday morning we had a puppy from the same litter pass away. Our older male dog had started licking him all of the time for about two days, and the puppy acted completely normal. Then we noticed on Friday night that the pup was peeing blood. We figured he had a UTI and took him to the vet Saturday morning. The vet confirmed UTI and sent us home with antibiotics. Then just shy of 24 hours later he was gone. I called the vet to ask if I needed to be worried about our other pets but was told he didn't believe so but since we had already buried our pup and couldn't perform an autopsy he could not make any guarantees. I suffer from horrible anxiety and am probably making a big deal out of nothing but now every move they make or don't make scares me. So any input would be greatly appreciated. The older male never humped our puppy that passed away just licked and whined. We do have a neighbor with a female dog (unsure if she is fixed or in heat or anything like that) and when he was last outside he was sitting facing their house and howling (he is a beagle). I'm sorry for rambling. TIA

Hello thankyou for this interesting question.  Whether or not there is a link between humping and peeing blood, both are problematic for the dog concerned.   The bigger dog sounds to be humping as an outlet for sexual behaviour - presumably they don't get the opportunity to mate very often, but the urge is still there and he has chosen the pups as the closest available outlet.  This must be unpleasant for the pup and appears to reflect frustration in the older dog.  I also wonder about prostate overgrowth or tumours of the prostate exaggerating the sexual behaviour.  Castration may be a good idea and is well worth discussing with your vet.   There are now temporary chemical methods as well as the surgical one.  Both have pros and cons.

So how about the pups?  Im sorry that you lost the puppy peeing blood.  Losing blood into the urine can happen with internal blood loss - clotting disorders, for example.  These can also cause weakness, so it might be something to ask your vet about.  I havent heard of it happening directly as a result of humping but can conceive that humping may be traumatic and therefore exacerbate blood loss in the urine secondary to something else. Stress can stress make an animal more likely to sucuumb to a urine infection too - althpugh most cases of blood in urine are not infections as far as I understand.  Overall, I wonder if an underlying illness may have played its part with that pup, but your vet is probably the best judge, having more context than I do here.

In summary then, we (humans) evolved anxiety for a reason - it can be a useful motivator for us to investigate things that affect our (or even our pets) survival.  There is some positive use you can put your anxiety to in this case;  it is worth speaking to your vet about the sexualised behaviour in your older dog to see if there is some way to treat it, and worth chatting about the cause of the apparent UTI in the pup.  Sometimes, lab pathologists can be helpful to chat to about causes of a UTI , especilly if the UTI was confirmed.  I hope that something there helps.

Finally, try a quick search for 'neutering, male' in our blog.  It will bring up a good article about implants and one or two others that might be helpful. Interestingly, you will read that blood in urine is a sign of prostate disease, but as it is the pups that have blood in their pee and the adult who is doing the extra humping, this may not be related.   We would be interested to know how you get on.