small dog, big dog

Question
I have a 2 1/2 yr old male mini schnauzer, my boyfriend just adopted a 2 yr old male lab x (maybe border collie)from the humane society. The lab x is altered, however my mini is not. We introduced the two for a brief period (about a 1/2 hour) yesterday. They seemed ok, no growling or barking. My mini wont stop sniffing the lab's genitals and he seemed to begin to get annoyed with it. Although still no growling. My boyfriend and I currently live separately, but there are plans for a spring time move. These dogs are just going to have to get along. My questions are:
1) What are the chances of a big dog, small dog becoming friends if they didn't grow up together?
2) Will altering my dog make a difference? I have no plans to stud him out.
3) If they don't get along, will the big guy give some sort of warning before attacking? My biggest worry is the lab demolishing my little schnauzer.

Any advice you could offer to make this a smooth move in the spring and to make them the best of friends would be greatly appreciated.

Answer
Dear Theresa,
Thanks for the questions.
1) Growing up together is not really a factor. Many dogs that didn't grow up together become the best of friends and many dogs that did grow up together become the worst of friends. It depends on the dogs, the environment, and the people.

2) Neutering a male dog has three well-documented, possible effects- reduction in roaming, reduction in marking behavior, and in a few cases, it may raise the threshold for reactive behaviors (i.e. the dog "puts up" with more stress before he reacts with fearful or aggressive responses)

3)Most dogs do give warnings - the problem is that people don't recognize them. Dogs communicate via body language -  type of gaze (hard staring or scanning or soft looks), body positioning, tail position, head position, state of muscles (stiff or relaxed), et cetera, all contribute to an overall measure of the dog's internal state.

Visit this web site. There must be a structured environment if you are to succeed.

http://www.vin.com/VINDBPub/SearchPB/Proceedings/PR05000/PR00470.htm

In addition, but the book, Feeling Outnumbered? How to Manage and Enjoy Your Multi-Dog Household. (Paperback)
by Karen B. London, Patricia B. McConnell

Please visit my past answers. I addressed specific exercises for "Joining a puppy with an older female dog"  two questions ago. The same exercises and tips apply to your situation. Thank you!

Happy Training!
AT