"The tipping point seems to be 4 dogs."
©Scott Sheaffer, CDBC, CPDT-KA, USA Dog Behavior, LLC
Many dog lovers have multiple dogs in their homes - including me. However, as with just about everything in life, too much of a good thing can be problematic sometimes.
Actually, math is the problem. The specific math formula (I promise no further math after this) is: nCr = n!/r!(n-r)!
This math formula calculates the exact number of unique relationships in a group. Every time you add a dog, you are introducing new dog relationships - all of which have to function peacefully. When dogs don't get along in a home we call it in-home aggression, or more informally, sibling rivalry. In-home aggression can be difficult to address and sometimes is quite resistant to treatment.
With 2 dogs there is only 1 dog relationship that needs to work. With 3 dogs there are 3 unique relationships that have to work. With 4 dogs there are 6 - you get the idea. The number of relationships grows at an ever increasing rate (please see graph below). The tipping point seems to be 4 dogs. By adding just 1 dog to 3 dogs, you double the number of unique dog relationships from 3 to 6.
With every new dog added to your household, you exponentially increase the number of doggie relationships that must operate harmoniously. You also increase the chance of in-home aggression.
However, with each dog you add, you also exponentially increase your happiness!
If you are experiencing in-home aggression with your dogs, please seek the help of a qualified and certified dog behavior specialist.