actually don't know if this is true but
Pack Instincts
If you have at least 2 pets with the same pack instinct under your control, each of those pets gets a bonus to their damage. Use Animal Lore to determine what pack instincts your pet has. Some typical pack instincts are: Arachnid, Canine, Feline, and Ostard. See the chart below for more information.
Pets in Pack
Damage Bonus
2- +25%
3- +50%
4- +75%
5- +100%
got this information here
http://update.uo.com/design_416.html
this is from update 2002.