It depends on their age, are they still intact (not neutered), their temperaments, etc.
I would not bring in 2 mature male Mastiffs together with no preparation. If you wish to keep 2 male mastiffs then I recommend you neuter them both first, introduce them slowly & properly. Keep them at first in separate areas where they can see each other. It is better to keep one of each sex if you wish to have 2 dogs. Keeping 2 males together is asking for trouble. It has been done but with people who know what they are doing. This is a large breed and once you have that first fight, they will hate each other forever.
Not if they are trained correctly.
8 weeks, or 2 lbs. ExceptiOn is for giant breeds (mastiffs, Danes, etc), and in that case, 18 mo
no 2 male hamsters will fight, I have a Male Hamster and so does my Brother, we put them next to each other and my Hamster jumped on top of his. if you out 2 male or female hamsters together, they will surely fight
Seperate them and put them in 2 separate cages
NOOO
No.
they wont fight they have to be the same BREED and LITTER to not fight each other .
No, only bull mastiffs.
When male and female cats fight, the more likely to fight each other would be 2 females if fixed, but more likely two males if they are not fixed.
If they had nothing to fight over, then yea.
They may, but will not do much harm to each other if they do.
Yes they will. Hamsters and gerbils are solitary creatures and they wil fight if they feel that someone else is in their territory.