My two JRT's are fighting

by Virginia
(Wagga Wagga, NSW, Australia)

I have 2 female Jack Russell's from the same litter they are about 5 months old and not de-sexed. recently they have been fighting with each other a lot and i cant find anything that triggers it other then me being around at first i thought it might be jealousy but even if i don't give them any attention they still attack each other. i have had to take my pup to the vet for the damage to her eye before. I don't know how to stop them when they fight its just between them at this stage not other dogs. I have to get in the middle and pull them from each other but when i let go their back into it. I separate them, one outside, one in the bathroom but then after 20 minutes they continue to fight. HELP how do i stop them ?