gerbil fighting

Question
We've had 2 male gerbils for 18 months and they are from the same litter and have always been very close and affectionate. Last night one chased his brother and faught with him and killed him . my kids are devestated and can't understand this behaviour. They have never fallen out in any way before. Is this unusual and why would he turn on his brother like that? Thank you

Answer
Hello J,
gerbils suddenly fighting and killing each other isn't that unusual but it's not as common as hamsters fighting. That's very unusual that they would start fighting at that age but it could be because they were fighting for territory. I'm really sorry this happened, but I honestly couldn't tell you exactly why they decided to fight.