We have two Yellow Belled Sliders (Yurtle and Mack
) who have been living happily together for over five years, and have been moved to a bigger tank (220l) with a floating island (cork bark).
Whilst Mack has always been the more dominant of the two, he's never really done anything more than push Yurtle out of the way when there is food going. However, over the past few weeks, he's been getting quite aggressive towards Yurtle, and gave him a fairly unpleasant-looking bite on the neck. Thankfully, that healed OK, but now he's taken to biting Yurtle's back flippers. It's got to the stage where Yurtle spends most of his time out of the water (Mack rarely climbs out), but even there, he keeps his back flippers and tail withdrawn.
When Yurtle does come into the water, Mack immediately swims underneath him, and hangs around his rear end, looking for opportunities to bite. Even when Yurtle's back flippers and tail are withdrawn, Mack will have a go at him. For some reason, he doesn't seem to go for Yurtle's front flippers or neck.
I have no idea what sex they are, as both have similar sized tails and claws, so I can't compare. Both have fairly flat plastrons, but I don't know if that's reliable enough to identify them.
Anyone know why he's become so aggressive, and what we can do about it? For the moment, I've had to wedge a piece of chicken wire into the tank, splitting it into two sections to keep Yurtle protected. This cuts down their swimming space though, so it's not a long-term solution.
Thanks for any help.