I agree with Wormwood. Now I am no expert and I do not have either of these species, BUT it is common knowledge that larger toad and frog species do not discriminate when it comes to a food source whether it be frog or a toad of the same species or related species and the more voratious eater are the worst for cannibalism and even fighting. For food. The Marine Toad will most definetly be the death of one or both of the Cane Toads. Also RELATED does not mean the SAME so their toxin will differ and can be harmful to one another. I would take the advice given. It is always beter to be safe than sorry especially when you yourself don't even know what the out come will be. If you knew you wouldn't have asked.