The fourth plague to harass the Egyptians consisted of hordes of wild animals roving all over the country, and destroying everything in their path. Only the province of Goshen where the children of Israel dwelt was immune from this as well as from the other plagues.
Again Pharaoh promised faithfully to let the Hebrews go out into the desert on the condition that they would not go too far. Moses prayed to G-d, and the wild animals disappeared.
But as soon as they had gone, Pharaoh withdrew his promise and refused Moses' demand.