Commentators explain that the verse creates a shocking contrast. Even wild animals, like jackals, instinctively nurse their young. However, the suffering in Jerusalem was so severe that mothers were forced into what appeared to be cruel behavior. Like the ostrich, which was known for abandoning its young (a theme also found in Job 39), the mothers of Zion were unable to provide for their starving children, highlighting a complete breakdown of the natural order due to the horrors of the siege.