The water sodium chloride system looks like this. Temperature on the vertical axis, concentrations of water and salt on the horizontal axis. It's called a phase diagram. https://www.researchgate.net/profile/Sayed-Badawy/publication/276999290/figure/fig3/AS:391864646684674@1470439220347/Phase-diagram-of-salt-water.png

When they are this young they don't have teeth. So they don't bite Mama's teats. The sucking is really pretty vigorous as I recall from long ago.