Like deer, moose look for winter feeding areas with little deep snow and a plentiful source of food. Moose remain in these yards for weeks, even months, as long as the food supply lasts. Most herbivores of the northern forest have difficulty obtaining enough salt. Twigs and bark are low in sodium and by the end of winter the moose's salt reserves are low. This is another reason for the moose to go swimming and diving during the summer.
Aquatic plants concentrate salt and other minerals.
Some aquatic plants have a sodium concentration 10 to 400 times that of the plants the moose browses on during the winter. The ideal lake for a salt hungry moose has a high mineral content and a good flow of water in and out of it. The plants growing in the shallow water allows the moose to store salt for the winter.