Bite marks
What type of bite marks? Small, insect holes or canine tooth marks? Animal pests might include racoons, deer, crows, and coyote. They like fruits and melons. Look for tracks near the garden. If your fruit is turning black and dying, this is usually a different problem called blossom end rot. Usually, the reason is dry weather and lack of water. Watermelon needs adequate moisture, especially as it matures.