Biologists find sea turtle nests by looking for a characteristically shaped mound of sand on the beach. They mark and record each nest and begin checking for signs of hatchlings about 45 days later. Although incubation takes about 60 days, the temperature of the sand determines the speed of embryo development, so the hatching period can cover a broad period of time. The speed of embryo development increases with increasing nest temperature. Cooler nests generally produce more males, and warmer nests generally produce more females.