Threats to sea turtles are numerous and have caused many sea turtle species to be endangered. Of the seven extant species of sea turtles, six in the family Cheloniidae and one in the family Dermochelyidae, all are listed on the IUCN Red List of Endangered Species. The list classifies six species of sea turtle as "threatened", two of them as "critically endangered", one as "endangered" and three as "vulnerable". The flatback sea turtle is classified as "data deficient" which means that there is insufficient information available for a proper assessment of conservation status. Although sea turtles usually lay around one hundred eggs at a time, on average only one of the eggs from the nest will survive to adulthood. While many of the things that endanger these hatchlings are natural, such as