Loggerhead Key existed on the island in the early 1900s. Fauna of Loggerhead Key includes sea turtles, which are monitored by park rangers with the Dry Tortugas National Park to document nesting and hatching rates. The loggerhead sea turtle is also present on the island. In August 2016, a National Park marine biologist stated that 113 loggerhead turtle nests existed on the island at that time. This was the highest recorded nest rate compared previous years. The island also has brown pelicans. In 1972, hundreds of rhesus macaque monkeys were brought from India to Loggerhead Key by Charles River Laboratories. This was
Loggerhead shrike shrikes may eat or discard their bodies or else feed them to their remaining young. The oldest recorded age of a loggerhead shrike was 12 years and 6 months. Loggerhead shrike populations have been decreasing in North America since the 1960s. Reasons behind the decline remain unclear, although suggestions include habitat loss, pesticide contamination, climate change and human disturbance. The eastern loggerhead shrike ("L.l. migrans") is critically endangered in Canada, with fewer than 35 known breeding pairs in Canada. The San Clemente Island shrike, "L. l. mearnsi", is critically endangered, with a population as low as 5-10 individuals during 1983-1988.