**1. Introduction**

For decades, the Kemp's ridley (*Lepidochelys kempii*) was one of the most elusive sea turtles, and its nesting sites were unknown. Study, ingenuity and a home movie shed light on what for many was a riddle. The first references occurred when fishers off the coast of Florida, USA reported that they caught "demonic turtles". The turtle's morphology was described as flat and grey with a large head and that they were very active when they were caught in fishing nets which resulted in broken nets. The encounters were reported to researchers, and Samuel Garman, a prominent herpetologist and ichthyologist at the Harvard Museum of Comparative Zoology, was the first person to describe the turtle characteristics and, it is thanks

to him that the Kemps ridley sea turtle received its name. In 1880, Garman named the species after Richard Kemp who had a fascination for natural history and sent specimens of the turtles to Garman for study. It was Kemp who first thought the turtles were hybrids from a mating between green (*Chelonia mydas*) and loggerhead (*Caretta caretta*) turtles, hence their nickname of bastard turtles [1].

Another authority in the kemps ridley story was Archie Carr, who wrote several publications on the species. Despite this, he was unable to locate the turtles nesting sites. However, one of his disciples and collaborators, Peter Pritchard, continued this work and established the species morphometric measurements and other key information, such as foraging sites, but the search for the nesting sites of the mysterious Kemp's ridley was unsuccessful.

#### **1.1 Discovery**

It took two further researchers and several years to start to unravel the mystery. One crucial player in the discovery was Ing. Andrés Herrera, a rancher and lover of the outdoors who lived in Tamaulipas, Mexico. Ing. Herrera listened to locals talk of beaches where sea turtles nested along the coasts of Tamaulipas. Luckily Andres was also a light aircraft pilot, armed with information that turtles nested on specific beaches in Tamaulipas during the spring, and he decided to start flying his aeroplane at that time to try and observe them. According to Ing. Herrera, on 18th June 1947, one of these flights was successful when he encountered a mass nesting event, or "*arribada*", which occurred on the beaches of the town of Rancho Nuevo near Barra Calabazas, Tamaulipas. He landed the aeroplane and made the famous film, "the film of Ing. Herrera". This footage not only documented Kemp's ridley nesting but also that this was a mass nesting event or "arribada" which was happening in broad daylight which was different to other sea turtles such as the green turtles which nest at night [2].

Another key to solving the kemps ridley riddle was the biologist Henry Hildebrand from the University of Corpus Christi who had heard and read about the stories of the *arribada* and the place where said nesting had taken place, as well as the writings of Archie Carr. At the beginning of the 1960s, Hildebrand learned footage made by Ing. Herrera and travelled to Tamaulipas to ask for permission to present it at the 1961 meeting of the American Society of Ichthyologists and Herpetologists at the University of Texas. After several decades of uncertainty, Hildebrand in 1963 presented the mystery of where this elusive turtle nested to the scientific community. Later, Carr and Hildebrand's reports estimated that the film's famous *arribada* accounted for around 40,000 Kemp's ridley nesters in a single day [3, 4].

#### **1.2 Population**

The Kemp's ridley turtle population baselines is an estimated 40,000 nesting females in a single day of an arribada. However, in 1966, the largest arribada was reported to include just 1,317 turtles [5] and the number of nests laid continued to decrease until the 1970s, when records show that in 1978, the number of nests fell below 1,000 [6].

Later, in the mid-1980s, only 702 nests were recorded at Rancho Nuevo, Tamaulipas. However, from 1985 to 1990, nesting stabilised, with nest numbers ranging from 702 to 839. Finally, the USA and Mexico introduced legislation to reduce bycatch, protect major nesting sites, and establish a binational agreement. These crucial changes contributed to the increase and later recovery in the numbers of nesting turtles, which increased from approximately 1,000 nests in the mid-1990s to over 21,000 nests on the beaches of Tamaulipas in 2009 [7–9].

**117**

Tamaulipas state [10].

**Figure 1.**

**2.1 Morphology**

**2. Biology (lifecycle and reproduction)**

an endemic species to the Gulf of Mexico.

or yellowish plastron [12].

*Rediscovering Kemp's Ridley Sea Turtle (*Lepidochelys kempii*): Molecular Analysis and Threats*

By the 2011–2012 nesting season, the kemps ridley turtle population had stabilised at 21,000 nests. However, in 2013 numbers of nesting turtles fell rapidly to around 16,000, and the downward trend continued with just 12,000 nests recorded in 2014. Over the last five years (2015–2020), an average of 1,500 nests have been protected per season at the Rancho Nuevo Sanctuary compared to the 3,868 on the other Tamaulipas beaches. During the 2020 nesting season, there were encouraging results with 15,210 nests in Rancho Nuevo and 4,995 from other Tamaulipas beaches (**Figure 1**). It is important to note that data for 2018 was unavailable and the data for 2019 and 2020 do not include the number of nests for beaches found outside of

*Number of protected Kemp's ridley (Lepidochelys kempii) nests in Mexico from 2007 to 2020 [10].*

The Kemp's ridley sea turtle (*Lepidochelys kempii*) is one of the seven species of sea turtles that exist worldwide. The species belongs to the Cryptodira turtles of the Cheloniidae family and is a direct relative of the olive ridley sea turtle *Lepidochelys olivacea* (**Table 1**). Studies on Kemp's ridley sea turtle genetics show that there is only one population within this species, which evolved and has existed for approximately 2.5–3.5 million years [11]. The Kemp's ridley is the smallest sea turtle and is

The Kemp's ridley (**Figure 2**) has usually a carapace as wide as it is long and contains five pairs of costal scutes that overlap the bony carapace (**Figure 2A, B**) and a triangular head with a slightly hooked bill (**Figure 2C**-**E**). The hatchlings are dark in colour on both sides. Adults generally present a greyish-green carapace with a pale yellowish plastron Each of the front flippers has a claw, while the rear flippers can present one or two claws. Juveniles have a dark grey carapace with a yellowishwhite plastron, and adults develop an olive-grey or dark green carapace and a cream

*DOI: http://dx.doi.org/10.5772/intechopen.96655*

*Rediscovering Kemp's Ridley Sea Turtle (*Lepidochelys kempii*): Molecular Analysis and Threats DOI: http://dx.doi.org/10.5772/intechopen.96655*

**Figure 1.** *Number of protected Kemp's ridley (Lepidochelys kempii) nests in Mexico from 2007 to 2020 [10].*

By the 2011–2012 nesting season, the kemps ridley turtle population had stabilised at 21,000 nests. However, in 2013 numbers of nesting turtles fell rapidly to around 16,000, and the downward trend continued with just 12,000 nests recorded in 2014. Over the last five years (2015–2020), an average of 1,500 nests have been protected per season at the Rancho Nuevo Sanctuary compared to the 3,868 on the other Tamaulipas beaches. During the 2020 nesting season, there were encouraging results with 15,210 nests in Rancho Nuevo and 4,995 from other Tamaulipas beaches (**Figure 1**). It is important to note that data for 2018 was unavailable and the data for 2019 and 2020 do not include the number of nests for beaches found outside of Tamaulipas state [10].
