Death simulation behavior of the lizard Lygodactylus klugei of the Gekkonidae (Reptilia: Squamata) family in northeastern Brazil

: Natural selection favors primary defense strategies that reduce the chance of prey being spotted and discovered by a potential predator, such as camouflage, aposematism, and secondary defense strategies that include tail loss and escape, immobility, and thanatosis. The behavior of thanatosis (playing dead) or tonic immobility (body paralysis) is a strategy adopted by the prey, in which the animal simulates immobility to avoid being ingested. This simulation is effective against visually oriented predators or predators that do not feed on dead prey. Belonging to a complex of cryptic species, Lygodactylus klugei is a gecko that has a wide distribution in Northeast Brazil, occupying areas of the Caatinga and Cerrado, and that has a diurnal habit. On August 25th and September 2nd, 2021, three individuals of L. klugei were observed exhibiting thanatosis behavior during plant suppression work in the Curaçá municipality, Bahia state, Brazil. This behavior is reported for the first time for L. klugei , and the species may use it if it is unable to escape from visually oriented predators. However, we suggest that future observations may generate new hypotheses about the benefits of this behavior in the species. Our observation adds important data to the behavioral repertoire of lizards from the Gekkonidae family, providing important natural history data to try to understand the defense mechanisms adopted by lizards in general.

Generally, when they are at high risk, prey shapes the use of their microhabitats, reducing predation rates.These inductions caused by predators can result in reduced growth and fecundity rates, since, when they detect the potential danger, heliothermic the lizards often pause foraging or warming up and seek out environments that offer more protection (Rocha, 1994;Downes, 2001).Natural selection can also favor primary defense strategies that decrease the chance of prey being spotted and discovered, such as camouflage (Rautenberg & Laps, 2010;Souza et al., 2020), aposematism (Tseng et al., 2014;Lee et al., 2018), and secondary strategies that can reduce the chances of these animals being predated, such as escape and tail loss, immobility, and thanatosis (Greene, 1988;Autumn & Han, 1989;Downes, 2001).
Gekkonidae is a family composed by small lizards, that have adhesive lamellae on their fingerips, which aid in displacement, and are inhabitants of trunks, trees and bromeliads, and have oviparous reproduction (Rocha,  ).According to Lanna et al. (2020), Lygodactylus klugei (Smith, Martin & Swain, 1977) comprises a complex of cryptic species with a diurnal habit and wide distribution in the Caatinga and Cerrado biomes in northeastern Brazil (Teixeira et al., 2013;Mesquita et al., 2017;Lanna et al., 2020).
On August 25, 2021 and September 2, 2021, respectively two and one individuals of L. klugei, respectively, were observed during vegetation suppression work in the Curaçá municipality, Bahia state, Brazil (9° 02' 22.5" S, 39° 55' 00.7" W).When manipulated, the first and third individuals turned their belly up, putting themselves in a simulated death posture for about two minutes, keeping their eyes open, while the second specimen turned on its side and left its mouth open for approximately one minute (Figure 1).
The same behavior was observed twice more for each individual, for about a minute each time, which only returned to its normal position when placed on tree branches.The specimens were rescued from the vegetation suppression area and released in a legal reserve area with Caatinga physiognomy close to the environment in which they lived.
All the specimens were adults, but it was only possible to identify the sex of the first and third individuals, both females.
In Gekkonidae, the first record of thanatosis was recorded for Hemidactylus mabouia (Moreau De Jonnès, 1818) (Anaissi et al., 2020), this being the second observation for the family.This behavior is not primary defense, and occurs after individuals are stimulated or disturbed, as observed in our data collection and literature (Table 1).This practice of pretending dead in L. klugei is reported for the first time, and the species may use it when thying to escape from faults, which may confuse possible visually oriented predators.However, we suggest that additional observations of this behavior may generate new hypotheses that could explain and help understand the benefits of the thanatosis or tonic immobility.
Our observation adds important data to the behavioral repertoire of lizards in the Gekkonidae family and, in addition, provides natural history data that are important for trying to understand the defense mechanisms adopted by lizards in general.

Behavior
Brief description Family (species) References

Death feigning, autotomy
When handled, the lizard specie exhibited death simulation behavior and caudal autotomy.Table 1.Thanatosis or tonic immobility behaviors with a brief description of the behavior in some families and species of lizards in the world.

Figure 1 .
Figure 1.Thanatosis behavior in the lizard Lygodactylus klugei, during plant suppression work in the Curaçá municipality, Bahia state, Brazil.Legend: records of the 1 st (A) and 2 nd (B) specimens in ventral view; and of the 2 nd (C) and 3 rd (D) specimens in lateral view.Photos: Silvilene Matias (2021). 1994