Yellow-headed gecko

Types

There are two

Males have a larger snout-vent length, distance from tip of head to the base of the tail. Both males and females reach sexual maturity at the same size with the ability to reproduce any time during the year.[16] They reach this size around the age of 6 months.^[17] Similar to other geckos, G. albogularis does not accumulate fat in their abdomens. This suggests that reproductive abilities are not influenced by the amount of fat a lizard has. Reproductive abilities are driven by other factors.^[18] G. albogularis is typically found in dry habitats but have also been observed in moist habitats. Their main diet consists of insects and spiders. G. albogularis is also a very territorial lizard. They defend their territories by primarily waving their tails and other behaviors.^[19]

Similar species

In the Lesser Antilles it is found on Aruba and Curaçao. Hummelinck proposed that this distribution is not natural and that the species is introduced on these islands. On Curaçao it is particularly common in the central portion of the island around the old plantations of Daniël and Siberië.^[11]

The populations in Venezuela are found in the

In the United States, G. albogularis is most prominent in Florida. With a tropical-like climate, non-native species are able to survive, and this lizard is no exception. It is most likely that the yellow-headed gecko migrated from the Key West into other parts of Florida. The first documented sighting was reported in 1934, but research suggests that they have been in Florida since 1929.^[19]

• Gonatodes albogularis bodinii

This taxon was first collected on

G. albogularis fuscus was first collected in Nicaragua, likely at the port town of El Rama, although as of 1988 the holotype is missing. It is also distributed in Panama, Costa Rica,^[4] El Salvador,^[11] and Cuba, including Cayo Santa María,^[4] and western Colombia.^[11]

This taxon was first collected around Miami, Florida, in 1934, and is thought to have spread from the Florida Keys, although the first specimen was only collected there in 1939. It may have been transported from the Keys to other areas in southern Florida in the early 20th century, but it seems to have naturally died out throughout the Florida mainland or never truly established breeding populations there. The last specimen was collected in Key West in 1989, and the last sighting of the species was in Key West in 1995. Monitoring for the creature by gecko specialist herpetologists from 1995 to 2005 throughout southern Florida failed to provide any evidence that the species remained extant in the region.^[19]

• Gonatodes albogularis notatus

This taxon was probably first collected in the city of

The species also occur in Mexico (Chiapas, Veracruz), Guatemala and Honduras, but it is unclear to which subspecies these populations belong. It has been stated to be found in Belize, but it has never actually been recorded in that country. The population on Cuba has also been said to represent the nominate subspecies which is generally from northern South America, as well as fuscus from southern Central America, although notatus is found on the surrounding Caribbean islands,^[4] and the species has also been said to be introduced to the nation.^[11]

Reproduction and parental care

Gonatodes albogularis prefers to lay their eggs in communal sites to maximize the hatching success and extra protection from predators.  Gonatodes albogularis can have multiple offspring in a year and does not have a preferential breeding season.

Site selection for egg laying

Females primarily nest in tree trunks laying single eggs. However, it has been observed for tree bases to be communal egg-laying spots in Costa Rica and Panama. These locations are also where most of these lizards can be found along with tree branches, under rocks, debris, and in soil litter. Soil litter provides the best conditions for communal egg-laying. These conditions often lead to higher reproductive success of females along with greater success of hatchlings. A high density of eggs in one area can provide moisture control, so the eggs will not dry out as quickly. This is especially valuable during the dry season when eggs are more susceptible to desiccation. Soil litter can also act as protection. The eggs are less visible when they are hidden in the litter, so they are less prone to predators.^[16]

Brood size

G. albogularis females only carry one egg at a time with the ability of having more than one offspring in a year. Although reproduction can happen anytime during the year, it happens significantly less from December–May which is during the dry season. They put all of their reproductive efforts towards ensuring that one offspring survives. [8] The egg will hatch in 2–4 months after it has been laid.^[19]

Physiology

Yellow-headed gecko are able to distinguish differentiate between coloration and brightness which direct consequences to mating partner selections

Vision

It is believed that the yellow-headed gecko is able to tell the difference in brightness and hues of conspecifics. The lens of the lizard is yellow. With the yellow lens, short wavelengths (less than 450 nm) are blocked, so there will not be as much damage to the eye. The lens also acts in limiting color distortion. Colors on these lizards can be highly reflective which influences their desirability for mating along with other behaviors. Longer wavelengths of light are consistent with duller colors. Females prefer males with brighter colors, so the ability to detect different brightness has direct effects on mate selection. Although this can be useful for choosing a mate, it can only be used when the lizards are in close proximity to another.^[22]

Mating

Yellow-headed geckos exhibit aggressive behaviors to defend territory and as anti-predator mechanisms. They also display different coloration to maximize mating success.

Male intraspecific interactions

Males have many aggressive behaviors that help them defend their territories from not only other males but also predators. Some of these behaviors include throat depressions, push-ups, tail displays, whole body waving, and bites. Males with high success in defending their territories exhibited more of these aggressive behaviors, and the behaviors lasted much, much longer. This gecko initially starts with more subtle movements by only moving one part of their body like throat depressions. If he feels more threatened, he will exhibit stronger, more aggressive behaviors such as push-ups or whole-body waving.^[23] These aggressive behaviors usually crest mid-day with high variability any other time of day.^[24] One hypothesis suggests that aggressive behaviors peak mid-day, because their predators are not as active. G. albogularis has a chance to increase their fitness by defending their habitat and searching for mates.^[24]

Similar to other species, a high body mass is often associated with more aggressive behaviors. Larger body mass is also associated with greater reproductive success because these males are more dominant. Testosterone is not a contributor to aggression level in this gecko. More aggressive males not only had a larger body mass but also smaller, lighter testicles. Increased hormones levels of adrenaline and noradrenaline are more likely to be associated with higher aggression levels.^[24]

Mate searching behavior

As with many species, natural selection and sexual selection are working against one another in G. albogularis. For mating purposes, females typically prefer males who have brighter colors. However, some brighter colors make the males more prone to predation. Being inconspicuous gives males a greater chance of survival but significantly decreases the chance of finding a mate. Yellower males are an exception to this. Compared to red males, yellow males are more likely to outcompete other males and have a decreased risk of predation. The coloration is also a sign of dominance, so they have an advantage in both sexual and natural selection.^[25] In one experiment, the colors of the male lizards were masked using a light. When the colors were masked, females seemed to prefer blue males. This suggests that females prefer blue males, but the yellow males are much more dominant, so they are able to mate with females at a higher rate than their counterparts.^[23]

Predators

One predator of the yellow-headed gecko is the Brown Vinesnake, or Oxybelis aeneus. There have only been reports of the snake killing the lizard, and the act of consumption has not been observed. The Brown Vinesnake ambushes its prey with its enlarged rear fangs and moderate venom.^[26] Some of their other predators are larger lizards, birds, and mammals.^[19]

Parasites

G. albogularis is prone to parasitism by many species of Nematoda. Some of the species include Cosmocerca parva, Parapharyngodon scleratus, Physaloptera retusa, Skrjabinelazia galliardi, Spauligodon bonairensis, and Spauligodon oxkutzcabiensis. These parasites are classified as generalist helminths and typically found in the digestive tract (stomach and small and large intestines). The most prevalent ones are Skrjabinelazia galliardi and Spauligodon oxkutzcabiensis with S. oxkutzcabiensis having the most detrimental effects to the health of the lizard.^[27]

Escape behavior

To decrease the risk of predation, the yellow-headed gecko will lose its tail if a predator latches onto it. The escape behavior theory says that the lizard will lose its tail only when the risk of predation outweighs the cost of fleeing. Although this action provides defense from the initial attack, losing the tail does decrease the chance of survival if there is a subsequent attack. After an individual loses its tail, they will exhibit more escape behavior. They will not allow predators to get as close to them, because they do not have that extra layer of protection. As the tail grows back, the escape behavior tends to decrease, because the lizard is not as susceptible to predation, because they have more protection.^[28] The lizards will also stay closer to their shelter once they lose their tail to limit flight initiation distance.^[28][29] Flight initiation distance describes “the distance between a prey and an approaching predator when the prey starts to flee.” In both male and female yellow-headed geckos, flight initiation distance and distance to nearest refuge were positively correlated. As flight initiation time increased so did distance to the nearest refuge.^[29]

Temperature can also play a role in whether or not this lizard exhibits escape behavior. High temperatures are more likely to be associated with a lesser distance between the lizard and its predator. In high temperatures, the lizard has higher activity levels. By waiting for the predator to get as close as possible, energy expenditures will be limited thus increasing fitness.^[29]

Escape behaviors are also indicative of the female Yellow-headed gecko's gravidity. This phenomenon is often referred to as behavioral compensation, gravid females will change their behaviors in flight initiation distance and eloped distance to balance the costs and benefits of avoiding predators. Gravid females are heavier and move slower but have a higher flight initiation distance, distance fled and lower distance to refuge.^[30]

Ecology

Yellow-headed geckos feed on insects.^[13] They are mainly diurnal,^[2][11] although they avoid direct sunlight.^[11] A study in Panama found that they may lay eggs on a seasonal basis, laying more eggs during the rainy season.^[31] Only one egg is laid at a time.^[11]

Habitat

The species seems to prefer tropical dry forest, forest edges and anthropogenic habitats.^[31] In Haiti it is primarily found along the coast as an "edificarian" -this means it prefers human buildings as habitat.^[21] They can sometimes be found indoors.^[11] As a result, they are likely to enter areas with human activity and interact with humans.

Relationship to humans

Up until the 1950s the pega-pega was much feared in the Antilles, where the superstition formerly existed that once it climbed on you it would latch itself so tightly it would be almost impossible to remove, with the best remedies being burning it off with a lit cigarette, a hot clothes iron or by pouring boiling water over it. Some also claimed it was poisonous. This superstition had largely faded among the younger generation by the turn of the century.^[11]

See also

• Dwarf yellow-headed gecko
• Yellow-headed day gecko

References