User:Edickerson1/Yellow-headed gecko

Added to Distribution
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. [10]

Added to Description
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. [9] They reach this size around the age of 6 months. [10] 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. [8] 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. [10]

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. [9]

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. [10]

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. [1]

Male/male interactions
Males have many aggressive behaviors that are 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 were had 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. [11] These aggressive behaviors usually crest mid-day with high variability any other time of day. [13] 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. [14]

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. [13] 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. [13] [14]

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. [7] 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. [11]

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. [2] Some of their other predators are larger lizards, birds, and mammals. [10]

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. [3] The lizards will also stay closer to their shelter once they lose their tail to limit flight initiation distance. [3][4] 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. [4]

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. [5]

Parasites
G. albogularis is prone to 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. [6]