Veiled chameleon
The veiled chameleon is a species of chameleon native to the Arabian Peninsula in Yemen and Saudi Arabia. Other common names include cone-head chameleon, Yemen chameleon, and Yemeni chameleon. They are born pastel green and without their distinctive casques on their head. When newly hatched veiled chameleons are surprised, they may drop to the ground and turn a bright red color due to stress.
As they mature, their casque develops along with more vibrant coloring, as well as a dramatic gular fold that will protrude from their throat and chin. They are known for their variable color changes due to a variety of factors, including to show aggression, social status, reproduction, and stress. Female lifespan is around five years while male lifespan is around eight, and they breed a few times a year.
Etymology
The term 'veiled chameleon' refers to the species Chamaeleo calyptratus. 'Veiled' describes their distinctive casque on the head, resembling a veil. This term highlights the species' unique feature. The generic term 'chameleon' is derived from the Greek 'χαμαιλέων', a compound of 'χαμαί', meaning 'low to the ground' and 'λέων', meaning 'lion', emphasizing the specie's nature as akin to a miniature lion, highlighting its dignified and perhaps majestic demeanor, much like a lion in miniature form, staying close to the ground. The species name 'calyptratus' comes from the Greek 'καλύπτρα', meaning 'veil' or 'cover', referring to the distinctive casque or veil-like structure on their head. This casque not only serves as a significant physical characteristic but also plays a practical role in channeling dew and rainwater towards the mouth for hydration.Description
The male is long from the snout to the tip of the tail. The female is shorter, no more than about, but it has a thicker body. Both sexes have a casque on the head which grows larger as the chameleon matures, reaching about in the largest adults. Newly hatched offspring are born pastel green in color and develop stripes and different colors as they mature. Adult females are green with white, orange, yellow, or tan mottling. Adult males are brighter with more defined bands of yellow or blue and some mottling.Coloration can be affected by several factors, including social status. In experimental conditions, young veiled chameleons reared in isolation developed to be darker and duller in color compared to those raised with other individuals. Females change color over the course of their reproductive cycles. Chameleons also tend to change to a much darker color when stressed.
Subspecies
- Chamaeleo calyptratus calyptratus A.M.C. Duméril & A.H.A. Duméril, 1851 – veiled chameleon
- Chamaeleo calyptratus calcarifer W. Peters, 1871 – short-casqued chameleon
Habitat and distribution
This chameleon lives in a number of habitat types in its native range, including plateaus, mountains, and valleys. Like most other chameleons, it is arboreal, living in trees and other large plants. It prefers warmer temperature, generally between.
Diet
The veiled chameleon is primarily insectivorous. Like other chameleons, the veiled chameleon has the ability to capture large prey but their diets mainly consist of small prey. Green insects seem to be a favorite. However, it is one of several chameleon species also known to consume plants, such as vegetables and fruits. This is believed to perhaps be used as a source of water during the dry season.Behavior
Reproduction and life cycle
Veiled chameleons reach sexual maturity at four to five months and breed multiple times in a year. The female lays large clutches of up to 85 white, tough eggs and buries them in sand. The embryos experience a diapause, a length of time when they are dormant in the egg before they begin developing, increasing temperatures in the substrate initiate development.A 2004 study found that the embryonic development of chameleons usually initiates at fertilization and continues until hatching, but sometimes development stunts at the gastrula stage for months after the eggs have been laid. The researchers involved discovered that moisture levels have little to do with this delay, but that temperature plays a determinant role in development time; an increase in ambient temperature initiates development of diapausing embryos.
Juvenile chameleons can grow up to two orders of magnitude in body mass within a year of hatching. The feeding mechanisms all grow rapidly while still needing to be functional. Thus, the musculoskeletal system of the feeding mechanisms grow with negative allometry relative to snout-vent length. Studies on captured veiled chameleons showed that velocity of jaw movement tends to be greater in adults than juveniles. Thus in the development phase between adult and juvenile, there is a change in energy storage and tongue projection release mechanisms.
It was found that unlike many other reptiles, the sex ratios of the veiled chameleon are not affected by incubation temperature. Even with differential mortality as a factor, the sex ratio bias is negligible. Anecdotal suggestions of temperature-dependent sex ratios in the veiled chameleon were accrued from reporting and statistical errors.
Veiled chameleons have a naturally short lifespan, so even with good care, they may only live 6-8 years. Males typically live longer than females.
Protective coloration
For color changing species such as the veiled chameleon, signaling is important between animals to prevent needless energy expended on attacking competition. Stable and nonaggressive states come with a static coloration and will have a dynamic change when that state is altered. Veiled chameleons will typically brighten their coloring before approaching a rival as a signal of aggression. They will also maximize their stripe brightness for as long as possible to signal the strength of their bite. The longer and brighter the stripe lasts correlates to a stronger bite. This may aid in deterring disproportionately weaker or stronger chameleons from challenging. In this way, both contestants will save time, risk, and energy by not challenging an asymmetrical rival. It is likely that such color changing behavior serves as an evolutionary stable strategy to mutually benefit individuals by preventing unnecessary escalation. Brighter and more yellow stripes are also a signal of increased aggression.While brighter strip coloring typically correlates to more willingness to approach an opponent, brighter head coloring signifies a higher tendency to win fights. Rapidity of color change is also telling of the success of a confrontational outcome. Veiled chameleons are one of the first species to undergo color changing studies focused on speed rather than just intensity of the color. Male veiled chameleons tend to engage in vehement intra-sexual aggressive behavior. Before engaging, males will typically engage the color change laterally from a distance to maximize the opportunity to assess the coloration. When males engage with one another, they tend to begin the confrontation head to head which offers a clear view of the vivid head color change.
All chameleons can engage in color change through a lattice of guanine nanocrystals embedded in a superficially thick layer of dermal iridophores. Veiled chameleons specifically exhibit two superposed layers of iridophores. The two layer structure may allow veiled chameleons to camouflage as well as relay behavioral signaling and may also provide thermal protection.
Mating
Males display for females during courtship, performing behaviors such as "head rolls" and "chin rubs". Females change color when they are receptive to breeding, and males are more likely to court them during this time.Females are receptive to mating when pale-blue spots appear on their dorsums. They undergo constant clutch cycles that correlate with their hormonal reproductive status.
Male courtship involves exhibiting bright colors, lateral body flattening, body swaying, and tail curling. Males will approach the females and nudge them with their chin while vibrating from an internal origin during contact. The female will then mount the male and the male uses tarsal spurs to caress the female's flank. Copulation can last anywhere from a few minutes to an hour and can occur several times per day. When copulation is successful, females will darken their green coloration and the intensity of their yellow patterns will increase. If a female is not receptive to the male, her body will turn dark brown to black with white or yellow mottled markings. She may also become aggressive or violent and bite the male if he continues to advance unwanted.
Parental care
After mating in captivity, a female chameleon will decrease feeding three to four weeks and will spend more time at the bottom of the cage searching for an appropriate egg-laying site. Tunnels will typically reach to the bottom of the container and will be covered with substrate debris after oviposition is completed. Females may dig another tunnel and lay more eggs after about a week. Females should be given easy access between higher sites in the cage and their tunnels via a branch or something similar.In captivity, eggs should be retrieved then placed into tupperware with a 1:1 ratio mix of vermiculite and water to a depth of about 1-1.5 inches with the eggs buried lengthwise and half covered. Eggs may absorb moisture and expand so they should be placed 0.5 to 1 inches apart from each other. Embryos have been shown to start development sooner when subjected to higher temperatures while degree of moisture showed no significant impact. Eggs should be incubated at 26 to 30 degrees Celsius at a humidity of 95%. Neonates should be allowed at least one day to roam their container before moving. Neonate nurseries should consist of a ten gallon screen top aquarium with a base one third to one half filled with decorative artificial plants. Two to six hatchlings should be raised together for the first few months then moved to adult enclosures with increased amounts of vegetation once they reach four to six inches. They can be placed individually from each other once they reach four to six months old.