Field work was conducted in 1996 on 13 days of February and March, noting the behavior of free-ranging chameleons during daylight hours. In addition, interviews of local citizens were conducted to expand upon the field observations; the cooperation of these individuals was helpful and sincerely appreciated.
The Jackson's chameleon became popular in the international pet trade in the 1970's (Dodd 1982). They were shipped by the thousands from Kenya primarily by exporter Jonathan Leakey. Some (via a southern California reptile wholesaler) reached Oahu legally in 1972 under a pet store import permit and were sold. A second shipment was in poor condition; these chameleons were released to recover on the property of the Kaneohe pet store owner and subsequently became a free-ranging population. These founders have been the source of an expanding chameleon trade and distribution. Since 1984, virtually every wild-caught Jackson's chameleon for sale in the continental United States has been of Hawaiian origin (McKeown 1995). By the early 1980's, the species had reached Maui in the Makawao-Pukalani area and began to spread as a free-ranging population (Loope 1994). During the late 1980's and early 1990's it was illegal to keep Jackson's chameleons in Hawaii, but in 1994 that ruling was rescinded; it remains illegal to transport them between islands in Hawaii but not to ship them to the mainland. At present, chameleons exist as free-ranging populations on Oahu, Maui, Hawaii, and most recently Kauai. They are most abundant in areas where daytime temperatures range from 21-32 C (70-90 F), nighttime temperatures range from 10-20 C (50-68 F), and rainfall is moderate (McKeown 1995).
By the mid-1990's, Jackson's chameleons were evident to many Maui landowners from the Olinda Road at an elevation of about 823 m (2700 ft) (Melrose, pers. comm.) downslope to approximately the Hamakua and Wailoa Ditches. Disjunct populations also occur; for example, in the past two years a new population has become established in Kula along the Omaopio Road at the 700 m (2300 ft) elevation (Simmonds, pers. comm.). The Makawaolani population appeared to peak by the early to mid-1990's and by the start of this study had noticeably declined, perhaps due to a two-year drought that ended late in 1995; in the summer of 1995, numerous dead chameleons were found on the ground in the Maliko Gulch area as if a die-off were occurring (Janiga, pers. comm.). The Kula population continued to flourish during the same drought, perhaps because of the existence of an extensive sprinkler system at the site (Simmonds, pers. comm.). By April 1996, the population around Maliko Gulch began to show signs of recovery (Janiga, pers. comm.).
Until the paper by Eason et al. (1988), morphological variation within Chamaeleo jacksonii had troubled taxonomists since Boulenger's description of the species in 1896. Their recent paper distinguished a new subspecies and clarified the variation noted within the now extant three subspecies native to East Africa. Subsequently, McKeown (1991) reported the Jackson's chameleons in Hawaii are the newly described Mt. Kenya subspecies, C. j. xantholophus.
The Jackson's chameleon is a woodland/montane forest species that exists over a range of mid- to high elevations of central Kenya and isolated regions of Tanzania, often coexisting with humans on farms and suburban parks (Fergeson et al. 1991). The known natural range of the Mt. Kenya subspecies extends from Kagumo and Kerugoya on the southern side of Mount Kenya eastward and northward to Meru on the northeastern side of the mountain; sites ranging in elevation from 1830-2440 m (6000-8000 ft.). Where the East African populations of Jackson's chameleons live, rainfall exceeds 127 cm (50 in.) per year and is seasonal; daytime temperatures commonly range from 16-27 C (60-80 F), whereas the range is 4-18 C (40-65 F) at night (McKeown 1995). Lin (1980) found Jackson's chameleons on the average exhibit clear signs of heat stress when body temperature exceeds 33 C; some desiccation is tolerated but survival without replenishing body moisture rarely exceeds two weeks.
Within C. j. xantholophus, adult males are light emerald green with vaguely defined yellow along the throat, shoulders, flanks, and crest scales; the head is darker green or turquoise. Males have three brownish annulated horns, consisting of two preocular horns and one rostral (the latter being longest). Females in the Mt. Kenya subspecies typically have no horns or greatly reduced ones; their body color (and that of immature males) varies, ranging from gray to green to dark olive, often having light blotches on the darker background color (Eason et al. 1988). Males normally attain a length of 25-30 cm, females commonly 5 cm shorter (Fergeson et al. 1991). The tail accounts for about half of the animal's length; it is prehensile and often curled in a laterally-flattened coil as the chameleon is perched motionless. The limbs are long and adroit. Sets of toes are fused medially giving the appearance there are two opposable paddle-like toes on each foot; these grip the arboreal substrate steadfastly.
Jackson's chameleons subsist on small invertebrates (e.g., insects, spiders, and small snails) captured with their rapidly extensible tongue, which can extend up to 1.5 body lengths. The sticky tip of the tongue can reach the prey in 0.06 sec (Martin 1992). Juvenile chameleons attain sexual maturity at approximately two years (de Vosjoli 1990). The species is ovoviviparous; thus after mating, the female retains the eggs and subsequently gives birth approximately three months later to 12-40 precocial young. Melrose (pers. comm.) observed the birth of 13 young, each encased individually in a flexible sac; the infants freed themselves from the membranes. Postpartum parental care seems not to occur. Being an aseasonal breeder, a female may produce another brood as early as six months later (Lin and Nelson 1981). At birth, the young are 52-55 mm long, with the tail accounting for 23-25 mm of the length; they utilize their tongue to capture food from the day of birth. At the age of five months, juveniles reach a length of 8-10 cm (Schifter 1975).
In captivity (and presumably also in the wild), daily water must be provided in a way that resembles rain drops or dew on leaves. The chameleons will ingest the shiny droplets dangling from the leaftips but will rarely drink from a pool of water. Adults do well in daytime temperatures of 25-29 C (75-85 F), with nighttime temperatures considerably cooler (but still above freezing). Juveniles are unable to tolerate the temperature extremes adults can endure and therefore do best within a range of 16-27 C (60-80 F) (de Vosjoli 1990). Rearing young chameleons in captivity has been difficult for zoos and pet owners; for example, the 13 infants bred and delivered in captivity under the care of Melrose (pers. comm.) seemed to do well for the first couple of months but then suddenly died.
During the present study, a solitary lifestyle was typical of chameleons of all ages. Smaller individuals avoided larger ones. McKeown (1995) noted that adult males will challenge equal-sized adult males to a horn-to-horn pushing duel and thus attempt to drive away opponents; the weaker individual eventually retreats. During the present study, individual chameleons were often found in the same tree or shrub day after day; nevertheless, they remained apart. Immatures as well as immatures plus one adult coexisted in the same plant, but rarely did they get within 0.5 m of each other. One silk oak tree (7 m high) was routinely occupied by a large emerald-green female plus an even larger emerald-green male. From day to day they changed locations within the tree, but both adults tended to space themselves >2 m apart.
Other than a slight hue change or general lightening of the overall color as the individual's body temperature increased, color patterns were not noted to change much from hour to hour or day to day. Each individual retained its own somewhat unique color pattern from one occasion to the next. This pattern plus other morphological features as well as behavioral traits allowed me to readily identify individual chameleons from one day to the next. Emerald-green individuals were always that color as were the charcoal, brown-gray, and gray-green individuals. Furthermore, blotchy and non-blotchy individuals tended to always be so. The horns of males varied between individuals; the size, general shape, and curvature varied.
Foraging occurred throughout the daylight hours, but only the eyes revealed the intent of the predator. The Jackson's chameleons were truly sit-and-wait (ambush) predators on moving invertebrates, opportunistically taking flying and crawling insects and spiders as their primary diet. While chameleons remained nearly motionless, their prey came within range. Initially the motion of prey was detected with one of the turret-like eyes that constantly searched the environment; each eye rotated independently of the other. When potential prey was located by one of the eyes, the head and forequarters of the chameleon turned and oriented toward the prey; at this time the second eye also oriented on the prey and the body sometimes extended to shorten the strike distance. If the distance was too great for a strike, the chameleon then moved toward the prey using its slow limb movements, adjusting up, down, right, or left. The chameleons seemingly tried to close the strike distance to approximately the length of their own body. The tip of the prehensile tail often acted as an anchor on a branch to steady the chameleon as it stretched toward the prey; some or all of the feet also maintained contact with branches. If a strike was imminent, the mouth opened slightly and the sticky tip of the tongue protruded, e.g., about 5-10 mm. Once the distance and aim were correct, the tongue suddenly elongated >10 cm, extending to make contact with the prey. Moisture on the tip of the tongue apparently caused the prey to adhere to the tongue. Immediately the tongue and prey were retrieved and lower jaw motion (chewing) occurred until the prey was swallowed. With large prey, several jaw movements seemed to be necessary to subdue or break the prey for swallowing. After swallowing, a brief series of additional movements of the jaw, mouth, and tongue (as if making final comfort adjustments) concluded the feeding sequence.
Under normal arboreal circumstances, the diet of chameleons commonly varies from one feeding bout to the next. I found prey size varied from tiny prey, like fruit flies, to large items, such as wasps. Melrose (pers. comm.) found locusts and katydids were usually rejected by his pet chameleons, crickets were not. Motion always seems necessary to attract the attention of hungry chameleons, thus inactive invertebrates, such as a spider motionless on a web, were ignored until they moved. Eason (1990) demonstrated the Senegalese chameleon (C. senegalensis) will only take a limited number of the same item, preferring instead a mix of prey species. The same may be true of Jackson's chameleons; in captivity they will ingest 4-7 small orthopterans then refuse more (Melrose, pers. comm.); whether such chameleons reach their capacity or merely tire (satiate) of the same prey is not clear. Drinking was not exhibited during my field observations.
When free-ranging chameleons were observed during the course of this study, they commonly had their body oriented in such a way as to gather solar radiation, especially in the morning hours. They exposed either the right or left side to the direct rays of the sun, often tilting the body to gain maximum lateral exposure. Even the tail was placed on the sunny side of the branch and curled to gain maximum solar radiation. Some chameleons stood horizontally on branches, others were found in a near vertical position on drooping branches, either with head up or down. When the tail was not coiled to one side of the branch, it was extended and in contact with the length of the branch. If the individual was settled to stay, the legs were flexed and the body's ventral surface was in contact with the branch; occasionally a hind limb would dangle in space. If the chameleon was about to change locations, the legs were extended holding the body well off the substrate; the neck and head were elevated above the body axis.
People who frequent the Makawao area occasionally see Jackson's chameleons on the ground or crossing roads during damp, nighttime conditions. The slow rocking locomotion is reported for these animals. Road kills certainly occur. Because sightings of chameleons on the ground are usually on rainy nights, it suggests such conditions are conducive to, if not a stimulus for, chameleon dispersal movements. Chameleons on the ground at other times are less common, but can be due to disturbances or other factors. Marshall Loope (pers. comm.) once observed a chameleon on the ground in daylight foraging on flies attracted to a pile of cattle dung.
Ground movements may also accomplish mating opportunities. Nothing is known about reproduction in the wild. Melrose (pers. comm.) observed what he interpreted to be courtship in his captive pair; one or both chameleons circled the other, jerking the head to one side then walking forward before jerking and walking again in the rocking pattern.
I noted young chameleons, and those not frequently exposed to humans, reacted to people by retreating whenever someone stood within 1 m of them. They became alert and slowly but steadily moved to more secluded parts of the plant. In the extreme of fear, Ferguson (1991) found Jackson's chameleons dropped to the ground; there they remained motionless, hidden in the grasses or leaf litter.
During nighttime and apparently in strong wind as well as harsh weather, Jackson's chameleons remain firmly attached to a branch in the same tree or shrub used during daylight hours. They shift to favorable locations within the plant as needs occur for shelter, foraging, rest, or thermoregulation. Their environmental and physiological needs must be met within their resident plant, for chameleons do not often change to a new plant. To do so imposes considerable risk. Therefore, food and water must occur regularly wherever they reside.
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Janiga, Jerry. 1996 interview. Owner of Maliko Farms, 460 Kaluanui Rd., Makawao, HI
Lin, J.-Y. 1980. Desiccation tolerance and thermal maxima in the lizards Chamaeleo jacksoni and C. hohneli. Copeia 1980:363-366.
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Loope, L. 1994. Preliminary notes on the Jackson's chameleon. Unpublished file report. NBS Research Laboratory, Haleakala National Park, Makawao, HI.
Loope, Marshall. 1996 interview. Maui resident who has field experience with chameleons.
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McKeown, S. 1995. Jackson's chameleons (Chamaeleo jacksonii): natural history, captive management, and breeding. Pg. 33-60 in P. de Vosjoli & G. Ferguson (eds.), Care and Breeding of Panther, Jackson's, Veiled and Parson's Chameleons, Advanced Vivarium Systems, Santee, CA.
Melrose, David. 1996 interview. Maui resident and teacher who reared chameleons.
Schifter, H. 1975. Family: Chamaeleonidae. Pg. 227-241, Vol. 6, in B. Grzimek (ed.), Grzimek's Animal Life Encyclopedia, Van Nostrand Reinhold, New York, NY.
Simmonds, Brook. 1996 interview. Maui resident who has successfully reared chameleons.