Jackson's chameleon (''Trioceros jacksonii''), also known commonly as Jackson's horned chameleon, the three-horned chameleon, and the Kikuyu three-horned chameleon, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of chameleon, a

lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Chamaeleonidae. The species is native to

East Africa East Africa, also known as Eastern Africa or the East of Africa, is a region at the eastern edge of the Africa, African continent, distinguished by its unique geographical, historical, and cultural landscape. Defined in varying scopes, the regi ...

, and introduced to

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

, and

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. Spawls S, Howell K, Drewes RC, Ashe J (2002). ''A Field Guide to the Reptiles and Amphibian of East Africa''. Academic Press. pp. 227–228. Global Invasive Species Database. (2010).
Chamaeleo jacksonii (reptile)
.'' Retrieved 16 November 2014.California Herps: A Guide to the Amphibians and Reptiles of California.

'' Retrieved 20 April 2017. There are three recognized

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

Taxonomy

Jackson's chameleon was described by Belgian- British

zoologist Zoology ( , ) is the scientific study of animals. Its studies include the structure, embryology, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems. Zoology is one ...

George Albert Boulenger George Albert Boulenger (19 October 1858 – 23 November 1937) was a Belgian-British zoologist who described and gave scientific names to over 2,000 new animal species, chiefly fish, reptiles, and amphibians. Boulenger was also an active botani ...

in 1896. (''Chamaeleon jacksonii'', new species).

Etymology

The generic name, '' Trioceros'', is derived from the Greek τρί- (''tri-'') meaning "three" and κέρας (''kéras'') meaning "horns". This is in reference to the three horns found on the heads of males. The specific name, ''jacksonii'', is a Latinized form of the last name of English

explorer Exploration is the process of exploring, an activity which has some Expectation (epistemic), expectation of Discovery (observation), discovery. Organised exploration is largely a human activity, but exploratory activity is common to most organis ...

and

ornithologist Ornithology, from Ancient Greek ὄρνις (''órnis''), meaning "bird", and -logy from λόγος (''lógos''), meaning "study", is a branch of zoology dedicated to the study of birds. Several aspects of ornithology differ from related discip ...

Frederick John Jackson, who was serving as the first

Governor of Kenya This article contains a list of chairmen, administrators, commissioners and governors of British Kenya Colony. The office of Governor of Kenya was replaced by the office of Governor-General in 1963 and then later replaced by a President of Kenya ...

at the time of Boulenger's description. The English word chameleon (also chamaeleon) derives from

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

''chamaeleō'', a borrowing of the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

χαμαιλέων (''khamailéōn''), a compound of χαμαί (''khamaí'') "low to the ground" and λέων (''léōn'') "lion". The Greek word is a

calque In linguistics, a calque () or loan translation is a word or phrase borrowed from another language by literal word-for-word or root-for-root translation. When used as a verb, "to calque" means to borrow a word or phrase from another language ...

translating the Akkadian ''nēš qaqqari'', "ground lion".

Subspecies

The following three

are recognized as being valid, including the

nominate subspecies In biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. ...

. * ''T. j. jacksonii'' – Jackson's chameleon * ''T. j. merumontanus'' – dwarf Jackson's chameleon * ''T. j. xantholophus'' – yellow-crested Jackson's chameleon ''

Nota bene ( ; plural: ) is the Latin language, Latin phrase meaning ''note well''. In manuscripts, ''nota bene'' is abbreviated in upper-case as NB and N.B., and in lower-case as n.b. and nb; the editorial usages of ''nota bene'' and ''notate bene'' fi ...

'': A trinomial authority in parentheses indicates that the subspecies was originally described in a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

other than''Trioceros''.

Habitat and geographic range

Jackson's chameleon is an arboreal lizard. It is native to woodlands and wet forests at altitudes of in south-central

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

and northern

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

.Waring GH (1996)
Preliminary Study of the Behavior and Ecology of Jackson's Chameleon of Maui, Hawaii.
' Southern Illinois University. Retrieved 11 November 2014. In these areas, the rainfall is seasonal but exceeds per year. Day temperatures are typically , and night temperatures are typically . In Tanzania, it is known only from Mount Meru in the

Arusha Region Arusha Region () is one of Tanzania's 31 administrative Regions of Tanzania, regions and is located in the northeast of the country. The region's capital and largest city is the city of Arusha. The region is bordered by Kajiado County and Narok C ...

, which is the home of the relatively small

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

subspecies ''T. j. merumontanus''. Jackson's chameleon is more widespread in Kenya, where it is even found in wooded areas of some

Nairobi Nairobi is the Capital city, capital and largest city of Kenya. The city lies in the south-central part of Kenya, at an elevation of . The name is derived from the Maasai language, Maasai phrase , which translates to 'place of cool waters', a ...

suburbs. The subspecies ''T. j. xantholophus'' (native to the

Mount Kenya Mount Kenya (Meru people, Meru: ''Kĩrĩmaara,'' Kikuyu people, Kikuyu: ''Kĩrĩnyaga'', Kamba language, Kamba: ''Ki nyaa'', Embu language, Embu: ''Kĩ nyaga'') is an extinct volcano in Kenya and the Highest mountain peaks of Africa, second-highe ...

region) was introduced to

in 1972 and has since established populations on all main islands and has become an

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

there.Holland BS, Montgomery SL, Costello V (2010). "A reptilian smoking gun: first record of invasive Jackson’s chameleon (''Chamaeleo jacksonii)'' predation on native Hawaiian species". '' Biodiversity and Conservation'' 19 (5): 1437–1441. .Chiaverano LM, Holland BS (2014). "Impact of an invasive predatory lizard on the endangered Hawaiian tree snail ''Achatinella mustelina'': a threat assessment". ''Endangered Species Research'' 24: 115–123. .Kraus F, Preston D (2012). "Diet of the invasive lizard ''Chamaeleo jacksonii'' (Squamata: Chamaeleonidae) at a wetforest site in Hawaii". ''

Pacific Science ''Pacific Science'' is a quarterly multidisciplinary peer-reviewed scientific journal covering the biological and physical sciences of the Pacific basin, focusing especially on biogeography, ecology, evolution, geology and volcanology, oceanograph ...

'' 66: 397–404
PDF
This subspecies has also been introduced to

. In Hawaii, it is found mainly at altitudes of in wet, shady places. Historically this population was the primary source of Jackson's chameleons for the exotic pet trade in the United States, but exports from Hawaii are now illegal. This has been done to prevent opportunists from willfully establishing further feral animal populations to capture and sell them.

Description

Jackson's chameleon is sometimes called the three-horned chameleon because males possess three brown horns: one on the nose (the rostral horn) and one above each superior orbital ridge above the eyes (preocular horns), somewhat reminiscent of the ceratopsid dinosaur genus ''

Triceratops ''Triceratops'' ( ; ) is a genus of Chasmosaurinae, chasmosaurine Ceratopsia, ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cretaceous Period (geology), period, about 68 to 66 million years ago on the island ...

''. The females generally have no horns, or instead have traces of the rostral horn (in the subspecies ''T. j. jacksonii'' and ''T. j. merumontanus''). The coloring is usually bright green, with some individual animals having traces of blue and yellow, but like all chameleons, it changes color quickly depending on mood, health, and temperature. Adult males reach a total length (including tail) of up to and females up to , but more typical lengths are . It has a saw-tooth shaped dorsal ridge and no gular crest. It attains sexual maturity after five months. The lifespan is variable, with males generally living longer than females. The largest subspecies of Jackson's chameleon is ''T. j. xantholophus'', which has been captively bred since the 1980s.

Ecology

Feeding habits

Jackson's chameleon lives primarily on a diet of small

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s. It also preys on

centipede Centipedes (from Neo-Latin , "hundred", and Latin , "foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', "lip", and Neo-Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, ...

isopod Isopoda is an Order (biology), order of crustaceans. Members of this group are called isopods and include both Aquatic animal, aquatic species and Terrestrial animal, terrestrial species such as woodlice. All have rigid, segmented exoskeletons ...

millipede Millipedes (originating from the Latin , "thousand", and , "foot") are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derive ...

spider Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...

s, small

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s, and

snail A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...

s (''Achatinella mustelina'') in their native habitat. It is considered to be a cruise forager, as it forages on the go instead of laying in wait. There is a threat of devastating impact by introduced invasive Jackson's chameleons to native ecosystems in Hawaii, South Africa, the Marshal Islands, Morro Bay, California, Texas, and the Florida Keys. It was found with mainly insects in its stomachs: planthoppers (genus '' Oliarus''), grasshoppers (genus '' Banza''), casebearing caterpillars (genus ''

Hyposmocoma ''Hyposmocoma'' is a genus of moths with more 350 species endemic to the Hawaiian Islands whose larvae are referred to by the common name of Hawaiian fancy case caterpillars. The genus was first described by Arthur Gardiner Butler in 1881. Most s ...

''), beetles (genus '' Oodemas''), dragonflies (genus '' Pantala'') and others. It also preys on land snails in Hawaii, including species from genera '' Achatinella'', '' Auriculella'', '' Lamellidea'', and '' Philonesia'', as well as '' Oxychilus alliarius''. It swallows whole snails, including the shells. Jackson's chameleons introduced to Hawaii are a substantial threat to native biodiversity of invertebrates and a serious threat especially to

endemic species Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

, such as critically endangered O'ahu tree snails (genus ''Achatinella'').

Territoriality

''T. jacksonii'' is less territorial than most species of chameleons. Males will generally assert dominance over each other through color displays and posturing in an attempt to secure mating rights, but usually not to the point of physical fights.

Reproduction

Most chameleons are

oviparous Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings kno ...

, but Jackson's chameleon and several other highland species in the genus '' Trioceros'' are

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a "bridging" form of reproduction between egg-laying oviparity, oviparous and live-bearing viviparity, viviparous reproduction. Ovoviviparous animals possess embryos that develo ...

, giving birth to offspring soon after they are ready to hatch from their egg sac; eight to thirty live young are born after a five- to six-month gestation. The subspecies ''T. j. merumontanus'' gives birth to five to ten live young.

In captivity

In captivity, Jackson's chameleon requires high humidity, and is in general very needy of colder temperatures during the night. Too much heat, or excessive humidity, can cause eye infections and upper respiratory infections in this species. In captivity, Jackson's chameleon can be expected to live between five and ten years. Jackson's chameleon requires an array of different food options to remain healthy.

References

External links

Jackson's Chameleon Care Information at Caresheets.net

''Chamaeleo jacksonii'' information from HEAR

(Dr. George H. Waring, Dept. of Zoology, Southern Illinois University) {{Authority control Trioceros Reptiles described in 1896 Taxa named by George Albert Boulenger Lizards of Africa Reptiles of Kenya Reptiles as pets Reptiles of Tanzania