A circulus is a rarely occurring reptilian social group where there is interaction and personal exchange between individuals. Members will often protect and defend young, even if not of direct genetic linkage. Circulus is a Latin based term; one definition of the word is "a social gathering or circle company". [1] Most reptiles are indifferent socially to each other as adults or to offspring.
Among crocodilians and certain lizards, there is a much greater interaction between members. Young will be guarded and defended for a considerable period of time. Crocodilians of both sexes carry and assist young hatchlings to the water and guard them. The gharial (Gavialis gangeticus) has to nudge young to the water because their teeth are too sharp to carry them. Sub-adult members of a crocodilian social group will often stand by a female laying eggs or retrieving young from a nest to keep predators away. The female Asian forest tortoise (Manouria emys) has been reported to guard a nest site for a short period after egg laying but this instinct is very short lived.
In stump-tailed skinks (Tiliqua rugosa) and Solomon Islands skinks (Corucia spp), long term bonding of pairs with each other and other members has been recorded. In the case of Corucia, orphaned young have been observed being adopted into the circulus.
The social bond and parental attention of reptiles appears equal in circulus containing egg-laying reptiles compared to those with live bearing reptiles. Another case of egg-laying lizards with a circulus is the red-eyed crocodile skink (Tribolonotus gracilis). The female will sit on the egg and guard the young. As in the case of Corucia, the young tend to stay close to the parents, especially, the mother who guards the neonate. The young skink will often climb on the abaxial area of the female or male for protection and security, just as in the case of the Solomon Islands skink ( Corucia zebrata ). [2]
Reptiles, in common parlance, are a group of tetrapods with an ectothermic ('cold-blooded') metabolism and amniotic development. Living reptiles comprise four orders: Testudines (turtles), Crocodilia (crocodilians), Squamata, and Rhynchocephalia. As of May 2023, about 12,000 living species of reptiles are listed in the Reptile Database. The study of the traditional reptile orders, customarily in combination with the study of modern amphibians, is called herpetology.
Crocodilia is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 94 million years ago in the Late Cretaceous period and are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria. Members of the order's total group, the clade Pseudosuchia, appeared about 250 million years ago in the Early Triassic period, and diversified during the Mesozoic era. The order Crocodilia includes the true crocodiles, the alligators and caimans, and the gharial and false gharial. Although the term 'crocodiles' is sometimes used to refer to all of these, crocodilians is a less ambiguous vernacular term for members of this group.
Skinks are lizards belonging to the family Scincidae, a family in the infraorder Scincomorpha. With more than 1,500 described species across 100 different taxonomic genera, the family Scincidae is one of the most diverse families of lizards. Skinks are characterized by their smaller legs in comparison to typical lizards and are found in different habitats except arctic and subarctic regions.
The Solomon Islands skink, also known as prehensile-tailed skink, monkey-tailed skink, giant skink, zebra skink, and monkey skink, is an arboreal species of skink endemic to the Solomon Islands archipelago. It is the largest known extant species of skink.
Egernia is a genus of skinks that occurs in Australia. These skinks are ecologically diverse omnivores that inhabit a wide range of habitats. However, in the loose delimitation the genus is not monophyletic but an evolutionary grade, as has long been suspected due to its lack of characteristic apomorphies.
The broad-headed skink or broadhead skink is species of lizard, endemic to the southeastern United States. The broadhead skink occurs in sympatry with the five-lined skink and Southeastern five-lined skink in forest of the Southeastern United States. All three species are phenotypically similar throughout much of their development and were considered a single species prior to the mid-1930s.
The American crocodile is a species of crocodilian found in the Neotropics. It is the most widespread of the four extant species of crocodiles from the Americas, with populations present from South Florida and the coasts of Mexico to as far south as Peru and Venezuela.
The gharial, also known as gavial or fish-eating crocodile, is a crocodilian in the family Gavialidae and among the longest of all living crocodilians. Mature females are 2.6 to 4.5 m long, and males 3 to 6 m. Adult males have a distinct boss at the end of the snout, which resembles an earthenware pot known as a ghara, hence the name "gharial". The gharial is well adapted to catching fish because of its long, narrow snout and 110 sharp, interlocking teeth.
The false gharial, also known by the names Malayan gharial,Sunda gharial and tomistoma is a freshwater crocodilian of the family Gavialidae native to Peninsular Malaysia, Borneo, Sumatra and Java. It is listed as Vulnerable on the IUCN Red List, as the global population is estimated at around 2,500 to 10,000 mature individuals.
The Orinoco crocodile is a critically endangered crocodile. Its population is very small, and they can only be found in the Orinoco river basin in Venezuela and Colombia. Extensively hunted for their skins in the 19th and 20th centuries, it is one of the most endangered species of crocodiles. It is a very large species of crocodilian; males have been reported up to 6.8 m in the past, weighing over 900 kg (2,000 lb), but such sizes do not exist today, 5.2 m being a more widely accepted maximum size. A large male today may attain 4.2 m in length and can weigh up to 450 kg (1,000 lb), while females are substantially smaller with the largest likely to weigh around 225 kg (496 lb). Sexual dimorphism is not as profound as in other crocodilian species. The coloration is light even in adults.
Tribolonotus gracilis, commonly known as the red-eyed crocodile skink, is a species of skink that is sometimes kept as an exotic pet. The species is endemic to New Guinea, where it lives in a tropical rainforest habitat. It was first described by Nelly de Rooij in 1909.
Plestiodon is a genus of lizards in the family Scincidae (skinks). The genus contains many species formerly classified under the genus Eumeces, except those now placed in Mesoscincus. They are secretive, agile animals with a cylindrical body covered with smooth, shiny scales. They are distributed from East Asia to throughout North America from southern Canada south to Mexico, including oceanic islands such as Bermuda.
The smooth-fronted caiman, also known as Schneider's dwarf caiman or Schneider's smooth-fronted caiman, is a crocodilian from South America, where it is native to the Amazon and Orinoco Basins. It is the second-smallest species of the family Alligatoridae, the smallest being Cuvier's dwarf caiman, also from tropical South America and in the same genus. An adult typically grows to around 1.2 to 1.6 m in length and weighs between 9 and 20 kg. Exceptionally large males can reach as much as 2.3 m (7.5 ft) in length and 36 kg (79 lb) in weight.
The Mauritian giant skink is a large, extinct species of skink It was found only in Mauritius. It became extinct around 1600, probably due to human-introduced predators.
The giant spiny skink or Poncelet's helmet skink is a species of lizard in the family Scincidae. The species is endemic to the Solomon Islands.
Oligosoma suteri, known commonly as Suter's skink, the black shore skink, the egg-laying skink, and Suter's ground skink, is a species of lizard in the family Scincidae. The species is endemic to New Zealand.
Saiphos equalis, commonly known as the yellow-bellied three-toed skink or simply three-toed skink, is a species of burrowing skink found in eastern Australia. It is the only species classified under the genus Saiphos.
Lankascincus dorsicatenatus, also known as the catenated lankaskink, is a species of skink, a lizard in the family Scincidae. The species is endemic to island of Sri Lanka.
Kaestlea is a genus of skinks. These skinks are small, shiny, smooth-scaled species. They are diurnal, terrestrial and insectivorous. They lay eggs to reproduce. These skinks are identified by their distinct blue tail colour. They live in tropical rainforest and montane forest habitats. These secretive skinks silently move through thick leaf-litter on forest floor. They are all endemic to the Western Ghats mountains and in some parts of Eastern Ghats (Shevaroys) of South India.