A circulus is a rarely occurring
reptilian social group
In the social sciences, a social group can be defined as two or more people who interact with one another, share similar characteristics, and collectively have a sense of unity. Regardless, social groups come in a myriad of sizes and varieties ...
where there is interaction and personal exchange between individuals. Members will often protect and defend young, even if not of direct
genetic linkage
Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction. Two genetic markers that are physically near to each other are unlikely to be separ ...
. ''Circulus'' is a
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...
based term; one definition of the word is "a social gathering or circle company".
[Andrews,E.A; 1875. ''Latin-English Lexicon.'' Harper & Brothers publishers, 329 & 331 Pearl Street, Franklin Square, New York, U.S.A. 1663 pp.]
Most reptiles are indifferent socially to each other as adults or to offspring.
Behaviours
Among
crocodilian
Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...
s and certain
lizard
Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia al ...
s, there is a much greater interaction between members. Young will be guarded and defended for a considerable period of time.
Crocodilian
Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...
s of both sexes carry and assist young
hatchling
In oviparous biology, a hatchling is a newly hatched fish, amphibian, reptile, or bird. A group of mammals called monotremes lay eggs, and their young are hatchlings as well.
Fish
Fish hatchlings generally do not receive parental care, similar ...
s to the water and guard them. The
gharial
The gharial (''Gavialis gangeticus''), 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 long, and males . Adult males have a distinct ...
(''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 skink
The Solomon Islands skink (''Corucia zebrata''), 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 lar ...
s (''Corucia spp''), long term
bonding of pairs with each other and other members has been recorded. In the case of Corucia,
orphan
An orphan (from the el, ορφανός, orphanós) is a child whose parents have died.
In common usage, only a child who has lost both parents due to death is called an orphan. When referring to animals, only the mother's condition is usuall ...
ed young have been observed being adopted into the circulus.
The social bond and parental attention of reptiles appears equal in circulus containing
egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
-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'', 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 ...
(''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