Crocodile - Kurokodairu (English spelling) crocodile

A general term for crocodiles belonging to the order Crocodylia, family Crocodylidae, class Reptilia. This family Crocodylidae includes large species with rough dispositions. They are found in freshwater lakes and rivers in subtropical and tropical Africa (except for the northern part), tropical Asia, New Guinea, northern Australia, and America, and some swim into the sea and reach Melanesia. Crocodiles are distinguished from the family Alligatoridae by the difference in the arrangement of their teeth, but there are exceptions to both, and their most distinctive feature is the presence of small depressions called follicles at the rear of each scale on the ventral surface. Generally, their snouts are long and slender with a pointed tip, but the snouts of the marsh crocodile Crocodylus palustris and the pygmy crocodile Osteolaemus tetraspis are short and wide. Many of the species are large, measuring 4 to 5 meters in length, including the American crocodile C. acutus , found in tropical America from the southern Florida peninsula, the saltwater crocodile C. porosus , found in tropical Asia and Oceania, and the Nile crocodile C. niloticus , found throughout Africa except for northern Africa and on the island of Madagascar, which can reach a maximum length of 6 to 7 meters. On the other hand, the pygmy crocodile found in West Africa is less than 2 meters in length at most and is docile in nature. Crocodylidae is divided into three subfamily Gavialinae (three genera and three species), which have extremely long snouts, and the other two subfamily Crocodylinae (13 species), which includes the genus Gavialis , which was once a separate family. Crocodylidae are nocturnal and have aggressive behaviors, but the saltwater crocodiles and Nile crocodiles are particularly dangerous to humans, while the latter is not considered to be so dangerous in some areas. Their food consists of mammals such as water buffalo and antelope, fish, amphibians, etc. Females dig burrows in the sand on the riverbank to lay their eggs, and many of them protect the eggs after laying.

[Takahiro Matsui]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

爬虫(はちゅう)綱ワニ目クロコダイル科に属するワニの総称。この科Crocodylidaeは、性質の荒い大形種を含む。北部を除くアフリカ、熱帯アジア、ニューギニア島、オーストラリア北部およびアメリカの亜熱帯、熱帯の湖沼や河川の淡水に分布し、一部は海に泳ぎ出てメラネシアに及んでいる。クロコダイルは歯並びの相違でアリゲーター科と分けられるが、両者に例外もみられ、腹面の各鱗板(りんばん)の後部に、濾胞(ろほう)という小さなくぼみがあるのが最大の特徴である。一般に吻部(ふんぶ)が細長くて先端がとがるが、ヌマワニCrocodylus palustrisやコビトワニOsteolaemus tetraspisでは吻部が短く幅広い。全長4～5メートルの大形種が多く、とくにフロリダ半島南部から熱帯アメリカに分布するアメリカワニC. acutus、熱帯アジアからオセアニアに分布するイリエワニC. porosus、北部を除くアフリカ全域、マダガスカル島に分布するナイルワニC. niloticusは最大6～7メートルに達する。他方、西アフリカ産のコビトワニは全長が最大でも2メートル足らずで、性質もおとなしい。クロコダイル科は下あごの関節骨形状の違いから、吻部のきわめて長いガビアル亜科3属3種と、そのほかの2属13種を含むクロコダイル亜科とに分けられ、前者にはかつて別科に分けられていたガビアル属Gavialisも含まれる。夜行性で、性質の荒い種が多いが、人にとってとくに危険なのはイリエワニとナイルワニで、後者は地域によってはそれほど危険視されていない。餌(えさ)はスイギュウやカモシカなどの哺乳類(ほにゅうるい)、魚類、両生類などである。雌が川岸の砂地に巣穴を掘って産卵し、産卵後は卵を守るものが多い。

［松井孝爾］

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