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Reptiles Prof. M. Srinivasan and Dr. S. Bragadeeswaran Centre of Advanced Study in Marine Biology Annamalai University eptiles are cold blooded vertebrates, which breath by lungs. They have originated before seven crore years ago. There are four orders under this group, which includes crocodilians (Crocodiles), Testudines (Turtle, Tortoises), Squamata (Lizards and Snakes) and Rhyncocephalia (with a single species known as Tuatera, Sphenodon punctuatus, found only in New Zealand). All reptiles are carnivorous except green turtle and green iguana. Reptiles are a most important group of predators, the interaction of which maintains the natural balance in the forests and deserts, rivers and lakes and the plains and hills. R The biodiversity of reptiles found in mangrove ecosystems has received less attention. Reptiles also play a major role in the food chain of mangrove ecosystems. Twenty five species of reptiles were reported from Southeast Asian countries mangroves, while 39 reptiles were reported by Kathiresan and Rajendran (2000) from east coast of India. Reptiles including crocodiles, alligators, lizards, snakes and turtles live in many mangroves. About 35 reptiles species are known from the Sundarbans of Bangladesh alone. The most notable ones are saltwater crocodiles (Crocodylus porous), Monitor lizards (Varanus bengalennis) V. solvator, V. glarasceus, King cobra (Ophiophagus hannah), Green fit vipers (Vipera trimeresurus), Rock pythous (Phythus molonus) and olive Ridly turtles (Lepidochelys olivacea) (Hussaian and Acharya, 1994). The fauna in mangroves is starting with zooplankton, benthos, shrimps, crabs, mollucs, finfishes, birds, reptiles, amphibians and mammals. Crocodiles keep the environment clean by eating dead and decayed meat. Turtles check the growth of water weeds. Lizards and snakes feeds on insects including pest species. Reptiles including crocodiles, alligators, lizards, snakes and turtles that live in many mangrove systems are mostly rare and endangered. Therefore, identification of reptiles and study of reptiles is need of the hour, so that conservation plan can be executed. 439 Reptiles
Collection and Preservation Sea snakes can be collected which are entangled from the gillnets and other fishing nets which are operated in mangrove and adjacent areas. These specimens are brought to the laboratory and washed with water and are injected with 10 % formalin through anal opening for small size up to 30 cm total length. For larger specimen incisions are made with a knife and preserved in formalin. Dead turtles washed ashore, can be collected and identified. Fourteen species of reptiles including crocodiles, turtles, lizard and snakes inhabiting mangroves are given in Table 1. Table 1. List of reptiles commonly reported from mangroves S. No. Reptilia Crocodilia 1 Crocodylus palustris 2 C. porosus Chelonia (Turtles) 3 Chelonia mydas 4 Lepidochelys olivacea Democheylidae 5 Demochelys coriacea Varanidae (Lizards) 6 Varanus sp. 7 Calotes varsicolar 8 Chameleon sp. Squamata – Ophidia (Snakes) Boidae 9 Python molurus Laticaudinae 10 11 12 Laticuda laticauda Columbridae Cereberus rhynchops Acrochordus granulatus Elopidaea 13 Naja naja 14 Ophiphagus hannah M. Srinivasan and S. Bragadeeswaran 440
Identification Techniques Crocodiles The body is covered with a rough hide like skin, underlined by bony plates. The elongated snout terminates in a rather bulbous nose with the nostrils positioned on top so as to enable the crocodiles to breathe without difficultly when the body is submerged. The eyes, which are also placed high on the head, are well protected by the eyelids and a movable transparent membrane so that the vision is not affected under water. The throat is provided with a fleshy valve that would permit the crocodiles under water to pursue the prey, without the risk of drowning. The tail is highly muscular and propels the reptile through water easily. The colouration of the adults is rather dull, but the young ones are brightly coloured, with dark brown spots or bars on the back. The three species of crocodiles found in India are mugger (Crocodylus palustris), the salt water or estuarine crocodile (Crocodylus porosus), and the gharial or gavial (Gavialis gangeticus). Easy identification of gharial, mugger and salt waters crocodiles can be made with the shape of head and jaws (Fig.1) Fig. 1. The three crocodilians found in India may be easily identified: the gharial (right) has the thinnest jaws. The mugger (middle) has the broadest. The saltwater crocodile (left) has a longer snout than the mugger and no large scales behind its head 441 Reptiles
Family : Crocodillidae Salt Water Crocodile Crocodylus porosus Schneider The estuarine crocodiles are recognized by longer muzzle and two prominent ridges running forward from the eyes and converging on the nose. The colour is dark olive green or brown or almost black above, and lemon yellow on the underside. The eye is yellow. It is really known to reach a length of 7 meters, although most specimens today are under 4.30 metres. This crocodile species is a truly seagoing reptile, which prefers mangrove swamps, deltas, estuaries and coasts as its habitats. It principally feeds upon fish and crustaceans, but also takes birds and mammals. The female lays from 40 to 60 eggs and buries them in to a mounded‐type nest. Incubations lasts from 75 to 90 days. Marsh Crocodile Crocodylus palustris Lesson Crocod ylus palustris is short and is devoid of any ridges. A square of four shields on the nape with four distinct scales between the large shield and the broad head are the most obvious features. The colour is olive or pale, with prominent dark spots in young, and black in adults. It may reach a length of 4 meters, but most specimens are under 3.25 meters. Although the species is called “Marsh Crocodile”, it is by no means restricted to marsh lands, but is also found in rivers, lakes and man‐made reservoirs, ponds or tanks. It is reported even from the Himalayan foothills and the salt lakes adjacent to estuarine area. Its principal food includes fish, frogs and crustaceans but occasionally turtles, birds and mammals. Turtles The varied usage of the words “turtle” and “tortoise” in English has given use to much confusion. In proper usage, tortoise refers to the strictly land dwellers with elephant like stubly feet, “turtles” are the aquatic forms inhabiting the sea, rivers and ponds with either flippers or webbed toes and “terrapins” are the hard shelled edible freshwater tortoise. Turtles are toothless but they have a beak with horney sheaths. They chew their food only to reduce in for swallowing. They are omnivorous, and like other reptiles, can survive without food for months. All turtles nest on land. Their maximum life span is 100 years or a little more but it is certain that they live longer than any other vertebrates including man. They vary greatly in size, from 72 cm to the 1.8 m long. Five kinds of exclusively sea living turtles, 22 species of M. Srinivasan and S. Bragadeeswaran 442
aquatic turtles and / or tortoise, and 4 varieties of land tortoise are found in India. Key to Genera of Turtle (Fig. 2) 1a. Horny scutes on carapace imbricated (overlapping in all except in all very old specimens‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐Eretmochelys 1b. Horny scutes on carapace juxtaposed (not imbricated) 2a. Four pairs of lateral (coastal) scutes on carapace; edge of lower jaw coarsely toothed; a single pair of prefrontal scutes; a single pair of claws on flippers‐‐‐‐‐‐‐‐‐ Chelonia 2b. Five or more pairs of lateral (coastal) scutes on carapace; 2 claws on each flipper 3a. Four pairs of inframarginal scutes on the bridge of the plastron, each with a small perforation or pore toward their hind margin; carapace semicircular‐‐‐‐‐‐‐Lepidochelys 3b. Three pairs of enlarged inframarginal scutes without pores on the bridge of the plastron; carapace heart‐shaped‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
Caretta. Keys followed by FAO (1984). Family : Dermochelidae Horny skin smooth, scute; carapace black with 7 narrow longitudinal ridge, white dotted plastron with 5 longitudinal ridge; upper jaw with a well‐defined cusp on each side, giving the horny beak a ‘W’‐ shaped appearance when viewed from the front; large flipper without claws, the anterior pair much bigger, the posterior broadly connected with the tail by a web in adults. 443 Reptiles
Dermochelys coriacea Body is depressed and covered by a smooth leathery skin lacking lamellae or scute. Head is small, ending in a horny beak with a well defined cusp at each side of upper jaw and a central cusp on lower jaw (beak ‘W’‐shaped when viewed from the front). Seven longitudinal ridges (including the outer or lateral pair) are on carapace and 5 on plastron. Flipper is very large, without claws. Upper side is dark brown to almost black; whitish spots on neck, increasing in number on the ventral and caudal areas. Egg are white, spherical, normally about 5.5 M. Srinivasan and S. Bragadeeswaran 444
cm in diameter and 75g in weight; the proportion of unfertilized small eggs may often be high. Family : Cheloniidae Shell, head and flippers were covered with horny lamellae (scutes); horny beak never ‘W’‐ shaped when viewed from the front; flippers with 1 or 2 claws. Chelonia mydas Agassizii Carapace oval, depressed, its width about 88% of the total length. Head small (about 20% of carapace length), with a single pair of prefrontal scutes; edge of lower jaw coarsely toothed, that of upper jaw with strong ridges on inner surface. Four pairs of lateral scutes on carapace, anterior pairs not touching the precentral scute; 4 pairs of inframarginal scutes on plastron; a single claws on each side. Upper side dark olive brown or black, scutes of carapace shiny with radiating yellow, green and black spots; underside pale grey or whitish. Eggs are white, spherical, about 4.5 cm in diameter, and 38 g in weight. It is interesting to note these turtles browse the leaves of Avicennia and the fruits of mangroves. Lepidochelys olivacea Carapace semicircular in outline, depressed, its width‐about 90% of the length. Head small (about 22%of carapace length) with 2 pairs of prefrontal scutes and a horny beak which may be finely serrated. Usually more than 5 pairs (sometime even 7) of lateral scutes on carapace, anterior pair touching the precentral scutes; 4 pairs of inframarginal scutes, each perforated by a pore towards its hind margin; adults with only one visible claw on each flipper. Upper side is olive brown; underside yellowish white. Eggs are white, spherical, about 3.9 cm in diameter and 33g in weight. Lizards Lizards are classified as sub‐order Sauria of the class reptilia. Lizards are characterized by a short body with four well‐developed limbs, a short, flat tongue and an external ear opening. Some limbless lizards which have elongated bodies are snake‐like in appearance but they can be identified by their distinctive ear openings and movable eyelids, which are quite foreign to the prey and also as sensory organs. The ability to shed the tail and regenerate a new one in its place is possessed by geckos, lizards and snakes. Most of the lizards can change colour, 445 Reptiles
depending on the light, temperature and the mood of animal. Males are larger and brilliantly coloured than females. Lizards principally feeds on insects and small animals. Indian lizards range from a 5 cm long sting to 2.5m long water monitor (Varanus salvator). There are no venomous lizards in India. Most commonly available lizards were Varanus, Chameleon and Calotes. Calotes are easily identified by colouration, while Chameleon with green colour and change its colour according to the environment. Tail end is always coiled. Varanus can be identified with the brown colour on the dorsal side and arranged bands. Varanus Varanus sp. was reported from the mangroves of east coast of India (Kathiresan and Rajendran, 2000). The name of “Monitor” bestowed upon these creatures has a curious origin, owing to a ridiculous etymological mistake. The Arabic term for lizard is “Ouaran”. This has been wrongly taken to mean warning lizard, hence the Latin word‐Monitor. One of the many synonymous of this genus varanus are Hydrosuarus and Psammosarus. Many of the “Monitors” are semi‐aquatic, and others inhabit dry, sandy areas, while others are in well‐wooded localities. They are rapacious, taking whatever animals they can master according to their size, which in some species amounts to 6 to 7 feet. Calotes varsicolar Calotes varsicolar has been reported from the mangroves of east coast of India (Kathiresan and Rajendran, 2000). Lizard is so familiar to most of us. It has a prominent crest on its back. The usual colouration is dull brown or grey above. During the breeding season, males show bright red colour in throat and neck often is mistaken as blood sucker for the harmless reptile. It attains a total length of 500mm, and 350mm of width of tail. It feeds on insets, spider and small frogs. A female lays eggs 10‐30 and buries in grounds. Chameleon Chameleons are arboreal lizards that live in the forest area, especially scrub jungles. They are distinctive groups because of their picer‐like feet, evaginated tongue, and remarkable powers for camouflage and mimicry. Only one species occurs in India. The tongue of the animal is longer than body. Its colour changes according to light, intensity, M. Srinivasan and S. Bragadeeswaran 446
temperature or mood of the animal. It feeds on insects. Female lays 12 to 30 eggs below the ground. Snakes Snakes, as a major group of reptiles, live on and below the ground, in trees and in fresh and salt waters. All snakes hunt and eat live animals. Out of 240 species of snakes in India, only 52 species are venomous in nature. From the mangrove environment, Kathiresan and Rajendran (2000) has reported 14 species of snakes, which include both terrestrial and aquatic snakes. Of which, important and frequently occurring snakes are described here. Snakes (Serpentes or Ophidian) are the second suborder of the order‐squamata of the class Reptilia. The body is elongated and covered with scales. The tail is proportionately short. The external limbs are absent although the vestiges of pelvis and hind limbs are found in the primitive snakes such as Boas and Pythons. Snakes have immovable eyelids, forked tongues and the absence of external ears. Snakes can be identified with the help of the key characters given by Smith (1935, 1943) and Murthy (1977, 1992, 1995; Murthy and Rama Rao, 1988) (Fig. 3 & 3a). Fig. 3. Snake head shield terminology ag., anterior genials (or chain shields); f., frontal; in., internasal; l., loreal; la., supralabial; la., infralabial; m., mental (or symphysial); n., nasal; p., parietal; pf., prefrontal; pg., posterior genials (or chin shields); pro., preocular; pso., presubocular; po., postocular; r., rostral; so., supraocular; t., anterior and posterior temporals; v., first ventral. 447 Reptiles
Fig. 3a. Different types of scales pattern in snakes A. Enlarged vertebral scales (8 represent keel); B. Normal scales; C. Oblique scales Hydrophidae Genus : Enhydrina Enhydrina schistosa (Beaked Sea snake) (Fig. 4) The oar‐shaped tail distinguishes this and other sea snakes, the well marked furrow on the chin and rostral projection well below the lip elongate, robust, sub cylindrical fore body. Compressed posteriorly. Head large, snout short, bowed in profile. Eye with dull green iris. Neck hardly apparent. There are 40‐50 scales rows on the neck, 42‐48 bands are counted from head to tail. The young are grey or bluish grey above whitish below, with dark grey or black annuli broadest dorsally, and these markings usually disappear in the adult, the back side being a uniform greyish colour. M. Srinivasan and S. Bragadeeswaran 448
Fig. 4. Beaked sea snake Enhydrina schistose figure shows the end of the snout extends beyond the lower jaw and looks like a beak of a bird) Subfamily : Laticaudinae (Egg laying sea snake) Genus : Laticuada Head shield entire, nostril lateral; nasals separated by the internasal, scales imbricate in 19‐25 rows, ventral large at least half as broad as the body. Body sub cylindrical, of equal diameter throughout. An amphibious, egg laying species of sea snake. Laticauda laticauda This is a light to dark bluish snake, with black bands above and yellowish below. The head is black with a curved yellow mark on the top. It attains a total length of 1.8 metres. This sea snake is partly terrestrial and partly aquatic. It is found in rocks along the shore, or in mangrove swamps, often far away from the coast. It is primitive hydrophid which is oviparous. It is mostly nocturnal in its habits, but is some times seen foraging among reefs during the day. The potentially venomous snake is mild in disposition, attempting to bite rarely. Family : Columbridae Genus : Acrochordus Species : Granulatus Acrochordus (chersydrus) granulatus (Popular name: Wrat snake) Strictly aquatic snakes, showing many of specializations seen in hydrophidae. Nostrils dorsal, scales on top of head small and granular, point of chin with projection fitting into deep notch in upper jaw, body skin loose, scales juxtaposed and tuberculate, no ventrals, tail short, round. These snakes inhabit in the both fresh and salt waters. The family contains in a single genus ‐ Acrochordus (Chersydus), including two species. Dark grey to black above, with white cross bars many of which become confluent near the mid body and disappear. Head flat, not distinct from neck, small, covered with granular and tuberculated 449 Reptiles
(triangular) scales 8 to 11 scales on a line between eyes; a series of enlarged scales on the lips separated from the border of the mouth by smaller scales, about 100 scales round the middle of the body 60‐63 black bands are present on the body and well defined nostrils are present on the head. Family : Columbridae Cereberus rhynchops (Popular name: Dog‐ faced water snake, Estuarine snake) Head small, scarcely distinct from neck, eye small, with vertically elliptic pupil. Lower jaw prominent, which gives the snakes face the appearance of a dogface. Snake’s body is stout, cylindrical, with strongly keeled scales in 23‐25 rows. (Murthy and Rama Rao, 1988). Tail short, tapering and slightly compressed. Maximum total length ‐ 1m. Grey, brown, olive or blackish above, with more or less distinct black spots or cross and greenish or yellowish below, with lack bars or spots. Non‐
poisonous snake and feeds voraciously. This snake is often caught in the gillnet operation in Pichavaram mangrove forests (Srinivasan and Bragadeeswaran, 2000). King Cobra Ophiophagus hannah The King cobra, is the most dangerous snakes in existence. It feeds on other snakes (Ophio‐snake, phagus‐eating). The great size – 5.4 metres is the important recognition feature. The king cobra is a slender, graceful serpent with a narrow head. Although it is a member of the cobra family, it has many uncobra like features. It cannot spread its hood as wide as the common cobra nor does it rear in any desired pose. But the sight when it rears nearly 1 metre high and stands motionless, staring fixedly as if in a scene surveying act cannot be easily forgotten. There is none of the nervous swaying or marked arching of the neck as in the cobra. The king cobra is an olive green snake with indistinct lighter cross bars across the back. The skin is beautiful velvety. The throat is yellow or orange. The young are black with conspicuous chevrons down the back. Adults in India range from 3 to 5 metres in length. The king cobra is reported from in Sundarbans and Andaman mangroves. Indian Python Python molurus This familiar snake is found in the marshes, mangrove, gallery forests, and around the west rocky areas near the lakes. It has two distinct colour phases. The more common form (Python molurus molurus) is the rock python which is greyish or yellowish‐brown in colour, with a M. Srinivasan and S. Bragadeeswaran 450
dorsal series of large reddish brown or black or black‐edged patches and spear like mark on the head and the stockier sub species is the dark Indian python (Python molurus bivittatus) which is cream coloured with pink markings and found in Assam. The tail is short and prehensile. The Indian python feeds on mammals of all kinds‐birds, reptiles and large sized frogs. The female lays eggs 20 to 40, and coiled around 60 to 90 days until the eggs hatch. Naja naja naja It is called as common cobra. This is the famous ‘spectacled or binocellate cobra’ which is named after the design of the spectacle like marings on the hood. The eyes are black with recard pupils. Adults attain a maximum length of 2 meters. It is found throughout India and Sri Lanka. The hood of this cobra is definitely narrower than the other cobras and is free of any pattern. The young are tan of buff, with regular crossbars, whereas the adults are uniformly brownish or blackish, with traces of broad dark cross bars. The underside is pale yellowish or white. Its venom is neuro toxin. Comparison with Other Environments Crocodiles In mangrove area, the reptiles like amphibians are occurring in different environments such as forest, land, water etc. Crocodiles are widely distributed in Asia, Africa, Madagascar, Australia, Papua New Guinea and in North and South America. At present the estuarine crocodile is confined within India to parts of the east coast of mainland and the Andaman and Nicobar Islands. It is recorded outside India mainly from the coasts of Sri Lanka, Burma, Malaya and Indo‐China through the Malay Archipelago to the Philippines, Northern Australia, New Guinea and Solomon Islands. The marsh crocodile is widely distributed in India although populations are fragmented and isolated. Its area of occurrence outside India includes Iran, Pakistan, Nepal, Bangladesh and Sri Lanka. Indo‐
pacific crocodiles Crocodylus porosus are abundant in the upper mangroves of the Kias river, Sabah, Malaysia. Small numbers are found in the Sundarbans where it has been depleted by hunting. In Orissa a population of 35 adults is found in the Bhitarkanika wild life sanctuary (Bustard and Choudhury, 1981). Populations are depleted in Andaman islands between 170 and 330. The population in the Nicobar is reported to be healthy but no precise data are available (Choudhury and 451 Reptiles
Bustard,1979). The Nicobar may be its last stronghold in India (Bagla and Menon, 1989). Breeding programmes are operated through the West Bengal Forest Department; the Orissa State Forest Department; and the Madras Crocodile Bank. Hatchlings are released in Bhtarkanika; in the project Tiger Reserve (Sundarbans); and in the Coringa Wildlife Sanctuary (Luxmoore et al., 1985). There is an urgent need for habitat protection and the species has received some protection in the Mahanadi Delta (Scott, 1989). Turtle Chelonia mydas exists throughout southward areas to 25o, especially around islands in the Mozambique Channel, Gulf of Oman, the ‘Gulf’ and the Gulf of Aden. Other subspecies of green turtle are found in the Atlantic and in the eastern and Central Pacific oceans. The main nesting areas are located on the islands of Mauritus, Europe, Aldaba, Comoro and Seychelles. The most important nesting areas are found on the coasts of Pakistan and slightly south of the west Indian borders; other important nesting beaches exist in northern Mozambique and on the southwest coast of Madagascar. The major nesting beaches for this species are outside the area, on the northeast coast of India, Orissa district. Lepidochelys olivaceae is most common turtle in India and the main population occurs in the Bay of Bengal. About 3 lakhs nest in Orissa, which have two important sights in the north east as Gahirmatha within the Bhitarkanika wildlife sanctuary and Nadiakhia Muhana and Akasa muhana. Mass nesting at Gahirmatha occurs annually, mainly around Ekkula where a total of 5 lakhs have been estimated to nest. Small numbers nest at any size elsewhere around the coast including the Gulf of Kutch, Sourastra, Peninsular, Gulf of Khambhat, Piraton island, and along the entire east coast, including near Madras and eastward area of Vedaranayam swamp, the Krishna delta, Sundarbans, Kanak island, Bakha beach, Lothian mechua syamarysayal and on the Andaman, and Nicobar and Lakhadweep islands Dermochelys coriacea is the least abundant sea turtle; it is present from Natal to the Tanzanian border, on Oman and the “Gulf” and on the southwest coast of India and Sri Lanka. Predominantly pelagic and highly migratory ones are usually found in the open sea, but approaching the land seasonally. The most important nesting beaches are found on the eastern part of the Malayan peninsula (Trengganu). M. Srinivasan and S. Bragadeeswaran 452
Snakes Snakes like Enhydrina schistosa (Beaked sea snake) are occasionally found in mangorve areas adjoining seas. Similarly Laticauda columbrine is found in mangrove areas for laying eggs. This is the only sea snake which lays eggs on the shore. Acrochordus granulatus (Estuarine snake or wrat snake) and Cereberus rhynchops (Dog face snake) are found in estuarine area, which is also found from mangrove forest. Python sp. Naja sp. and Ophiophagus live in terrestrial habitats and also in mangroves. Python molurus, the Indian python, considered vulnerable by IUCN is known from the Sundarbans (Scott, 1989). This species is widely distributed throughout the country and is threatened by habitat loss and the skin trade. Information on coastal distribution and the status of coastal populations is unavailable. Some 20 species of sea snakes have been recorded in India, most of which are common, but all are poorly known (Whitraker, 1985b). Elsewhere these reptiles are subject to extensive mortality as by catch in the prawn trawl industry but the extent of such impacts on Indian populations is not known. Factors Affecting Biodiversity A great number of reptiles are slowly disappearing mainly due to the human interference with rapid growth of industrialization and land exploitation. Snakes and crocodile are hunted for skin as a leather, some time for meat. Turtles are hunted for meat and eggs. Similarly Varanus are killed for meat. Turtle breeding beaches have also been threatened by sand quarrying, egg poaching and pollution. Wild life Act (1972) banned the hunting of reptiles. Murthy (1992) discussed in detail the reptiles of India and has given a list of threatened species as given is presented in Table 2. Table 2. Some threatened Reptiles in India Group Crocodiles Lizards Snakes Family Crocodyliae Cheloniidae Varanidae Boidae Colubridae Species Crocodylus palutris Chelonia mydas, Lepidochelys olivacea Varanus salvator salvator, Varanus bengalensis bengalensis, Varanus flevescens Cereberus rhynchops, Python mourus 453 Reptiles
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Srinivasan, M. and Bragadeeswaran, S. (2000). Seasnakes of Parangipettai coast. Monograph, CAS in Marine Biology, Annamalai University, 1‐19. Whitaker, R. (1985b). Rational use of estuarine and Marine reptiles. In: Proceeding of symposium of Endangered Marine Animals and Marine parks. Cochin, 12‐16 January. Marine Biological Society of India, 1(24). Writaker, R and Daniel, J.C. (1978). The status of Asian Crocodilians. Tiger paper, FAO, Bangkok, 5(4) : 12‐17.