With the emancipation of the dinosaurs across the world in the 2018 sci-fi film Jurassic World: Fallen Kingdom, a big question of their co-existence with humans is raised at the end of the film. Well, in their sci-fi world, the sequel will provide the answer but, we humans have been co-existing with the dinosaurs’ relatives: the present-day reptiles for thousands of years.
Reptiles are a group of air-breathing vertebrates that have internal fertilization, amniotic development and epidermal scales covering all or part of their body. With 11,570 species (as of May2021) worldwide, and approx. 610 species in India , the living reptiles include turtles (order Testudines), tuatara (order Rhynchocephalia ), lizards and snakes (order Squamata) and crocodiles (order Crocodylia or Crocodilia).
What are the main features of reptiles?
Reptiles have external epidermal scales made up of the protein- keratin. They are ectotherms: animals whose main source of body heat comes from the environment and poikilotherms: animals whose body temperature vary rather than remain stable (the reason why crocs are seen basking in the sun), are sexually reproducing having internal fertilization. They generally lay eggs, except a few which give birth to live young ones (e.g., Snakes of the family Viperidae ) Asexual reproduction by parthenogenesis also occurs in some groups. (e.g. – Whiptail lizards of Teiid genus found in the Americas).
What type of reptiles are found in India?
- Turtles include terrestrial, marine and freshwater species, having a shell made up of a dorsal carapace and a ventral plastron. Teeth are absent in them having being replaced by a horny beak. (6) All turtles are oviparous, laying spherical eggs in nests made in the ground. Examples include the mass-nesting (arribada) of the Olive ridley sea turtles (Lepidochelys olivacea) on the beaches of Odisha and Maharashtra, Indian Flapshell Turtle (Lissemys punctata), Indian Star tortoise (Geochelone elegans) etc.
Snakes
With the absence of eyelids, limbs and external ear openings and an independently movable lower-jaw , snakes are a group of slithering reptiles having a wide distribution in India: from the seas to the snowline in the Himalayas. They have imbricated scales that form patterns characteristic of the species. Majority of them lay eggs with parental care seen in many instances (e.g.- Indian Cobra Naja naja) while many are ovoviviparous and give birth to young ones.
Many species have capacity to produce venom. The venom glands are specialized salivary organs and inoculation of venom is through grooved teeth (fangs). Snake venom is a mixture, chiefly of proteins varying in composition from species to species. E.g. – * Non- Venomous: Rock Python (Python molurus), Rat snake (Ptyas mucosus) etc. *Venemous: Kraits (Bungarus sp.), Russell ‘s viper (Daboia russelii) etc. However, it is generally difficult to differentiate between venomous and non venomous snakes.
Unfortunately, snakebite is one of the deadliest tropical diseases. In the last 20 years, over 1 million people have lost their lives to snakebite in India. Fortunately, numerous initiatives have been taken, such as the use of software, to mitigate this form of human wildlife conflict.
Lizards
With the presence of eyelids, lizards are mainly insectivorous, a few are herbivorous and some are carnivorous. The shape of the body is indicative of the habit of the species Except for a few ovo-viviparous forms, Indian lizards lay small clutches of eggs with calcareous, parchment-like or hard shells. None of Indian lizards are poisonous. E.g.- Tokay Gecko (Gekko gecko), Indian Chameleon (Chamaeleo zeylanicus) etc.
Crocodiles
Crocodiles belong to an ancient group of reptiles in existence for millions of years. Their senses of sight, smell and hearing are well developed. Crocodiles are excellent swimmers, their tail being the main propellant. They lay oval, hard-shelled eggs which are buried in the soil or in the nest of soil and vegetation for incubation. Three species are found in India- the iconic Gharial (Gavialis gangeticus), Saltwater crocodile (Crocodylus porosus) and Marsh Crocodile (Crocodylus palustris). In the late 20th Century, this taxa was on the verge of extinction in the subcontinent. However, some revolutionary conservation initiatives taken by former Prime Minister, Indira Gandhi, helped revived these ancient creatures.
The Ecological Importance of Reptiles
Any species present today on earth has an intrinsic importance in maintaining the ecosystem. It is one of the many threads that keeps the network of the ecosystem intact. Reptiles like lizards and snakes are important in controlling the insect and rodent population. Hence, there presence is crucial in agriculture. Cobras are known to be one of the best controllers of agricultural pests. Crocodiles are important in maintaining fish population numbers. Also, reptilian species like the Gharial act as a flagship species for the preservation of the Ganga river.
Primary Threats to Reptiles
- Since reptiles are sensitive to temperature variations, climate change induced warming is causing northward and and/or higher up in elevation shifts of their home ranges.(where the temperature gets cooler than their present home-ranges)
- Skewed sex Ratio- For many reptilian species, the sex of the individual at birth is determined by the temperature at which the eggs incubate. This is known as Temperature Dependent Sex determination. The warmer the sand, the higher the ratio of female turtles. In case of crocodiles, it is vice versa. However, increase in temperature is causing greater biased sex ratio towards one sex, thus, threatening the survival of the species.
- Habitat loss, fragmentation and modification- Reptiles are very sensitive to these factors. Loss in meta- population connectivity is detrimental to the survival of various species. Western Ghats which forms a hotspot of reptilian diversity is an example. Monoculture plantations, tea and coffee agriculture farms, industries etc. are causing a complete change in habitat, that is affecting reptiles amongst other taxa.
- Illegal wildlife trade- The hemi- penis of monitor lizard ( hatha- jodi) is unscientifically popularized as a medicine. The skin of crocodiles and snakes is used for making bags, purses etc. Reptiles like various species of testudines, chameleons etc. are illegally kept as pets. This is causing of a huge network of people to get involved in illegal extraction of these species from their natural habitats.
Reptile Conservation
- Awareness- One of the most essential factors in conservation is awareness – about the species, their role in the ecosystem and how without them the ecosystem will falter. Also, for snakes and lizards, it is important that people clear their misunderstandings and behave correctly on any chance encounter.
- Habitat preservation- Either through protected areas, community- owned conservation areas or even active stakeholder participation in private lands, preservation of natural habitat of species can help in co- existence of reptiles with humans.
- Ex- situ conservation measures- Proper scientific breeding programs and reintroduction into the wild for various reptilian species can help in population recovery.
- Research- Understanding natural history of species, description of new species, studying effects of habitat change on various species etc. forms a base for conservation planning of reptiles.
Written by Vaishnavi Apte.
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References
- Zug, George R. and Dowling, Herndon G. “reptile”. Encyclopedia Britannica, 11 Feb. 2021, https://www.britannica.com/animal/reptile. Accessed 4 October 2021.
- https://reptile-database.reptarium.cz/
- Kamdar, A., A, Jangid, P. Roy, and K. Kunte (eds.) 2021. Reptiles of India, v. 1.26. Indian Foundation for Butterflies. https://www.indianreptiles.org/
- Characteristics of Reptiles. 6 Mar. 2021, https://bio.libretexts.org/@go/page/13929.
- Laurie J. Vitt and Janalee P. Caldwell, Herpetology An Introductory Biology of Amphibians and Reptiles, Fourth Edition 2014, Elsevier Inc.
- R.L. Kotpal, Modern Textbook of Zoology Vertebrates (Animal Diversity-II), Fourth Edition 2017-2018, Rastogi Publication, Meerut
- J.C. Daniel, The Book of Indian Reptiles and Amphibians,2018, Bombay Natural History Society, Oxford University Press.
- NOAA, What causes a sea turtle to be born Male or Female? National Ocean Service website, What causes a sea turtle to be born male or female? (noaa.gov) ,03/01/21