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lunes, 26 de agosto de 2013

Not-So-Dangerous Snakes of Laguna Blanca

Paraguay has a very diverse range of snake species. The reason for this is because there is a wide variety of habitat types within its boundaries. Only a few of these snakes can be considered dangerous to man. Most of the time these fascinating creatures will avoid humans, but as our population increases and habitat destruction continues, more dangerous encounters occur. Fortunately protected havens can be found for these threatened reptiles. One of these havens is Reserva Natural Laguna Blanca. We have approximately 35 species recorded to date, and only 4 of these are considered dangerous to man. These are the Neotropical Rattlesnake (Crotalus durissus), Urutu Lancehead Viper (Rhinocerophis alternatus), Painted Lancehead Viper (Bothrops diporus) and Southern Coral Snake (Micrurus frontalis). There are a few mildly venomous species such as the “Racers” in the genus Philodryas that can give a nasty bite, but in general the symptoms are mild and medical attention is not required. The Green Anaconda (Eunectes murinus) has no venom, but can reach a very large size. Even though this could be considered a threat, these snakes are elusive and critically endangered within Paraguay. In the last few weeks we have encountered some of these fascinating creatures and I would like to share our experiences with you. Annie was on her way back to the station after an evening searching for bats in the transitional forest, when she came across a big snake on the path. She ran back to the station and woke me up. Ryan and I jumped out of our beds and were on our way to see if the snake was still in the area. Fortunately for us it was a chilly morning, and the snake was sluggish. We got to the site to see a massive female Rattlesnake slowly moving down the path. What an adrenaline rush. These beautiful Vipers are widespread in South America and can be found in a variety of habitat types. They have a lethal venom that effects the nervous system and the brain. They use this strong venom to immobilize their prey. Rattlesnakes and Lancehead Vipers from the Americas and certain species of Vipers from Asia, have pit sensors near the front of the head, and are commonly referred to as “Pit Vipers”. They are excellent ambush predators that use these sensors to distinguish their prey from other objects. A single rapid bite with their large fangs is all it takes to kill its victim. They don’t hold on to it because of potential injury that can be inflicted by the prey, so they release it and let the venom take effect. It doesn’t get far. The snake uses its strong sensory organ tongue to track down the dead rodent. Unfortunately human encounters with this snake are common, and because of their sluggish behaviour, they are often stood on. It was great to see such a large female in the reserve. Large snakes like this are rarely encountered because of human encroachment. After a few photographs we let her be on her way. A few days later I went for an evening walk to look for frogs near the seasonal pond. I decided to check a new trapline that we had recently installed. Success. An adult male Painted Lancehead Viper sat in one of the buckets. He could easily get out, but he sat there, probably waiting for an unlucky rodent to fall in. These snakes are common throughout the reserve and can be encountered crossing a pathway or just basking in the early morning. There has been a lot of discussion on what species of Bothrops occur in the area because of all the taxonomical changes of late. For now we have two species, the other being the Urutu Lancehead Viper which is restricted to wetland areas. Bothrops have a potent venom that is similar to the Rattlesnake, with the addition of a tissue destroying venom. These snakes are the cause of a lot of snake bites in South America. They are often found near human habitation because we provide the perfect components for their existence, food and shelter. Last week we were called to a local fishermen’s house as he had captured a large snake in his fishing net. We arrived in the hour to see a 2.1metre male Green Anaconda sitting at the bottom of a hole. My heart was racing. A life-long dream fulfilled. He was a gem, very calm and didn’t once attempt to bite. Anaconda’s are widely distributed in South America, and live in fresh water systems. They reach their southern most limits in the North-East of Paraguay, and are nationally threatened due to human degradation, pollution and over-fishing. These snakes have no venom and use their large size to constrict their prey. Females are much bigger than males, and have been recorded at over 6 metres in length. Their eyes are positioned towards the top of their head, instead of the side like most other snakes. This allows the Anaconda to be great ambush predator. They peer just above the surface of the water, waiting patiently for an unlucky victim to stray to close. On the reserve there is an abundance of prey items for our Anacondas, including fish, reptiles, birds and mammals. We were delighted to release this magnificent male into the lagoon to join our resident population, and hopefully we will see some juveniles in the near future. Check out the video on this little beaut. Fear is the main reason why snakes are seen in such a bad light. At the reserve we are teaching the local community to respect them and to try see them in a different way. I am confident that our hard work will pay off, so we can co-exist with these fascinating creatures long into the future. Visit our website below if you would like to help us track down rare and endangered creatures in this amazing part of the country. Until next time, JP

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