In this science blog we investigate the two principal ways in which snakes kill their prey which include poisoning and ‘constricting’. We also confront Homer Simpson’s negative attitude about snakes.This article follows on from Evolution-from Lizards to Snakes
Every year on May 11th the citizens of Springfield hold a snake ‘whacking day’ when rattlesnakes are hunted down and killed with sticks.
In preparation for this annual event Homer Simpson practices his whacking skills.
He even buys a shiny new ‘whacking stick’….
…much to the disgust of Lisa who pleads with Homer not to join this barbaric event. Homer does not listen to Lisa’s pleas.
On May 11th the people of Springfield, in a carnival atmosphere, meet up in the Town Square. The people listen to the town choir singing the ‘whacking day’ song.
The Beauty Queen declares the event ‘open’ and invites the people of Springfield to start ‘whacking.’
Banging their ‘whacking sticks’ on saucepan lids, the citizens set off in pursuit of Springfield’s rattle snakes.
Terrified, the snakes slither in the opposite direction and jump over a man sitting on a park bench.
Bart and Lisa Simpson are horrified at the prospect of this needless slaughter. Can they save the snakes? To be continued….!!!
Let’s educate Homer about snakes!
1) Snakes only attack when they are hungry or feel threatened
When Homer is hungry he can buy food from his local supermarket. When snakes feel hungry they have to catch their own food.
All snakes are carnivorous and only eat meat; there are no vegetarian snakes!
If you don’t want to be a tasty ‘snake snack’ don’t get too close! If you do get too close snakes might think you are a predator and attack you.
It’s common sense!
Gaboon vipers from West Africa have among the longest fangs of any venomous snake and can look quite scary.
Gaboon vipers wait silently on the forest floor to ambush their prey. The truth is that they are very timid and shy snakes; they do not seek to bite passing mammals that they are not intent on eating.
In fact, they are sometimes killed after being accidentally trodden on by leopards, hippos and elephants ( and even humans!)
Gaboon vipers can wait…wait.. wait…for several weeks before they have the opportunity to bite and inject venom into passing prey; this prey may include birds, rats, rabbits, monkeys, porcupines and small antelope. They can go several weeks without a meal because they have such low metabolism; as they wait to ambush a passing animal they expend very little energy.
Lying camouflaged in wait for prey to ambush is safer than slithering around in search of prey. If they did slither around in search of prey they might be heard and their intended prey could easily escape.
Ambushing as a way of catching prey also means that Gaboon vipers can kill prey than can move faster than they can.
2) Other strategies snakes use to stay alive
The Black Mamba from Southern Africa, one of the fastest of all snakes, uses its lightening speed to escape predators. Black mamba predators include eagles and badgers.
It is one of the most feared, venomous and aggressive of all snakes but it will still try to escape if it hears humans approaching.
The venomous, marine Yellow Lipped Sea krait has developed an ingenious way of not being eaten. When this snake forages for food its head is often hidden inside holes and crevices of coral reefs.
With its head hidden it leaves its long body and tail very exposed; it has no means of defending itself and is vulnerable to attack by sharks and snake eating fish.
The Yellow Lipped Sea krait has evolved an ingenious solution to make it less vulnerable to attack as it forages.
Its has evolved a tail that resembles its head. (Sharks can see the similarities even if the similarities are less obvious to us humans!)
Passing sharks avoid attacking the snake because they fear a venomous bite! Two heads are better than one!
The venomous Spectacled Cobra from India rises up and displays a spectacled hood when it feels threatened.
This display tricks predators into thinking that the snake is much bigger than it really is; this strategy often deters predators from attacking.
Stay away! I’m bigger than you are!
When threatened the Cuban Dwarf Boa Constrictor releases an incredibly smelly white slime from its anus.
It is able to burst tiny blood vessels (capillaries) in its eyes and mouth which results in its eyes and mouth turning red. This behavior is called ‘auto haemorrhaging.’
As the snake wriggles around, blood becomes smeared all over its body. Finally the snake coils into a tight ball with its head completely hidden.
This behavior gives predators the impression that the snake is somehow sick and diseased and would not make a good meal.
If you were a predator you would not wish to make yourself ill by eating a diseased snake, would you!?
(After photos were taken by the scientist this snake was released unharmed.)
3) Snakes perform a vital role in any eco system
Many species depend on snakes for food and in some eco systems snakes themselves are top predators.
Image a world without snakes! Where would we be? Plagued with rats?
4) Snakes protect bird eggs
Strange but sometimes true! Snakes not only eat bird eggs but also indirectly protect the eggs of some species.
Great Crested Flycatchers…..
…actively look for shed snake skins with which to line their nests.
Any nest lined with snake skins would smell disgusting to some animals. However the smell to us humans is barely detectable.
Like all birds Great Crested Flycatchers have no sense of smell; it is believed that Great Crested Flycatchers line their nests with snake skin to deter flying squirrels….
…. from entering their nests and stealing their eggs.
Flying squirrels are themselves are prey for rattlesnakes; flying squirrels avoid the smell of rattlesnake and so steer clear of any bird’s nest lined with shed skins.
4) Snake venom helps save lives!
Scientists are using snake venom to help find better drugs for treating heart disease, strokes, Alzheimer’s disease and cancer. Strange but true!
Snake venom is a form of modified saliva. Is Homer Simpson’s saliva venomous!?
The following diagram summarizes the symptoms people can suffer after being bitten by a venomous snake.
Snakes have been slithering on our planet for a l-o-o-o-o-n-g time; more than 120 000 000 years to be precise!
In contrast Homo sapiens, the species to which Homer Simpson thinks he belongs, has only been around for 195 000 years.
Show more respect to snakes, Homer!
We now develop Homer’s understanding of the main differences between venomous and constricting snakes.
The ability to produce venomous saliva evolved 200 million years ago in common ancestors of snakes and lizards. These common ancestors were able to produce venomous saliva in their mouths which could enter victims’ blood after they were bitten.
Distant cousins of snakes are alive today which still kill their prey using venomous saliva. These distant cousins include Mexican beaded lizards with those impressive beads on their bodies….
Pittsburgh Zoo, Pennsylvania, USA
….. and Komodo Dragons.
Cincinnati Zoo, Ohio, USA
The Komodo Dragon bites its prey and then tracks the wounded creature using its sense of smell. It will then wait for its prey to die before eating it. Using venom to kill prey gives a Kimodo Dragon the remarkable ability to kill far larger mammals.
Sophisticated fangs. as found in vipers and cobras, evolved 80 million years ago.
Early vipers and cobras evolved rear fangs with grooves along which venom could flow. Over millions of years these rear fangs moved forwards from the back to the front of snakes’ mouths. These front fangs eventually evolved into hollow teeth through which snakes could pump venom….
…just like a hypodermic syringe injects liquid medicines.
Spitting cobras inject their prey with poisonous venom but when they feel threatened they will blind any predator by spitting venom into its eyes.
Snake venom contains a mixture of up to 100 different poisons, depending on the species. If snake venom only contained one or two poisons it would be easier for any prey to evolve resistance to being bitten. There are few organisms that have developed resistance to snake venom.
One such organism that has developed resistance to snake venom is the King Cobra!
Constrictors, which include boas and pythons, branched off from their venomous cousins 80 million years ago.
Constrictor’s teeth point backwards and have no venom-injecting front fangs.
Using lightening fast speed, a constrictor will grab hold of its prey using its teeth; backwards facing teeth means that it is more difficult for any prey to struggle free.
Having taken hold of its prey, a constrictor will wrap its body around its prey and will squeeze (‘constrict’) until its prey can no longer breathe. It will then swallow the animal whole.
It’s a bit gruesome showing a constrictor snake squeezing another animal so instead we see one constricting a tree !
With the citizens of Springfield chasing after the rattlesnakes Lisa and Bart happen to see Barry White walking past their house. They persuade the famous singer with the deep voice to sing outside their house. The snakes are attracted by Barry White’s singing….
They all slither into the Simpsons’ house to escape the approaching mob.
After all the snakes have entered his house Bart shuts the door leaving the angry mob waiting outside. Bart tells the mob about the origins of the 11th May ‘Whacking Day’ event.
He explains how the event originated in 1922 as an excuse to beat up Irish people; somehow beating up the Irish changed over the years to whacking snakes instead.
Bart’s explanation was verified by an old Irishman who said,”Tis true, I took many a lump, but ’twas all in fun!”
In light of Bart’s explanation the mob changed its mind and decided not to whack any more snakes. They allowed all the snakes to leave the Simpson’s house unharmed and they all slithered off into the sunset.
Interesting science fair projects could include: