Spiders are among the most common and numerous predators in terrestrial ecosystems. With more than 49,000 species, they exhibit extremely diverse lifestyles and foraging strategies. While spiders have long been thought to rely almost entirely on live insects or other small arthropods for their diets, studies in recent years have shown that spiders' feeding habits are much more diverse than previously thought.
There are always some "strange foods" in the natural recipes of spiders, which include invertebrates such as earthworms, veliform worms, slugs/snails, crayfish, freshwater crabs and other invertebrates.
There are also a variety of small vertebrates, including birds, bats, voles, shrews, lemurs, pygmy possums, fish, frogs, toads, lizards, salamanders, lungless salamanders and so on.
And in the vertebrate diet, the most unusual food,
I'm afraid it is— snakes.
Observations of spider-eating snakes have been reported around the world. Two researchers from Basel and the United States integrated and analyzed more than 300 reports on this unusual predation strategy.
A brown widow spider preys on the Brahmin blind snake B Moth spider preys on the Texas blind snake
Dr Martin Nyffeler, a spider scientist at the University of Basel, and Professor Whitfield Gibbons, an American herpetologist at the University of Georgia, delve into this phenomenon in a meta-analysis. Their findings on 319 times of this unusual eating behavior were published in the American Journal of Spiderbing.
It turns out that spiders have had snake-eating incidents on every continent except Antarctica.
80% of incidents occurred in the United States and Australia (probably more reported). In Europe, this spider foraging behavior is rarely observed – less than 1%) and is limited to small, non-venomous snakes of the small blind snake family Typhlopidae. In Switzerland, for example, there have never been any reports of spiders preying on snakes. One possible explanation is that even the largest Swiss spiders cannot subdue native Swiss salamanders and venomous snakes because they are so large and heavy that they are too difficult to deal with.
A non-widow spider preys on the southern ring-necked snake B Brown widow spider preys on juvenile eastern banded snakes
Black Widow was particularly successful
Data analysis showed that spiders from 11 different families were able to catch and eat snakes.
"With so many different species of spiders sometimes eating snakes, this is a completely new discovery," Nyffeler emphasizes.
Of about half of the observed events, Black Widow appears to be the most successful "snake hunter." Their potent venom contains a toxin specifically targeted at the nervous system of vertebrates. These spiders construct webs made of extremely tough silk, allowing them to catch larger prey such as lizards, frogs, mice, birds, and snakes.
A Black Widow Spider Preys on Two-Lined Snake B Black Widow Spider Preys on juvenile Scarlet King Snake
How？
Another new finding from the comprehensive analysis: Spiders can subdue snakes from seven different families. They can defeat snakes that are 10 to 30 times larger than them.
The largest snake caught by the spider is up to one meter long, and the smallest is only about six centimeters. According to a statistical analysis by the two researchers, the average length of the captured snake was 26 centimeters. Most of the snakes caught are very young newly hatched animals. Some spiders are able to subdue oversized prey thanks to their potent neurotoxins and strong, tough webs.
A black widow spider preys on a king snake larvae B Black widow spider preys on sub-adult coral snakes
Speculation about the effects of spider venom
Spider species that kill and eat snakes have venom and can be fatal to humans.
This means that the venom of various spider species has a similar effect on the nervous systems of snakes and humans. For this reason, observations of spiders that eat vertebrates are also important for neurobiology, as they can draw conclusions about the mechanism by which spider neurotoxins affect the nervous system of vertebrates.
"While the effects of black widow venom on the nervous system of snakes have been well studied, other species of spiders largely lack this knowledge." Therefore, more research is needed to find out which components of the venom specifically target the nervous system of vertebrates. The system is responsible for paralyzing the spider and killing the larger venomous snake," Martin Nyffeler said.
A Black Widow Spider Predates Juvenile Eastern Brown Iao Snake B A widow spider preys on the Cape Sahara viper
The captured snakes themselves are not necessarily "unarmed": about 30% are venomous snakes.
In the United States and South America, spiders sometimes kill highly venomous rattlesnakes and coral snakes. In Australia, the brown Eo snake is often prey to the red-backed spider (Australian black widow). Martin Nyffeler said: "This snake is one of the most venomous snakes in the world and it's really unusual to see them lose their battle with spiders. ”
A large round spider preys on the red-bellied snake B Golden web spider preys on the eyelash pit viper
Actually can't eat...
When a spider successfully catches a snake, it usually spends hours or days enjoying such a large prey
Spiders and snakes are very similar in that they both have irregular eating patterns. When there is a lot of food available, they will overeat and then starve for a long time afterwards. They store excess food in their bodies as an energy reserve and use it to survive longer periods of starvation.
Still, spiders usually eat only a small fraction of dead snakes. Scavengers (ants, wasps, flies, mold) will eat what's left
A Amazonian bird preys on spearhead pit viper larvae B Amazonian bird preys on coral snake larvae
No fuss
Spiders can prey on small snakes, and some snakes also prey on spiders. Everything is a law of nature and cannot be used to argue that "one side is stronger/more terrible". Demonized by certain film and television cultural works, snakes and spiders are often mistaken for powerful, evil top predators. In fact, "spider" and "snake" are just a general term for thousands of different creatures, they are large and small, strong and weak. Most of them are not as powerful as they are described in the documentary: the vast majority of snakes, and almost all spiders, are only in the middle and lower layers of the food chain, trying and struggling to survive.
A genus B predatory coarse-scaled spearhead viper larvae B Black fishing spider prey on the American burrowing snake
It seems to be a winner's spider, and it is not easy to win,
Every meal is done with all your might,
The snake that seems to be a loser never loses,
Because they never give up the desire to live.
- Martin Nyffeler, J. Whitfield Gibbons. Spiders (Arachnida: Araneae) feeding on snakes (Reptilia: Squamata). The Journal of Arachnology, 2021; 49 (1) DOI: 10.1636/JoA-S-20-050