#I didn't even get into the various times venom has evolved

[c-is-for-circinate]

Hey! I can help with this.

First: holy shit yeah no that might be a vague rule of thumb for snake bites but I would NOT count on it as diagnostic. Coral snakes are weird, rattlers (and others) don't always inject venom when they bite, and a lot of snakes have mild toxins in their saliva that won't do much more than irritate a human unless there's allergies involved. Also just for personal experience I have for sure been bit by a corn snake and because of the angle it was two pinpricks, so yeah. You're much better off looking for signs of swelling, redness, or (this is very bad!) blackening around the wound, and snake bite treatment is its own whole thing that you should be learning from a dedicated source if you're in a rural area where you expect it to happen. If you're expecting venomous snakes to be an issue where you live, it's also worth checking up on the symptoms of those specific local snake venoms, because neurotoxin vs hemotoxic vs necrotic venom can have pretty different effects and need very different treatments. (I am NOT enough of an expert to teach you those, please find a real one.)

In terms of evolutionary pressure: yes there's a drawback to developing venom! Venom is biochemically expensive to make, requiring a lot of proteins and energy. It's also way less useful than you'd think! Constrictor snakes are just fine at catching prey, generally, since a quick strike to grab and then suffocating your prey via squeeze is pretty effective all by itself. Hell, depending on diet venom may not even make sense: a snake that specializes in eating eggs isn't going to have much use for it; a snake that specializes in earthworms or snails doesn't need a venom that's good against mammals; very large snakes like anaconda would need huge amounts of venom to take down prey of appropriate size; and a king snake that specializes in eating other snakes then also has to have digestive immunity to a venom that directly targets species very similar to itself (which some do! but that's an additional expense).

The biochemical expense is also why many venomous snakes, including common domestic US venomous snakes like rattlers, can often choose whether to inject venom or not! A quick confirmatory Google scholar check suggests that we still don't know for sure why some species are more prone to "dry" (unvenomated) bites than others. There's evidence that defensive bites can carry either more venom (because predators are usually quite large and need far more venom to take down) or less venom (because the snake is not going to get a meal to replenish its energy) than feeding bites. Not seeing a paper on it right now from my 30-second 2am google, but I've been told by at least a couple of herpetologists that bites from baby rattlesnakes are actually more likely to be dangerous because they haven't learned to moderate their venom injection yet!

Anyway, snakes are much like spiders: some bites are barely noticeable, some can be deadly, and quite a few can fall in a middle zone of 'irritating, and could probably kill a mouse, but won't do too much damage to something as big as a human'. For example, the common Northern water snake is not venomous, but it's got a mildly hemotoxic saliva that makes their bites a little more annoyingly painful than your standard rat snake.

Anyway that was an overly long 3am infodump on snake venom that barely scratches the surface, but in my defense I have a masters degree in frog evolution that I literally never get to use these days and I miss herpetology. It's super interesting stuff!

hey can any snake special interest havers on this website tell me why all snakes dont have venom? is there some sort of hidden evolutionary cost to producing a magic liquid that does the work of killing stuff for you? because much like carnivorous plants that sounds pretty awesome and suspiciously devoid of possible drawbacks for the creature on paper.

this question comes courtesy of my emt textbook saying that all (wild) venomous snakes in the US will produce a bite that looks like two pinpricks, as opposed to nonvenomous snakes that will produce a horseshoe shaped bite. it says you can tell by looking at the bite if it might be dangerous or not using this distinction. is this true? and if so, are more teeth part of the price you pay for magic liquid that kills stuff for you?