Skinks are definitely not poisonous. Although some lizards have poison glands (beaded lizards, gila monsters, and it is now known that some monitor lizards produce poison) none are poisonous if eaten. In fact, I know of no reptile (an obsolete taxon, but It's the best thing to call them for know...) that is poisonous in itself, if eaten. However, box turtles have been known to be toxic if they have been feeding on poisonous mushrooms. Its the amphibians, particularly toads and newts, that can be toxic....in some cases, very, very toxic (tetrodotoxin- fatal at 4 mcgs!) Take care, Eric ( I have 2 leopard geckoes, too many snakes, including a batch of corn snake eggs that have yet to hatch, 2 Russian tortoises, an overgrown redear slider, and a wife with a PhD in herps....)
...I know of an incident where I am sure a cat died from eating the 5-lined skink... it was an ugly sphynx cat, and the owner (a close friend of my family) found it laying strangly and panting among her 2 other cats on her porch. She took it to the Vet, where they determined the cat ate a native skink. I don't know how long it took for the cat to die, but it was the same day. That's where I first heard about them being poisonous. I have also heard from friends who attend this camp in AL, that some of the feral cats chase and eat the skinks, and are later found dead in the middle of camp... when a 5-lined skink is a juvenille, it has the lines, when it grows older, I think they lose their color. Perhaps they develop a poison or toxicity in age or something?
I stand partially corrected....from what I have read, there have been anecdotal reports of juvenile broad-headed (not 5-lined) skinks poisoning pets...I have yet to encounter any analysis of this suspected neurotoxin, and most importantly, it is not a consistent response. This leads me to suspect that its not the skinks themselves that are poisonous, but the possibility that they have ingested insects that had been poisoned by insecticides, and the skinks were then (possibly slowed down and dying) eaten or chewed by the cats or dogs. Another possibility is that some have fed on some naturally toxic prey, and accumulated the toxin themselves, similar to poison arrow frogs...another possibility, one paper discussed the attraction of some skink species to poisoned baits...Take care, Eric
Skinks are real easy to get to drop their tails upon handling (a classic lizard defense). If the animal was poisonous and used the tail as a warning, it would not be adaptive to loose the tail so easily.
I've seen snakes eat skinks without dieing too.
There are allot of lizards that can produce some foul smelling musk (including many skinks), and horned lizards can shoot blood from sinuses in the corners of their eyes. The blood has a particularly offensive smell to dogs, and it is speculated that this is a defense against coyotes and foxes.
The blue tail is found mainly on juveniles, and is used to add to the distraction...a twitching blue tail is definitely more visually compelling than a dull brown lizard, at least for the predators that have color vision...Take care, Eric