Older, wiser, deadlier: "blood nuking" effects of Australian brown snake venom acquired with age

A shield-snouted brown snake (Pseudonaja aspidorhyncha) from Northern Territory, Australia. Photo by Christopher Watson There's an age old belief that baby snakes are more dangerous than adult ones. There are generally two proposed reasons why this could be: either a) young snakes have yet to learn how to control how much venom they inject, so they deliver all of their venom per bite, or b) that because the snakes are smaller, they need more potent toxins to successfully take out their prey. The first is misleading, because even if baby snakes did dump all their venom into each bite, they still have so much less venom than adults that it doesn't matter (and there isn't any real evidence they lack self-control*). The second, though, warrants closer investigation: do younger, smaller snakes really have deadlier venoms? A new study on brown snakes in Australia says no—and in fact, the opposite can be true. A lot of things change as an animal ages. Whether referring to hormone levels or limb proportions, scientists refer to the physiological shifts that occur as an individual grows up as ontogeny or ontogenetic changes. So to ferret out the truth about the idea that baby snakes are more dangerous, the technical term for what scientists are looking for are ontogenetic changes in venom potency. There's little doubt that smaller, juvenile snakes experience a different world than their their full-grown counterparts. They are more vulnerable to attack due to their slighter frames, and when it comes to diet, they can be limited by what animals are sized to fit in their mouths and stomachs. Given these differences, it could be advantageous for a species to undergo an ontogenetic shift in venom, including a change from wielding a highly potent toxic cocktail as a young serpent to a weakened version as an adult. But, of course, just because a trait could be useful doesn't mean a species will evolve that way.