From the May Landcare Newsletter…
Physical Shape Arises from a Combination of Genes and Upbringing – at Least as far as Snakes are Concerned.
A couple of examples of evolution and upbringing leading to differing physical characteristics amongst Tiger and Black Snakes have recently been documented.
The first study (summarised here) found that mainland Tiger Snakes (Notechis scutatus) that eat frogs and mice were found to have smaller heads than those from an offshore island that eat larger gull chicks. Interestingly, when the offshore young were fed just mice and frogs they developed small heads – but the mainland young developed small heads regardless of their diet.
An alternative example is provided by another study on the response of tropical Red-belly Black Snakes (Pseudechis porphyriacus) to the invasion of Cane Toads (Bufo marinus). Here, natural selection drove rapid evolution to a population with smaller heads and larger bodies. Smaller heads mean they consumed smaller toads and thus less toxin. Larger bodies dilute the impact of that toxin on the snake.
Natural selection at work folks!