Although snakes traditionally have been regarded as asocial animals, recent studies have revealed complex interactions among neonatal snakes and their mothers. We noticed frequent aggregation by captive neonatal Australian elapids (tiger snakes, Notechis scutatus), and conducted simple experiments to clarify the proximate causation of, and potential consequences of, aggregative behaviour. Litters of neonates exhibited statistically significant aggregation (clustering) in empty containers, especially if the test area was subjected to rapid cooling. Aggregation was most pronounced inside shelter-sites, and familiar shelters (i.e. containing scent cues from the litter) attracted snakes more than did novel (unscented) shelters. Snakes in larger aggregations cooled more slowly (reflecting their higher combined mass and thus, thermal inertia) and higher body temperatures facilitated neonatal locomotor performance, retreat-site location and anti-predator tactics. Plausibly, aggregation in neonatal tiger snakes (and other reptiles) functions to retard cooling rates, with the result that the young snakes are better able to evade or repel attacks by predators.