Why sea snakes have big ladies who have big babies

Two sea snake sssssstudies by Australian experts shed light on why females tend to be bigger than males and why they give birth to larger offspring than snakes on land. The first study suggests moving from land to sea meant the usual way snakes find a mate, by following scent trails, didn’t work anymore. So, females became larger while males evolved bigger eyes, making it easier for the males to spot a potential mate. The second study suggests sea snakes give birth to fewer, larger young than snakes on land because sea snakes are vulnerable to predators when they swim to the surface to take a breath. Experiments with snake shaped lures showed smaller baby snakes were more likely to be attacked.

Journal/conference: Royal Society Open Science

Link to research (DOI): 10.1098/rsos.231261

Organisation/s: Macquarie University, Australian Institute of Marine Science (AIMS)

Funder: Australian Research Council.

Media release

From: The Royal Society

Sexual dimorphism in aipysurine sea snakes (Elapidae, Hydrophiinae)

When sea snakes evolved from land-dwelling snakes, they had to adapt to a new set of challenges. That included their mating habits, because the usual method for males to locate females (scent trails) don’t work underwater. In turn, those shifts imposed new pressures for the evolution of differences in body size and shape between males and females. 

The adaptive significance of large size at birth in marine snakes

Why do some species produce a few large offspring whereas others produce many small offspring? For example, sea snakes have fewer larger babies than do land snakes. We recorded rates of attack by predatory fishes to snake-shaped fishing lures (without hooks) in a coral-reef habitat, and showed that smaller snakes are at high risk of attack whenever they need to swim to the surface to take a breath. That may be the reason why sea snakes have such large babies. 


Leave a Comment