Normally skittish male northern map turtles are coming out of their shells with the help of some nifty 3D printing.

Carleton University biologist Grégory Bulté studies the breed and has been wondering for years whether male northern maps are attracted to larger females.

But the turtles don't do well in captivity, have nervous characters and mate at the bottom of lakes, making it difficult to study their mating patterns. So Bulté and his team printed two 3D replicas of female northern map turtles, identical except for their size: one was made bigger than the other.

The researchers then rigged the models with cameras and submerged them to record behaviour underwater.

As expected, Bulté found that size does matter. The male turtles approached and tried to mate with the larger female replica.

Bulté believes male turtles are attracted to larger females to increase their offspring's chance of survival, as there's a correlation between the size of a mother turtle and her hatchlings.

You can watch the turtle behaviour above in a video Bulté posted to YouTube.