Most male humpback whales in a Pacific Ocean population do not have offspring — and bad singing might be to blame, new research reveals.

Scientists recently conducted a paternity analysis of a population of humpbacks off the coast of New Caledonia, an island about 750 miles east of Australia, according to a study published Jan. 8 in the Royal Society Open Science.

Their analysis — which involved examining genetic data and 25 years’ worth of photos — revealed that just 7% of male humpbacks showed evidence of having sired offspring.

Further, males who sired at least one calf were at least three times more likely to sire more offspring than would be expected if mating were random.

The results indicate that “becoming a father is a very rare outcome for a humpback male and one which they have to compete very strongly for,” Luke Rendell, one of the study authors, told The Guardian.

But how exactly do the males compete for reproductive success? Researchers offered up several ideas.

They noted that male humpbacks have been observed “physically competing to be closest to a female within competitive groups.”

The males also create complex “songs,” which might function as an elaborate sexual display to entice females — much like male birds do.

“Older, more experienced males might be more skillful singers and/or better or faster learners, and thus, could be preferred by females,” researchers said.

The young males, meanwhile, might be outsung and lose out on a chance to mate.

This idea of singing as a form of courtship “may in part explain the extreme nature of the song display, one of the most complex songs in the animal kingdom that males spend hours and hours producing during breeding season,” Rendell told The Guardian.

The linkage between song characteristics and male reproductive success has not yet been investigated, though.

In addition to Rendell, the study authors were Franca Eichenberger, Emma Carroll, Claire Garrigue, Debbie Steel, Claire Bonneville and Ellen Garland.

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