Gannets 'divorce', study suggests

Australasian gannets are not monogamous as previously thought, but have a significant "divorce" rate, Auckland University researchers say.

The divorce rate from one breeding season to the next was about 40 per cent, research leader Steffi Ismar said.

The research team studied banded Australasian gannets at Cape Kidnappers during consecutive breeding seasons in 2007-2008 and 2008-2009.

Their results were published in the European journal Naturwissenschaften.

The study showed gannets that divorced and found a new mate were less likely to successfully raise a chick in their first breeding season, compared to those who kept the previous year's partner.

The researchers believed this was due to the species requiring teamwork to raise their young, and having to gain experience of co-operating with a new partner.

The high rate of re-partnering suggested gannets had to choose between waiting too long for their former partner to arrive and missing out on breeding altogether, or making the best of a suboptimal breeding opportunity.

Data from the upcoming breeding season and further analyses would give further insight into why pairs separated, whether the same individuals repeatedly divorced, and whether new pairs had greater breeding success in their second year.

- NZPA