A decade and a half had passed since this rare species of sea snake was last spotted, and conservationists were just about to give up hope. Now a recent sighting, reported in the latest issue of Biological Conservation, confirms that the snakes haven't left for good.

Researchers found the pair of Australian short-nosed sea snakes (Aipysurus apraefrontalis) swimming over Ningaloo Reef off Australia’s western coast. To further add to the excitement, they appeared to be courting. This suggests that the specimens are part of a larger breeding population of Australian sea snakes in the area.

The snakes are originally thought to have been native only to Ashmore Reef in the Timor Sea, but they mysteriously vanished from their natural habitat between 1998 and 2002. The species was officially categorized as critically endangered on the International Union for Conservation of Nature Red List in 2010, but so much time had passed since they were last seen that conservationists began to fear the worst. These new photographs, validated by the ARC Center of Excellence for Coral Reef Studies at James Cook University, have sparked new hope for the species’ survival.

Australian short-nosed sea snakes are considered marine hydrophiines, which means they are “true” sea snakes that live exclusively in water. The cause of the species’ decline is still uncertain, but some researchers suspect commercial fishing may be to blame. Sea snakes have been shown to be vulnerable to the nets used for trawling, but this still doesn’t explain why the sea snakes disappeared from Ashmore Reef specifically. For conservationists looking to save the species, identifying their biggest threats will be a major priority moving forward. You can read the full report in the February 2016 edition of Biological Conservation.

[h/t: Gizmodo]