New Zealand Science Teacher

Possible new homes found for NZ sea lions

27/06/2016

Formerly known as the Hooker’s sea lion, the critically threatened New Zealand sea lion (Phocarctos hookeri) might have a few more places to spread out: new sites on mainland New Zealand have been identified which might be ideal breeding grounds.

Currently, the New Zealand sea lion has only three breeding colonies, in the sub-Antarctic islands. Although since 1993 there has been evidence that the animal is moving back to mainland New Zealand in small numbers, to sites in the Otago and Southland regions, these sites have limited potential for truly effective regeneration of the species, because they are often in close proximity to urban development.

The archeological record suggests that New Zealand sea lions were once found across the entire length of mainland New Zealand’s coast - North and South Islands - Stewart Island, the Auckland Islands, and the other sub-Antarctic islands. The finding of New Zealand sea lion remains indicates that they were hunted by both pre-European Maori and post-settlement Europeans.

When the Auckland Islands were discovered in 1806, New Zealand sea lions were hunted for their prized pelts for 24 years, until there were no longer enough left to support an industry. In the late 1880s, laws were introduced to protect the species, in a remarkably early example of conscious protection of the environment.

In 1993, a female sea lion nicknamed “Mum” decided to have her pup on an Otago Peninsula beach. This was the first sea lion born on the mainland in over 100 years. Now, over 150 sea lions live on the mainland, and the Otago peninsula averages 4 new pups born each year, almost all related to “Mum.”

NZ sea lions are also starting to breed in the Catlins and on Stewart Island.

Now, researchers from Otago University and the Department of Conservation have identified several promising new sites on the Otago and Catlins coast, which could serve as ideal breeding grounds for New Zealand sea lions. The researchers used data on both wild and urban environmental features, such as road or estuary locations, to map out suitable areas matching sea lions' preferences. The researchers say it is important to find new places to protect for recolonising sea lions, because their current habitats are fragmented thanks to urbanisation. The scientists also point out that this approach could be used to find more suitable land for other species under threat of extinction.

Author of the new study Tony Moore says that he and his colleagues were driven to complete their programme of study because they could see that limited recolonisation of the South Island coast was taking place, and this led to the question ‘what kind of habitat do New Zealand sea lions prefer?’ when thinking about how to further encourage the species to breed.

“We could see that this recolonisation was taking place on the New Zealand South Island mainland in a limited number of places. This led to the question of why do they occupy some locations and not others? Based on environmental and anthropogenic geographic knowledge that were known to affect the presence of sea lions, we wanted to identify, through spatial analysis and GIS, whether the current breeding locations were identified and more importantly, whether new locations with similar properties were identified.

“Quite simply, the New Zealand sea lion is a threatened species and… the facilitation of mainland breeding colonies is a significant step to its long term survival. If this was not to happen, then their distribution would be limited to only three breeding colonies in the subantarctic islands, making them far more endangered.”