Otago Daily Times

Reclaiming breeding grounds

As sea lions become an increasing­ly common sight on Dunedin beaches, new research is helping advocates for the species tell an important story. From Southland up to Northland, New Zealand’s entire coastline is sea lion habitat. The massive marine mammals

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FROM North Cape south, New Zealand’s mainland was once teeming with sea lions.

When humans arrived, that all changed.

New Zealand sea lions were hunted relentless­ly and wiped from the map.

The endemic animals were driven into a refuge in the Auckland Islands, where sealers’ wooden boats could not venture, and only recently has the now nationally vulnerable species returned to the mainland.

In the beginning, a single female, Mum, arrived in Dunedin in the 1990s, and she had a pup.

Now, conservati­onists are hopeful a growing population of her descendant­s breeding along the city’s coast could signal the beginning of the species reclaiming their former breeding grounds.

Exactly when and where they might be found in future remains unknown, but an American PhD student, who has never seen a New Zealand sea lion in the wild, has developed a tool expected to be used to predict and plan for their return to the coasts of both the North and South Islands.

Help from abroad

Veronica Frans is an ecologist and a PhD student at Michigan State University who developed an interactiv­e map, now hosted on the Department of Conservati­on (Doc) website, using something called an ‘‘integrated species distributi­on model database’’.

The database she created not only makes the map easier to interpret, it also allows for additional evaluation­s for decisionma­king and conservati­on action, she said.

Using data collected through previous research in breeding colonies in the Auckland Islands, Ms Frans was first able to create a model of ‘‘habitat preference’’ for the species and overlay that model on to a map of the mainland.

The map showed sites that would be suitable for sea lions to again establish breeding colonies along the coast.

The assessment identified 395 sites along the coasts of both the North and South Islands where colonies of 35 or more females could settle.

Ms Frans, whose master’s research focused on the species and who has studied at Lincoln University, said it was a sign of hope for the species’ recovery.

‘‘We never imagined 395!’’ Ms Frans said via email.

‘‘It was definitely a surprise to us.’’

The database she created was produced after conversati­ons with Doc rangers, decisionma­kers and sea lion experts, so as to refine the initial modelling. The overlappin­g assessment­s it allowed showed that the actual suitabilit­y of 90% of the 395 potential breeding colony sites was questionab­le because of human activity.

More than half of them contained humanmade barriers such as fences or pasture, and threequart­ers had roads nearby.

Further, only 5% of the predicted colony sites were in protected areas.

The work, recently published in the British Ecological Society journal Methods in Ecology and Evolution, offered new opportunit­ies for conservati­on planning and community outreach, Ms Frans said.

But the main thing it displayed was the potential for the New Zealand sea lion to one day be found all over the country, she said.

‘‘One day, I really hope to see one,’’ she said.

‘‘It would be a dream after studying them for so long.

‘‘For now, I do what I can from a distance, using data that others have collected on the ground, and am happy to help where I can.’’

Here and there, a difference

Here in New Zealand, WildCoastN­Z environmen­tal consultant Amelie Auge said the map Ms Frans created highlighte­d the need to educate New Zealanders that the large mammals belong here, so ‘‘get used to it’’.

It was Dr Auge’s GPS tracking work that was used by Ms Frans to build the map.

Dr Auge said sea lions’ behaviour in Otago was markedly different from the Auckland Island population.

In the Auckland Island subantarct­ic population centre, harems of females gathered and were protected by a dominant male.

The breeding season here was marked by single mothers stealing away to have their pups in peace, safe from overzealou­s males and other dangers.

The accepted thinking here was that once numbers increased on the mainland, sea lions would reach a ‘‘critical mass’’, and their behaviour would change.

‘‘The accepted idea — and we’ll have to see if it’s right — is that when there’s more females here, the idea is that they will start forming those breeding aggregatio­ns [harems].

‘‘It’s just that at the moment there is not enough of them for them to benefit from gathering, because they gather basically to protect [themselves] from other males and stuff.’’.

However, another change might be more noticeable, Dr Auge said.

Sea lions could also reach a critical mass on the mainland and, after years of slow growth, the population could then undergo ‘‘exponentia­l growth’’.

‘‘If it happens . . . you think there’s a lot at the moment, potentiall­y you could have a lot more.’’

Few people know Dunedin’s small population of sea lions as well as Doc biodiversi­ty ranger Jim Fyfe.

He said it would likely take 1015 years of growth before Dunedin could properly say it had a sea lion ‘‘population’’ around the city.

The technical definition of a colony is a site where females have produced 35 pups a year for five consecutiv­e years; last year Dunedin’s sea lions produced a record 22 pups.

And yet the animals have already become a common sight at city beaches.

Surfers at St Clair are learning to coexist with them with different degrees of success, and every summer Doc rangers and others have to do work from Warrington to Brighton as sea lions and people meet at the beach.

‘‘Imagine if we were having 100 pups being born,’’ Mr Fyfe said.

‘‘Now that they’re coming back, we are having to relearn our relationsh­ip with them.’’

A refuge, and a second chance

The species’ stronghold, where around twothirds of all New Zealand sea lion pups were born, was Dundas Island, in the Auckland Islands archipelag­o, Mr Fyfe said.

It was roughly the size of a couple of rugby fields, but its sandy shelf was completely surrounded by rocky reefs, which once kept sealers’ boats at bay.

From this refuge, sea lions would travel nearly 100km to foraging grounds and would dive regularly to 200m to find food.

Off Otago Peninsula, the fishing was much closer.

Whereas it was not unusual for Auckland Island sea lions to head out on a threeday trip to forage for food, here the animals swam a few kilometres, dove down to 20m for a feed, and were ‘‘home by lunchtime’’, Mr Fyfe said.

Ms Frans’ map showed how extensive sea lion habitat was around New Zealand’s coast, he said.

It highlighte­d that pups were found in middens all the way up in North Cape.

However, what it really promised was a tool for people planning for coastal infrastruc­ture or sealevel rise to take into account where sea lions might be found one day.

In terms of district councils or regional councils creating plans for the future of their coasts, taking into account sea lion habitat would be important, he said.

‘‘We’ve got sea lions here and they’re voting with their flippers,’’ he said.

‘‘Female sea lions — and they’re the ones we are really worried about because they’re the ones that produce pups and keep the species going — they need choice.’’

Otakou head Edward Ellison said there was evidence of sea lions once populating the area in good numbers.

There were various accounts of chiefs or ancestors having encounters with sea lions up and down the coast, he said.

There were place names that might relate to sea lions, as well.

‘‘They were obviously quite prolific in number and there were encounters,’’ Mr Ellison said.

‘‘There were a few accounts of bravery, I suppose.

‘‘They were also hunted, obviously, because they’re big beasts and they may have had bones that were of use besides the meat.

‘‘I think it’s a good sign that they are resuming their place.’’

❛ Imagine if we were having 100 pups being born. Now that they’re coming back, we are having to relearn our relationsh­ip with them Doc biodiversi­ty ranger Jim Fyfe

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 ?? PHOTO: GERARD O’BRIEN ?? Just chilling . . . A large male sea lion yawns from his paddling pool at Taieri Mouth.
PHOTO: GERARD O’BRIEN Just chilling . . . A large male sea lion yawns from his paddling pool at Taieri Mouth.
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 ?? PHOTO: LLOYD PALMER ?? Playtime in the surf . . . A friendly sea lion comes into shore alongside local surfer Mike Farrell at St Clair Beach.
PHOTO: LLOYD PALMER Playtime in the surf . . . A friendly sea lion comes into shore alongside local surfer Mike Farrell at St Clair Beach.
 ?? PHOTO: JOHN BURKE. ?? First time mum . . . Basking at an undisclose­d Dunedin location is 5yearold Mika and her first pup. Mika is the greatgreat­granddaugh­ter of Mum, the matriarch of the Dunedin sea lion population.
PHOTO: JOHN BURKE. First time mum . . . Basking at an undisclose­d Dunedin location is 5yearold Mika and her first pup. Mika is the greatgreat­granddaugh­ter of Mum, the matriarch of the Dunedin sea lion population.

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