Stormy success for sea lions

When we’re out doing our field work it’s not often that we ever pray for bad weather, but recently in Kaikoura and the Wairarapa we did, and we were not disappointed. A couple of perfect storms blew through, just at the right time…

Q: When do you ever wish for bad weather?

A: When you want to test shelters on seal pups designed to protect sea lion pups from storms.

But why are we testing shelters designed to save sea lion pups on seals?

The background: Based on Campbell Island, deep in the New Zealand subantarctic, is the southern-most breeding population of New Zealand sea lions (Pakake). It is not the nicest place for a young pup to spend its early months. It is windy, wet, muddy, and cold. Pup mortality is notoriously high.

2019 and 2020 was the highest reported incident of pup mortality at Campbell Island – 81%. It appeared to be related to exposure, as more pups were found dead after periods of high rainfall and low windchill. Together with partners we set out to devise something that would help protect these pups until they are big and strong enough to withstand the cold climate. We held an engineering challenge to seek out potential shelter designs to trial. Auckland Zoo put forward the winning design, and we decided to also test a simple culvert pipe design for comparison.

So did it work?

Before hauling shelters to Campbell Island, 700 kms south of Bluff, we wanted to know:

1. Would the pups use it?
2. Are they safe using it?
3. Will it withstand the weather and adults bumping into it?

But to test this on the New Zealand mainland, we needed:

1. Enough pups
2. Bad weather, and
3. Colonial breeding (so we have adults to bump into it!)

Pakake on mainland New Zealand do not breed colonially. While they breed on the Otago Peninsula (let’s face it the Otago summer is way too nice compared with Campbell Island), the pups would be too big and too spread out in winter. So, we decided to test our shelters with New Zealand fur seals (kekeno) whose pups would be the right size, at the right time for a storm.

Kaikoura trial:

We decided to run the trial in two stages. This was helpful to get a sense of how the seals would react to the shelter and work through some teething problems. From 28 June to 7 July we tested the culvert pipes at one of the kekeno breeding colonies on the Kaikoura Peninsula. We were able to successfully anchor them without any permanent impact on the whenua (this was one of the criteria of the project). We were also lucky enough to have a storm front come through – you might remember it – they say it snowed in Wellington that day! With the increased winds we got at the site we were pleased to see a pup fast asleep in one of the shelters.

We were even more excited when we started downloading images from trail cameras set up to view the shelters overnight, as this showed that there was plenty of pups investigating the shelters.

Cape Palliser trial:

On the 13^th of July, we kicked off our mahi with Ngati Hinewaka kaitiaki at Matakitaki a Kupe, Cape Palliser kekeno colony, and Auckland Zoo, to test out their shelter design.

We hoped for good weather on the 13-14^th to inspect the site and install the shelter, to be followed by bad weather to put the shelter through its paces. We got what we wanted and installed the shelter in beautiful sun, and the days that followed brought record-breaking rain and wind.

From our observations we knew that at least three pups used the shelter, but it wasn’t until we downloaded the footage from our surveillance cameras that we realised how popular it was. During the trial the shelter hosted:

• Four pups overnight (between 10-12 hours)
• One pup from the middle of one night and until morning (about 6 hours)
• Five more pups for short respites from the weather (between 20-60 minutes)
• Nine pups passed through the shelter (though some of these were likely the same pup trying to come in on multiple occasions and being chased out by the current inhabitant).

Our next steps are to do some analysis of the pups’ behaviour and temperatures inside the shelter versus the outside. However, given these successful preliminary results, we will now refine the design and start planning shelter deployment to Campbell Island for later this year, and hopefully save sea lion pup lives. Thanks to all those people who made this trial happen including Ngati Hinewaka, Ngati Kuri, Auckland Zoo, several volunteers and staff from all over DOC. And a special thanks to the kekeno for helping out your southern cousins!

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In these trials we were able to make use of the curious and exploratory nature of 8 month old fur seal pups. It’s important to remember that at this time of year they do explore further afield and may find themselves in unusual places. If you come across a seal in an unusual place remember these key tips found here