Sea lions, spiders, slugs and slime molds: Curious critters of Auckland Island

As a botany curator, Heidi Meudt pays a lot of attention to plants, however, she is also curious about the other living things she sees when out in the field. When she was on Motu Maha Auckland Islands in January 2023, she tried to photograph as many of these non-plant critters as she could, and upload them to the citizen science platform, iNaturalist. Although most of her iNaturalist observations were of plants, about 15% of them were of native animals, including birds, mammals, insects, arachnids, molluscs, and even slime molds. Of the 173 animal observations representing over 50 different species, here are some of the notable, interesting and curious critters she saw during the four weeks of the Strannik 2023 Auckland Island Expedition.

Big critters

Birds

Motu Maha Auckland Islands are home to 45 bird species with breeding populations, including eight that are only found there (endemic) (Miskelly & Symes 2020). The islands are known for their amazing seabirds, including several albatross species. Few seabirds currently breed on the main Auckland Island due to predation and other effects by pigs, mice and cats, so we did not see many of them. 

Instead, most of the bird observations I made on Auckland Island were in fact small land birds. These include korimako | bellbird (17 iNaturalist observations), Auckland Island pipit (14 observations), silvereye, tomtit, tūī and kākāriki. These birds were rare and seemingly tame, which meant I could more easily capture them on cameras that were more suitable to photographing plants rather than soaring seabirds.

We were also fortunate to see or hear hoiho | yellow-eyed penguins at a few sites. It was great to see these penguins for which Motu Maha and Motu Ihupuku Campbell Island are now thought to be their stronghold, due to ongoing declines on mainland New Zealand.

But my favourite bird by far was in fact a seabird, the toroa pango | light mantled sooty albatross (7 observations). These birds really took my breath away. As they dipped and soared in pairs in the winds above us, they were so elegant and beautiful. Toroa pango have a circumpolar breeding distribution, but about 25% of their breeding population is on inaccessible cliffs on Adams Island in Motu Maha (Miskelly & Symes 2020).

Mammals

Motu Maha is also home to a number of native marine mammals, including whales, seals, and sea lions. We saw some evidence of whales on shore one day, including a whale carcass and some bones.

We also saw whakahao | sea lions frequently (many more than the 9 observations I made), including some that were more interested in us than we would have liked… However, generally it was easy to stay at a safe distance from them, such as this one, who seemed to be posing for the photo.

The Auckland Islands comprise 80% of the breeding population of the entire species. Nineteenth century sealing decimated whakahao | sea lion populations, which are now closely monitored by the Department of Conservation (you can see some of their data here).

Small critters

Insects

There are 239 native species of insects from Motu Maha, according to an article by Chown & Conley (2016), and about a third of these are endemic. I only saw a few of these, making 12 observations of insects, capturing a variety of different types.

Worms

I also found several earthworms – under rocks and rotting logs – that have not yet been identified to species level (4 observations). There are around ten native species of earthworm on Motu Maha, which are all unfortunately eaten by introduced pigs (Miskelly & Symes 2020).

I also found this unusual land flatworm:

Arachnids

Although I was actively looking for one type of arachnid – the harvesters – I actually found way more spiders. There are two dozen species of spiders on Motu Maha. I made 9 observations of spiders, most of which were found under the rocks when looking for harvesters. The arachnid I observed most often was Neoramia crucifera (6 observations), which have been identified by Te Papa spider expert, Phil Sirvid.

Slime molds

I made 8 observations of what I thought were fungi, but it turns out they are slime molds (Myxomycetes). Slime molds are neither plants, nor fungi, nor animals, and they have a relatively complicated and unique life cycle (Stephenson 2023).

There are at least 36 species of slime molds on Motu Maha (Stephenson 2011). I have learned a little bit about slime molds from Sarah Lloyd, who has identified some of my observations on iNaturalist, and I highly suggest you check out her website to learn more about these enigmatic organisms and see some of her amazing photographs.

Molluscs

I saw quite a few molluscs on Auckland Island, mostly in marine coastal areas. This marine top snail, a subantarctic island endemic, was especially beautiful:

There are also native land molluscs on Motu Maha, at least two dozen species (Barker 2005), including putoko ropiropi | leaf veined slugs.

As I was searching under rocks and logs for harvesters, I kept finding leaf veined slugs, and so I ended up making 20 observations of them! The diversity of colours, shapes, patterns and textures of these critters was amazing.

Not much is known about putoko ropiropi. There are about 30 species in New Zealand, and so far my observations have only been identified to subfamily Athoracophorinae.

The importance of adding observations and images to online databases

I’ve put my Auckland Island plant and critter images on iNaturalist, in the hopes that these observations are of interest and use to the research community. I’ve also added some of the images – including most of the ones in this blog – to Wikimedia Commons, where they can be used to illustrate these species on Wikipedia, Wikidata, and elsewhere.

All of the biodiversity on Auckland Island – from sea lions to spiders to slugs to slime molds and beyond – is really amazing, and I hope that sharing these photos will help deepen our appreciation, curiosity and understanding of these special critters.

Further reading

• Barker, Gary M. 2005. The character of the New Zealand land snail fauna and communities: some evolutionary and ecological perspectives. Records of the Western Australian Museum 68. Supplement: 53-102.
• Chown, Steven L., and Peter Convey. 2016. Antarctic entomology. Annual review of entomology 61 (2016): 119-137.
• Miskelly, Colin, and Craig Symes (eds.). 2020. Lost Gold: Ornithology of the subantarctic Auckland Islands. 436 pp. Te Papa Press, Wellington.
• Stephenson, Steven L. 2011. Myxomycetes of the New Zealand subantarctic islands. Sydow 63(2): 215-236.
• Stephenson, Steven L. 2023. Past and Ongoing Field-Based Studies of Myxomycetes. Microorganisms 11(9):2283.

Acknowledgments

Thanks to Brian Rance and Alex Fergus for their contributions to this blog. A massive thanks to all the online naturalists who have identified my observations on iNaturalist!

Previous blogs in this series

• Scientific collections and observations from the Strannik 2023 Auckland Island Expedition
• Plantago aucklandica is a megaherb!
• The megaherbs of Motu Maha Auckland Islands
• The 2023 Strannik Auckland Island Expedition: Our favourite places and plants
• Flora of Motu Maha Auckland Islands
• The 2023 Strannik Auckland Island Expedition: An extraordinary botanical voyage to the subantarctic