Most kiwis are acutely aware of the plight of New Zealand’s most iconic endemic birds, but what of the vast array of invertebrate species that are just as important ecologically – and in some cases, even more in danger of extinction?

At Auckland Zoo we have the skills and experience to work with our peers at a range of institutions, including our partners at the Department of Conservation, to learn more about and protect Aotearoa’s taonga (treasures) before it’s too late. It’s a vital part of our mission, and today, we’re sharing our involvement in a recent expedition to search for one of the world’s most endangered beetles.

Video

Searching for Aotearoa's Mokohinau stag beetle

Join Don McFarlane and a crew of researchers and experts, as they set out to locate an 80 million year old and ecologically significant stag beetle.

Early one December morning in 2018, a crew of researchers and experts set out on a 9-hour journey by land and by sea, to reach a group of islands located 62km northeast of Tāmaki Makaurau, Auckland. Their destination? A series of volcanic stacks known as the Mokohinau islands that rest on the edge of a continental shelf; the only location of a rare and ecologically significant stag beetle.

This specialised search crew included Dr Greg Sherley and Ian Stringer from the Department of Conservation, consultant Rob Chappell and Auckland Zoo’s team leader of ectotherms, Don Mcfarlane, who set off from Kennedy Bay after a necessary biosecurity check.

The largest and most well-known of the Mokohinau islands are Fanal Island (Motukino), Flax Island (Hokoromea), Trig Island (Atihau) and Burgess Island (Pokohinu), but within their spread is a site of the utmost importance to our experts and their mission – a small rocky outcrop with the undistinguished name of ‘Stack H’. Don describes this tiny 1.2ha landmass as a “giant bald head with an incredibly bad toupee sitting on top” and it is where the Mokohinau stag beetle was last seen in 2008.

Slow-moving, flightless and nocturnal, the Mokohinau stag beetle has been on this earth for an astonishing 80 million years – filling its own important ecological niche. First described by Thomas Broun, the Mokohinau stag beetle or Geodorcus ithaginus, was discovered by a Burgess Island lighthouse keeper, P. Stewart Sandager in 1893.

There are approximately 1,200 species of stag beetle globally with a moniker quite clear even for a lay-person – their mandibles (jaws) are reminiscent of a stag’s antlers and are similarly used as a weapon to fight other males for food, defend their territory and to secure a mate. In Aotearoa we have 39 stag beetle species and 35 of these are endemic – meaning they’re naturally found nowhere else on earth.

It is thought the Mokohinau stag beetle would have originally occupied the entire Mokohinau island-chain but land clearance, burning, grazing and the introduction of the kiore, or Polynesian rat, devastated their populations over many years. It’s the case with many of New Zealand’s islands; the arrival of humans brought scourges that these shores – and the wildlife well-adapted for life here - had never seen before.

Beetles exoskeletons are incredibly hard, hard-wearing and they last, so how long ago did these beetles die? That’s the big question, it’s very, very difficult to know.

Don McFarlane, ectotherms team leader at Auckland Zoo

Rats were eradicated from the islands in the 1990s but even with this crucial and necessary achievement, it can be difficult for species to recover without human intervention. Now the Mokohinau islands are managed as wildlife sanctuaries by the Department of Conservation and landing on these islands, with the exception of Burgess Island, is not allowed without a permit.

Upon arriving on the island, the search team sought out small, layered underground shelters or ‘condominiums’ that were placed there ten years ago, as well as thoroughly searching the undergrowth and leaf litter for signs of life. The larval stages of the beetle are known to burrow into soil, hide under rocks and in tussock grass, or nestle within the New Zealand ice plant (Disphyma australe) so careful attention was given to these very limited areas.

When no live specimens were discovered, patches of earth were carefully and painstakingly dug through and assessed for evidence of larvae but only other beetle species were found. Many of the surrounding islands were also searched, such as Lizard Island, though the beetle has not been officially seen there since 1893.

​Over the coming days several precious native species were seen on the islands - copper skinks, a rare Duvecells gecko, Mokohinau gecko, red crowned kakariki and a variety of other birds and invertebrates, which all demonstrate the value in keeping these islands pest-free. Yet sadly, a live Mokohinau stag beetle (adult or larvae) could not be found.

Remnants of beetle body parts were uncovered, such as the head, thorax and wing casings (called elytra) of both males and females, though it’s hard to know how long they have been there. As Don says, “beetles exoskeletons are incredibly hard, hard-wearing and they last, so how long ago did these beetles die? That’s the big question, it’s very, very difficult to know.”

Some may ask, “but…why is a beetle so important?” and this question touches on a range of ecological and even ethical topics.

In Radio New Zealand’s Critter of the Week, DOC’s threatened species ambassador Nicola Toki says, “if you think about beetles as the underground workers of our ecosystems, we really can’t afford to lose those things that…keep the ecosystems going and we don’t know what will happen if something like that drops out (of the ecosystem)”

As a conservation-based organisation rooted in science and research we know that humans have had a very significant and overall negative impact on the environment and its many animal species, some reports suggest half of all species have been lost over the last 40 years - but we also have the tools to reverse and restore this balance to the best of our abilities.

With your support, through your visits and your donations, we’ve been instrumental in reversing the decline of other endangered species. If a pair of stag beetles were able to be located in the future, an ideal situation would be to carefully breed this stag beetle in a managed environment in order to boost their population. Our successful wētāpunga programme has seen Auckland Zoo’s ectotherm team breed and release over 4,000 of an endangered invertebrate from only 24 founder pairs and release them to new habitats on Motuora, Tiritiri Matangi and the Noises islands to flourish.

It may be too early to know whether this stag beetle is extinct and further search efforts are planned by the Department of Conservation.