Tuatara survey for 2023: plentiful reptiles become bigger, bolder and more colourful

Take a walk on Tiritiri Matangi at night and you’re likely to see a tuatara – or 10. Not only has the Island’s population begun to flourish, but the island-born tuatara are beginning to outgrow their parents.

The third survey of the reptiles has herpetologists excited. The largest male found this year weighed more than a kilogram – and he is still a youngster.

A short 20 years ago, October 2003, Dr Graham Ussher and a team of very enthusiastic volunteers translocated 60 tuatara (20 males and 40 females) on to Tiritiri Matangi and released them in four separate sites across the northern half of the Island – 5 males and 10 females at each.

These tuatara originated on Atiu Island (aka Middle Island, in the Mercury Island group). Most reptiles of this size live in very warm countries. Most New Zealand reptiles are either crepuscular (that is, appearing or active at twilight) or they are nocturnal. This, combined with our temperate climate, means our reptiles have to operate at much lower temperatures; for tuatara, this is as low as 12-15°C.

The originals, or founders, were all suitably weighed, measured and injected with a glass-encapsulated PIT (passive integrated transponder) tag. When a tuatara is caught as part of a survey on Tiritiri Matangi, a tag reader is used to scan the tuatara and display its tag number, if it has one. This allows us to identify the founder individuals.

both surveys and anecdotal evidence showed tuatara were healthy and doing well, there was insufficient scientific data to confirm the population was established.

The third survey was organised almost 20 years on from translocation. Over two weeks this March, a group of 22 dedicated volunteers, led by Graham Ussher, Roger Wallace and Malcolm de Raat, scuttled around the Island by night and day, searching for the reptiles. One bite and several scratches later they amassed 104 total tuatara captures, comprising 76 unique individuals in a range of sizes and colours, including some absolute whoppers. Of the 76, 10 were founder animals and the other 66 all born on the Island and, by definition, no more than 19.5 years old.

Tuatara are the sole survivors of a chain of dinosaurs known as “beak heads”, the rhynchocephalians, genus Sphenodon. Fossil records suggest they have had little anatomical change in 170 million years.

On release, founders were estimated to be between 20 and 40 years old, which means they are now between 40 and 60 years old. Living on Tiritiri Matangi has clearly been beneficial as all founders caught are now heavier and longer than their release statistics. The largest founder tuatara captured were a male at 815g, measuring 531mm long (SVL – or snout to vent length –280mm), and a female at 590g, 435mm long (SVL 260mm).

In 2009 and 2015, surveys were carried out to see how the post-release tuatara population was faring. The 2009 survey captured 30 individuals, including 24 founders. In 2015 the survey captured 31 individuals, including 22 founders. While

The real eye openers are the island-born tuatara who have had a great start to life on Tiritiri Matangi. Remembering they are no more than 19.5 years old, the largest Island-born tuatara captured were a male at 1100g, 642mm long (SVL 297mm), and a female at 495g, 430mm long (SVL 250mm).

The youngest and smallest tuatara captured was a juvenile, estimated to be one to two years and weighing in at 80g, 295mm long (SVL 140mm).

These tuatara have an amazing range of colours, from the expected olive-grey-green through to an unexpected very bright orange and very bright red.

Further analysis of the data is yet to be done, including estimating the overall Island population, but there are several observations that are already clearly evident:

• It is common for visitors staying overnight to see tuatara when out on night walks. One recent and very credible visitor reported seeing “45+ tuatara” on a single night walk. The survey data backs this up with plenty of evidence tuatara have spread out over most of the Island.

• All tuatara caught have been in good health and are very well fed.

• Island-born tuatara are outgrowing their parents.

• The team still needs to confirm it scientifically using the data gathered but, anecdotally, from the survey’s perspective, it is looking very likely the population is established.

• Our gratitude and thanks to Louis Vavasour, our sponsor from Booster Wine Group who so kindly covered all the expenses for our ecologist Dr Graham Ussher of RMA Ecology. Thanks, Louis, for the financial support and, more importantly, for taking time out of your very busy schedule to join in and be an integral part of our team. Our gratitude and thanks also to Marilyn Kelly and Auckland Council who so kindly covered our cultural induction expenses.

• Our gratitude and sincerest thanks to our amazing team of volunteers (Alison, Andrew, Annette, Beth, Dave J, Dave W, Diane, George, Gerhard, Graham, Hester, Jacqui, Jane, John P, John S, Keith, Louis, Mark, Rachel, Sarah, Talia, Zac) for your time, all your support, hard work, and willing help. You all rock.

Moths and butterflies on Tiritiri Matangi impress expert

Jacqui Knight, aka Madame Butterfly, the founding trustee of the Moths and Butterflies NZ Trust, visited Tiritiri Matangi late last year and was impressed with what she found. This is a condensed version of Jacqui’s article which featured in the summer issue of Butterflies.

On my visit to the Island I was interested to see if the focus of the Supporters of Tiritiri Matangi was purely on plants and birds – or whether it included our invertebrates as well. Walking along the Wattle Track to the lighthouse, listening to delightful bird song, I noticed a great deal of signage explaining the “damage” on various trees and bushes. For example, beside some of the flax, Phormium tenax, there were signs about the flax looper or windower, (Orthoclydon praefactata), which chews narrow strips on the underside of the leaves, exposing the fibre and leaving a thin window in the leaves. The caterpillars are green at first but change to a pale yellow with red stripes, eventually becoming a brown moth with a wingspan of about 3.5-4cm. The other moth caterpillar found on flax is a looper, Ichneutica steropastis, which chews the leaves in a distinctive triangleshaped notch or hole. This one turns into a brown moth with a wingspan of about 4cm. Both caterpillars eat at night and shelter during the day in rolled up, dead leaves or debris. Neither of these do great damage to the bush but might be a problem if you were harvesting flax for weaving.

There was also excellent signage about other Lepidoptera species, including the pūriri moth. What I particularly liked was the fact that there was no mention of the word “pest”, or suggestions of ways in which the caterpillar(s) could be eliminated. Rather, in its wording visitors are encouraged to think of the bigger picture – the fact that the caterpillars could live in harmony with their host plant and those around them.

No doubt many of the caterpillars provide food for the birds that abound on Tiritiri Matangi – but there are still plenty to sustain the moth species and not enough to become a problem for any one plant species. And that’s what biodiversity is all about!

Looking at iNaturalist (left), I noticed that no monarchs or admirals had been recorded on Tiritiri Matangi. Their host plants are not on the Island, but I thought there might have been some “island-hopping”, or being blown on to the Island from the mainland. And I was right!

According to the biodiversity team, admirals –both the NZ red (Vanessa gonerilla) and yellow (V. itea) – have been seen on the Island. A lesser wanderer (Danaus chrysippus) has been recorded, as well as a male blue moon (Hypolimnas bolina). These Australian migrants are frequently blown across the Tasman on the cyclones of late summer. As well, long-tailed blues (Lampides boeticus) are evident on the Island, no doubt breeding on pasture weeds like lotus

I need to go back to the Island next summer to take a better look for butterflies!