Friday, 2 January 2015

Book Review: Tuatara: Biology and conservation of a venerable survivor by Alison Cree

There are very few species of small(ish) reptile which are famous outside their native range unless they are venomous or brightly coloured, but the Tuatara Sphenodon punctatus of New Zealand is certainly among that select number. Their fame is due to their being the sole survivor of a unique lineage of reptiles separate from the turtles, the archosaurs, and the lizards, although they are most nearly related to the last, although since they split from the common ancestor with the lizards well over a quarter of a billion years ago even that is not close. The book reviewed here is a summary and survey of the whole of tuatara-related research, and covers not just the biology and ecology of the living animal, but its evolutionary history, interactions with humans, and their past, present, and future conservation status.

Part 1 of the book covers the tuatara’s origins, including origins of the rhynchosaurs, the larger group of which it is the sole survivor, the geological history of New Zealand, and also its place in Maori tradition. Part 1 ends with its discovery by western Science and the first 200 years of research.

Part 2 covers the biology of the living animal, including feeding ecology and behaviour, reproduction, and environmental specialisations. That last is particularly key for tuatara, which have unique adaptations to activity at amazingly low temperatures for a reptile, down to only a few degrees above freezing.

Finally, Part 3 covers the future survival of the species, including current actions to conserve the species on offshore islands and even recent attempts at reintroduction to the mainland in protected reserves.

In their early days the rhynchosaurs were reasonably diverse, with a global distribution. Oddly, until recently one of the few places there were no fossils known was New Zealand itself, but a partial jaw from around 19-16 mya has recently been found. Among fossils, those with the closest similarity to tuatara are known from Mexico of all places. They declined after the end of the Jurassic, although they were still present in Argentina in the late Cretaceous, and presumably survived the K-T impact on land in the far south. At that time estimated temperatures in Zealandia (the largely drowned continent of which modern New Zealand and its related islands are the topmost peaks) was similar to that on South Island today, even though the land was close to the pole. It is possible that the low-temperature adaptations of tuatara derive from that ancient time, when their ancestors shared their habitat with polar dinosaurs.
New Zealand was one of the last parts of the world to be colonised by humans, with the ancestors of the Maori arriving as recently as 1230 AD, having made a 3000km journey by ocean-going canoe from the Society Islands. The catastrophic ecological effects of human hunting, and worse the introduction of mammalian predators is well documented, especially with regards to such famous birds as the multiple species of moa, but reptiles were also hard hit. Tuatara are extremely vulnerable to rat predation, and among the livestock the Maori brought with them as a source of food was the Polynesian Rat or Kiore, Rattus exulans. This was probably responsible for the extinction of mainland Tuarara, which now only survives on offshore islands. More of these are now being cleared of rats in turn, and even some areas of the mainland have been fenced off with rat-proof fencing, enabling reestablishment of tuatara in areas where they have been wiped out.

One problem with the conservation of tuatara is their low metabolic rate. They do everything slowly, including reaching maturity (often taking nearly 20 years to do this) and then taking as long as 5 or 6 years between producing clutches. Although stories of their living to 300 years are the result of a misunderstanding, lifespans of 80-100 or quite probable. As a result of this, even when conditions are improved, it can take a long time for populations to recover.  Nonetheless, as a result of the intense protection it receives and the number of islands it is found on, the IUCN Red List classes it as Least Concern.
Outside New Zealand tuataras are almost never seen in zoos, but Chester Zoo in England has a group. Unfortunately, as they spend most of the hours of daylight sitting quietly in their burrows, they are not especially charismatic exhibit animals, but no trip to Chester should leave out an attempt at least to see them.

To summarize, this book will undoubtedly be the standard reference work for anyone interested in the species for many years to come, and is packed with useful and interesting information. It needs to be on the bookshelf of anyone interested in reptile conservation, palaeontology, or herpetological research.

(image from Wikipedia)

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