Biological Diversity 2001


This photo courtesy of Mt Bruce National Wildlife Centre

 

Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Rhynchocephalia
Suborder: Sphenodontidae
Family: Sphenodontidae
Genus: Sphenodon
Species: guntheri and punctatus

 

 


Photo courtesy of Kiwi Conservation Club

 

Conservation Organizations

New Zealand, Department of Conservation (DOC): Te Papa Atawhai: The DOC has been a primary organization in Tuatara conservation including the establishment of three predator free offshore habitats for Tuataras.

Mt Bruce National Wildlife Centre: A wildlife sanctuary that allows Tuataras to live and be seen in there natural habitat.

Auckland Zoo: The zoo has been involved with breeding and releasing Tuataras into habitats after five years of captivity into predator free offshore habitats.

Victoria University of Wellington, New Zealand: Working with Zoological Society of San Diego and DOC since 1988 helping in the capitivy and breeding of Tuataras as well as the formation of offshore habitats.

 

Photo Courtesy of BillyBear4Kids.com.

 

Tuatara foraging. Photo courtesy of Big Jude.

 

Kiore, an animal pest repsonsible for Tuatara declines. Photo courtesy of http://www.zealand.org.nz/.

 

Another mammalian pest, the feral cat. Photo courtesy of Encarta.

Rhynchocephalia

Introduction

Tuataras. Superficially, they resemble lizards, reptiles of the order Squamata, but superficial resemblance is all there is. Tuatara (recently split into two species, Sphenodon punctatus, and Sphenodon guntheri) are the last representatives of an ancient , successful, order of reptiles, Rhynchocephalia.

Rhynchocephalians appear shortly before the dinosaurs, and only began to decline during Cretaceous (Raven & Johnson 2002). Tuatara were once quite widespread throughout New Zealand and islands surrounding it, but now are confined to about twenty surrounding islands. The story of Sphenodon is in many ways a metaphor for the decline of their entire order, with numbers dwindling as better predators and competitors invade (only these extirpations are human facilitated). Estimates of their numbers across the islands vary, ranging from less than 50,000 (IUCN for instance suggests less than 1000 for S. guntheri) to slightly over 100,000 (Cassey and Ussher 2001). Tuatara have continued to decline in recent times disappearing from New Zealand and the surrounding islands. Causes of these extinction are primarily habitat loss and the introduction of mammalian predators, kiore (the pacific rat, Rattus exulans) and feral cats.

Tuatara have skulls that are characterized by the presence of a beak like structure on the upper jaw, acrodont teeth, two complete temporal fossae,
granular scales and a mid-dorsal row of spines (Iverson 2001). Tuatara also possess a parietal eye. It is an eye concealed beneath a thin layer of scales that may play an important role in thermoregulation (Raven and Johnson 2002, Iverson 2001). Tuatara, and rhynchocephalians in general, are small bodied reptiles averaging about 60 cm. They inhabit burrows (often with petrels, shearwaters and prions). Like many reptiles tuatara exhibit temperature dependent sex determination (Cree et al 1995). They reach sexual maturity only after 15 years and take fifteen months to incubate their eggs (Mlot 1997). Tuataras are, remarkably long lived, with age records for individuals of 75 years (Mlot 1997). It is suspected that they can reach ages of 100 years or more. They are carnivores that are active at temperatures much colder than other reptiles. Their diets are rich in beetles, weta, worms, millipedes spiders and, not nearly as often, bird eggs and chicks (DOC Te Pap Atawhai 2001).

Conservation Status

IUCN Red List 2000: Sphenodon guntheri is listed as vulnerable (VU D1+2) (www.redlist.org).

CITES (Convention on the International Trade in Endangered Species): Sphenodon guntheri is and Appendix I species (www.cites.org/eng/resources/fauna.shtml).

Conservation Issues


The World Conservation Union (IUCN) on their Red-List of threatened species, classifies the Brother Islands tuatara (Sphenodon guntheri) as vulnerable. Specifically they rate S. guntheri VU D1+2(www.redlist.org 2001).
The Cook Islands Tuatara (S. punctatus) made the Red-List in 1990, 1994, where it was listed as rare, and again in 1996 where it was upgraded to lower risk, least concern (www.cites.org). The 2000 Red-List lacks the S. punctatus altogether. Perhaps for it the danger has lifted some.

What are the problems faced by both Cook and Brother Islands tuatara? What are the most pressing dangers facing these utterly unique organisms? Most pressing is the presence of two mammalian predators, the kiore or pacific rat, Rattus exulans, and feral cats, Felis catus (Cree et al 1994, Veitch 2001). Both species are excellent predators of Tuatara. Kiore may actually be causing population declines in tuatara not only by predation on young, but by direct competition for other resources. This idea remains open for further testing (Ussher 1999). Certainly kiore are a cause of egg failure and young mortality as comparisons of kiore inhabited and uninhabited inhabited islands have shown (Cree et al 1994). The work of Cree et al, which found no adolescent individuals, very few juvenile tuatara and in general fewer tuatara on islands (reduced density) where kiore had yet to be eradicated, than on kiore free islands supports the hypothesis that kiore have a negative impact on Sphenodon punctatus. A huge aspect of tuatara conservation has been the extermination of kiore.

The other mammal involved in the severe reduction of tuatara numbers is the feral cat. Feral cats are a problem for conservationists the world over. They are spectacularly efficient predators of birds, small to mid-sized mammals and reptiles. They are the cause of millions of bird deaths every year. They have had their paws in several extinction both local and worldwide. They contributed to the complete extinction of the Barrier Snipe (Coenocorypha aucklandica barrierensis), as well as the NewZealand area extinction of the North Island Saddleback (Philesturnus caruncultus rufusater) (Veitch 2001). They are also responsible for the severe declines of many lizards and amphibians and birds the world over (Veitch 2001). The eradication of feral cats began in earnest in 1977 and on islands where cats have been completely eradicated (as on Little Barrier Island) has shown to facilitate increases in recruitment. Further conservation will have to increase the extirpation of feral cats from surrounding islands as well as institute measures that will prevent cats from being re-released to areas where they have been eradicated. This will ensure that tuatara numbers continue to grow, hopefully reaching pre-feral cat numbers. With such efficient predators as cats and rats, the tuatara has little defense, either anatomically, or behaviorally. Much of the evolutionary environment of the genus Sphenodon has occurred in the absence cats and rats. Their evolution has not prepared them for these relatively new threats.

Ultimately though, we must return to the Red-list rank to see the most important problem facing the genus Sphenodon. VU D1+2 . The abbreviation VU stands for, vulnerable. The World Conservation Union defines vulnerable as "facing a high risk of extinction in the wild in the medium-term future" (www.redlist.org/info/categories_criteria.html). The latter part of the ranking, in the case of Sphenodon, D1+2, describes the specific threats to the long term viability of a species. For the tuataras specifically the most pressing threat they face is one of distribution. That is to say their geographic distribution is incredibly restricted. They inhabit no more than 20 to 30 islands around New Zealand. Restricted distribution is really dangerous for species. Restricted distribution enhances the chances of extinction by stochastic events. Imagine a hurricane strength storm hitting the area of New Zealand. Such a storm may greatly reduce the numbers of tuatara, leaving them incredibly vulnerable to any other event that affects the whole of their distribution. One way to counter the effects of limited distribution might be to have rather large numbers. Actually total numbers of tuatara are not known with absolute confidence. Recent estimates place the tuatara at roughly 50 to 100, 000 (Cassey and Ussher 1999). Knowing the numbers will be essential to any future conservation plans to be implemented. It seems likely that any feasible long term plan for tuatara conservation program will involve the reintroduction of tuatara to mainland New Zealand. Repopulating that large island, as well as the surrounding islands, will go a long way toward protecting tuatara from stochastic extinction. Such plan however would require tough feral cat and kiore eradication and may at the present time be an expense that is difficult to justify.

 

Literature Cited

Cassey, P., G.T. Ussher. Estimating abundance of Tuatara. Biological Conservation 88:3:361-366.

Cree, A., M.B. Thompson, C.H. Daughtery. 1995. Tuatara Sex Determination. Nature 375:543.

Cree, A., C.H. Daughtery, and J.M. Hay. 1995. Reproduction of a Rare New Zealand Reptile, the Tuatara Sphenodon punctatus, on Rat-free and Rat-inhabited Island. Conservation Biology 9:9:373-383

Iverson, J. 2001. Vertebrate Biology: Lab Supplement. Earlham College.

Mlot, C. 1997. Return of the Tuatara. Science News 152:300-1.

Towns, D.R., Daughtery, C.H., Cree, A. 2001. Raising the prospects for a forgotten fauna: A review of 10 years of conservation effort for New Zealand reptiles. Biological Conservation 99:1:3-16.

Ussher, G.T. 1999. Tuatara (Sphenodon punctatus) feeding ecology in the presence of kiore (Rattus exulans). New Zealand Journal of Zoology 26:2;117-125.

Veitch, C.R. 2001. The eradication of feral cats (Felis catus) from Little Barrier Island, New Zealand. New Zealand Journal of Zoology 28:1:1-12.

Mount Bruce National Wildlife Centre. Tuatara.
http://www.mtbruce.doc.govt.nz/tuatara.htm aAccess date 11/08/2001


Elanora Heights Elementary School. Feral Cat.
http://www.schools.ash.org.au/elanorah/fercat.htm Access date 11/08/2001

New Zealand. A beautiful country.
http://www.zealand.org.nz/ Access date 11/08/01

Kiwi Conservation Club. Tuatara Conservation.
http://www.kcc.org.nz/animals/tuatara/conservation.htm
Access date 11/08/2001

Tuatara : The worlds most unique reptile.
http://www.bigjude.com/Tuatara.html
Access date 11/08/2001

Ferus, L.W. Tuatara, the Living fossil. Copyright © 1996 - 2001
http://www.billybear4kids.com/
Access date 11/08/2001

Department of Conservation Te Papa Atawhai
http://www.doc.govt.nz/index.asp Access date 11/08/2001

Auckland Zoo. Conservation Projects.
http://www.aucklandzoo.co.nz/conservation/index.php Access date 11/08/2001

Victoria University of Wellington. Conservation Efforts
http://www.vuw.ac.nz/index.shtml Access date 11/08/2001

World Conservation Union (IUCN). 2000 Threatened Species List.
http://www.redlist.org Access date 11/08/2001

Cites Species Database.
http://www.cites.org/eng/resources/fauna.shtml Access date 11/08/2001

Authors: Melissa Quinn, Max Driffill, and Zack Seymour
Creation/revision date: 12 November, 2001



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Earlham · Biology Department · Biology 26: Biological Diversity

Copyright ©-2001 Earlham College. Revised 1 October 2001. Send corrections or comments to quinnme@earlham.edu