Threats to Tuatara

                              Tuatara Hatchlings newly emerged, with egg cluster, Stephens Island
                       (http://tpo.tepapa.govt.nz/print/PrintImageDetail.asp?ID=0x000a4e21&Language=)
                                   
       Organisms live within a limited range of temperature because of their physical structure, and how their system functions. When the temperature range begins to increase like in the recent case of high temperature, they begin to have problems (Portner & Farrell 2008). Digging deep into how Tuatura lives: In tuatara, incubation may take 11-16 months. Tuatara constructs their nest at depths between 10-230mm. Sex is determined when males are produced from incubation temperatures above 22 °c (week 7 of an average 21 week incubation period), while females are produced at 20 ° c (week 11 of an average 31 week incubation period).(Nelson, Moore et al, 2010)
       Nesting mostly occurs in spring from early November because temperature is still high; female tuatara lay a clutch of eggs every 2-5 years.They construct shallow nest in open areas and not in forest because the temperature is too low for the development of their embryos. Therefore, eggs come earlier in the season as a result of high temperature affecting the nest, due to the nest being exposed to a longer summer period. As a result of this nest exposure, nesting seasons 1998/1999 in a study showed more males (64%) due to high temperature (Nelson, Thompson et al, 2004)




A  study showed  how tuatara sex ratio is predicted by temperature (Mitchell, Nelson et al, 2006)

Incubation temperatures and sex ratios from wild populations of tuatara. Ti = constant incubation temperature, Ni = number of sexed embryos, Mi and Fi = number of males and females and * = eggs collected from female tuatara that were held in captive for different studies. 
Two species of Tuatara Sphenodon guntheri and Sphenodon punctatus. Their pattern of TSD (Temperature dependent sex determination) is above. In S. guntheri, it is known for 73 hatchlings incubated at six temperatures. Also we can see that two temperatures produced hatchlings of both sexes. In S.punctatus, it is known for 402 hatchlings incubated at eight temperatures. Also we can see that three temperatures produced hatchlings of both sexes (Mitchell, Nelson et al, 2006).

Main Point: Tuatara offspring sex determination is dependent on temperature and at higher incubation more males are produced than females



Other threats
Global warming impact on species is likely to vary geographically but mechanisms to know its magnitude or where species can be affected is not really yet developed (Deutsch et al 2008). In tuatara, they could see some observations, for example,
-Tuatara cannot persist in areas where rats are present due to competition because rats are fast breeding rodents. Rats do not occur in Brother's Island but they can spread to this place by boats and on driftland
- Introduced animals such as dogs and cats can predate on Tuatara.

(http://www.arkive.org/brothers-island-tuatara/sphenodon-guntheri/)