Reproductive ethology of the Tuatara: Sphenodon punctatus: applications in captive breeding

Gillingham, James C.; Miller, Tracy J.

doi:10.1111/j.1748-1090.1991.tb03479.x

Cited by 21 publications

(4 citation statements)

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“…It is currently unknown what triggers a female's within-season receptivity. A previous estimate suggests that 23 out of 25 observed courting attempts in tuatara failed due to female non-receptivity (Gillingham & Miller, 1991); it is likely that the reason we observed a comparatively higher success rate during the 2021 and 2022 seasons is that we did not report a considerable number of unsuccessful stolzer Gang displays that we observed in passing.…”

Section: Discussioncontrasting

confidence: 42%

“…After mounting, the male will use his legs to rotate the female's pelvis and align their cloacae; in this way, mating on Takapourewa has been observed lasting for up to 90 min (Gillingham et al., 1995; Moore, Daugherty, Godfrey et al., 2009). Males will climb over moderate obstacles in their path to complete circles around potential mates; where obstacles are significant, males may adapt their stolzer Gang into a semi‐circle pattern (Gillingham & Miller, 1991). Additionally, two males have been reported to quietly ‘grunt’ during their displays (Cree, 2014), though females have not been heard vocalizing during courting or mating.…”

Section: Introductionmentioning

confidence: 99%

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Novel mating behaviours in male tuatara (Sphenodon punctatus) expand our understanding of reptile courtship

Lamar,

Ormsby,

Nelson

2024

Austral Ecology

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Observations of reptile courting and mating behaviour are relatively scant in the literature. Here, using the largest sample of observed courting attempts and matings in tuatara (Sphenodon punctatus) ever published, we describe novel behaviours in this rare species: mirrored head bobbing between courting pairs, purring vocalizations by displaying males, and several potential instances of anejaculation in otherwise normal matings. These results highlight the complexity of reptile mating displays and have implications for how we manage this vulnerable species.

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Section: Discussioncontrasting

confidence: 42%

Section: Introductionmentioning

confidence: 99%

Novel mating behaviours in male tuatara (Sphenodon punctatus) expand our understanding of reptile courtship

Lamar,

Ormsby,

Nelson

2024

Austral Ecology

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“…Tuatara have long-term site fidelity where individuals were recaptured at the same locations over several decades . As social reptiles, tuatara defend spaces using a set of behaviours, such as body inflation, positioning, crest erection, head-shaking, chasing and biting (Gillingham et al, 1995;Gillingham & Miller, 1991). In the Takapourewa (Stephens Island) tuatara population where there is an even sex ratio, males maintain larger territories than females, and large males have dominance in overlapping with more females in their territories and excluding other males more effectively from their territories (Gillingham et al, 1995;.…”

Section: Introductionmentioning

confidence: 99%

“…They are sexually dimorphic in body size and head dimensions, with males being larger than females (Gillingham et al, 1995;Herrel et al, 2010). As social reptiles, male tuatara defend access to females within their territories using a set of behaviours, such as body inflation, positioning, crest erection, head-shaking, chasing and biting (Gillingham et al, 1995;Gillingham & Miller, 1991). Research on a well-studied tuatara population on Takapourewa (Stephens Island) showed males have larger territories than females (Gillingham et al, 1995;.…”

Section: Introductionmentioning

confidence: 99%

The Effects of a Long-Term Male-Biased Sex Ratio on Population Dynamics and Viability of Tuatara (Sphenodon punctatus)

Liu

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Sex ratio is a critical parameter in the population dynamics and ecology of a species. Changes in population sex ratio can influence sexual selection and individual behaviour, which ultimately impact reproductive rates and population viability. For territorial species, sex ratio variation can influence territorial behaviour, and thus, the pattern of activity areas where animals acquire critical resources to perform biological processes. However, empirical studies addressing population consequences of sex ratio through behaviour and patterns of activity are rare. A biased sex ratio has been recognized as a major factor contributing to extinction in small populations, due to the vulnerability to environmental, demographic, and genetic stochasticity. Species with temperature-dependent sex determination (TSD) are prone to sex ratio biases because hatchling sex ratios are influenced by thermal conditions during embryonic development. A warming climate poses an increasing concern for the population viability of species with TSD, because rapidly shifting temperatures may strongly skew offspring sex ratios. Tuatara (Sphenodon punctatus) are long-lived reptiles endemic to New Zealand. They are particularly at risk based on their rare pattern of TSD, where males hatch at higher nest temperatures. Since the late 1990s, there has been an increasing male bias in a small, isolated tuatara population on North Brother Island. Survival and body condition of adult tuatara have declined, with a steeper rate of decline in females. Population viability analyses predicted the extinction of this population under the previous demographic parameters. However, longer term studies are needed to examine whether the sex ratio ultimately fluctuates around a more balanced sex ratio despite fluctuations based on the climate, or if the male bias becomes more extreme under climate warming. I explored the effects of a male biased sex ratio on population dynamics and viability of tuatara on North Brother Island using updated survey data over 30 years. I estimated the current sex ratio, body condition, survival rates, and population size and temporal trends in these parameters. In addition, I quantified tuatara activity areas on North Brother Island and in two translocated populations, which can reflect resource competition and the effects of sex ratio and population density. Then, I performed behavioural observations on captive populations to investigate how dominance is associated with intra-specific interactions to understand the implications of a male bias for population viability. Lastly, I updated the population viability of North Brother tuatara population based on the recent population parameters. There has been a continual male bias over 30 years in the North Brother Island tuatara population. Survival and body condition have declined over time, with a steeper rate of decline in females. In my recent data, I found a decrease in population size, as well as a further lengthening of the female breeding cycle. By contrast, the male bias has become less skewed over time in new cohorts of this population after 2005. Also, there has been an increase in male body condition and in survival of both sexes in new cohorts. The activity areas in males are larger than females, and activity areas became larger more recently under a smaller population size. Behavioural observations on captive tuatara showed larger males had an advantage in accessing females based on smaller distances to females, males had dominance over females through maintaining larger activity areas, and males and larger individuals had dominance in aggressive interactions. Based on the updated population parameters, the population viability analysis predicted a lower probability of extinction for this tuatara population than previous studies. However, the low female fecundity and the likely further skewed male bias under a warming climate could drive this population to extinction at a rapid rate if demographic parameters further shift. This project revealed how a male bias can influence individual behaviour and patterns of activity areas, and impact parameters, such as body condition, survival and population size, and ultimately, influence population viability. As more new cohorts enter this population, the population could experience a less skewed sex ratio and improved survival over time. Therefore, longer-term monitoring of the North Brother Island tuatara population is needed to investigate the lagged impact of environmental temperature on sex ratio and other population parameters, as well as population viability. Changes in sex ratio can be an early indicator of decline due to the effects of climate warming for species with TSD, an issue that thus far has not been detected in other tuatara populations. This study provides implications for the conservation and management of other species with TSD, which can also be prone to skewed sex ratios in a warming climate.

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Anguimorpha as a model group for studying the comparative heart morphology among Lepidosauria: Evolutionary window on the ventricular septation

Gregorovičová

Bartoš

Jensen

et al. 2022

Ecology and Evolution

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Reproductive ethology of the Tuatara: Sphenodon punctatus: applications in captive breeding

Cited by 21 publications

References 10 publications

Novel mating behaviours in male tuatara (Sphenodon punctatus) expand our understanding of reptile courtship

Novel mating behaviours in male tuatara (Sphenodon punctatus) expand our understanding of reptile courtship

The Effects of a Long-Term Male-Biased Sex Ratio on Population Dynamics and Viability of Tuatara (Sphenodon punctatus)

Anguimorpha as a model group for studying the comparative heart morphology among Lepidosauria: Evolutionary window on the ventricular septation

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