Search

The bacteria of a host's digestive tract play crucial roles in digestion and pathogen resistance. Hosts living in captivity often have more human interaction and antibiotic use, in addition to differences in diet and environment, compared to their wild counterparts. Consequently, wild and captive animals frequently harbour different bacterial communities. We tested whether diversity of diet provided in captivity shifts the gut bacteria of tuatara, an endemic New Zealand reptile, at three captive sites, and examined how the gut community of these tuatara compares to those in the wild. Dietary manipulation did not cause a strong overall shift in tuatara gut bacteria, but individual tuatara did experience bacterial shifts during manipulation, which subsequently reverted after manipulation. We found that Bacteroides , a genus common in most vertebrate guts but rare in tuatara, increased significantly in the gut during manipulation, then decreased post-manipulation. Finally, the gut bacteria of captive tuatara significantly differed from those of wild tuatara, though most of the dominant bacterial genera found in wild tuatara persisted in captive tuatara. This work represents a first investigation of the captive tuatara bacterial community and establishes the sensitivity of the gut community to dietary manipulation and captivity for this relict reptile. [ABSTRACT FROM AUTHOR]

Abstract: The nest environment for eggs of reptiles has lifelong implications for offspring performance and success, and, ultimately, for population viability and species distributions. However, understanding the various abiotic and biotic drivers of nesting is complex, particularly regarding variation in nesting behavior of females and consequences for sex ratios in species with temperature‐dependent sex determination (TSD). We investigated how nest construction and nesting phenology affect the incubation environment of a reptile with TSD, the tuatara (Sphenodon punctatus), a species that is at risk from climate‐mediated male bias in population sex ratios. Using longitudinal behavioral data, we addressed the following questions. (1) Does nesting behavior vary with seasonal or location cues? (2) Does variation in nesting phenology or nest construction affect the incubation environment? We aimed to investigate whether female tuatara could modify nesting behavior to respond to novel environments, including a warming climate, allowing for successful incubation and balanced population sex ratios, maintaining population viability throughout their historic range. We predicted that earlier nesting after warm winters increased the likelihood that females will be produced, despite the sex determining system where males are produced from warmer temperatures. Further research is needed to understand the extent to which nesting behavior varies by individual through time, and across the range of tuatara, and the importance of habitat variability in maintaining production of females under future climate warming. [ABSTRACT FROM AUTHOR]

Most reptiles thermoregulate to achieve body temperatures needed for biological processes, such as digestion and growth. Temperatures experienced during embryogenesis may also influence post-hatching growth rate, potentially through influencing post-hatching choice of temperatures. We investigated in laboratory settings whether embryonic temperatures (constant 18 °C, 21 °C and 22 °C) influence selected body temperatures ( T sel ) of juvenile tuatara ( Sphenodon punctatus ), providing a possible mechanism for differences in growth rates. We found that incubation temperature does not influence T sel . Although the average daily mean T sel was 21.6 ± 0.3 °C, we recorded individual T sel values up to 33.5 °C in juvenile tuatara, which is higher than expected and above the panting threshold of 31–33 °C reported for adults. We found diel patterns of T sel of juvenile tuatara, observing a general pattern of two apparent peaks and troughs per day, with T sel being significantly lower around dawn and at 1500 h than any other time. When comparing our results with other studies on tuatara there is a remarkable consistency in mean T sel of ~ 21 °C across tuatara of different ages, sizes and acclimatization histories. The ability of juvenile tuatara to withstand a wide range of temperatures supports their former widespread distribution throughout New Zealand and warrants further investigation into their plasticity to withstand climate warming, particularly where they have choices of habitat and the ability to thermoregulate. [ABSTRACT FROM AUTHOR]

Nest-site selection in ectothermic animals influences hatching success and offspring phenotype, and it is predicted that females should choose nesting sites that maximise their reproductive fitness, ultimately through the reproductive success of their offspring. We completed nest-site choice experiments on a nocturnal lizard, the egg-laying skink (Oligosoma suteri), to determine whether eggs (and subsequent hatchlings) from cooler nests do better at cooler incubation temperatures, and conversely if those laid in warmer nests perform better at warmer incubation temperatures. We provided a simple nest-choice experiment, with oviposition-retreat sites available in either a hot or a cool sector of the enclosure; in the wild females nest under objects. Female O. suteri laid eggs both during the day and night, and nested more in the hot than cool sector. Eggs from each clutch were split across three egg incubation temperatures (18°C, 22°C, 26°C) to decouple the impact of initial nest-site choice from the subsequent incubation temperature regime. Whether eggs were initially laid in the hot or cool sector was not related to hatching success, offspring phenotype or offspring locomotor performance. We conclude that offspring phenotype and performance is primarily influenced by the temperature during incubation, rather than the initial thermal environment of the nest location. Thus, female O. suteri may select warmer nesting sites to ensure higher incubation temperature and enhanced offspring fitness. [ABSTRACT FROM AUTHOR]

Although parental care is generally rare among reptiles, nest-guarding occurs in some species and is usually attributed to defense against nest predation. Nest-guarding also occurs in the Tuatara (Sphenodon punctatus), but nest predation on rodent-free islands does not appear to be a significant threat to nesting success in this species. We studied a population of colonially nesting Tuatara on rodent-free Stephens Island, New Zealand, over four years and tested the hypothesis that female Tuatara guard their nests to defend them from excavation by conspecific females. We located 73 nests for which females could be assigned based on observations during oviposition. Nearly 25% of these nests were subsequently excavated by another female, but only 56% of the nests were guarded by the females that constructed them. We found a trend where guarded nests were less likely to be excavated than unguarded nests. Females were more likely to guard their nests, and guarded nests for longer, as the activity of Other females oh the date of oviposition increased. Nest-guarding in Tuatara appears to be adaptive in that it tends to reduce the likelihood of nest excavation by other females, but social interactions may affect females' propensity to guard, because guarding behavior was influenced by the activity of conspecifics at the time of oviposition. [ABSTRACT FROM AUTHOR]

The aims of this study were: (1) to examine changes in immune parameters in tuatara (Sphenodon punctatus) sampled three times between winter and spring and (2) to examine the possible effects of gender and tick burden on peripheral blood cells. The three blood samples were taken from each of two male and two female captive tuatara at 4- to 6-week intervals from July through October 2003. A single blood sample was also obtained from each of 39 wild tuatara captured on Stephens Island in October of the same year. For each blood sample of captive and wild tuatara, total leukocyte and erythrocyte counts were made with the aid of a haemacytometer and differential leukocyte counts were made from Giemsa stained blood smears. Among captive tuatara, counts of total leukocytes (WBC), heterophils, and lymphocytes varied between samples but with an insignificant increase from winter into spring. Wild tuatara had lower numbers of erythrocytes (RBC) compared with captive tuatara, accompanied by a larger number of erythrocyte precursors, more so in wild females than males. In wild tuatara, an increase in total leukocytes (WBC) was associated with tick burden. [ABSTRACT FROM AUTHOR]

Abstract: Tuatara are the sole survivors of an entire order of reptiles that thrived during the age of the dinosaurs. Therefore, knowledge of their physiology is critical to understanding the phylogeny of reptiles. Previous studies of the immune system of the tuatara did not assess T cell function. We analyzed T cell function among six captive tuatara by assessing concanavalin A (Con A), phytohemagglutinin (PHA) and mixed lymphocyte reaction (MLR) induced T cell proliferation. Peripheral blood mononuclear cells from six out of six and four out of four tuatara tested exhibited significant proliferative responses to Con A and PHA, respectively, as measured by an MTT reduction assay. A lower level of proliferation was detected in an MLR. However, Con A activated lymphocytes were not cytotoxic for a xenogeneic murine mastocytoma cell line (P815). [Copyright &y& Elsevier]

Translocations of reptiles and amphibians have been questioned as a conservation tool because they generally have not been successful. However, translocation is the only method by which many species can be restored to parts of their former range, which increases their conservation security. Tuatara ( Sphenodon spp.), sole surviving members of the reptilian Order Sphenodontia, are restricted to offshore islands of New Zealand. Dispersal into former habitat on the mainland or other islands, following removal of the causes of extinction, is unlikely. Captive rearing of reptile hatchlings from eggs collected in the wild to produce founders for new populations is also a conservation technique that has had mixed success. However, captive incubation and rearing are techniques that allow large numbers of tuatara to be produced to start new populations without detrimental effects on small source populations. We document the first contemporary translocation of S. guntheri , providing details on selection of release sites and founders. Release sites were chosen on a rodent-free island that provided a variety of habitats for tuatara as well as abundant food and shelter. The release propagule comprised 18 wild-caught adults and 50 captive-reared juveniles. Four separate release sites were established to separate adults from juveniles during the establishment phase. Five years of monitoring indicate that at least 57% of tuatara survived translocation and that reproduction has occurred on the new island. All tuatara increased in weight and length, demonstrating that tuatara have an indeterminate growth pattern. The 56% of recaptured juveniles represented a cross section of the sizes released. We evaluated the use of head-started juveniles as founders, based on survival and growth data. Because tuatara are long-lived, late-maturing reptiles with slow reproduction, establishment of a self-sustaining population will take decades of monitoring to confirm. [ABSTRACT FROM AUTHOR]

Aim We estimated population size, survival, longevity and sex ratio of tuatara (Sphenodon guntheri Buller 1877) on North Brother Island and determined whether recruitment was occurring, to aid management and identify potential problems for population viability. Location This study was conducted on North Brother Island, Cook Strait, New Zealand. This 4-ha island supports the sole remnant population of S. guntheri. Methods Demographic variables were estimated using capture-recapture methods. Tuatara were individually marked and recaptured during twelve trips, spanning a decade. Population size was estimated for selected trips using the CAPTURE package and finite mixture models, and survival was analysed using the Jolly-Seber (J-S) model. Longevity was estimated using tuatara individually marked in 1957. Results Approximately 350 adult tuatara profile likelihood interval (PLI) (294-427) inhabit North Brother Island, and the sex ratio is strongly biased towards males (1.7M: 1F). Annual adult survivorship is high (0.95) for both sexes and some tuatara live for at least 61 years. Main conclusions The small size and biased sex ratio of this population may make it susceptible to demographic stochasticity, Allee effects, and/or loss of genetic variation. Harvesting for translocation could exacerbate such problems. In addition, tuatara have temperature-dependent sex determination (TSD), with males produced at higher incubation temperatures. Global warming may therefore skew the sex ratio further unless female nest site choice or adaptive shifts in pivotal temperatures compensate for rising temperatures. [ABSTRACT FROM AUTHOR]

Tuatara are the sole extant species in the reptile order Rhynchocephalia. They are ecologically and evolutionarily unique, having been isolated geographically for ~84 million years and evolutionarily from their closest living relatives for ~250 million years. Here we report the tuatara gut bacterial community for the first time. We sampled the gut microbiota of translocated tuatara at five sanctuaries spanning a latitudinal range of ~1000 km within Aotearoa New Zealand, as well as individuals from the source population on Takapourewa (Stephens Island). This represents a first look at the bacterial community of the order Rhynchocephalia and provides the opportunity to address several key hypotheses, namely that the tuatara gut microbiota: (1) differs from those of other reptile orders; (2) varies among geographic locations but is more similar at sites with more similar temperatures and (3) is shaped by tuatara body condition, parasitism and ambient temperature. We found significant drivers of the microbiota in sampling site, tuatara body condition, parasitism and ambient temperature, suggesting the importance of these factors when considering tuatara conservation. We also derived a 'core' community of shared bacteria across tuatara at many sites, despite their geographic range and isolation. Remarkably, >70% of amplicon sequence variants could not be assigned to known genera, suggesting a largely undescribed gut bacterial community for this ancient host species. [ABSTRACT FROM AUTHOR]

Global climate change is of particular concern for small and isolated populations of reptiles with temperature-dependent sex determination because low genetic variation can limit adaptive response in pivotal temperatures, leading to skewed sex ratios. We explore the demographic consequences of skewed sex ratios on the viability of a tuatara population characterized by low genetic diversity. We studied the rare species of tuatara ( Sphenodon guntheri) on the 4 ha North Brother Island in New Zealand over two nesting seasons and captured 477 individuals, with a 60% male bias in the adult population. Females first breed at 15 years and have extremely low rates of gravidity, producing clutches of three to eight eggs every 9 years. Simulations of the population using population viability analysis showed that the current population is expected to persist for at least 2000 years at hatchling sex ratios of up to 75% male, but populations with 85% male hatchlings are expected to become extinct within approximately 300 years (some eight generations). Incorporation of inbreeding depression increased the probability of extinction under male biased sex ratios, with no simulated populations surviving at hatchling sex ratios >75% male. Because recent models have predicted that climate change could lead to the production of all male S. guntheri hatchlings by 2085, we examined whether periodic intervention to produce mixed or female biased sex ratios would allow the population to survive if only males were produced in natural nests. We show that intervention every 2–3 years could buffer the effects of climate change on population sex ratios, but translocation to cooler environs might be more cost-effective. Climate change threatens tuatara populations because neither modified nesting behaviour nor adaptive response of the pivotal temperature can modify hatchling sex ratios fast enough in species with long generation intervals. [ABSTRACT FROM AUTHOR]

Successful reproduction is critical to the persistence of at-risk species; however, reproductive characteristics are understudied in many wild species. New Zealand's endemic tuatara (Sphenodon punctatus), the sole surviving member of the reptile order Rhynchocephalia, is restricted to 10% of its historic range. To complement ongoing conservation efforts, we collected and characterized mature sperm from male tuatara for the first time. Semen collected both during mating and from urine after courting contained motile sperm and had the potential for a very high percentage of viable sperm cells (98%). Scanning electron microscopy revealed a filiform sperm cell with distinct divisions: head, midpiece, tail, and reduced end piece. Finally, our initial curvilinear velocity estimates for tuatara sperm are 2–4 times faster than any previously studied reptile. Further work is needed to examine these trends at a larger scale; however, this research provides valuable information regarding reproduction in this basal reptile. [ABSTRACT FROM AUTHOR]

Females of many reptile species engage in colonial nesting. Proposed advantages to colonial nesting include breeding synchrony, predator satiation and nest site copying by young or inexperienced females. However, nest site copying may also present costs to individual females in that previously laid nests may be intentionally or unintentionally destroyed by females that nest later at the same site. Conspecific nest destruction may be prevented if females guard their nests following oviposition, although nest guarding presents additional costs. Nesting by female tuatara, Sphenodon punctatus, was investigated in seven rookeries over 5 years on Stephens Island. Nest site copying appeared to be common, with approximately 30% of nests being constructed at sites showing evidence of a previous nest, e.g., old eggshells, recent eggs, or the previous year's hatchlings. The majority of copied nests were constructed by a female digging up eggs laid earlier in the season, and replacing them with her own. Nests constructed earlier in the season were more likely to be dug up than those laid later in the season. Twenty-two percent of nests were guarded by females following oviposition, with length of time spent guarding ranging from 1 to 10 days. Half of the observed nests were destroyed by conspecific females, but 92% of destroyed nests were unguarded. Inter-female interactions in tuatara nesting appear to involve a tradeoff between individuals using the nest site of other females as a cue in nest site choice, and guarding their own nest against other females making the same choice. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms underlying population declines is critical for preventing the extinction of endangered populations. Positive feedbacks can hasten the process of collapse and create an ‘extinction vortex,’ particularly in small, isolated populations. We provide a case study of a male-biased sex ratio creating the conditions for extinction in a natural population of tuatara (Sphenodon punctatus) on North Brother Island in the Cook Strait of New Zealand. We combine data from long term mark-recapture surveys, updated model estimates of hatchling sex ratio, and population viability modeling to measure the impacts of sex ratio skew. Results from the mark-recapture surveys show an increasing decline in the percentage of females in the adult tuatara population. Our monitoring reveals compounding impacts on female fitness through reductions in female body condition, fecundity, and survival as the male-bias in the population has increased. Additionally, we find that current nest temperatures are likely to result in more male than female hatchlings, owing to the pattern of temperature-dependent sex determination in tuatara where males hatch at warmer temperatures. Anthropogenic climate change worsens the situation for this isolated population, as projected temperature increases for New Zealand are expected to further skew the hatchling sex ratio towards males. Population viability models predict that without management intervention or an evolutionary response, the population will ultimately become entirely comprised of males and functionally extinct. Our study demonstrates that sex ratio bias can be an underappreciated threat to population viability, particularly in populations of long-lived organisms that appear numerically stable. [ABSTRACT FROM AUTHOR]

The costs of nesting to female animals can be substantial, and may dictate patterns of nest-site choice. In particular, females that travel longer distances to nest likely incur greater energetic costs and may be at greater risk of losing territories to conspecific competitors. We examined patterns of nesting migrations for a population of Tuatara on Stephens Island, New Zealand, over 5 yr. We found that only about 7% of female Tuatara observed nesting in a rookery also lived in that rookery. Of 140 females for which we had both residence and nesting locations, 42% traveled to a nesting rookery from their residential area. The average distance traveled by these females was 84 m, and travel was directed toward the rookery closest to a female's residence area. Our results demonstrate that female Tuatara on Stephens Island minimize the distance traveled on nesting migrations. We suggest that the patterns in nesting travel we observed in this population may be due to natal philopatry of nesting females, or to females minimizing the costs of nesting-related travel. [ABSTRACT FROM AUTHOR]

Climate change poses a particular threat to species with fragmented distributions and little or no capacity to migrate. Assisted colonization, moving species into regions where they have not previously occurred, aims to establish populations where they are expected to survive as climatic envelopes shift. However, adaptation to the source environment may affect whether species successfully establish in new regions. Assisted colonization has spurred debate among conservation biologists and ecologists over whether the potential benefits to the threatened species outweigh the potential disruption to recipient communities. In our opinion, the debate has been distracted by controversial examples, rather than cases where assisted colonization may be a viable strategy. We present a strategic plan for the assisted migration of tuatara ( Sphenodon punctatus), an endemic New Zealand reptile. The plan includes use of extant populations as reference points for comparisons with assisted-colonization populations with respect to demography, phenotypic plasticity, and phenology; optimization of genetic variation; research to fill knowledge gaps; consideration of host and recipient communities; and inclusion of stakeholders in the planning stage. When strategically planned and monitored, assisted colonization could meet conservation and research goals and ultimately result in the establishment of long-term sustainable populations capable of persisting during rapid changes in climate. [ABSTRACT FROM AUTHOR]

Estimates of population size are necessary for effective management of threatened and endangered species, but accurate estimation is often difficult when species are cryptic. We evaluated effectiveness of mark-recapture techniques using the Lincoln-Peterson estimator for predicting true census size of a population of tuatara (Sphenodon punctatus), a burrowing reptile that is a conservation priority in New Zealand. We found that Lincoln-Peterson estimates (NN^ = 85) were accurate for predicting the census size (N = 87) after only a 3-day mark-recapture survey. We recommend this method as a cost-effective way to accurately estimate population size for isolated, inaccessible tuatara populations, because it requires limited personnel, expertise, and time, and has low environmental impact on fragile sites. [ABSTRACT FROM AUTHOR]

We investigated whether incubation treatment or size influence sprint speed of tuatara (Sphenodon punctatus) as artificial incubation is often used to produce founders for new populations of this endangered reptile. Sprint speed was affected by age, clutch and incubation regime (natural vs. artificial incubation). Older juveniles ran faster than younger juveniles. Maternal influence, represented by clutch, accounted for 18% of the variance in sprint speeds at one month of age. Naturally incubated juveniles were the smallest animals of any incubation regime, but at 10 months of age these juveniles were the fastest runners. Naturally incubated juvenile tuatara were more aggressive and faster for their size than artificially incubated juveniles, suggesting they may have higher fitness when released. [ABSTRACT FROM AUTHOR]

Background: The sex of many reptiles is determined by the temperature an embryo experiences during its development. Three patterns of temperature-dependent sex determination (TSD) have been defined, but one pattern where only males are produced above an upper temperature threshold (Type IB) is controversial. Here we report new data on the relationship between constant temperature incubation and sexual phenotype in two species of tuatara (Sphenodon), archaic reptiles of enormous zoological significance as the sole representatives of a once widespread reptilian order. Results: In both species, the pattern observed with constant incubation temperatures from 18 to 23°C (or 24°C) supported a female→male (FM or Type IB) pattern of TSD: in Sphenodon guntheri males were produced above a pivotal temperature of 21.6°C, and in S. punctatus (unnamed subspecies on Stephens Island, Cook Strait), males were produced above a pivotal temperature of 22.0°C. The pivotal temperatures and scaling parameters differed between species (p < 0.001). The thermosensitive period (TSP), where temperature influences gonad morphogenesis, occurs between 0.25 and 0.55 of embryonic development. While it is possible that the more common female→male→female (FMF or Type II) pattern exists, with a second pivotal temperature above 23-24°C, we review several lines of evidence to the contrary. Most notably, we show that in S. punctatus, the warmest natural nests during the TSP produce predominantly males. Conclusion: An FM pattern of TSD could be currently adaptive in promoting sexual size dimorphism in tuatara. However, an FM pattern has particularly serious consequences for S. guntheri because current patterns of global warming could exacerbate the male bias already present in the relic population. [ABSTRACT FROM AUTHOR]

Abstract: Tuatara (Sphenodon punctatus) are threatened New Zealand reptiles with temperature-dependent sex determination (TSD). Higher incubation temperatures produce males, and less than 1 °C separates production of males and females. We investigated variability in nesting ecology to assess whether global warming is likely to result in increasingly male-biased populations. We examined nesting seasons during 1998/1999 and 2002/2003 in New Zealand''s largest tuatara population on Stephens Island, and collected hourly temperature recordings and physical descriptions from 70 nests. Nest depths were not significantly different between years, and ranged from 10 to 230 mm from the soil surface to the top egg. Incubation temperatures in successful nests throughout the year-long incubation period ranged from 1.6 to 38.4 °C. Sex ratios of nests were correlated with incubation temperature: 64% males were produced in 1998/1999, a relatively warm season, but we predict an equal sex ratio was produced in 2002/2003. Although temperatures varied over the 2002/2003 season with respect to monthly long-term averages, 2002 was the second warmest year on record. Stephens Island supports a wide range of nesting habitat, a relatively large population of tuatara, and nest characteristics are highly variable. As such, this population is likely to be resilient to global warming in the short term because an equal sex ratio was predicted from a relatively warm season. However, most other islands where tuatara occur are smaller, have smaller populations, and have fewer open areas for nesting and/or shallower soils. These conditions are more likely to produce a male bias in hatchlings because female tuatara do not appear to vary construction of nests with respect to temperature or location. In the extreme, this could lead to the extinction of small populations. [Copyright &y& Elsevier]

The article discusses the effective cross-cultural collaborations between universities and indigenous communities. It cites as example of such partnership the collaboration between the Victoria University of Wellington researchers and the Te Atiawa Manawhenua Ki Te Tau Ihu (Te Atiawa) iwi (tribe) in their effort to conserve the tuatara (Sphenodon spp.). The tuatara are the last living representation of the whole order of the ancient reptiles (Rhynchocephalia) that are endemic to Aotearoa (New Zealand).