The tuatara is a unique New Zealand reptile, the sole surviving member of the ancient order Rhynchocephalia, a lineage that once flourished alongside the dinosaurs of the Mesozoic era. Endemic to a handful of offshore islands, this creature is often regarded as a living relic due to its remarkably unchanged body plan over millions of years. This distinctive species possesses a suite of unusual biological traits that set it apart from modern lizards and snakes, including a specialized dental structure and a vestigial “third eye” on the top of its head. The most fascinating of these traits, however, is the tuatara’s extraordinary capacity for long life.
The Tuatara’s Exceptional Lifespan
The average tuatara in the wild is expected to live for over 60 years, with many individuals routinely surviving to reach 100 years of age. This longevity places the tuatara among the longest-living reptiles, second only to some species of giant tortoises. Recent studies suggest they can live for up to 137 years.
The most famous example of this extreme longevity is a male tuatara named Henry, who resided at the Southland Museum in New Zealand and became a father at the age of 111. Researchers verify these extreme ages through a technique called skeletochronology, which involves examining growth rings in the tuatara’s bones, similar to counting rings in a tree trunk. This method, combined with decades of long-term mark-and-recapture studies on island populations, helps scientists track individual animals and accurately confirm their advanced ages.
Biological Mechanisms Behind Longevity
The tuatara’s secret to long life is rooted in its ectothermic, or cold-blooded, physiology and its adaptation to New Zealand’s relatively cool environment. Unlike most reptiles that thrive in much warmer conditions, the tuatara has the lowest optimal body temperature of any known reptile, operating efficiently between 16 and 21 degrees Celsius. This preference for cooler temperatures directly influences the animal’s basal metabolic rate, slowing down all internal processes.
The resulting low metabolic rate minimizes the rate of cellular wear and tear throughout the tuatara’s body. This reduction in metabolic activity means fewer byproducts of energy production, such as reactive oxygen species, are generated. Reactive oxygen species are unstable molecules that can cause oxidative stress, leading to cellular damage and accelerating aging.
Genetic analysis reveals that the tuatara’s genome contains a high number of genes that code for selenoproteins. These specialized proteins play a significant role in antioxidant defense and DNA repair, offering enhanced protection against the oxidative stress that contributes to aging. This physiological and genetic combination allows the tuatara to maintain its tissues and organs in better condition for a far longer period than most other vertebrates.
Slow Life Cycle and Reproductive Maturity
The tuatara’s extreme lifespan is accompanied by an exceptionally slow life cycle and developmental timeline. They are among the slowest-growing reptiles, continuing to increase in size for the first 35 years of their lives before reaching full adult size. This extended growth period is a clear sign of their overall slow pace of life, which contrasts sharply with fast-growing, shorter-lived species.
Attaining sexual maturity is an equally drawn-out process, taking between 9 and 20 years, depending on the population and individual. While some females may begin breeding at nine years old, males often do not become reproductively active until they are closer to 20 years of age. Even once mature, the reproductive cycle remains infrequent for females, who typically lay eggs only once every two to five years.
The incubation period for the eggs is also remarkably long, lasting between 11 and 16 months, sometimes with development temporarily stopping during the cold winter months. This protracted reproductive timeline, from slow development to infrequent breeding, is linked to the tuatara’s low metabolic rate and its strategy for longevity. This combination of slow growth, late maturity, and infrequent reproduction makes the tuatara particularly vulnerable to environmental threats.