A vegetarian diet and putting off sex until late in life could be the secret to living longer, at least if you’re a reptile. These are the interesting conclusions drawn by a large new study that looked at how longevity, environmental characteristics and life-history traits are connected in ectotherms, or “cold-blooded” animals. While the researchers have yet to extend their work to include mammals and birds, they predict that the same is probably true for these animals as well.
For the study, which has been published in Global Ecology and Biogeography, an international team of researchers looked at the lifespans of over 1,000 lepidosaurs, which are reptiles with overlapping scales. They gathered a large amount of data for each species, which included 672 lizards and 336 snakes, such as information on body size, age at first reproduction, body temperature, diet and clutch or litter size.
They discovered that overall, lepidosaurs with “slow” life-history traits tended to live longer. These are characteristics such as delayed reproduction, less offspring and colder body temperatures. Conversely, individuals that started popping out young earlier in life and invested more in reproduction, i.e. had frequent and large clutches, had shorter lifespans. This is likely because reproduction incurs both ecological and physiological costs, such as increased energy demands and suppression of immune function. Interestingly, those that had large eggs compared to their body size live longer, probably because reptiles lay fewer eggs if they’re larger.
“We observed that more sex (or at least more pregnancies) means shorter life, very much like the rock star adage ‘live fast, die young,’” study author Dr. Daniel Pinchiera-Donoso said in a news release.
With regards to diet, herbivores trumped the competition and lived longer than carnivorous species. This is probably due to the fact that meat will provide the animals with more protein. Animals indulging in meat will therefore likely grow faster and reproduce more, whereas herbivores will reach sexual maturity later and hence experience diminished reproduction rates. However, it’s also possible that shorter lifespans experienced by carnivores could be due to the fact that pursuing prey can be dangerous and result in injury or death. Furthermore, eating meat also carries a higher risk of acquiring parasites.
Lastly, the team also found that body size and habitat can influence longevity. Larger species living at higher latitudes in cold regions were found to generally live longer, which is likely due to the fact that animals living at lower temperatures often hibernate and therefore have shorter seasons of activity. Warmer environments, on the other hand, will lead to high metabolic rates and faster growth, and hence a fast rate of living.
While the study involved collecting a large amount of data, the findings could probably be made more watertight if the investigation was extended to include lab studies in which diet could be controlled.