Reptiles That Wait for Sex Live Longer
Reptiles that have sex early and frequently in life and feast on meat tend to live fast, die young.
Reptiles that have sex early and frequently in life and feast on meat, tend to "live fast, die young," as the rock-and-roll saying goes, according to a new study.
A team of researchers examined longevity in scaled reptiles (Lepidosaurs) by looking at 1,014 species, including 672 lizards, 336 snakes, five worm lizards and a lizardlike creature called a tuatara. The reptiles were more likely to die at young ages if they reached sexual maturation earlier and laid eggs or gave birth more times than their counterparts did, the study found.
"We observed that more sex (or at least more pregnancies) means shorter life," researcher Daniel Pincheira-Donoso, an evolutionary biologist at the University of Lincoln, in the United Kingdom, said in a statement. "The study revealed that reptiles sexually mature at a younger age will likely have shorter lives, while those who prefer to delay sexual maturity will probably live longer." [Album: Bizarre Frogs, Lizards and Salamanders]
Small herbivorous and omnivorous reptiles also lived longer than similarly sized carnivorous reptiles, the researchers found.
"Vegetal food is an intrinsically low-nutrition food, so we think that those who have these diets experience a reduction in reproductive rates, which in turn increases their lifespan," Pincheira-Donoso said.
The results suggest that vegetarian male and female reptiles that wait until they are older to have offspring and reproduce more slowly tend to live longer lives than their counterparts, the researchers said. They added that the findings support key predictions about longevity and life-history theory, the study of how natural selection influences life events, such as juvenile development and age of sexual maturity, to help animals successfully reproduce. For example, animals that don't reproduce too early in life tend to live longer, research shows.
The researchers looked at detailed information for each species, including data on body size, earliest age of first reproduction, field body temperature of active individuals, reproductive mode, clutch or litter size, brood frequency, diet, and activity time.
Overall, reptiles that lived the longest tended to have "slow" traits. For instance, the longer-living species had delayed reproduction, fewer babies, smaller clutch sizes, larger hatchlings and colder body temperatures compared to their reptile peers that lived shorter lives.
In contrast, reptiles that had frequent and large-sized clutches tended to have short lives. But species with large eggs, compared to their size, tended to have long lives, likely because reptiles lay fewer eggs if the eggs are large than if they are small, Pincheira-Donoso said.
The team also found that reptiles that ate meat tended to grow faster and have sex earlier and more frequently, which may explain why carnivores, such as snakes, tend to have shorter lives. Herbivorous animals probably ate less protein- and nutrient-rich food, leading them to reach maturity later in life and live longer, the researchers said. It's also possible that hunting for meat is more risky than finding fruits and vegetables, which could affect lifespan.
Other studies can test these ideas by feeding a group of species different diets and examining how the food affects growth time and maturity in each animal, the researchers said.
The study was published Oct. 22 in the journal Global Ecology and Biogeography.
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Scaled reptiles, such as this Chinese gecko, have longer lives if they skip sex when they're young.
Hugging trees feels good and can even be healthy for many animals, according to a study in the latest issue of
. There are several perks to being a tree hugger, but a surprising one is that trees help to regulate the hugger's body temperature. That's one reason why koalas are so often seen hugging trees.
In fact, koalas have evolved bodies that are perfectly suited for the task. "Koalas have thinner fur in their bellies, which we suspect is to aid close contact with the tree trunk," senior author Michael Kearney told Discovery News. On hot days, he said that koalas "are aiming to cool the vital organs in their chests as well as their brains by losing heat through their chests and groin areas." Kearney is a zoologist at the University of Melbourne. He conducted the study with project leader Natalie Briscoe and four other researchers.
As part of the study, Briscoe, Kearney and their team examined how tree hugging affected koala body temperature. In this thermal image, purple tones are the coldest, with the lightest (yellow) colors indicating warmth. Orange tones show temperatures in between those two extremes. Trees gain heat from the koala body. As this happens, the koala cools off.
Kearney explained that as a koala hugs, "The blood flowing through the body would continually replenish cooled blood near the parts of the koala in contact with the tree with warm blood from other parts of the body, with the ultimate effect of cooling the whole body down."
Briscoe, Kearney and colleagues shared that other animals, such as leopards, hug trees too. Leopards, other big wild tree cats and even tree-climbing house cats might look like they are just lounging on branches, but they too tend to hug trees, using the tree's cooler internal temps to cool down their bodies.
Many bat species go to a lot of trouble to hug trees, having to hang on with their toenails. Some trees turn out to be better than others for body temperature regulation.
Kearney explained, "Trees with smooth bark seem preferable because they have what's called a 'high thermal conductivity,' which means heat flows faster into or out of the object. Also, larger trees with thicker trunks are cooler."
Group hug, anyone? Many species of bats, and particularly those that consume fruit, frequently hug trees en masse. In addition to regulating body temperature, trees can provide food and shelter. Kearney added, "It helps to stay attached to the tree on a windy day."
Cold-blooded animals, such as small reptiles, are more vulnerable to temperature extremes. By hugging trees, they help to control their body temps. Briscoe and her team are not sure if trees help to warm animals on cold days, but they haven't ruled out that possibility.
This green tree monitor lizard appears to have found a perfect spot on a tree. Another green tree monitor lizard nearby benefits as well. The study found that Acacia trees were amongst the coolest during hot days. Acacias are therefore sought out by koalas and other animals.
Both big and small primates (such as this tiny tarsier) seem to enjoy hugging trees, gaining the body temperature regulation benefits. It's not entirely clear why trees are so good at keeping their cool.
"We don't fully understand the mechanism," Kearney said, "but suspect it has to do, in part, with cool ground water being drawn up by the tree as it transpires, and in part because of the tree's thermal inertia." "Thermal inertia" is the degree of slowness with which the temperature of a body approaches that of its surroundings.
One of the two young chimps shown here is hugging what's left of a tree. Deforestation harms countless species. The new findings suggest that animals, ranging from large primates to small invertebrates, could become overheated during hot days without the cooling effect of trees on their bodies.
Squirrels, as for big cats, use trees as the ultimate lounging pads. Squirrels, such as this one, could be hugging trees to cool their body temperature. The squirrels and other animals might not consciously know this. To them, it likely just feels good.
Being primates, our human ancestors likely spent a lot of their time hugging trees. Most trees are the perfect shape for hugging, given that we and many other animals can wrap two or more limbs around them.