Cane Toad Personalities Key to Territorial Takeover
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.Why Koalas Sound Like Barry White
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.Koalas Change Trees From Day to Night
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."
David Berkowitz, Wikimedia Commons
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.PHOTOS: Snow Leopard Cub Makes its Debut
US Fish and Wildlife Service
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.The Amazing Link Between Bats and Dolphins
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."Bizarre Sighting: Cane Toad Eating a Bat?
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.Once 'Extinct' Pinocchio Lizard Pokes His Nose Out
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.
Kok Leng Yeo
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.PHOTOS: Funniest-Faced Monkeys
"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.
Delphine Bruyere, Wikimedia Commons
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.
Mr. TinDC, Flickr
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.Innovations Inspired by Animals
Cane toads with the personality to boldly go where no cane toad has gone before pave the way for more timid toads to rapidly take over new territories, say Australian researchers.
First introduced into Queensland in the 1930s, cane toads are now found as far south as Sydney and as far west as Kununurra. Despite originating from the rainforests of South America, the toads have managed to conquer some of the hottest and driest parts of the Australian continent.
To understand why cane toads continue to venture into new and potentially hostile environments, the scientists put cane toads from a recently established population in the Northern Territory through a mix of behavioural tests.
They found that some toads were bold and daring, while others were shy and cautious, they report in the journal PLoS One .
It is this mix of bold and shy personalities that has given the cane toads a foothold in Australia, says study co-author Professor Rick Shine of the University of Sydney.
"It is a pretty amazing situation that most frogs are stay-at-home creatures and don't really move too far from where they live, yet here we have got cane toads romping across the landscape," Shine says.
"But if cane toads were all timid then presumably they would still be sitting in Queensland."
To examine how personality traits varied within a cane toad population, the researchers set up feeding stations in the field using artificial lights to attract both insects as food and wild cane toads.
At some of the feeding stations the researchers placed a single cane toad in a mesh enclosure while the other feeding stations were left empty, allowing the wild toads to choose between an empty foraging site or one with another toad present.
A total of 95 cane toads approached the feeding stations within a two-hour period, with an almost even mix between those happy to eat on their own and those that preferred another toad to be present.
Shine says the presence of another toad in the area provided some of the toads with valuable social cues about the suitability of the area for foraging. But for those toads that fed alone, the social cues weren't needed.
To further test their personalities, the researchers placed each toad into a makeshift shelter in the laboratory and timed how long it took for the toad to leave the shelter and begin exploring its new environment.
They found the cane toads that happily ate on their own left their shelters much quicker than the more social cane toads, which tended to be more timid.
Bold v timid toads
"The bolder toads were happy to waltz out and walk around and the other guys stayed hiding," says Shine.
"It shows that some toads are prepared to leap out there into the unknown while some are scaredy-cats."
Shine believes it is the bold cane toads that venture forth and invade new areas. The shy toads follow on later, using social cues from the bolder toads to guide them. The result is a rapid swell in cane toad numbers in the first few years following the invasion into a new area.
"To boldly go where no toad has gone before is probably the sort of thing that a bolder individual is going to do better than a shy individual."
While there are advantages to being a bold toad, such as less competition for food, Shine says there is also the added risk of greater predation.
"Being the bold toad may well pay off or it may end up with you being dinner for the local rats," he says.
"So a population with a mix of personalities is probably going to do better than either one alone. You need a few extroverts as well as a few introverts."
Article originally appeared on ABC Science.