Rodents Show Empathy for Loved Ones in Pain
The findings may help scientists better understand human disorders such as autism and schizophrenia, where a person's sense of empathy is disrupted.
Dogs, dolphins and elephants are known to show empathy when a loved one is in pain, and now researchers have found the first consoling behavior in a rodent, known as the prairie vole.
Researchers say the findings, published Thursday in the US journal Science, could help scientists better understand human disorders such as autism and schizophrenia, in which a person's ability to sense the emotions of others is disrupted.
The secret to empathetic behavior lies in the hormone oxytocin, which promotes maternal bonding and feelings of love among humans, too.
Scientists at the Yerkes National Primate Research Center at Emory University created an experiment in which they isolated prairie voles - dark rodents which mate in long-term monogamous pairs and raise their offspring together - from others they knew.
Then they gave one prairie voles a series of mild shocks before returning it to its loved one.
Once reunited, the unaffected rodents swiftly began to lick and groom the fur of the animals that were in distress after the shocks.
They "licked the stressed voles sooner and for longer durations, compared to a control scenario where individuals were separated but neither was exposed to a stressor," said a statement from Emory University.
Consoling behavior was also not seen in prairie voles that were unfamiliar with each other before being separated.
Knowing that in the human brain, the receptor for oxytocin - also known as the love hormone - is associated with empathy, researchers decided to block this neurotransmitter in the brains of some of the animals.
They found that blocking oxytocin caused the animals to stop consoling each other.
"Many complex human traits have their roots in fundamental brain processes that are shared among many other species," said co-author Larry Young, director of the Silvio O. Conte Center for Oxytocin and Social Cognition at Emory University.
Young said his research points to a potential role for oxytocin in the treatment of autism spectrum disorder, though more work is needed.
"We now have the opportunity to explore in detail the neural mechanisms underlying empathetic responses in a laboratory rodent with clear implications for humans."
According to study co-author Frans de Waal, who first discovered animal consolation behavior in chimpanzees in 1979, the findings also shed new light on the range of animals that feel empathy, and how empathy is separate from complex cognition.
"Scientists have been reluctant to attribute empathy to animals, often assuming selfish motives," he said.
"These explanations have never worked well for consolation behavior, however, which is why this study is so important."
Rats aren't exactly known for their social graces. Certainly where there is one rat, there are bound to be many more, and rats in a large-enough group can create swarms at cause plagues. Humans typically associate rats with selfish behavior, however. Consider the idiomatic expressions related to rodents. "To rat" on someone means to speak out against an individual's bad behavior to enhance one's own reputation. "A rat race" refers to a fiercely competitive struggle. Rats do exhibit selfless behavior, find researchers at Champalimaud Centre for the Unknown, in Lisbon, Portugal. Experimenters placed rats into pairs and provided one of the rats a choice: open one door and get a food morsel for yourself; open another and both rats receive a reward. Out of 15 rats tested, all but one made unselfish choices consistently. The rats in fact selected the prosocial outcome around 70 percent of the time. These findings are in line with previous studies that show rats seem to have each other's back. They will attempt to free a trapped comrade and exhibit pain and anxiety responses at the sight of another rat in distress. Rats aren't the only animals that have found a survival advantage in altruism. In fact the animal world is full of species you might not expect to be quite so selfless.
Red squirrels may be furry and cute, but they're typically solitary and territorial animals. Red squirrels set out on their own between nine and 11 weeks of age. From then on, the only interactions they have with other squirrels are when squirrels pair up to mate and care for their young. Despite their isolation from one another, scientists who published a 2010 study in the journal Nature Communications found that
if the mother dies while caring for her young. Squirrel adoption is an exceedingly rare event, however; the researchers only observed five cases out among more than 2,000 litters over two-decade-long period.
Dogs famously are referred to as man's best friend, but there are other species as well with whom dogs have established friendships. Like red squirrels, dogs will take in orphans in need of a parent's care and attention. Unlike red squirrels, dogs don't necessarily care whether the animal is a family member or even a member of the same species. Dogs have been documented adopting
, lambs and more. This behavior is selflessly altruistic, as the dog couldn't expect any benefit from caring for a member of another species.
Dolphins are animals that may as well swim in a conga line because they always seem to have each other's backs... or dorsal fins as the case may be.
documenting the ways researchers observed dolphins supporting other members of their pod. If one dolphin were injured, another might stay behind to act as a guardian, potentially exposing itself to predators. If a dolphin were enfeebled and couldn't easily surface for air, another might swim underneath and provide a nudge for the assist. Dolphins have come to the aid of one another, but also other species, including humans. There have been numerous stories of pods of dolphins rescuing humans from sharks,
who was stalked by a shark on a swim to raise money for whale and dolphin conservation in 2014.
Are all primates as charitable as humans? Looking at the evidence regarding chimpanzees suggests one of our closest human relatives can be altruistic as well. Although some previous studies had concluded chimps were indifferent to the welfare of their own kind, research published in the Proceedings of the National Academy of Sciences in 2011 shows that these
, based on an experiment similar in design to the one conducted on the rats, with a food reward either going to one animal or a pair depending on the choice of the subject. Another study conducted in 2007 at Ngamba Island Chimpanzee Sanctuary in Uganda found that chimps were even willing to help humans without the immediate possibility of reward. Chimps in the wild have also shown similar cooperative behavior, with relative regularly sharing food and adopting orphans within the group whose parents had died.
Fish travel in schools, so it makes sense that they cooperate with one another. But some species will work with others in order to achieve a mutually beneficial outcome. Grouper will partner will eel and wrasse during a hunt, while coral trout will join up with octopuses in order to catch their prey,
. Both the grouper and the coral trout use a rudimentary form of "sign language" to signal prey to their hunting party.
The raven was anything but accommodating to the narrator of Edgar Allen's most famous poem. Aside from their black feathers, ravens are also known for their intelligence. But like a human with too much intelligence and not enough sense, are these birds so clever they don't feel the need to be charitable? Apparently not,
who spent three years observing these birds in the forests of Maine during the 1990s. When a hungry raven stumbled unto a major kill, rather than immediately gorging itself, as any animal solely interested in its own survival would be expected to do, the raven lets out the equivalent of a yell to alert other birds in the area of the available meal. The call signals not only relatives but other ravens who are completely unknown to the food finder. The behavior serves a purpose, however. Ravens belong in one of two groups, according to the researchers: residents and wanderers. Residents have backup in case their find food, but wanderers don't. In sounding the food bell for the whole neighborhood to hear, a wanderer can attract a big enough crowd, particularly other young wanderers, that it won't be displaced by residents who might otherwise claim a kill for themselves.
Vampire bats aren't cuddly creatures. Anything with a reputation for consuming the blood of its prey won't win many friends. But vampire bats do look out for their own. Given that vampire bats have a fast metabolism and will die if they don't feed every day or two, one might expect that it was every bat for itself come meal time. However, bats will share their food supply not only with juveniles but also adults who weren't fortunate enough to find their own grub,
. A successful hunter will regurgitate enough blood into a hungry bat's mouth to allow the roostmate to live another day. The gift of a meal one night could be reciprocated the next, so it pays for bats to answer the door, metaphorically-speaking, when its neighbor comes knocking for a spot of blood.
Given that a single colony can include up to tens of millions of members, ants certainly possess teamwork skills. This trait can be credited for giving ants a foothold on every continent except Antarctica. Colony unity depends on individual ants working to fulfill their respective roles. Sterile worker ants, for example, will care for the offspring of the queen of a colony. Some ants go even further, however, giving up their lives for the sake of the colony. When they fall ill or are near death, worker ants of the species
will leave the colony and spend the last of their energy getting as far away as possible in order to prevent illness from spreading,
. Other ants,
, explode in a poisonous spray if they are in a losing fight with a potential threat to the colony.
Similar to ants, honeybees operate as a kind of superorganism with a well-defined hierarchy. The queen is on top, and the worker bees and drones spend their lives supporting the colony, toiling within an age-based system determining division of labor. Given that the queen is the lynchpin for the entire colony, it's fair to assume her absence would lead to anarchy.
A study published in the journal Current Biology/url], however, found that honeybees can function even in the absence of the queen through which they are all related. In the absence of a queen bee, a number of workers will split their time between reproduction, an arguably selfish but metabolically challenging task, and foraging and defense duties, prosocial but risky. The specialists become generalists to try to keep the colony buzzing. Unfortunately, unless the colony was in the midst of raising a new queen before the old one died, a queenless colony is a doomed enterprise, as workers can only produce male drones. Once all of the worker bees are gone, the colony collapses.