Why do baby mammals tend to play?

Why do babies of any mammal tend to play ? From humans to small dog pups, cubs of a lion, baby bears, etc.

*I am not sure if the tag I chose is correct or not. Please correct me if I'm wrong.

Paternal care

In biology, paternal care is parental investment provided by a male to his own offspring. It is a complex social behaviour in vertebrates associated with animal mating systems, life history traits, and ecology. [1] Paternal care may be provided in concert with the mother (biparental care) or, more rarely, by the male alone (so called exclusive paternal care).

The provision of care, by either males or females, is presumed to increase growth rates, quality, and/or survival of young, and hence ultimately increase the inclusive fitness of parents. [2] [3] [4] In a variety of vertebrate species (e.g., about 80% of birds [5] and about 6% of mammals), [6] both males and females invest heavily in their offspring. Many of these biparental species are socially monogamous, so individuals remain with their mate for at least one breeding season.

Exclusive paternal care has evolved multiple times in a variety of organisms, including invertebrates, fishes, and amphibians. [7] [8] [9]

Why Children Like Repetition, and How It Helps Them Learn

“Again!” My 4-year-old son Edwin likes to yell over and over again when he finds a new activity or joke that he likes. My 16-month-old, Charlie, likes to repeatedly throw objects on the floor from his high chair or even against the wall if it makes an interesting sound. They both like to hear the same stories every night before bed, they like to eat the same foods for lunch, they like to play with the same toys and watch the same movies every day. When they find something they like, they want to do it over and over and over again.

Why do children like repetition so much? An early developing preference for the familiar is actually quite common in infancy and early childhood. These preferences begin to develop before a baby is even born—in the third trimester of pregnancy. At that point, fetuses can taste, smell, and hear, and as a result, at this time, they begin to develop preferences for familiar flavors from their mother’s food in the amniotic fluid that floats around them (Schaal, Marlier, & Soussignan, 2000 Menella, Jagnow, & Beauchamp, 2001). They also develop preferences for familiar sounds, like the sound of their mothers’ voice (Kisilvesky et al., 2003), their native language (Moon, Cooper, & Fifer, 1993), or even familiar stories that are read to them from outside the womb (DeCasper & Spence, 1986). This trend continues after they’re born, and only after a few hours of exposure, newborns develop a fast preference for their mother’s face (Field, Cohen, Garcia, & Greenberg, 1984). Soon after, they develop preferences for faces in general (Johnson & Morton, 1991), all based on familiarity.

This preference for the familiar might be adaptive—creating an early affinity for the people that are most likely to take care of them.

So perhaps it’s not surprising that children like to read the same books, watch the same movies, and sing the same songs on repeat every day. In fact, there is evidence that this repetition might even support learning.

Not surprisingly, research has shown that children learn better from reading a book over and over again than just reading it once or twice. In one study, researchers presented 3-year-old children with the same new words in three stories over the course of a week. The new words were exactly the same for all children, but half of the children were presented with the words in the same exact story repeated three times, while the others heard the same words in three different stories. Children learned the words better when they heard the same story repeated than when they heard the same words presented in three different stories (Horst, Parsons, & Bryan, 2011).

The same trends have been found for babies. In a similar study, researchers presented 18- to 24-month-olds with a storybook that detailed specific actions needed to make and shake a toy rattle. Infants were read the book either twice or four times, and the researchers found that the more the babies were read the book, the more they imitated the actions they learned (Simcock & DeLoache, 2008). Repeated exposure to actions presented on television also leads to more frequent imitation (Barr, Muentener, Garcia, Fujimoto, & Chavez, 2007).

People often say that practice makes perfect. Research certainly supports this, especially in children. In fact, studies have shown that repetition can be critically important for learning in general (e.g., Karpicke & Roediger, 2008)—especially for memory (Hintzman, 1976) and language learning (Schwab & Lew-Williams, 2016). So while adults can easily pick up new information from a single exposure, when kids ask to watch the same movie they’ve already seen a hundred times or read the same book before bed for the 10th night in a row, it might just be their way of learning the storyline. And although it might be boring or even annoying to do the same thing over and over and over (and over and over) again, this extra practice might be just what children need to learn new things.

Barr, R., Muentener, P., Garcia, A., Fujimoto, M., & Chávez, V. (2007). The effect of repetition on imitation from television during infancy. Developmental Psychobiology, 49(2), 196-207.

DeCasper, A. J., & Spence, M. J. (1986). Prenatal maternal speech influences newborns’ perception of speech sounds. Infant Behavior and Development, 9, 133-150.

Field, T. M., Cohen, D., Garcia, R., & Greenberg, R. (1984). Mother-stranger face discrimination by the newborn. Infant Behavior and development, 7(1), 19-25.

Hintzman, D. L. (1976). Repetition and memory. In Psychology of learning and motivation (Vol. 10, pp. 47-91). Academic Press.

Horst, J. S., Parsons, K. L., & Bryan, N. M. (2011). Get the story straight: Contextual repetition promotes word learning from storybooks. Frontiers in Psychology, 2, 17.

Johnson, M. H., & Morton, J. (1991). Biology and cognitive development: The case of face recognition. Oxford, England: Basil Blackwell.

Karpicke, J. D., & Roediger, H. L. (2008). The critical importance of retrieval for learning. Science, 319(5865), 966-968.

Kisilevsky, B. S., Hains, S. M. J., Lee. K., Xie, X., Huang, H., Ye, H. H., Zhang, K., & Wang, Z. (2003). Effects of experience on voice recognition. Psychological Science, 14, 220-224.

Mennella, J. A., Jagnow, C. P., & Beauchamp, G. K. (2001). Prenatal and postnatal flavor learning by human infants. Pediatrics, 107(6), E88.

Moon, C., Cooper, R. P., & Fifer, W. P. (1993). Two-day-olds prefer their native language. Infant behavior and development, 16, 495-500.

Schaal, B., Marlier, L., & Soussignan, R. (2000). Human fetuses learn odours from their pregnant mother’s diet. Chemical Senses, 25, 729-737.

Schwab, J. F., & Lew-Williams, C. (2016). Repetition across successive sentences facilitates young children’s word learning. Developmental Psychology, 52(6), 879-886.

Simcock, G., & DeLoache, J. S. (2008). The effect of repetition on infants' imitation from picture books varying in iconicity. Infancy, 13(6), 687-697.

Why Is Same-Sex Sexual Behavior So Common in Animals?

For a very long time, scientists have known that animals engage in sexual behavior with individuals of the same sex. Such same-sex sexual behavior (SSB)* can include, for example, mounting, courting through songs and other signals, genital licking or releasing sperm, and has been observed in over 1,500 animal species, from primates to sea stars, bats to damselflies, snakes to nematode worms.

In recent decades, numerous hypotheses have been proposed and tested to understand why animals engage in these sexual behaviors that do not directly lead to reproduction. In a theoretical perspective published in Nature Ecology and Evolution, we reflect on the hypotheses proposed by biologists to explain SSB, and on the widespread but unquestioned assumptions that underlie them.

Common to all the hypotheses proposed to explain SSB is the characterization of SSB as an &ldquoevolutionary paradox&rdquo because it persists without obviously contributing to an animal&rsquos survival or reproductive success (what biologists call &ldquofitness&rdquo). As a &ldquoparadox,&rdquo SSB is assumed by biologists to be so obviously costly that it must either yield tremendous benefits or be otherwise impervious to elimination by natural selection.

Moreover, most scientists who study SSB tend to focus exclusively on its presence in a single species of interest, leading to the unacknowledged assumption that SSB evolved independently in each of the animal species in which it is observed. But are these assumptions well-founded? We argue that they are not, and that they are perhaps rooted more in cultural norms than in scientific rigor.

First, the costs of SSB are often assumed to be high because engaging in SSB leads individuals to waste time, energy and resources without obvious gains in fitness. The costliness of SSB is often emphasized in comparison to the benefits of having sex with an individual of a different sex (different-sex sexual behavior or DSB). While DSB can certainly lead more obviously to higher fitness through the production of offspring, these comparisons assume that DSB is highly efficient.

However, animals often mate many times to produce just a few offspring, and acts of DSB frequently do not result in reproduction for a whole host of reasons. In other words, DSB can be costly too, and it is rarely clear whether mating with an individual of the same sex is comparatively costlier than any other reason why sexual behavior may not lead to reproduction.

Second, for other traits that are as widespread across so many species as SSB, biologists often consider the evolutionary possibility that the trait evolved just once or a few times in the species&rsquo common ancestor, rather than many independent times. As far as we can tell, no such evolutionary scenario has been considered for SSB. Finally, both of these assumptions underlying previous research on SSB are reinforced by a heteronormative worldview under which SSB is seen as aberrant, perhaps explaining where these assumptions came from and why they were so rarely questioned.

In our paper, we argue for a subtle shift in perspective that offers new ways of understanding the diverse and endlessly fascinating world of animal sex, including SSB. We explicitly move away from viewing SSB as aberrant or as mutually exclusive from DSB, instead acknowledging that individuals and populations of animals can engage in a spectrum of sexual behaviors that include both DSB and SSB in a vast array of combinations.

This perspective leads us to propose the following alternative scenario: what if SSB has been around since animals began to engage in sexual behavior of any kind? In our hypothesis, the ancestral animal species mated indiscriminately with regard to sex, i.e., they mated with individuals of all sexes, if only because it is unlikely that the other traits required to recognize a compatible mate&mdashdifferences in size, shape, color or odor, for example&mdashevolved at exactly the same time as sexual behaviors.

Indeed, indiscriminate mating can be more beneficial than it is costly. Mate recognition can require physiologically and cognitively costly adaptations, and being excessively discriminating in choosing mates can lead individuals to miss out on mating opportunities that lead to reproduction, a significant fitness cost.

And so, we hypothesize that present-day diversity in sexual behavior in animals stems from an ancestral background of indiscriminate mating among individuals of all sexes. In some branches of the animal tree of life, where SSB is actually quite costly, this behavior might be selected against.

But in other taxa where SSB isn&rsquot relatively costly, it may have persisted and even been co-opted to serve other beneficial functions. Scientists currently lack comprehensive knowledge of how common SSB is across species, largely because these behaviors have historically been regarded as unseemly or irrelevant and have only been recorded incidentally. We predict that the systematic documentation of SSB across animal taxa, and the quantification of the costs and benefits of both SSB and DSB, would reveal that it is both more common and less costly than is currently widely assumed.

In presenting our hypothesis of the ancestral origins for SSB in animals, we suggest nothing about conceptualizing human sexual behavior. It should never be the place of science to make normative arguments about people. Indeed, we suggest that human culture has likely had far more impact on the study of biology than vice versa. Instead, we hope our hypothesis will expand understanding of the diversity of the natural world. We encourage scientists to consider what discoveries in evolutionary biology are possible when we break free from the cultural norms and assumptions that have historically constrained scientific creativity.

In this regard, scientists have much to learn from other disciplines, such as science and technology studies (STS), that apply critical lenses to the processes of science. Interdisciplinary collaboration with scholars in such fields has the potential to make science more robust by teaching scientists to account for the inevitable role society and culture play in all forms of research.

The questions we ask shape our understanding of the world, but these questions are also shaped by our understanding of the world. Who we are influences the hypotheses we craft and the assumptions we make. Thus, scientists should be thoughtful about the critical lenses, biases and assumptions we bring to the process of asking questions, designing experiments and interpreting results. Widening the range of perspectives and cultures that have a voice in academic science is critical to the improvement of scientific practice and knowledge-building. Who knows what hypotheses new voices will bring to science in the future?

*Note: We intentionally do not use terms such as &ldquoheterosexual&rdquo or &ldquohomosexual&rdquo to prevent any conflation between human sexuality and nonhuman animal sexual behaviors. Moreover, the terms same-sex sexual behavior (SSB) and different-sex sexual behavior (DSB) more accurately describe the observation of individual sexual interactions, without making assumptions as to how those same individuals may behave in other encounters.

The views expressed are those of the author(s) and are not necessarily those of Scientific American.

Why Whales Got So Big

It’s often said that the ocean releases them from the constraints of life on land. It’s actually the opposite.

The first time I came face to face with a sea lion, I nearly screamed. I was snorkeling, and after a long time spent staring down at colorful corals, I looked up to see a gigantic bull, a couple of feet in front of my mask. Its eyes were opalescent. Its long canines hinted at its close evolutionary ties to land-based predators like bears and dogs. And most unnervingly of all, it was huge.

Mammals tend to get that way when they invade the ocean. The pinnipeds—seals, sea lions, and walruses—tend to be immense blobs of muscle and blubber. The same could be said for manatees and dugongs. And whales are almost synonymous with bigness. Time and again, lineages of furry mammals have gone for a swim and over evolutionary time, they’ve ballooned in size. Why?

Most of the explanations for this trend treat the ocean as a kind of release. The water partly frees mammalian bodies from the yoke of gravity, allowing them to evolve heavy bodies that they couldn’t possibly support on land. The water unshackles them from the constraints of territory, giving them massive areas over which to forage. The water liberates them from the slim pickings of a land-based diet and offer them vast swarms of plankton, crustaceans, and fish to gorge upon.

But William Gearty from Stanford University has a very different explanation. To him, the ocean makes mammals big not because it relieves them of limits, but because it imposes new ones.

“As you enter the water, you start to lose heat from your body that you aren’t losing on land or air,” he explains. To counteract that constant loss of heat, humans use wet suits, whales have blubber, and otters have thick fur. “But really the easiest way to counteract it is to get bigger,” Gearty says. As bodies balloon, volume increases faster than surface area does, so you produce more heat in your body but lose comparatively less of it from your skin. But animals can’t become infinitely big because larger bodies also demand more fuel. There’s only so much food that an animal can reasonably find, catch, and swallow.

So, the need to stay warm sets a floor for the body size of oceanic mammals, while the need to eat sets a ceiling. And the gap between them, Gearty found, is surprisingly narrow—and far more so than on land.

Together with Jonathan Payne, also from Stanford, and Craig McClain from the Louisiana Universities Marine Consortium, Gearty collected data on the sizes of almost 7,000 mammal species, both living and extinct. He showed that the marine groups—whales, manatees, and seals—have all independently hit an average optimum mass of around 1,100 pounds.

There’s obviously a lot of variation around that—a sperm whale is clearly not the same size as a dolphin. But crucially, that variation is much lower in the sea than it is on land. “The minimum size in these aquatic groups is thousands of times larger than the minimum for terrestrial groups, but the maximum size is only 25 times larger,” says Gearty. “I found it strange that no one had noticed before.”

These trends aren’t consistent with the idea of the ocean as a release. Instead, it suggests that the water imposes strict constraints. To thrive in it, mammals must be just the right size—big, yes, but not too big and not too small. And Gearty could calculate the boundaries of this Golidlocks zone with a set of equations that connect a mammal’s size with the heat it loses to the water and the rate at which it can find food. These equations predicted both the optimum 1,100-pound average that seagoing mammals have evolved toward, and the narrow range of sizes around that ideal.

That makes sense, says Samantha Price from Clemson University, who studies mammal evolution. “But evolution is complex,” she says, “and energetic trade-offs may not have driven the evolution of large size in complete isolation.” It’s possible that the other proposed factors, like increased buoyancy, made it easier for marine mammals to hit that Goldilocks zone, by reducing the costs of being larger.

And as always in biology, there are exceptions. Sea otters, for example, are unusually small for marine mammals—they’re about as big as a Labrador. That might be because their extremely thick fur, with up to a million hairs per square inch, allows them to stay warm without being big. They also spend a lot of time on land, where heat loss is less of a problem.

Why do mammals such as canines and felines tend to give birth to a large litter of 3-5. When mammals such as humans, primates, and even cows only have one baby at once?

In the wild, the main goal of animals is thought to be "survivorship", or passing down their DNA to future generations. With this goal in mind, there are two main strategies.

Give birth to a small number of offspring, and care for them for a long time before allowing them to be independent. This way, when they are the most vulnerable at a young age, they have your protection and are unlikely to die. You are sacrificing number of offspring for the benefit of being able to care for the small number.

Give birth to a larger number of offspring, so that at least one of them is likely to survive, purely based on chance. You sacrifice caring for the offspring for the benefit of having a high number of offspring.

I believe this is called the r/K selection theory. More evolved and complex animals tend to have fewer offspring, but spend more time with them.

From a physiological standpoint:

With mammals, the reason why some species like dogs and cats are physically able to have multiple offspring is due to the fact that they release multiple eggs during ovulation. Humans, on the other hand, only release one egg each month, and therefore can only have one child (generally speaking).

This is a pretty good answer. The only thing is that wolves are definitely K-selected.
They have a fairly large litter and about half of the pups will die before they reach sexual maturity, which would sound like r-selection. But they also invest 2-3 years in the pups that do survive. The giant parental investment is a hallmark of K-selection. As is living in a stable group, learning from members of the group, and generally being a predator.

In wolves the large litter size facilitates learning and dispersal. Most of the pups leave the pack after sexual maturity and go to join another.

Also, the r/K theory really comes from things like Lotka-Voltera. Which was developed in lynx. So cats area also K-selected. Again, predators, large parental investment, stable territories and environments, etc. These are all things that would predict K-selection.

The large litters predicting r-selection come into play with things like mice. Mice can easily count on most of their offspring becoming a meal. So they invest very little in each individual offspring and instead produce as many as possible.

So you were on the right track, and your reasoning was good. Just the wrong conclusion.

National Science Foundation - Where Discoveries Begin

A Valentine's Day special on the science of monogamy

Slide show: The many faces of monogamy.

February 13, 2013

Ever have a relationship that qualified as "faithless love"? If so, you're in good company: Almost all adults in the animal kingdom have also experienced, if not a faithless love, then at least a faithless pairing.

Faithless pairings are so common in the animal kingdom because only a handful of animal species practice true monogamy--defined as pair bonding between a male and female, which exclusively mate with one another, raise offspring together and spend time together.

The pair bonds of some monogamous species may last for the long term, even perhaps for a lifetime. Those of other species may last for only the short term, perhaps for only a single mating season.

Who's your daddy?

All expressions of true monogamy--whether characterized by short-term or long-term pairings--have long been considered to be a rarity in the animal kingdom. Nevertheless, since the advent, in the 1990s, of DNA fingerprinting--which is similar to paternity tests used in the courts--scientists have discovered that true monogamy is even rarer than previously believed.

As it turns out, many species that were once considered to be truly monogamous really practice what is known as social monogamy. This form of monogamy is defined as pair bonding between a male and female, which mate with one another, raise offspring together and spend time together, but may nevertheless occasionally mate outside of their pair bond.

Scientists call such outside matings "extra pair copulations."

DNA fingerprinting has revealed that even swans--those icons of love and fidelity--may participate in extra pair copulations, probably during quick, furtive trysts. What's more, about five to six percent of pair bonded swans ultimately "divorce" for unknown reasons.

Looking the other way

The frequency of extra pair copulations among socially monogamous species begs the question: Why would any socially monogamous species tolerate promiscuity?

No one knows for sure. But one theory is that females may tend to pair bond with males that are particularly good providers and offer potential stability, but are lured into extra-pair copulations by males that offer "something else" not provided by their pair bonded partner.

That "something else" may be superior genes, as reflected in the male's physical features, such as his weight or resistance to disease, or his control of particular resources, such as a large territory.

On the other side of the pair bond, males may seek extra-pair copulations in order to increase their chances for reproductive success--even if it turns out that their pair bonded partner is sterile or genetically unfit in some way through promiscuity, a male may fertilize multiple females, and thereby avoid putting all of his genes in one basket.

How rare is rare?

Some statistics on the frequency of monogamy in the animal kingdom:

  • Not a single mammal species has, thus far, been definitively shown to be truly monogamous. (Nevertheless, individual pairs of mammals may be truly monogamous.) Scientists now estimate that only about three to five percent of the approximately 4,000 + mammal species on Earth practice any form of monogamy.
  • Before the advent of DNA fingerprinting, scientists believed that about 90 percent of bird species were truly monogamous. But paternity testing suggests that the reverse is true: Scientists now believe that about 90 percent of bird species are socially monogamous, and that true monogamy among birds is the exception rather than the rule.
  • Some insects, including cockroaches, are monogamous.
  • Any form of monogamy among fish and amphibians is exceedingly rare.

Because of the paradigm-shifting revelations produced by DNA fingerprinting, many scientists are now reluctant to classify any species as truly monogamous until it has undergone rigorous DNA fingerprinting.

Possible reasons for monogamy

The ultimate purpose of life for each individual animal on Earth is to reproduce, and each individual that reproduces successfully helps perpetuate its species. Building on these facts, some scientists believe that monogamy evolved in species whose members are more likely to achieve reproductive success through pair bonding than through promiscuity.

Such species may include those whose populations are relatively small and dispersed: in such cases, the male's investments in monogamous pair bonding may yield more offspring than would his investments in repeatedly searching for hard-to-find females.

Another theory: Monogamy may have evolved in some species in order to support their special caretaking needs. Consider, for example, emperor penguins.

Until an emperor chick becomes independent of its parents, it must be protected in its colony from the harsh Antarctic elements and from predators by one parent, while the other parent travels back and forth to distant seas to feed itself and gather food for the chick--dual responsibilities that a single mother could not possibly fulfill on her own.

Therefore, monogamy may have evolved in emperors in order to support the intense parental cooperation needed by emperor chicks. This theory is supported by the fact that once emperor chicks become independent of their parents and thereby outgrow their need for cooperative parental caregiving, the overwhelming majority of emperor parents (about 85 percent) permanently part ways. (Adult emperors practice serial monogamy, and usually form a new pair bond every breeding season.)

Also, some scientists believe that monogamy may have evolved in some species because their young can be cared for by both of their parents. Such species include bird species whose young survive on food brought to them by both of their parents, which are equally equipped for the task. Because the monogamy of such species supports fatherly caregiving, and thereby promotes reproductive success, the evolution of such species apparently favored some form of monogamy, as the theory goes.

By contrast, baby mammals must be fed via breast-feeding--a need that obviously can only be fulfilled by females. So, almost by definition, the males of most mammal species are generally unequipped to help feed their young. Therefore, such species would not necessarily benefit from a social structure that supports fatherly caregiving, and so their evolution would not necessarily have favored monogamy, as the theory goes.

However, theories about the evolution of monogamy that are based on its support for fatherly caregiving are countered by the fact that the males of some monogamous species do not typically help care for their young--even though the reverse is apparently true: All species in which males typically help care for their young are monogamous, as far as we know.

The joy of monogamy

While environmental factors may influence the evolution of monogamy, so too may genetic factors. Some possible genetic influences on monogamy have been discovered through recent research on prairie voles, which form lifelong social attachments. Specifically, this research identified special hormone receptors located in the reward centers of the brains of male prairie voles. Such special receptors may give the voles a sense of pleasure from monogamy and taking care of young, and thereby help promote these behaviors.

This research also involved transferring the special hormone receptors of prairie voles to other vole species that are promiscuous and do not form social attachments. The result: The promiscuous voles became monogamous, like prairie voles.

What's more, the prairie voles' special receptors are very similar to receptors found in the brains of humans and bonobos. Bonobos, or pygmy chimpanzees, display empathy and maintain strong social bonds. By contrast, these receptors are not present in the brains of common chimpanzees, which are less empathetic and more aggressive.

These results suggest that the special hormone receptors may influence species-to-species differences in social structure. In addition, individual variation in these special receptors among human males may help explain some of the individual variation among men in their attitudes towards commitment, monogamy and marriage.

Probably because varied and complex combinations of genetic and environmental factors influence the reproductive behavior of each species, virtually every species that practices true monogamy or social monogamy expresses their monogamy in a unique way. (See slide show.)

Learn more about the biology of love and other animal emotions in an online chat featuring NSF program director Diane Witt.

Fascinating facts about monogamy from behavioral neuroscientist Bruce Cushing.
Credit and Larger Version

Related Websites
NSF press release on research on monogamy in voles:
Online chat about the science of love and other emotions in the animal kingdom featuring NSF program manager Diane Witt:

Fascinating facts about monogamy from behavioral neuroscientist Bruce Cushing.
Credit and Larger Version

Southern Fried Science

Image from

When people learn that I’m a marine biologist, they often assume I got into this career because I want to be a dolphin trainer. The general public seems to believe that marine mammals are cute and cuddly and innocent, but sharks are cruel and evil and bad. In reality, nature is an amoral place- our morality is, by necessity, anthropocentric and doesn’t really relate to the wild behavior of animals. If this wasn’t the case, though, here are ten reasons why marine mammals aren’t as cute and cuddly and innocent as people sometimes think they are.

1) Female dolphins who have recently given birth are not interested in mating, since they are spending their time and energy taking care of their new baby. Male dolphins know this…and have been known to kill baby dolphins so that the mother is more interested in mating with them.Baby dolphins, I’ll admit, can be cute. Killing a baby dolphin so that you can sleep with the grieving mom is not cute.

2) Dolphins torture and kill baby sharks. While dolphins attacking and sometimes killing adult sharks to protect their babies is understandable, isn’t torturing and killing small animals a sign that you may become a sociopath? At the very least, torturing and killing small animals is not cute.

3) Like sharks, dolphins are efficient and brutal predators. I’ve never understood why people think that sharks are vicious but dolphins are cute when both have similar diets. Dolphins are, if anything, more clever in how they kill their prey. Being better at killing certainly does not make something cute.

4) A beach in Florida was recently shut down because of a mile-long stretch of it was covered by an unknown and disgusting smelling substance. After some research, the substance was determined to be manatee poop. While you and I can speculate if this was intentional economic terrorism all day, logic tells us that something can not simultaneously be disgusting and cute.

5) This image, first discovered by David Honig, is cleverly entitled “Leopard seal pulling the head right off a penguin“. Awesome? Yes. Cute? No.

6) Several of the most common marine mammal diseases are sexually transmitted. Come on now, dolphins. Lots of small children idolize you. You aren’t being very good role models. Wait until you’re married. STD’s are very, very not cute.

7) Orca whales can kill great white sharks, the stereotypical vicious predator. Again, being better at killing than something infamous for being vicious does not make you cute.

8 ) The very existence of Wet Goddess makes dolphins less cute. Just as I can never think of apple pie the same way after watching “American Pie”, I can’t think of dolphins the same way after reading some of what the author wrote. Is that the dolphin’s fault? No, but I don’t care- read some of that book and you will never think of dolphins as cute and innocent again.

9) There is something called a “dolphin assisted birth“, which is like a water birth…except there are dolphins nearby. While this is again not really the dolphin’s fault, inspiring hippies to do crazy things does not a cute animal make.

Again, the very concept of “morality” and “right and wrong” doesn’t apply to the behavior of wild animals. Wild animals just do what they do to survive. However, marine mammals are clearly not as cute and cuddly and innocent as some people believe.

Dinosaurs come out to play (so do turtles, and crocodilians, and Komodo dragons)

The proofs for one of my books arrived the other day, so I have been busy busy busy. This (in part) explains the lack of action here on the blog, and the preponderance of recycled stuff. Sorry about that. In fact, sorry, here's another recycled article from Tet Zoo ver 1. Hopefully I'll have the time to produce some new content over the next week, but don't hold your breath. And sorry about all the dinosaur stuff: I know you much prefer it when I post on frogs, lizards, mice and passerines. Anyway.

As a kid I always got the impression from textbooks that the only tetrapods (and thus only animals) that engage in play behaviour are (1) mammals and (2) a few really smart birds, like corvids and some parrots [Kea Nestor notabilis shown here]. Raptors are also known to engage in play behaviour, with it being relatively well documented that adults will drop feathers in front of their flying juveniles. The juveniles catch the feathers as if they're pretend prey.

But it would seem that play behaviour is not allowed to occur in lissamphibians, non-avian reptiles, or the majority of birds. They just don't do it, or at least no one has ever recorded them doing it. So why do mammals and oh-so-clever corvids and parrots, and predatory raptors, play, and why do other tetrapods not? Maybe so-called 'higher tetrapods' engage in play behaviour because full-blown endothermy allows this sort of superfluous, energy-wasting behaviour maybe it's a result of enhanced encephalisation or maybe it's only possible if extensive parental care allows juveniles enough behavioural 'security' to indulge in carefree behaviour.

All of the above is crap

Well, here's the news. All of the above is crap. You might be surprised to hear that play behaviour is far from unique to mammals and a minority of birds, but has also been documented in turtles, lizards, crocodilians and even lissamphibians and fish (Bekoff 2000, Burghardt 2005). But because the reports discussing or mentioning play behaviour in these animals have been mostly anecdotal, and hence only mentioned as brief asides in larger behavioural studies or in brief one-page notes published in obscure journals, they have largely gone overlooked until recently [Sandhill cranes Grus canadensis, one apparently at play, shown here. From Querencia, taken by Cat Urbigkit].

Hold on: play behaviour in reptiles, amphibians and fish? Before looking at this further we need to sort out exactly what 'play' really is. How can it be defined? Of course this is something that ethologists have been arguing about for decades, and lengthy papers and virtually entire books (see Smith 1984 and Bekoff & Byers 1998) have been devoted to this topic alone. A rough working definition of play might be: a repeated behaviour, lacking an obvious function, initiated voluntarily when the animal is unstressed.

Most play behaviour - namely that observed in mammals and the more intelligent birds - is easily recognized by us because it resembles the sort of activities that we ourselves already recognize as playful. But this creates the obvious problem that play behaviour in other animals might be difficult to recognize because it is rather different from the sort of behaviours we 'expect' to represent play. Juvenile mammals tend to employ obvious honest signals when they're playing: we're all familiar with the 'play face' and bow-like action that canids (wild and domestic) use to initiate play, for example, and the play behaviour that they indulge in - chasing, play-biting, tussling and role-reversing - recalls human play behaviour.

However, if we employ the rough definition used above, behaviours reported widely among tetrapods can be seen in a new light. It turns out that several non-mammalian, non-avian vertebrates engage in repeated, apparently functionless behaviour that is initiated voluntarily in unstressed individuals. Sometimes this behaviour is directed toward inanimate objects (so-called manipulative play or object play).

Most of the key research in this area has been produced by Gordon M. Burghardt (his website is here), and if you're interested in his research it's worth checking out his book (Burghardt 2005). There's stuff here about apparent play behaviour in fish and - shock horror - even, outside of vertebrates, in cephalopods. I'm particularly interested in the play behaviour that's now been documented in captive trionychid and emydid turtles (Burghardt 1998, Burghardt et al. 1996, Kramer & Burghardt 1998).

Thinking about this reminded me of an activity indulged in by one of the Red-eared sliders Trachemys scripta we used to have in my UOP office [another of the UOP turtles, Cuthbert, is shown above. We could never work out what he was: check out that narrow nuchal scute]. One of the terrapins used to regularly remove the plastic hose from the filter box in its tank, and then nudge the filter box around the tank. This was irritating as we (we = myself and Sarah Fielding) had to keep repositioning the box and reconnecting the hose. I honestly didn't think at the time that this behaviour 'meant' anything, but I'm wondering now if it was a form of play. Certainly those animals were bored with nothing to do in their little tank, so maybe they were in need of behavioural enrichment, and hence searching for objects to manipulate.

Crocodilians and dragons

By introducing objects like wooden blocks and chains into enclosures, Burghardt and colleagues noted object manipulation occurring in turtles, crocodilians and lizards. An Orinoco crocodile Crocodylus intermedius rated particularly high in terms of its response to the objects, and appeared to exhibit both curiosity and playfulness toward them. There's also a published account of an American alligator Alligator mississippiensis exhibiting playful behaviour directed at dripping water (Lazell & Spitzer 1977), and there are also accounts of crocodilians possibly playing with carcasses, and apparently surfing in waves (go here for more on these accounts). I've seen a short sequence of film of two sibling Nile crocodiles Crocodylus niloticus tussling with one another in what looked like play behaviour.

The best data however comes from monitor lizards, and in fact from one individual monitor lizard in particular. Kraken [shown above] is a well-studied female Komodo dragon Varanus komodoensis kept at the Smithsonian National Zoological Park in Washington, D. C. Developing a close bond with her keepers, it began to be noticed that she directed an unusual amount of curiosity toward shoe laces and to objects concealed in people's pockets (such as handkerchiefs and notebooks). Kraken would tug at or sever shoe laces (with her teeth), and would gently pull objects out of people's pockets. The keepers then began to introduce boxes, blankets, shoes and Frisbees into Kraken's enclosure, and many of Kraken's reactions would be interpreted as playful if witnessed in a mammal. Kraken has also been recorded to play tug-of-war with her keepers.

In a detailed, thorough study of Kraken's interactions with objects and her keepers, Burghardt et al. (2002) concluded that play-like behaviour in Komodo dragons definitely meets the formal criteria for play: 'Kraken could discriminate between prey and non-prey and showed varying responses with different objects (i.e., ring and shoe). Large lizards, such as the Komodo dragon, might be revealed as investigative creatures, and further expressions of play-type behaviors should be confirmed and explored. These findings would imply that non-avian reptiles in general and large long-lived species in particular are capable of higher cognition and are much more complex than previously thought' (p. 116). It's interesting to note that probable play behaviour was reported in Komodo dragons as early as 1928, incidentally. Other people have now documented play behaviour in other monitor species.

So - if you'll excuse me here for bringing in some vertebrate palaeontology - did non-avian dinosaurs play? Several authors have speculated about this, but only in fictional essays: Stout & Service (1981) depicted baby tyrannosaurs chasing, wrestling and play-biting one another, and Bakker (1995) imagined dromaeosaurids and troodontids sliding down snowy slopes in a Cretaceous winter (which explains the Luis Rey painting you can see here). Of course we don't know whether dinosaurs played, and we never will, but given how widespread play behaviour is in living reptiles, phylogenetic bracketing indicates that at least some extinct dinosaurs almost certainly would have engaged in this. So, artists, feel free to depict baby dromaeosaurs running around with feather or stick toys in their mouths.

And, finally, here is the proof showing the tyrannosaurs really did play with micro-machines.

For previous articles on surprising facets of extant animal behaviour see.

Bakker, R. T. 1995. Raptor Red. Bantam Press, London.

Bekoff, M. 2000. The essential joys of play. BBC Wildlife 18 (8), 46-53.

Burghardt, G. M. 1984. On the origins of play. In Smith, P. K. (ed). Play in Animals and Humans. Basil Blackwell, Oxford, pp. 5-41.

- . 1998. The evolutionary origins of play revisited: lessons from turtles. In Bekoff, M. & Byers, J. A. (eds). Animal Play: Evolutionary, Comparative, and Ecological Perspectives. Cambridge University Press, Cambridge, pp. 1-26.

- . 2005. The Genesis of Animal Play: Testing the Limits. MIT Press, Cambridge, MA.

- ., Chiszar, D., Murphy, J. B., Romano, J., Walsh, T. & Manrod, J. 2002. Behavioral complexity, behavioral development, and play. In Murphy, J. B., Ciofi, C., de La Panouse, C. & Walsh, T. (eds) Komodo Dragons: Biology and Conservation. Smithosonian Institution Press (Washington, DC), pp. 78-117.

- ., Ward, B. & Rosscoe, R. 1996. Problem of reptile play: environmental enrichment and play behavior in a captive Nile soft-shelled turtle, Trionyx tringuis. Zoo Biology 15, 223-238.

Kramer, M. & Burghardt, G. M. 1998. Precocious courtship and play in emydid turtles, Ethology 104, 38-56.

Lazell, J. D. & Spitzer, N. C. 1977. Apparent play behavior in an American alligator. Copeia 1977, 188-189.

Smith, P. K. 1984. Play in Animals and Humans. Basil Blackwell, Oxford.

Stout, W. & Service, W. 1981. The Dinosaurs. Bantam Books, New York.

Little time for dreaming?

The elephants also wore a collar with a gyroscope attached to it, which told the researchers whether they were standing up or lying down. Each elephant slept lying down on only 10 of the 35 days.

This finding implies that the animals spent very little time in rapid-eye-movement (REM) sleep, the stage when we have vivid dreams that is thought to be important for memory consolidation. During REM, the muscles usually relax, making it impossible to remain standing.

Either elephants only experience REM every few days, or they can enter this phase in short bursts of 5 to 10 seconds while standing, as birds do, says Manger. Alternatively, like whales and dolphins, they may not need REM at all. “We’re not sure which of those is true yet and that’s something we’d like to follow up and discover,” he says.

Bigger animals generally tend to sleep less, probably because they have to spend so much time eating. “Elephants can eat up to 300 kilograms of food a day, so obviously it takes a long time for the trunk to get all that into their mouths, and that leaves less time for sleep,” says Manger.

But even among large mammals, elephants seem to be light sleepers. The considerably larger grey whale sleeps for 9 hours a day and the giraffe for almost 5 hours. The domestic horse, at nearly 3 hours, is its closest rival.

The use of trunk motion to infer sleep state is clever, says John Lesku at La Trobe University in Melbourne, Australia, but he adds that it will be important to learn more about how posture and trunk movement reflect waking, sleeping and REM sleep.

“For instance, ruminants can stand, have their eyes partially open and even continue to chew their cud during non-REM sleep, raising the possibility that elephants might have more sleep than appreciated,” he says.

Watch the video: ΘΑΛΑΣΣΙΑ ΘΗΛΑΣΤΙΚΑ ΤΗΣ ΕΛΛΑΔΑΣ και ΤΟΥ ΙΟΝΙΟΥ (January 2022).