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...
- Amazing social life of the Green iguana
- Do crocodilians (sometimes) feed their young?
- Alligators eat fruit
- Shocking inter-racial sex scenes
- Leopard vs crocodile (better late than never)
- Hard-shelled sea turtles and a diet of glass
- Hell yes: Komodo dragons!!!
- Coprophagy and the giraffe-neck program: more on plethodontids
Refs - -
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.
- Log in to post comments
According to the Reefquest Centre for Shark Research, the porbeagle shark (Lamna nasus) engages in what appears to be play behavior. They have been seen tossing floating objects into the air and playing with kelp fronds.
Very interesting post!
In 2002, I depicted a family of Deinonychus, with one of the chicks playing with the mouth of an adult. In more recent years, Iâve considered that scene too speculative, and âmammal-likeâ. But if there are evidences showing that play behaviours are more widespread than among mammals and some neornithines alone, that image could be a little more possible.
You can see the picture here: http://4.bp.blogspot.com/_6fVePgcYTJc/ShOsaJ9SVSI/AAAAAAAAB7w/J0h2-k9SS….
This is interesting! And for some reason I find it reassuring that playing runs through many types of creatures. As for dinosaurs of many types--of course they played! Haven't you seen "Land Before Time"? I have seen I-XII, courtesy of my kids, so I am well versed.
A really terrific post, Darren! Play behavior in the animal kingdom has interested me: is it merely humans imposing anthropomorphism? What is its function? What constitutes and play (and what doesn't)? This great article has led me to think that our own anthropocentrism might have LIMITED our scope of how widespread play behavior might be in various animal groups, beyond mammals and a few birds. Great job, Darren!
Part of the problem is that humans cannot recognize play in behaviors very dissimilar to our own play.
So kitten jumping at the toy is playing. But birds playing at the wind are not easily recognized as playing.
'is it merely humans imposing anthropomorphism? '
Of course not. Many animals interpret behaviour in the context of their own species, which may be better called 'zoomorphism'. One zookeeper reported that kangaroos were very scared of him walking, but not when crouching. Because fully upright posture for a kangaroo means agression.
" I know you much prefer it when I post on frogs, lizards, mice and passerines. Anyway..."
I actually prefer a lot more frogs,lizards, mice and passerines than non-avian dinosaurs. I like it even more when it is about pterosaurs. Because I'm tired of dinosaurs appearing everywhere to steal all the other animal's right to be scientifically investigated.
And yes, I remember this post from Version 1
Hey, my first impression looking the Keas was remembering the Laelaps illustration from Knight.
From the uneasy admission of other primates (not us) using tools in the 60s, I see humans recognizing more and more animal behaviors not "human-only" but also not "Superior Life-only" (read this as Vertebrate/Homeotherm/Big Brains).
I'm sure some day we'll discover even bacteria loves to play with its tiny sex pili.
This is so cool! I remember reading this the first time, but i had forgot most the info. Very glad you re-posted it Darren. I've always thought that the whole "reptiles are stupid, crappy organisms that don't have the brain capacity to do anything but eat and sleep" thing was nonsense.
@Andrea Cau, #2: You actually managed to make them cute! I still wouldn't want to be closer than binocular range and even then in a Land-Rover.
Harumph... a bit vertebrocentric, aren't we?
Expected of course, and, of course, why we read the blog, but don't forget other -more wonderful- animals also play.
The article cited below was the first definitive article on cephalopod play, but there have been others since:
MATHER J. A. ; ANDERSON R. C. 1999, Exploration, play, and habituation in Octopuses (Octopus dofleini. Journal of comparative psychology. 113 (3)333-338.
The species is now Enteroctopus dofleini.
The neat thing about Mather and Anderson's work is that they used the pschological definitions for "play" in humans to explore play in octopuses. There was really no doubt that their research animals played. And E. dofleini are "cool" animals,in all senses of the word, :-) ectothermic of course, but also BIG; 150 kg is reasonable weight for a big one, and an arm span of 15m tip-to-tip is about right.
And their playing is balanced off by the behavior discussed in one Anderson's newer papers:
Anderson, Roland C., R.Shimek, J. A. Cosgrove, and S. Berthinier. 2007. Giant Pacific Octopus, Enteroctopus dofleini, attacks on divers. Canadian Field-Naturalist 121(4): 423-425.
Jenny Islander, nÂ°10: THEROPODS (EXTINT AND EXTANT) ARE BOTH CUTE AND DANGEROUS! ;-)
Apropos of nothing, I recently read an interesting novel (Time Spike by Eric Flint and Marilyn Kosmatka) in which people and beasts from different times in Illinois are flung back into the Hauterivian (Early Cretaceous) along with chunks of their associated landscape, so you have part of Hernando de Soto's expedition bumping into a seminomadic Indian tribe from A.D. 800 while stegosaurs scratch their flanks against the walls of the Illinois State Penitentiary. It got me to thinking about how the ecosystem would shake out. If you dumped a saber-toothed cat into the Hauterivian, would it be able to hunt? IIRC, their jaw architecture restricted them to prey of a certain size range (unlike, for instance, leopards). Now, there would be a lot of herbivores of the right general size, but wouldn't they all have tough pebbly skin? Even if they could pierce a dinosaur's hide, would the main blood vessels be in the right area for the Sabertooth Death Pinch (if that's actually what they did)?
Oh, I just remembered why this came to mind. The alien performance artists (no, really) who designed this time salad thought it would be cool to have Utahraptor in the mix, so they put in a whole flock. Their first encounter with humans is with a group of Cherokee exiles and their U.S. Cavalry guards. It's written very well from both viewpoints.
I'd assumed that generally play was for learning behaviours, such as hunting and fighting in a 'safe' wa, but seems like there is more to it.
Amazing animals as they are, I'm not sure how keen I would be to have a komodo dragon sneaking things out of my pockets or chewing on my shoelaces.
Thanks for comments, great stuff. Ron Shimek (comment 11) wrote...
Well, as you said (1) this site is called Tetrapod Zoology. Anyway (2) I specifically referred to cephalopods in the article! I just didn't discuss it at length.
Indeed, cephalopods were mentioned. Was late at night when I read it, I am sorry I missed it.
"Kraken" responds to her keepers, much as a large female octopus responded to Anderson at the Seattle Aquarium. I think the discovery of the widespread nature of "play" is one of the more recent exiting ideas in the behavioral sciences.
Interesting that you have a book coming out - what will be the topic please?
Ron Shimek wrote... (about Enteroctopus dofleini)
Gerald Wood says they can "regularly exceed" a 3.7 m spread and 25 kg, but apparently the average (or mode?) is only about 15 kg. The largest ever measured was 71 kg and while there may have been some specimens exceeding this, enormous figures (150 kg, 272 kg!) are almost certainly based off of over-enthusiastic estimates.
Where the heck is 15 meters coming from? I have never heard an estimate for the species even approaching that! Assuming it is proportional with other members of the species it wouldn't weigh 150 kg, more like 750 kg.
I'm only a dabbler, so grain of salt etc. Could play be connected with the SEEK emotion? As in, deliberately stimulating the emotions of anticipation and discovery because they feel good?
Says Clive (comment 17)...
@Jenny Islander: Interesting question! I read Time Spike pretty recently, actually. I've speculated before (especially after reading [i]Footprints of Thunder[/i] by James F. David) on the effects of mixing Mesozoic and modern ecosystems before, but not that specific aspect. I always assumed, considering how well placental mammals have done in forcing marsupials into marginal niches (pretty much just opossums, except for one South American species, outside Australia) and wiping out large ground birds (South American phorusrhacids during the Pleistocene, and a variety of large island species that fell victim to rats/pigs/etc. introduced by humans), that most dinosaurs would eventually fall to placental competition. (Even the biggest-brained dinosaurs were in the range of ostriches; theropods weren't as smart as big cats, say, much less bears.) The giant sauropods would probably be unharmed; no mammal shares a similar niche (except -maybe- elephants, but the bigger sauropods were probably in a different class; and the dinosaurs might be successful competitors with mammals in the rhino-elephant size range anyway.) Hadrosaurs might be OK, too; they seemed pretty efficient at their niche, and some (especially [i]Lambeosaurus laticaudus[/i] and [i]Shantungosaurus[/i]) would be big enough to have no niche-overlap with mammals.
William Miller wrote:
This is one of those cases where uniformitarianism becomes misleading. It is tempting to look at our current eutherian dominated world, and think that mammals have some kind of superior ability over other animals (often related, however dubiously, to brain size).
It's pertinent to point out that mammals had the entirety of the Mesozoic to "outcompete dinosaurs." Placentals seemed well in place by the Cretaceous, yet they didn't seem to even budge dinosaur dominance during that time. The rampant success of mammals didn't even happen right after the dinosaurs died out, despite how it is often portrayed. The dominant predators of the Paleocene and Eocene were terrestrial crocodylians and flightless birds (a dominance that seemed to wane more with change in climate than anything else).
Mammals may be the dominant large vertebrates on the planet today, but it is probably due to a set of traits they possess that give them an advantage at this particular point in time, rather than an inherent, and universally advantageous trait.
"one of your books"? As in, you have more than one coming out in the foreseeable future? I wish I'll get the chance one day to casually drop a line like that... Seriously though, congratulations on the dino discovery book! And one could certainly do a lot worse than have it published by the University of California Press.
Speaking of books, any updates on 'Tet Zoo: the Book'?
Well, I'm not complaining; I'm quite omnivorous when it comes to tetrapodological topics.
But if you're taking requests: posts on obscure-ish mammals, extant or extinct, would be particularly appreciated...
Yes, for the past several months I have been working on two books. I will discuss them here in due course. As for a third one (Tet Zoo: Book 1), I've shelved it due to lack of time. What with my other commitments (and there's a long list), I just haven't had time.
It's easy to see why cooling climate may disadvantage crocs, but why would early Cenozoic climate change favour mammals over birds?
Darren's other book is a team work of the SV-POW! crew entitled "Sauropod Vertebrae for Dummies". :-)
What would happen if you put dinosaurs and mammals side to side?
I guess dinosaurs would outcompete mammals and then shrink to mammal size.
This is an analogy to Mediterranean islands, which held elephants but lost deer and rabbits. Simply - the biggest herbivore can feed on plant unavialable to smaller herbivores, and then survive on fat reserves when the smaller herbivore dies of starvation.
It wouldn't. The random effects of the Eocene-Oligocene boundary mass extinction(s) might. And it's still not clear if the gastornithids really were predators (...the pristichampsids, however, were, and they were clearly terrestrial, too).
Mark my words: Let kangaroos loose anywhere, and they take over. (Well, unless maybe if they're tree kangaroos.)
Some possum or other got all the way to Sulawesi, AFAIK.
Is that so? We haven't got anywhere near enough fossils to tell, have we?
You say it: island. That means species that used a K-strategy but didn't protect their offspring (or themselves) enough for an environment with terrestrial predators in it because, until then, they simply didn't need to.
A leopard tortoise I had for some time was once observed investigating a sunbeam that had been refracted into a rainbow as it passed through an aquarium. The rainbow was shining at floor level in my kitchen and the tortoise ambled over to investigate it. He sniffed it and then tried to bite it. Whether that qualifies as play is anyone's guess, but it was interesting behavior.
Oh yeah, he also liked to look behind a mirror that I had set on the floor, apparently hoping that the tortoise he could see in the mirror was on the other side.
I've had conversations with colleagues in which we've speculated about whether the marsupial breeding system might be advantageous over the placental system in unpredictable climates prone to long periods of unproductivity, such as present-day arid Australia. Once a placental mammal becomes pregnant, it's pretty much committed to bearing that foetus to term or suffering an energy-draining miscarriage, even if the amount of available resources crashes in the meantime. Once marsupial joeys have transferred to the pouch, on the other hand, they could potentially be hoicked out and abandoned with much less damage to the mother.
Not to mention that kangaroos have that incredible ability to put the development of a foetus on hold until conditions improve.
The cuscus species Ailurops ursinus and Strigocuscus celebensis are found in Sulawesi. Phalanger orientalis doesn't quite reach Sulawesi, but it is found in Timor.
I'm not sure. It is interesting to note that large flightless birds only live(d) in tropical/subtropical parts of the globe. Even the phorusrhachid Titanis only made it up to Texas and Florida, of temperate North America. Maybe there is a thermal limit to where they can lay their eggs and/or raise their young.
Or maybe it's just a coincidence.
I have a whole essay on the ecology of Time Spike in my computer and if I could get into Baen's Bar I might post it there (I can never get a password to work for long). Rough summary of what I would expect to see 100 years after the Time Spike within a few days' ride of a human settlement:
PLANTS: Local soils are thin and sour (conifer forests and dryland fern meadows) or boggy and sourer (wetlands). Angiosperms have established themselves either with human help or in natural burns where a Holocene-style succession can take hold beginning with windborne seeds and fungus spores. The giant conifer forest, however, is very robust; saplings of some species are used to growing in the shade of their elders, like modern redwoods, and can't be shaded out by fast-growing angiosperms. Local ecosystem is a mosaic in which clearings and creeksides are a more tender green while the dominant vegetation is still native.
CRITTERS AND VARMINTS: Modern climbing rodents instead of Hauterivian rodent-ish things. Foxes, coyotes, shrews, raccoons, weasels, crows, magpies, owls, and possibly hawks or falcons instead of little bipedal dinosaurs/flightless birds. Rabbits, gophers, turkeys, small perching birds, etc., mainly near the original transplanted patches of Holocene land; deer and wapiti much further out, migrating through the forest from browse patch to browse patch. A few modern waterfowl migrating along with their distant ancestors. (The Holocene transplants were mostly snatched in midwinter, so there are not as many bird species on them as there might have been.)
MEGAFAUNA: Biggest Pleistocene herbivores all shot out long ago. Pleistocene horses rounded up and crossbred with surviving saddle horses; too precious to let go feral at present. Bison shot out and cattle cosseted as closely as horses. Feral pigs, on the other hand, are a menace. No big mammalian predators remain except for Pleistocene jaguars. Dogs are well cared for as a precious early warning system and rarely go feral. On the dinosaurian side, ceratopsians and small bipedal herbivores are in trouble near human territory because they have developed a taste for certain crops, so they are shot whenever they are seen. The ceratopsians in particular are a menace to civilized life. Sauropods and hadrosaurs continue much as they always have and are likely to do so as long as the forests remain. Stegosaurs have not been seen recently; probably the transplantees didn't make it, but they may have migrated elsewhere. Sickle-claws are attracted to comparatively ill-armed and poorly armored mammals and so are shot where seen--the transplanted Utahraptors may have been wiped out. The biggest neat-eaters have learned to avoid settlements but are a menace in remote areas. Giant pterosaurs have landed in human fields, although so far they have not hurt anyone. Maybe they're just curious. They may all be transplantees establishing new homes elsewhere.
Disclaimers: Amateur, don't have access to most scholarly sources online, all errors mine.
Alas, the red-necked wallabies didn't do so well in the UK, in the long jump run. I think they went extinct in the 1990ies or shortly thereafter. (Introduced macropodids seem to be doing rather better in New Zealand and Hawaii, though.)
Indeed; there are native, extant marsupials outside Australasia and the Americas. Technically anyway: Sulawesi and Timor are geographically parts of Asia.
Not entirely true. New Zealand's South Island (where there were moas) and Tasmania (where there were emus, until the 19th century) are not subtropical. And the lesser rhea Rhea (Pterocnemia) pennata lives in Patagonia, very near the southernmost tip of the South American continent, where it can get quite chilly.
> If you dumped a saber-toothed cat into the Hauterivian,
> would it be able to hunt?
good question. Was there a saber-tooth niche in the K, or in the Mesozoic in general? There was *Moschorhinus* in the Induan, but that doesn't really count. Then there were some ziphodont crocs that had elongated pseudo-canines, and looked a bit like faux gorgonopsians, but I think those were early Palaeogene rather than Mesozoic critters.
> pretty much just opossums, except for one South American
> species, outside Australia
what do you mean with "one species that isn't an opossum"? The Monito del Monte? Or the caenolestids? But AFAIK there are three or four species of queen lestes, not just one. Anyway, South American marsupials might look pretty uniform on the first glance, but they have quite diverse sizes, dietary habits and ecological roles, there are terrestrial and arboreal insectivores, omnivores, microvertebrate hunters and even a semi-aquatic predator.
I have observed aquarium fish at play, it may be in the form of a mating ritual, or a chase, as long as no harm is done .
Great topic, Darren. Many more books could be written on this!
I'm speculating here. I reckon as
said: something to do with nesting and eggs. I figure a cold wet dark or hot dry scenario could adversely affect survival of unattended eggs more than of young mammals. Some thought would have to be given to comparing periods of gestation and eggs-laying-to-hatching. There may also be aspects of environmental stress affecting eggshell thickness or availability/otherwise of nesting material and nest sites, or having to up and move with litters (harder to do with eggs - reckon they would be abandoned).
Of course birds often forage using flight (to pursue and catch, or spot from afar, food) and visually (though some have acute hearing eg owls), whereas except for bats (many nocturnal and with echo-location) mammals forage on a substrate (ground or tree). I wonder if an impactor scenario or mega-volcano, darkening the skies prolongedly, could make flight-and-sight-dependent foraging near-impossible while leaving scuttling/clambering/scurrying/burrowing, scent-dependent modes of food location unimpaired?
Conversely though, flying birds (and bats) could more readily and rapidly evacuate a hostile locale for a better one, and similarly re-colonise an abandoned locale when things there improved.
Extreme weather (with accompanying noise) could render both flight hazardous (and hearing-dependent foraging problematic).
We need some anecdotes on comparative zoological impact of extreme events on different genera and niches, depletion ratios and re-colonisation speeds. Adaptability and diversity of behaviours and foods for any given species/individual could play a part.
That brings me back to play. I think it likely that play is about creatures finding things out, re both their environment and their own capabilities.. practising a wider range of behaviours experimentally and opportunistically in case useful one day.
It is easy to see how exploratory, nest-building and food-seeking behaviours can grade into and benefit from 'play', and how proficiency in all aspects of locomotion and social/predatory behaviour can be worked up to, through play; and parental care and coaching of young, a setting for much such.
Play in arthropods would be neat.. Highly-manipulative ones such as spiders and social insects, a good place to look?
I used to keep a pair of relatively large, relatively neurotic (I assumed) softshelled turtles, who routinely destroyed their filters or at best had them pumping out onto the floor. I bought them street hockey pucks after reading the anecdotal reports of reptile play from zoos. All filter breaking stopped. They instead would mock hunt the hockey pucks, much like cats do... stalking them and striking at them, but never attempting to actually eat them. My RES tank, on the other hand, hated floating water toys. They immediately stuff them behind their filter tubing so they stop floating around.