From reptiles to spiders, some unlikely creatures
seem to have the ability to mess around.
Why do they do it, asks Michael Marshall
at least not immediately: my kitten may
attack her toy mouse, but she doesn’t get any
nutrition from it. It also should be voluntary,
perhaps because it is enjoyable, and it needs
to be different from the functional equivalent:
when animals play-fight, they either don’t
bite or only do so gently. What’s more, the
behaviour must be repeated, and it only counts
as play if animals do it when they are relaxed
and sated, not hungry or fearful. “All five
criteria needed to be met before I was
confident that the behaviour we were seeing
was play,” says Burghardt.
This is a good definition, but assessing
whether something is play or not still requires
skilled judgement, says Isabel Behncke at the
University for Development in Santiago, Chile.
It is crucial to know how the animal normally
acts, otherwise behaviours with real but
obscure functions might be misinterpreted
as play. Nevertheless, among vertebrate
animals, there are now many
unambiguous instances of
play – and new oneskeep being discovered, such as the play-
fighting of grey mouse lemurs. Among birds,
black swans have been observed repeatedly
riding the crests of waves, like human surfers,
while herring gulls seemingly play by dropping
and catching objects.
But it isn’t just warm-blooded mammals
and birds that appear to enjoy mucking about.
Perhaps the clearest example is the Komodo
dragon, the largest lizard in the world. In zoos,
they regularly play tug of war with their
keepers over plastic rings. This isn’t a form of
hunting behaviour, because when the “toy” is
covered in blood or tasty oil, the playfulness is
replaced by possessiveness. Crocodiles, too,
seem to enjoy playing. In 2015, Vladimir Dinets,
then at the University of Tennesse, Knoxville,
documented a host of different playful
behaviours, including crocodiles repeatedly
surfing down streams of water, toying with
pink flowers and knocking balls around.
Most bizarre of all is a group of thick-toed
geckos that were aboard the 2013 Russian
BION-M1 space experiment in zero gravity.
One of them wriggled out of its identity
collar and the geckos proceeded to repeatedly
nudge the floating object, whereas mealworms
that drifted by were treated mainly with
indifference. One individual was particularly
playful. “We saw how one of the geckos, with an
aimed push of the snout, throws the collar into
a hole in the shelter, like a basketball into a
basket,” says Victoria Gulimova at the ResearchA
S I write, my kitten is having a funny
5 minutes – or rather a funny 2 hours
and counting. A toy mouse has been
thoroughly tortured and my laptop keyboard
co-opted for a tap-dancing session.
It seems obvious to me that Peggy is playing,
and that she is enjoying herself. We are used to
the idea of certain warm-blooded creatures,
especially our pets, larking around. But what
about a crocodile toying with a ball or Komodo
dragons playing tug of war with their keepers
seemingly for the hell of it?
It could be that these animals really are
playing – or that we are projecting our own
playful nature onto their behaviour. “There’s
lots of anecdotal little stories out there,”
says Gordon Burghardt at the University of
Tennessee, Knoxville. In the past, “without
photographic or film evidence, they could
be easily dismissed by scientists”, he says.
Today, though, evidence of play in unexpected
creatures is building. Biologists have reported
examples from the furthest reaches of the
animal kingdom: not just primates and house
pets, but reptiles, fish, octopuses and even
spiders and wasps. Play isn’t universal, says
Burghardt, but it is more common than was
once thought. So why is it beneficial to spend
time mucking about?
To answer this, we need to understand how
and why the capacity to play evolved. A key
problem is how to define play – especially as
we can’t ask animals if they are having fun.
Many thinkers have tackled this
question, and Burghardt has
attempted a synthesis of the
various definitions. He
devised five criteria for
whether a behaviour
counts as play. The action
shouldn’t achieve anything,When geckos
play basketball
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18/25 December 2021 | New Scientist | 77>