Not all animals have a sense of humour, I admit. It’s fairly hard to work out whether a gerbil is amused, in my experience, and probably even more difficult if you choose to associate with spiders, reptiles or fish. I can’t imagine anything resembling an expression crossing the face of an alligator, for instance, or a grasshopper. These animals may express themselves and their opinions through behaviour, but they don’t emote.

I assume that humour is a function of intelligence, as it seems clear that horses, dolphins and most primates are very capable of enjoying a good joke, or a simple pratfall, and even of creating or setting up comic situations. But there are two other highly intelligent species, with which I am more familiar on a day-to-day basis – cats and dogs. It seems to me that they both enjoy humour, but in very different ways.

Your average cat, for example, might look reserved and expressionless to an uninformed non-cat person, but anyone who lives with one or more of the little darlings will be able to tell you that the vast majority of the things a cat does are done for one reason only – because it amuses them. Whether it’s picking at a single thread until they’ve unravelled an entire carpet, pushing a fellow pet down the stairs, eating a fly, staring into a corner of the skirting-board until they’re cross-eyed, hanging upside-down off the curtains, hoarding rolls of sellotape, pretending they’re possessed or ferociously guarding a plastic bottle-cap as if it’s one of the treasures from Tutankhamen’s tomb, the cat has the sole aim of keeping itself amused. If they happen to amuse you at the same time, this is largely irrelevant – unless you laugh. Laughter slightly worries cats. They’re not averse to a secretive snigger, and their entire faces can light up with glee if you do something funny, but laughing out loud is rather foreign to them, and they’d prefer you didn’t, if it’s all the same to you.

Dogs, on the other hand, if you laugh at them, or with them, or even nearby, will laugh along, a grin stretching all over their silly faces, even if they didn’t actually understand the joke – just for the fun of joining in the hilarity. It’s easy to stereotype dogs as more stupid than cats for this reason (a topic I shall return to in my next post), but in essence they’re simply more social in their humour. If they’re amused they want you to know about it, and if they think you’re amused they want to show they appreciate it. Our dog plays roughly the same amount as our cats, and often in similar ways, but she’s only really happy if you join in and play with her. She’s fiercely intelligent when she actually slows down enough to think things through, but she’s also impulsive, clumsy and clownish, and never happier than when you’re in fits of laughter at something stupid she just did. Like most dogs she has no inhibitions, and no concept of embarrassment.

Dogs, in common with most animals, live almost entirely in the moment, and it’s one of their greatest qualities as companions. They don’t brood over the past, or fret about the future, they just enjoy now, and think about maybe the next five minutes. I watch ours in the garden, and I imagine her thoughts.

“The sun’s hot. Where’s my ball? I like my ball. Is it time for walk yet? No? I like walk, running and sniffing. Maybe playing chasey-ball? I like chasey-ball. I need to poo. Ooh, a bee! Gone now. Where’s my ball? No, wait, I do need to poo. That’s better. I like pooing. I like my ball. There it is – how did it get under there? Ooh, ooh, itchy – I loooooove scratching. Is it walk yet? Walk? No? I’ll chase my ball here then. I like it here. I like my bed too. When I’m in bed I’m a Good Dog, and I get a treat. I like the garden, but sometimes in the garden I’m a Bad Dog. I can’t remember why. I’m pretty sure digging is always Bad, but I like digging. I like snails. And worms. And my ball. Butterfly! Where did it go? Where’s my ball? I like my ball.”

The cats’ thought processes are rather different, although equally immediate. We have two, Arnie and Pepper, and they like to sunbathe on the table in the bay window.

Arnie: “Sun hot. Sleep. Nice, warm. Sleep more. Food now? No? Sleep then. Sleep nice. Warm. Table warm. Sun hot. Nice. Sleep. Food soon. Sleep now.”

Pepper: “Sun warm. Stretch, maybe sleep. Bored. What’s Arnie doing? Nothing. Bored. What happens if I poke this? Huh. It’s on the floor now. I want to poke it again. Shall I get down? No, sun warm, table warm. Maybe I’ll poke fat Arnie instead, see what happens. Nothing, still asleep. Stupid Arnie. Poke harder. Ha ha haaaaaaaa! Funniest thing ever! Arnie on the floor now! No no no, not coming back up – my table now. What now? Bored. What else can I poke? Maybe I’ll hide in the curtain.”

Cats will create their own amusement, whereas if bored the dog will whine, sulk or destroy something.

But I have to hand it to the dog for doing the single funniest thing I’ve ever seen any animal do, which was to let out a small squeaky fart and then turn round and stare at her own backside in utter astonishment.