The hot car is not how most British dogs get heatstroke

Every June the same photograph goes round, and it is a dog in a parked car. The message is worth repeating and it is not wrong.

It is also not where most of the danger is.

What the record actually shows

The largest study of heat related illness in British dogs looked at 1,259 cases and could identify what triggered 879 of them. The split was not close.

Exercise triggered 74.2 per cent. The surrounding environment, meaning a hot room, a conservatory or a garden with no shade, accounted for 12.9 per cent. Vehicles accounted for 5.2 per cent. The paper is called Dogs Don’t Die Just in Hot Cars, which saves anybody the trouble of summarising it.

The companion study, drawn from the records of 905,543 dogs under veterinary care in a single year, found that of the confirmed cases, 14.18 per cent were fatal.

So the common picture is close to inverted. The classic case is not a dog shut in a car by somebody careless. It is a dog taken for its normal walk, by somebody who loves it, on a day that did not feel dangerous.

Why the walk is the dangerous part

A dog does not sweat to any useful degree. It loses heat by panting, which means evaporating water from the airway, and that is a much weaker mechanism than the one you have.

Exercise generates heat internally at exactly the moment the cooling system is already working at its limit. A person on a hot walk is producing heat and shedding it through the skin over their whole body. A dog is producing heat and shedding it through its mouth.

Some dogs start from further back. The risk factor study found that flat faced breeds had 2.10 times the odds of heat related illness compared with normally proportioned ones, dogs over 50 kg had 3.42 times the odds of dogs under 10 kg, and dogs of twelve or over had the highest odds of any age group. Chow Chows, Bulldogs and French Bulldogs came out worst by breed.

A flat faced dog is panting through a shortened airway. That is the whole mechanism, made narrower.

The number of days this matters is small, and that is the trap

This site stores the daily temperature record back to 1950 and counts the days above 25 degrees for each town in it.

Cambridge has gone from about 3 such days a year in the 1960s to 20 this decade. London from 3.3 to 17.7. Manchester from 0.6 to 7. Glasgow is at 2.8 and Belfast at 0.5.

Two things follow from those numbers, and they pull in opposite directions.

The first is that hot days are becoming ordinary in the south and east in a way they were not within living memory. Twenty days a year is three weeks of summer.

The second is that they are still rare enough, nearly everywhere, that nobody builds a habit around them. A Manchester owner gets seven of these days a year. There is no routine to fall back on, no instinct built from repetition, and the walk happens at half past two because that is when the walk happens.

The longest run of consecutive hot days is worth knowing too, because that is when it compounds. In the towns here the longest spells on record reach sixteen and seventeen days, and in recent years a typical longest spell in the south is about five. Over a spell the house does not cool overnight, and neither does the dog.

What to change, in practice

Move the walk, do not shorten it. Early morning is genuinely cooler. Evening is second best, because the ground has been absorbing heat all day. A shorter walk at two in the afternoon is still a walk at two in the afternoon.

Check the ground with your hand. Hold the back of your hand against the pavement. If you cannot hold it there comfortably, it is too hot for a paw, which has no shoe on it. Tarmac in direct sun runs far above air temperature and stays hot after the sun has gone off it.

Drop the intensity, not just the distance. Fetch, running with a bike, and play with other dogs are all exertional. A dog will keep going past the point its owner would stop, because it is enjoying itself and because chasing a ball is not a decision.

Watch the dogs that cannot tell you. Flat faced, elderly, overweight, very large, or thick coated. The odds are measurably worse and the warning signs arrive later.

Leave water and shade that stays shade. A patch of garden shaded at eleven is in full sun at three. Dogs left out for the afternoon get caught by the sun moving, not by the sun being there.

Heatstroke in a dog is an emergency measured in minutes rather than hours. If you think one is in trouble, start cooling it and ring a vet while you do.