What dog breeds are most heat tolerant?

Sometimes here in Britain, it feels like the sun never makes an appearance. It seems like we constantly live under a blanket of thick grey cloud with or without various forms of precipitation. However, in recent years, from around May onwards, we have started to experience something called ‘heat’. There has been a lot of talk around global warming and El Niño and we are being warned to expect a lot more ‘heatwaves’ such as we have already experienced this year, in the future. Not only would this affect us and how we live (try getting hold of an air conditioning unit at the moment!), it will also have an impact on our pets. So, in anticipation of this, which dog breeds are more likely to cope with the increase in temperatures and which will really struggle?

How do dogs stay cool?

When thinking about heat-tolerant dogs, it can be helpful to firstly understand how dogs stay cool when the temperature rises.

Dogs can’t sweat in the same way as us. They do have special sweat glands called merocrine glands but only in their paw pads which is why you may sometimes see wet paw-prints on the floor on a hot day. They don’t have functioning sweat glands on their body like we do – we have eccrine and apocrine glands to produce sweat, they only have apocrine glands which produce pheromones that help with scenting and identification.

Another way that they stay cool is by panting. Panting utilises the idea of evaporation – by rapidly breathing in and out and moving air over their tongue and throat, the moisture on these surfaces evaporates thereby cooling the body. Panting looks like hard work, and it can be. The effort of panting will actually generate a small amount of heat itself, so in particularly hot conditions, panting alone will not be enough to keep the body at a safe temperature.

All mammals will also use vasodilation and vasoconstriction as a way of keeping body temperature regulated. Vasodilation is when blood vessels, especially those close to the surface of the skin, dilate allowing the heat from the warm blood to radiate into the surrounding air. You may see dogs preferring to lie on cool tiles or a stone floor in hot weather which will also help to dissipate any excess body heat.

When does it get dangerous?

The normal body temperature of a dog is around 38.2°C to 39.2°C. Within this temperature range, the body can function safely and efficiently. If they have an infection or other illness, their temperature may rise, like ours would do. This can actually be beneficial as it can help to stimulate the immune system to fight the problem. However, if their temperature reaches around 41°C, this is when it gets dangerous and can lead to heatstroke, causing organ damage and even death.

The risks of heatstroke

Under normal environmental conditions, the risk of heatstroke is low. However when the outside temperature rises, a dog’s cooling techniques are put under stress and can sometimes not be enough to prevent a dangerous rise in their body temperature. This risk increases further with exercise, or if they are left in a hot car or unventilated area. Some dog breeds are also classed as high risk such as those with a brachycephalic conformation or a double coat. Old dogs or overweight dogs as also highly vulnerable.

The signs of heatstroke include:

lethargy
excessive and heavy panting
wobbliness
fast heart rate
vomiting or diarrhoea
collapse
seizures
death

Treatment involves immediate cooling by the most effective method available. This advice has changed in recent years as it used to be thought that it was dangerous to cool them too quickly. But now, immersion in cold water or hosing them down thoroughly, before getting them to a vet has been shown to lead to a higher chance of survival.

Heat-proof dogs

No dog is truly heat-proof, but there are some breeds that are much more able to cope when the temperature rises. These breeds will typically share certain characteristics which give them this ability. These features are, unsurprisingly, the opposite of those found in dogs that don’t cope well in hot conditions.

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Long muzzle

By having a long muzzle, these dogs have a greater mucous membrane surface area over which moisture can evaporate through breathing or panting, meaning this method of cooling is more efficient for them than it would be for a short-nosed dog.

Thin hair coat

Although dogs can’t sweat through their skin, having less hair means they will immediately be more comfortable in the heat than a heavy or double- coated dog.

Light coloured coat

Light colours absorb less heat than dark colours (think about the difference you would feel when wearing a black t-shirt as opposed to a white t-shirt in hot weather) so it makes sense that paler coated dogs will be more amenable to higher temperatures.

Tropical origins

Dog breeds that originate from countries with warmer climates will naturally tend to have builds and features that mean they are more likely to cope with any heatwaves, although there will be some individual variation.

Lean dogs

Dogs with less fat covering have a lower chance of overheating when compared to higher body condition dogs, just like in people.

Cardiovascularly stable

Cardiovascular or respiratory disease can strike any breed but some are certainly more prone than others. These guys just don’t cope well in the heat and are much more likely to decompensate than a healthy dog. During a heatwave, many vets will report that old, frail dogs and those with heart or lung problems will often suffer more than others.

Upright ears

Having ears that sit upright rather than flop over means there is a larger available surface area over which to lose heat. Ears tend to have thin hair covering and lots of blood vessels close to the surface so they’re very efficient at this.

So after all that, which dog breeds are most heat tolerant?

Basenji

These dogs originate from Africa and are well suited to warmer climates with their short, light coloured hair coat and big upright ears.

Pharaoh Hound

This Maltese breed is very lean with a short, tan coat and even bigger upright ears.

Chihuahua

Originally from Mexico, Chihuahuas come in many different colours though the lighter shades tend to be more popular. They come in long or short coated varieties.

Chinese Crested

Have very little hair altogether! With most of their body hair-free, they can very effectively control their body temperature. It is worth noting though, because of this, they can be prone to sunburn and should have suncream applied when outside.

Greyhound

Large body surface area, long muzzle, thin skin, blood vessels close to the surface of the skin and very sparse hair coat, Greyhounds are almost perfectly suited to warmer climates.

Ibizan Hound

Very similar to the Pharaoh hound but they come from Ibiza and often carry a short white coat

Whippet

A smaller version of the Greyhound.

Xoloitzcuintli

A Mexican breed and similar to the Chinese Crested in that many varieties are hairless or have a very sparse hair coat. They also have large, erect ears.

With regards to future UK heatwaves, we may not have to go to the extreme of choosing such a specifically heat-tolerant dog breed, but it is worth being aware of how all dogs cope in the heat. Dogs should not be walked during the day – early morning and late evening will always be cooler and hard surfaces less likely to burn their paws. Providing plenty of water and encouraging drinking, using cool mats and fans and keeping the house as cool and shady as possible will all help them cope. Heatstroke can rapidly be fatal and it is simply not worth taking the risk with any dog in hot weather.