Gentle giants! Heavier dogs are significantly LESS likely to be aggressive

Gentle giants! Heavier dogs are significantly LESS likely to be aggressive – while small pups with short snouts like Pugs and Bulldogs are most badly behaved, study finds

• Scientists studied 665 pet dogs across 57 breeds of varying size
• The heavier the dog, the less likely they were to display aggressive behaviours 
• Small, short-snout breeds such as Pugs and Shih Tzus were most badly-behaved

If you're afraid of dogs, you may find yourself wary around large pooches such as Dobermans or Great Danes.

But the results of a new study could refocus your attention away from these breeds, and towards smaller pups.

Researchers from the University of Sao Paulo have revealed that heavier dogs tend to be more obedient than lighter pets.

In contrast, small, short-snouted breeds such as Pugs, Bulldogs and Shih Tzus are the most badly-behaved breeds, according to the study.

If you're afraid of dogs, you may find yourself wary around large pooches such as Dobermans or Great Danes (stock image). But the results of a new study could refocus your attention away from these breeds, and towards smaller pups

What dog breeds are the most aggressive?  

Experts from Helsinki studied the behaviour of 9,000 dogs, and claim the most aggressive breeds are:

1. Rough Collie 
2. Miniature Poodle 
3. Miniature Schnauzer 
4. German Shepherd 
5. Spanish Water Dog 
6. Lagotto 
7. Chinese Crested 
8. German Spitz Mittel 
9. Coton de Tulear 
10. Wheaten terrier  
11. other 
12. Pembroke Welsh Corgi 
13. Cairn Terrier 
14. Border Collie 
15. Finnish Lapphund 
16. Chihuahua 
17. Smooth Collie 
18. Jack Russell Terrier 
19. Staffordshire Bull Terrier 
20. Shetland Sheepdog 
21. Lapponian Herder 
22. Golden Retriever 
23. Labrador Retriever  

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In the study, the team set out to understand the factors that influence aggression in pet dogs.

They enlisted 665 pet dogs across 57 breeds of varying size.

The dogs' owners completed three online questionnaires – one on themselves, one on the characteristics of their pet, and one on the nature of any aggressive behaviour, such as barking or attacking.

The results revealed that the heavier the dog, the less likely they were to display aggressive behaviours.

In fact, for every extra 2.2lbs (1kg) of body mass, aggressive behaviour was found to decrease by three per cent.

However, small dogs with short snouts were found to be the most aggressive.

Flavio Ayrosa, first author of the study, said: 'Aggressiveness toward the owner was 79% more likely among brachycephalic than mesocephalic dogs.'

Brachycephalic dogs have short, squashed faces and include Pugs, Bulldogs, Boston Terriers and Shih Tzus.

In contrast, mesocephalic breeds including Beagles, Golden Retrievers and Labrador Retrievers have more intermediate skulls.

The pet's sex also appears to influence its aggression.

'The likelihood of aggressive behaviour toward the owner was 40% lower among female dogs than among males,' Mr Ayrosa said.

In addition, the team found a link between the owner's own characteristics and their pet's aggression.

Aggression in dogs was 73 per cent more frequent among male owners than female owners, while dogs walked every day by their owners were less aggressive.

Small, short-snouted breeds such as Pugs, Bulldogs and Shih Tzus are the most badly-behaved breeds, according to the study. Pictured: a French Bulldog wearing a muzzle