Many animals have the ability to breathe through their mouths as well as their noses. This allows them to continue breathing even if their nasal passageways become blocked or constricted. Mouth breathing is common in mammals, birds, reptiles, amphibians, fish, and even some invertebrates.
Mammals That Can Breathe Through Their Mouth
Most mammals can breathe through their mouths. This includes pets like dogs, cats, rabbits, guinea pigs, and more. It also includes livestock like cows, horses, pigs, sheep, and goats. Wild mammals like bears, big cats, deer, rodents, and primates can also mouth breathe.
Mammals breathe through their noses most of the time. However, they can switch to mouth breathing if their nasal passages become obstructed due to mucus, inflammation, foreign objects, or any other blockages. Some examples of mammals that breathe through their mouths include:
- Dogs
- Cats
- Rabbits
- Guinea pigs
- Hamsters
- Gerbils
- Chinchillas
- Rats
- Mice
- Horses
- Donkeys
- Mules
- Cows
- Pigs
- Goats
- Sheep
- Deer
- Moose
- Elk
- Bears
- Big cats (lions, tigers, etc.)
- Monkeys
- Apes
- Bats
- Opossums
- Raccoons
- Skunks
Basically any furry, warm-blooded, milk or meat producing mammal can use its mouth to breathe if its nose becomes blocked or unavailable.
Birds That Can Breathe Through Their Mouth
Like mammals, birds also primarily breathe through their nostrils (nares). However, they can also use their mouths (oropharynx) for breathing if needed.
Some examples of birds that are able to breathe through their mouths include:
- Chickens
- Ducks
- Geese
- Turkeys
- Pigeons
- Parrots
- Parakeets
- Finches
- Canaries
- Cockatiels
- Owls
- Eagles
- Hawks
- Vultures
- Ravens
- Crows
- Penguins
- Ostriches
- Flamingos
- Peacocks
Birds may switch to mouth breathing when they are overheated, suffering from respiratory infections, have nasal blockages, or are experiencing high altitudes with low oxygen. Their ability to alternate between mouth and nose breathing gives them respiratory flexibility.
Reptiles That Can Breathe Through Their Mouth
Many reptiles are also able to breathe through their mouths in addition to their nostrils. Some examples include:
- Lizards
- Geckos
- Iguanas
- Skinks
- Tegus
- Monitor lizards
- Snakes
- Turtles
- Tortoises
- Terrapins
- Crocodiles
- Alligators
- Caimans
Reptiles typically breathe through their nostrils. However, mouth breathing allows them to bypass obstructions in the nasal cavity. Snakes rely heavily on mouth breathing while swallowing large prey items. Turtles may also mouth breathe to take in oxygen while retracted in their shells.
Amphibians That Can Breathe Through Their Mouth
Most amphibians breathe through gills as juveniles and develop lungs as adults. Adult amphibians that transition from water to land breathe air through their nostrils and mouths. Some examples include:
- Frogs
- Toads
- Salamanders
- Newts
- Caecilians
Amphibians that spend time both in water and on land, like frogs, toads, and salamanders, rely on mouth breathing for supplemental oxygen when out of water. Fully aquatic adult amphibians, like mudpuppies, breathe mainly through gills but can also mouth breathe.
Fish That Can Breathe Through Their Mouth
Most fish breathe through gills that extract dissolved oxygen from water. However, some fish can also breathe air directly into their mouth when out of water. Fish that can mouth breathe include:
- Lungfish
- Gar
- Bowfin
- Betta fish
- Gouramis
- Snakeheads
- Eels
- Catfish
- Cod
- Herrings
- Killifish
These fish can survive for extended periods on land by breathing air. Lungfish can even breathe air through their mouth and a primitive lung. Other fish mouth breathe only when water oxygen levels drop or to travel on land between water sources.
Invertebrates That Can Breathe Through Their Mouth
Some invertebrates have simple respiratory systems and can perform gas exchange through their moist skin or inside their body. However, others have specific mouthparts for breathing air including:
- Arachnids (spiders, scorpions, etc.)
- Millipedes
- Centipedes
- Insects (grasshoppers, cockroaches, beetles, etc.)
- Annelids (leeches and earthworms)
- Snails and slugs
These invertebrates use openings on or near their mouth (spiracles) to deliver air directly to tissues or respiratory structures. Insects can open and close spiracles to control air intake. Spiders and centipedes rely on book lungs connected to their mouths to breathe. Snails and slugs use a pneumostome connected to a lung.
| Animal Class | Examples of Mouth Breathing Species |
|---|---|
| Mammals | Dogs, cats, rabbits, horses, cows, deer, primates |
| Birds | Chickens, parrots, eagles, ostriches |
| Reptiles | Lizards, snakes, turtles, alligators |
| Amphibians | Frogs, toads, salamanders |
| Fish | Lungfish, gar, eels, catfish |
| Invertebrates | Spiders, insects, annelids, snails |
Benefits of Mouth Breathing for Animals
The ability to breathe through the mouth provides many key benefits and advantages to animals including:
- Allows breathing to continue when the nose is blocked
- Provides an alternate air passageway if the nasal cavity is damaged
- Allows animals with long snouts and small nostrils to meet oxygen needs (dogs, horses)
- Enables very large animals to take in more air (whales, elephants)
- Allows animals to pant – important for thermoregulation
- Essential for animals that swallow large prey whole (snakes, pelicans)
- Critical for vocalization in some animals (dogs, frogs)
- Supports olfactory senses since breath doesn’t pass over smell receptors
The mouth also often contains sensitive thermoreceptors that provide feedback about air temperature to the brain and allow animals to adjust breathing rates accordingly. Overall, mouth breathing provides essential respiratory flexibility for many types of animals.
Challenges of Mouth Breathing for Animals
While mouth breathing is very useful, it can also pose some challenges including:
- Increased risk of mouth drying and irritation
- Greater exposure to environmental toxins, pollutants, allergens
- Less ability to warm and humidify inhaled air
- Bypassing of nasal turbinates that filter airborne particles
- More vulnerability to respiratory infections
- Increased water loss through exhalation
- Reduced sense of smell
- Greater likelihood of brachycephalic issues in flat-faced animals
Animals that rely too heavily on mouth breathing may require extra hydration and nasal care. Brachycephalic (short-nosed) breeds can develop serious health issues without corrective surgery. So while mouth breathing is very useful, animals also need healthy nasal breathing for optimal respiration.
Conclusion
Mouth breathing provides an essential backup mechanism for many types of mammals, birds, reptiles, amphibians, fish, and invertebrates. It allows animals to bypass obstructions and damage to the nasal cavity. This flexibility provides key respiratory advantages that enable survival and adaptation to diverse environments and conditions. However, animals also rely heavily on healthy nasal breathing, so a balance is ideal.