Guinea pigs like to run around outside, breathe the fresh air, and feel the grass on their feet. But when it comes to being in the sunlight, how much sunlight should a guinea pig get?
A Guinea Pig’s Body Temperature
A guinea pig’s normal body temperature is between 102° and 104° F (39 – 40°C). Guinea pigs can’t sweat (other than on their feet).
Other than sweating, though, they regulate their body temperature the same way people regulate theirs. When they get cold, their blood vessels constrict, and blood gets diverted to the torso to keep the vital organs warm. When they overheat, blood vessels dilate so heat can be transferred out of the body and into the environment through convection and radiation.
If a guinea pig gets hot, he will try to find a cool place or a place with shade to cool down. If he can’t cool himself down, he can develop heat stroke and die very quickly. If a guinea pig is in an ambient temperature as low as 86°F, he can develop heat stroke in as little as 15 minutes.
Effect of Sunlight on Guinea Pigs
Being in direct sunlight can potentially cause a guinea pig to overheat, even when the ambient temperature isn’t very hot. Wild guinea pigs are crepuscular, meaning they’re most active at dawn and dusk. So, guinea pigs do not naturally venture out and stand in the sun in the middle of the day when the sun is beating down.
Sunlight helps the body make vitamin D, but windows block the UV-B rays of the sun which are required for the body to make vitamin D. So, sitting in front of a sunny window isn’t going to do much for synthesizing vitamin D, in people or in guinea pigs.
There is no set requirement for the amount of Vitamin D a guinea pig should have, but studies show that to grow properly, they need at least 1,000 IU vitamin D/kg. Since a typical adult guinea pig weighs between 1.5-2.5 pounds, that’s 680 – 1,130 IU of Vitamin D a day. However, a deficiency is hardly ever a concern because a diet with quality pellets and fresh fruits and vegetables will supply the all the vitamin D he needs.
How to Safely Let Your Guinea Pig Experience the Sun
When you set your guinea pig’s home up indoors, never place it in direct sunlight. The sun can cause her to heat up with no chance to escape and cool down.When you take your guinea pig outside for some recreational exercise, do so in the mornings or in the evenings when it’s cooler and there isn’t any direct sunlight. Also, make sure he has access to shade and fresh water. This is important even if you don’t think it’s very hot out (anything above 65°F).
Of course, you’ll need a safe enclosure to ensure he doesn’t run away and to protect him from any predators, but position his enclosure so that part of it is always in the shade. Simply using a hideaway isn’t effective enough, because heat could build up inside it, especially if it’s made of plastic. It could become an oven instead of a shaded cool-down area.
Hairless guinea pigs need special precautions. Just as with humans, the ultraviolet rays of the sun can cause skin cancer on their exposed, vulnerable skin. And no, you cannot slather them with sunscreen!
The most important thing is to always watch him and look for signs of overheating. Never leave your guinea pig outside for long periods unattended. Warning signs include:
- Excessive drooling
- Rapid breathing or panting
- Lying flat on its stomach or total inability to move
- Bright red tongue
- If it starts convulsing, it needs immediate and quick intervention.
If your guinea pig shows signs of overheating or heat stroke, bathe him in cool water. It’s the fastest and most effective way to get his body temperature back down to a normal level. Then contact a vet immediately. Sometimes intravenous fluids or corticosteroids will be needed.
Some people leave their guinea pigs locked in a cage in the basement or somewhere where they never see or experience natural light. In my opinion (and this is not backed by research anywhere), animals were created to breathe fresh air and experience natural light. It is not natural to let them live their entire lives without occasional forays out into the natural environment where they get to experience nature as they were meant to. But again, that’s just my opinion.
How long or how often a guinea pig should experience natural sunlight is not mandated in any veterinary manual. You, as their caretaker, should decide what’s best for them. Take heed of the precautions here (e.g., being attended and watched while outside, having access to shade and fresh water, taking them out when the ambient temperature is not too high, etc.). But by all means, enjoy some time with your cavies outside occasionally.
You might also want to check out “Can Guinea Pigs Live Outside?“