Seeing Through Their Eyes: Understanding Pig Vision to Improve Sanctuary Care
As caregivers it is important to deepen our understanding of how the residents we care for experience the world around them. Doing so allows us to connect better with our residents, providing thoughtful, individualized care. While it may seem best to assume they perceive the world similarly to us, as might be the case when we think how we would feel if someone were giving us a shot, there are many situations where that genuine expression of empathy may not accurately reflect the residents’ experience. Using our own experiences can still be a useful tool when balanced by a strong understanding of how different species experience the world through their senses. We evolved differently and our biologies can interact with the world around us in unique ways. So, while we all experience excitement, frustration, contentment, how we experience that can vary greatly between species.
For example, humans are said to have “20/20 vision,” yet many wear glasses. Pigs, too, show individual differences in vision. Despite individual differences, all species have general traits that we can learn about and apply to our interactions and care decisions to connect and provide the best care for our residents.
This article is part of a five-part series exploring how pigs experience the world through their senses. First up, how goats see the world around us, how that may differ from our own experience, and how this can direct the care we provide.
Pig Vision: More Than Meets the Eye
When we think of pigs, we often picture their strong snouts, rooting through the soil or eagerly exploring a snack. Their excellent sense of smell is well-documented, as is, to a lesser extent, their acute hearing. Vision, on the other hand, is often overlooked.
Pigs aren’t known for having particularly sharp vision. But stopping there doesn’t give us the full picture. Understanding what pigs can see and how they interpret visual information can assist caregivers in how we approach them, design their living spaces, and offer appropriate enrichment. A good place to start is learning about the basic structures of their eyes.
Pig Eye Anatomy: A Quick Overview
Interestingly, the eyes of pigs are quite similar in structure to our own. Their eyeballs are about the same size, and they have round pupils and a retina similar to ours. But while the basic structures are familiar, there are some key differences—especially in how pigs process light and color and their field of vision. Understanding the anatomy of the pig eye can help us better learn their visual abilities and the limitations they might face.
Let’s break down some of the basic parts of the eye and how they function in pigs:
- Cornea: The cornea is the clear, dome-shaped part of your eye. If you have contacts, it is the part you touch your contact lens to. It protects the eye and allows light to enter.
- Sclera: This is the white portion of the eye that provides the majority of the structure.
- Iris: The iris is the colored part of the eye, and in pigs, it’s typically a shade of brown, ranging from light amber to deep chocolate. Some pigs may even have pale grey or blue irises or a unique mix of brown and grey/blue. The iris also helps regulate how much light enters the eye and is part of the uveal tract, which supplies blood to parts of the eye.
- Pupil: The pupil is the black, round opening in the center of the iris. It controls how much light enters the eye by expanding in low light and contracting in bright light.
- Lens: The lens its behind the iris, changing shape deepening on the distance of what the eye focuses on and focuses light onto the retina. It will thicken if the looker is viewing something close up and then if the object is far away. This shape-shifting is controlled by the ciliary muscles (not shown in basic diagram).
- Retina: The retina is the inner lining at the back of the eye. It contains millions of photoreceptors—light-sensitive cells known as cones and rods—that convert what the individual sees into electrical signals. These signals are then transmitted to the brain via the optic nerve.
- Cones: Cone cells are responsible for vision in bright light and for detecting color.
- Rods: Rod cells help with vision in low light. Pigs, like many animals, rely heavily on rods to help them see in dimmer conditions but lack the structure (tapetum lucidum) that allows some animals, like cats, raccoons, horses, nocturnal birds, and certain species of fishes see in the dark.
Pigs have fewer cone cells than humans and only two types of cones, compared to our three. This means they primarily perceive blue and yellow-green, and some reds, but may struggle to distinguish certain reds. However, one study found that while female piglets preferred blue water dispensers, male piglets chose red water dispensers. Another study found piglets used blue food containers the most, followed by red, and yellow was the least preferred. Yet another found a difference in color preferences between breeds, with one breed preferring blue and red, and another blue and yellow.
So while pigs don’t have especially sharp vision and the colors they are able to see aren’t as diverse as our vision, they do have well-developed visual structures that serve them well in their environments. Understanding these basics can help caregivers accommodate how pigs actually see, rather than how we assume they do.
*Please note that this is not a full list of the structures of the eye. There are many more structures, but we have included those that should help provide a basic framework.
A Wide View, Limited Depth
Perhaps one of the most interesting aspects of pig vision is their field of vision. Pigs have a field of vision of about 310 degrees which is much wider than a human’s 180 degrees. This meanse they have the ability to see almost around their entire bodies which helps detect potential threats in their environment.
However, this comes with a trade-off. Because their eyes are positioned on the sides of their heads, pigs rely mostly on monocular vision—each eye sees a different part of the environment. This means they have limited binocular vision, where both eyes focus on the same object to judge depth. As a result, pigs aren’t great at gauging distances and struggle with depth perception.
That being said, they are excellent at detecting movement, which can make sudden gestures or unexpected motion startling if they’re unsure how far away the source is. Knowing this can help us better understand why a pig resident startles when we lift a food bucket, although we are a good ten feet away.
Pig Recognition: Faces and Familiarity
Although their vision isn’t their sharpest sense, they are more visually capable than once believed. Studies have shown that pigs can recognize humans not just from the front, but also from behind. This suggests they’re able to distinguish individual human features and associate them with past experiences.
When Vision Is Compromised: Fat Blindness and Eye Conditions
While most pigs share these general visual traits, some—particularly potbellied pigs—are prone to unique eye challenges. Potbellied pigs often have shorter faces and sunken eyes, and if they become overweight, fat deposits around the eyes can impair their vision, a condition often called “fat blindness.”
In addition, potbellied pigs are more prone to eye irritation, including entropion, a condition where the eyelid turns inward, causing the eyelashes to rub against the eye. (We all know how uncomfortable it is to have a single lash in our eye.)These issues can cause discomfort, infections, and long-term vision problems if left unaddressed. Regular health checks and prompt veterinary care are essential.
While far from a health condition, it is also important to note that pigs, like us, don’t have night vision. If we can’t see something in low light, it’s likely they can’t either! Then there is simply losing vision over time due to age or other eye conditions.
How Can Caregivers Support Pig Vision?
Hopefully, you can now “see” how understanding how residents perceive the world through their senses is an important part of developing best care practices. This knowledge can improve how you plant enrichment, health checks, and simply how you engage with your residents day to day. Let’s go how the information provided in this resource can be applied in a sanctuary environment. Here are some ways caregivers can apply this knowledge to enhance resident well-being:
- Avoid Startling Approaches: Be mindful of pigs’ blind spots, particularly directly behind or beneath their snouts. Approach from an angle where they can see you clearly. Check out this resource on flight zones.
- Design with Vision in Mind: Create living spaces with open sightlines and minimize obstacles that require fine depth perception to navigate.
- Consider Lighting: Remember, if you are struggling to see in low light, likely, they are too. Add appropriate lighting to make living areas easier to navigate and increase feelings of safety.
- Choose Smart Enrichment: Use toys and visual stimuli in colors pigs can see and play around with different colors to see what individual preferences your residents may have! Keep in mind that high-contrast items may be more engaging for them to interact with.
- Monitor Eye Health: Pay attention to signs of vision problems, especially in potbellied pigs. Weight management and prompt treatment of eye issues can prevent unnecessary discomfort or blindness.
- Consider The Individual: While it is important to consider the species of the resident, everyone is an individual. Ensure you observe each resident for behavioral signs of visual impairment.
In Summary
To recap, pig residents have a wide field of vision, the ability to recognize familiar faces, preferences for different colors, and are sensitive to movement. These traits make their sight an important part of their sensory world. A better understanding of what they do–and don’t!– see allows caregivers to develop care routines to better align with their needs and preferences.
When we make an effort to see through their eyes, it can deepen our relationships and create a more resident-friendly, supportive environment. If you have related experiences or questions, please reach out!Next up in this sensory series: how pigs experience the world through sound.
Infographic
Check out this fun infographic covering a few facts about the visual abilities of pig residents. This is a fun and easy way to share information about pig residents with your community!
pig vision by Amber D Barnes
SOURCES
Genome‐wide Association Studies For Iris Pigmentation And Heterochromia Patterns In Large White Pigs | Animal Genetics (Non-Compassionate Source)
Pigs Form A Visual Concept Of Human Faces | Phys.Org (Non-Compassionate Source)
Behavioral Assessment of Vision in Pigs | American Association for Laboratory Animal Science (Non-Compassionate Source)
Visual Acuity Of Pigs At Different Light Intensities | Applied Animal Behaviour Science (Non-Compassionate Source)
Colour Preferences In Pigs | Scientific Annals of Polish Society of Animal Production (Non-Compassionate Source)
