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Sibling Sucking: What to do When Kittens Nurse on Each Other

Sibling suckling, also known as cross-sucking or non-nutritive suckling, is a behavior that can occur in orphaned kittens. While it may seem like a harmless habit, it can quickly become dangerous and even life-threatening if not recognized and addressed early.

Why Do Kittens Suck on Littermates?

Suckling is a natural instinct in kittens, and is used both for purposes of eating and for self-soothing. When a kitten is hungry or seeking comfort, they will instinctively root around, searching for mom’s nipple to nurse. Sometimes, the kitten will find a littermate’s body part like their ear, belly or genitals, and begin to suckle. Unfortunately, this behavior can become a compulsive habit that causes harm to the kitten being suckled, the one doing the suckling, or both.

Sibling sucking is thought to arise from a combination of biological need, emotional distress, and environmental factors. Research by Dr. Mikel Delgado and others at UC Davis found that several factors significantly increase the risk of cross-sucking:

• Orphaned kittens are about 6x more likely to engage in this behavior than those raised by their mother

• Bottle-fed kittens are at significantly higher risk than those nursing naturally

• Early separation from the mother increases risk

• Younger age is correlated with increased incidence

• All-male litters see the highest rates of sibling suckling

• Male kittens are more likely to be the victims, particularly when the genitals are involved

Unpublished data also strongly suggests a connection between overnight feeding schedule and likelihood of developing sucking behaviors. When kittens receive less nutrition overnight, the distress and hunger may lead them to suckle their sibling. Kittens may develop something akin to nipple preference, where a specific body part becomes linked to comfort through conditioned scent response. Once that connection is established…it can be a very hard habit to break!

Watch my Video on Sibling Sucking:

The Risks of Sibling Sucking

Sibling sucking comes with serious and even fatal risks that can impact both the kitten doing the sucking and the kitten being sucked on.

Risks to the sucker:

• Poor nutrition

• Weight loss

• GI distress

• Skin irritation or infection on the face

• Emotional stress

Risks to the sucking victim:

• Trauma to the genitals

• Infection, inflammation, necrosis, or prolapse of the penis or prepuce

• Abnormal adhesions of tissues

• Urethral obstruction and blockages

• Abscesses and skin ulceration

• Bladder infections, kidney infections, and UTIs

• Deadly sepsis

For kittens with severe structural damage, emergency surgery can be required.

How to Recognize Sibling Sucking

All kitten caregivers should know to be on the lookout for signs of sibling sucking, such as:

• Witnessing it happening

• A wet or dirty face, especially if urine or feces is caked near the mouth

• Wet, swollen, protruding, or inflamed genitals

• Trouble urinating or an enlarged bladder

• Signs of injury or ulceration to any body part

• Frantic sniffing or rooting behaviors from one kitten to another

What Not to Do

• Clothing or socks on the kittens: Restricting movement during early development can interfere with muscle and bone formation. Clothing also traps urine and feces, potentially leading to discomfort or infection. There are also safety risks inherent in leaving kittens unsupervised in clothing. For these reasons, clothing is not recommended.

• Head coverings, netting, or pillow cases: Putting cloth over the face of a kitten is extremely unsafe and can cause distress or suffocation. Never cover a kitten’s face!

• Bitter sprays or foul-tasting substances: Foreign substances of any kind should not be applied to a kitten’s body, especially not to sensitive areas like the genitals, without veterinary guidance. They are unlikely to be effective for compulsive behavior and may cause pain or harm.

What to Do Instead

1. Separate the kittens

• House the suckler separately from the victim using modular playpens, divided bins, or a separate incubator.

• When possible, pair kittens with a friend—but only if neither is sucking on the other. Monitor closely to ensure the behavior doesn’t begin again with a new victim.

• Allow supervised play sessions, but separate them if sucking begins or if leaving them unsupervised.

• For kittens who are self-sucking, it’s recommended to use an e-collar to prevent the kitten from doing damage to their skin or genitals.

2. Support the suckler emotionally and physically

• Feed on a proper, consistent feeding schedule, especially overnight.

• Provide tactile comfort such as a toothbrush grooming to mimic maternal licking.

• Create a quiet, warm, and secure environment.

3. Monitor for medical complications

Check both the sucker and the victim daily:

• Palpate the bladder: if it feels overly full (like a balloon), the kitten may be obstructed and in need of urgent veterinary care.

• Inspect genitals: look for swelling, discharge, or changes in shape or size.

• Track weight: make sure all kittens, especially sucklers, are gaining steadily.

Will The Sucker Eventually Stop?

Sibling sucking is a habit that takes some time to break, so be patient with your little ones. It’s recommended to separate the kittens for at least 10 days, then carefully supervise to see if the habit is still present. Some kittens outgrow the behavior after weaning, but some may need more time before they can be reintroduced to their littermates safely.

Be Patient and Kind

I get it; it’s easy to feel frustrated when a kitten just won’t stop engaging in this harmful behavior. But it’s important to recognize that for the kitten doing the sucking, there is very likely a history of an unmet need. They may have been hungry and afraid as a little one, especially if they lost their mother at a young age. Ultimately, these babies are self-soothing. Having empathy for the kitten’s situation will help both of you as you work to provide them a loving, comforting environment where they discover that they are perfectly safe.