Egg-binding, also referred to as 'dystocia,' 'egg retention,' or 'post-ovulatory stasis' is common in many reptile species, including iguanas, snakes, and turtles. In many cases it is preventable with good nutrition and husbandry. It is extremely important to determine the cause of the egg-binding prior to treatment. Do NOT try to treat egg-binding yourself — always take your herp to a veterinarian.

What Is Egg-Binding?

Egg-binding occurs when a female cannot pass the mature eggs formed in her reproductive system. In one survey it was found to occur in approximately 10% of the reptile population. It is reported more often in snakes and turtles, and less so in lizards. It is unclear if the difference is due to more snakes and turtles being bred, or if there actually is more dystocia in these species.

Complications of egg-binding include death of the young or eggs, peritonitis, inflammation and scarring of the reproductive tract leading to decreased fertility in the future, and death of the female.

What Causes Egg-Binding?

Egg-binding can be due to:

• An anatomical defect in the female causing an obstructive dystocia, which makes it physically impossible for the egg to pass
• An overly large or malformed egg, or one that is not positioned correctly, is broken, or joined to other eggs (fractured)
• Poor condition of the mother (e.g., inactivity can lead to poor muscle tone and the inability to produce strong, repeated contractions). A female may become exhausted before she completes laying of all the eggs.
• Lack of or improper nesting site. A private, quiet area is needed, with the correct depth and selection of substrate for the species. (Lizards, especially, may make repeated attempts at digging a nest, but then never lay down to lay the eggs if the right nesting material is not present.)
• Improper temperature or incorrect temperature cycling, improper humidity, and/or incorrect lighting or photoperiod
• Malnutrition, especially if resulting in hypocalcemia (low blood levels of calcium). Obesity may also be a cause of egg binding.
• Dehydration
• Stress, such as overcrowding or too small of an enclosure.
• Hormonal or disease conditions such as infections of the reproductive organs, dehydration, or kidney disease (kidneys may become enlarged and partially block the pelvic area.)
• Breeding animals that are too young or too old, ill, or not in good condition. Excessive breeding of the same animal may also result in dystocia.

What Are the Signs of Egg-Binding?

The signs of egg-binding differ by species.

Snakes: In many cases, some eggs may be laid, but there remains a swelling in the caudal (towards the tail) half of the body. This may be hard to determine in large, well-muscled snakes such as pythons. Snakes may be egg-bound for days without showing any abnormal signs. Some snakes may show birthing efforts but are not able to produce an egg. They may become more activie and show signs of discomfort by writhing.