Tarantula Diseases & Health
Tarantulas are hardy animals that rarely become ill when kept correctly. The vast majority of health problems seen in captive tarantulas are husbandry-related — caused by incorrect temperature, inadequate hydration, or preventable injuries. This guide covers the most common health issues, how to identify them, and what to do.
Dehydration
Dehydration is the most common health issue in captive tarantulas and is frequently overlooked because the signs develop gradually. A healthy tarantula has a plump, rounded abdomen. A noticeably shrunken or wrinkled abdomen is the primary indicator of dehydration.
What to do: Ensure a shallow water dish is available immediately and that the enclosure provides an appropriate moisture gradient. Keep the enclosure quiet and avoid handling while the tarantula rehydrates. If dehydration is severe or the spider cannot access water on its own, seek advice from an experienced keeper or exotic veterinarian.
Prevention: Always provide a water dish for adults and sub-adults. Maintain an appropriate moisture gradient in the substrate. See our Best Tarantula Water Dishes guide.
Failed Molt
A failed molt occurs when a tarantula cannot fully shed its old exoskeleton. It is one of the most serious health events a tarantula can experience and is often fatal if the spider becomes stuck. Common causes include dehydration, low humidity, disturbance during the molt, or underlying health issues.
Signs: The spider has been on its back for an unusually long time without progress (more than 12–24 hours), or appears partially encased in the old exoskeleton after the molt.
What to do: Keep the enclosure quiet and ensure fresh water is available. Do not disturb the spider. Intervention is rarely successful and can easily worsen the situation. If you are considering assisting a failed molt, seek guidance from an experienced keeper or exotic veterinarian first.
Prevention: Ensure the enclosure has an appropriate moisture gradient, a water dish is always available, and the spider is not disturbed during pre-molt or molting. See our Tarantula Molting Guide for full details.
Prey Injuries
Live prey left in the enclosure is one of the most preventable causes of injury in captive tarantulas. Crickets in particular are aggressive and will bite a resting, molting, or post-molt tarantula. A freshly molted tarantula with a soft exoskeleton is especially vulnerable.
Signs: Visible wounds on the abdomen or legs, missing limbs, or a spider that appears distressed after prey was left in the enclosure.
What to do: Remove all live prey immediately. Minor wounds often heal at the next molt. Severe abdominal injuries may be fatal. Keep the enclosure clean and quiet and allow the spider to recover undisturbed.
Prevention: Always remove uneaten prey within 24 hours. Never leave live prey in the enclosure with a spider showing pre-molt signs or that has recently molted.
Abdomen Rupture
Abdomen rupture is caused by a fall and is one of the most common causes of sudden death in captive tarantulas. Heavy-bodied terrestrial species are particularly vulnerable. Even a fall of a few inches can be fatal if the spider lands on its abdomen.
Signs: Fluid leaking from the abdomen, the spider unable to move normally, or sudden death following a fall.
What to do: Minor leaks have sometimes been managed by experienced keepers using cornstarch as a temporary measure, but success is unpredictable. Severe ruptures are usually fatal.
Prevention: Avoid tall enclosures for terrestrial species. Handle close to the ground or over a flat surface. Do not handle during pre-molt or post-molt when the spider is more fragile.
Parasites
Parasites are uncommon in captive-bred tarantulas but can be introduced via wild-caught animals, contaminated substrate, or live prey. The most commonly encountered parasites in tarantula enclosures are mites.
Signs: Small moving dots on the spider or enclosure surfaces. Not all mites are harmful — white substrate mites are often harmless scavengers, while mites attached directly to the tarantula — particularly around the mouth or book lungs — are much more concerning and can interfere with respiration.
What to do: Remove the tarantula to a clean temporary enclosure. Discard all substrate and clean the enclosure thoroughly. Replace with fresh, dry substrate. If mites are on the spider itself, consult an exotic veterinarian. Substrate mites are often harmless scavengers but indicate conditions that are too moist.
Prevention: Purchase captive-bred animals from reputable breeders. Avoid substrate that has not been properly dried or sterilized. Do not leave uneaten prey or food debris in the enclosure.
Lethargy and Inactivity
Tarantulas are naturally sedentary animals and spend most of their time motionless. Inactivity alone is not a sign of illness. However, there are situations where reduced activity warrants closer attention.
Normal: Sitting motionless for days or weeks, reduced appetite, staying in the hide, sealing the burrow entrance.
Potentially concerning: The spider is on its back outside of a molt, has a visibly shrunken abdomen, is positioned awkwardly with legs curled under the body, or has not changed position for an unusually long time while also showing other concerning signs.
A tarantula with curled legs that is not molting may be dying. Ensure water is available and the enclosure conditions are correct. If the spider does not respond to water access within 24–48 hours, consult an exotic veterinarian.
Is My Tarantula Dead or Molting?
New keepers frequently mistake a molting tarantula for a dead one. A tarantula on its back is almost always molting — this is the normal molting position. Do not disturb it. Never attempt to flip a tarantula onto its feet if it is lying on its back — you could interrupt a normal molt. A dead tarantula will typically be curled up with its legs drawn under the body (the "death curl"), not flat on its back with legs extended.
If you are unsure, wait and observe. A molting tarantula will show movement — even subtle flexing — over the course of the molt. A dead tarantula will not.
When to See a Vet
Exotic veterinarians with experience in invertebrates are not available in all areas, but they are the appropriate resource for serious health concerns. Situations that warrant veterinary consultation include suspected parasites on the spider itself, severe injuries, prolonged failed molts, and any situation where the spider appears to be in distress and husbandry corrections have not helped.