Wild baby rabbit suddenly died

Question
We found a baby cottontail 3 weeks ago.  He was laying motionless under our trampoline.  We have been caring for him since then and he was fine - eating grass, hoping, drinking, etc.  I read that they should be let go when the white spot on their head disappears.  His did not.  This a.m. when I checked on him, he was laying on his side barely breating.  He died about 1 hour later.  What could have happened?  He was fine as of 10 p.m. last night.

Answer
Dear Sheryl,

I'm very sorry about the loss of the baby cottontail.  One of the main reasons it's recommended that wild babies be left alone is that they do so poorly in captivity, even in the hands of experience wildlife rehabilitators.  The baby you found was very likely being cared for by his mother, since mama will feed only twice a day, and then stay away from her young to avoid attracting predators.

Baby cottontails are very susceptible to infection by the bacteria we have on our hands.  If you saw any sign of runny stool, then the most likely cause of death was an intestinal infection of E. coli, which is very common in these little ones.  Another common cause of death is respiratory infection, especially in those being fed formula, since they often aspirate (inhale the formula) when being fed artificially.

Rehabbers have a term called "captive stress" to describe what happened to your little guy.  They seem to be doing fine, and then suddenly they die.  The only way to know for sure exactly what happened is to have a necropsy done by an experienced rabbit vet, including histopathology on all major organ tissues.  That is pretty expensive, and few people are willing to go that far.  So sadly, the exact cause of the baby's death will never be known.

Thank you for trying your best to care for him.  Next time you find a baby cottontail, you'll know it's best to leave him alone and let mama do her job in getting him grown and independent and wild.

Take care,
Dana