You've looked in your gerbils' cage, and found blood.
Some possible causes:
- Fighting: if the gerbils are actively fighting, or if one has bite wounds, they will need to be separated. See the section on Declanning.
- Injury from a sharp spot on a cage toy. See the section on Injury.
- Toenail loss: see the section on Toenail Loss.
- Ear infection: if the gerbil's ear is hurting, he may scratch at it. He will need antibiotics and pain medication. See the section on Ear Infection.
- Ear growth: an ear growth may be annoying him or be painful, also causing him to scratch. See the section on Tumors.
- Scent gland tumor: the gerbil may have a scent gland tumor that he's bothering. See the sections on Scent Gland and Tumors.
- Other external tumors: these may be tumors that bleed due to their nature, or growths that the gerbil is picking at.
- Blood in the urine: he will need to go to the vet. This could mean an infection. See the section on Urinary Tract Infection.
- Mating: occasionally a few drops of blood appear during mating. This is normal.