Signs of Pain in Rats

Signs of pain in rats due to illness, injury, or surgical procedures can vary based on severity. The signs of pain have been listed here by category based on the following: mild to moderate pain, severe or chronic pain, or post-procedure pain. Note that some signs of pain, depending upon severity and type, may overlap into another category. Not every sign may present based on the level of pain, and the individual rat’s personality. Knowing your rat’s normal daily behavior will better allow you to recognize the signs of pain your rat may exhibit and to aid your veterinarian in achieving better pain control for your pet rat.

Mild to Moderate Pain

  • Squinting eyes
  • Porphyrin around eyes/nose
  • Piloerection/rough coat
  • Increased aggression
  • Decreased exploratory behavior
  • Vocalization when prodded (may or may not present)
  • Licking/scratching/self-trauma
  • Guarding (protecting painful area)
  • Reluctance to move
  • Grinding of teeth (not attributed to pleasure)
  • Reduce appetite
Severe or Chronic Pain

  • Eyes closed
  • Poor skin tone
  • Muscle wasting
  • Dehydration
  • Weight loss
  • Depressed
  • Unresponsive
  • Sunken/distended abdomen
  • Hypothermia
  • PICA (eating of non-food substances)
  • Self-trauma
  • Inappetence
  • Change in fluid intake
  • Hunched posture- Head tucked
  • Head pressing/bumping
  • Vocalization- May or may not be present (do not rely on this sign alone)
  • Abnormal gait (e.g.,ataxia, limping)
  • Poor grooming
  • Incontinence
  • Labored breathing
  • Curling up biting own feet (seen primarily with ureteral/bladder stones)
  • Avoidance of contact with human
  • Huddled facing corner in cage
  • Whimper (similar to dog whine but softer sounding heard in acute, severe pain)
  • Tachycardia (faster than normal heart rate)
  • Tachypnia (faster than normal breathing)
Post-procedural Pain

  • Squinting of eyes
  • Decreased activity
  • Increased back arching
  • Horizontal stretching
  • Abdominal Writhing
  • Abnormal gait (e.g.,falling/teetering/staggering)
  • Guarding (protecting painful area)
  • Twitching
  • Decreased grooming
  • Porphyrin
  • Piloerection of hair
  • Decreased food and water intake
  • Aggression
  • Avoidance of contact with human
  • Tachycardia (faster than normal heart rate)
  • Tachypnia (faster than normal breathing)
  • PICA (eating of non-food substances, note: may be seen with the use of certain opioids)

Adapted from:

  1. Flecknell, P., & Waynforth, H. (1992). Experimental and Surgical Technique in the Rat, Second Edition. New York: Academic Press.
  2. University of Wisconsin–Milwaukee Animal Care Program. Signs of Pain and Distress in Rodents.
  3. Fallon et,al. Post-Procedure Care of Mice and Rats in Research: Reducing Pain and Distress.
  4. Kohn et,al. (2006). Guidelines for the Assessment and Management of Pain in Rodents and Rabbits.
  1. Takeda, N., Hasegawa, S., Morita, M., & Matsunaga, T. (1993). Pica in rats is analogous to emesis: an animal model in emesis research. Pharmacology, biochemistry, and behavior, 45(4), 817–821.
  2. Additional references listed on References page of Rat Health Guide Index.


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