Assessing the Sick Lizard

Normal behavior and handling cautions

Lizard behavior varies with the species, however the normal lizard tends to be alert, responsive, and curious. Some species, like the bearded dragon (Pogona vitticeps) and leopard gecko (Eublepharis macularius) tend to be particularly active and animated while most chameleons are more delicate and “bird-like” (Fig 1).

Figure 1. Normal lizard behavior can vary, but most individuals tend to be alert, responsive, and curious in the exam room.

Remember that some species like iguanids and geckos possess tail autotomy or a defense mechanism that utilizes tail loss. A vertical fracture plane of fibroconnective tissue and cartilaginous runs through each caudal vertebrae. This means that the tail can fall off when grasped, sometimes when very little pressure is applied. The tail will regrow as a cartilaginous rod. Tail autonomy generally does not occur in agamid lizards, monitors, and true chameleons. Aggressive behavior can increase the risk of tail lashing and subsequent tail trauma. Signs of aggression and territoriality in lizards can include:

• Head nodding
• Standing sideways to the perceived threat
• Swallowing air to increase body size
• Standing high off of the ground
• Lashing at the threat with the tail

Signs of illness

Exotic animal medicine requires a delicate balance between medical concepts true for all living creatures (“one medicine”) and species-specific information and this is true for lizards (Table 1).

Figure 2. Emaciated leopard gecko (Eublepharis macularius) (left); overweight gecko (right). Provided by Dr. M. Scott Echols. Click image to enlarge.

Figure 3a. A normal leopard gecko exhibiting carpal lift. Note the normal-sized tail. Click image to enlarge.

Figure 3b. A green iguana (Iguana iguana) down on all four limbs. Lack of carpal lift is a non-specific sign of lethargy or weakness. Click image to enlarge.

Figure 4. Dark, lethargy veiled chameleon (Chamaeleo calyptratus).

Figure 5. Lizards shed in patches. Image provided by Jeanette Wyneken, Ph.D. Click image to enlarge.

Physical examination

• Rostrum: Abrasions can be common in active lizards like water dragons and basilisk lizards and is typically caused by repeated trauma with cage walls.
• Although the dewlap may be used to gently yet firmly open the mouth in some individuals (Fig 6), an oral speculum is often needed to evaluate the oral cavity. Take care not to damage the teeth when opening the mouth.
  

  Figure 6. Although a mouth speculum must be used in many instances, the dewlap can be used to gently yet firmly open the mouth in some individuals. Image provided by C. Pollock. Click image to enlarge.

  • Mucous membranes are generally paler in reptiles when compared to mammals. Mucous membrane color is often pale pink to white. Normal adult bearded dragons and many chameleons may appear yellow-orange. This should not be confused with icterus. Some species of monitor, gecko, and chameleon have dark mucous membranes that appear black to dark purple.
  • The teeth of many lizards are “pleurodont” or attached to the sides of the mandible without sockets. Pleurodont teeth are regularly shed and replaced. Some species like the bearded dragon, water dragon (Physignathus cocincinus), frilled lizard (Chlamydosaurus kingii), and chameleon have “acrodont teeth” which are not replaced except in the very young animal. Periodontal disease has been reported in captive  lizards with acrodont teeth. Clinical signs may include gingival erythema and recession, calculus, and in severe cases, osteomyelitis and abscess formation.
  • Chameleons and monitors have long protrusible tongues that retract into a sheath rostral to the glottis. Early signs of hypocalcemia in chameleons may include flaccid paralysis of the tongue.
  • The tip of the tongue is normally darker in the green iguana (Iguana iguana).
  • Examine the oral cavity for exudates or lesions consistent with stomatitis. The presence of excessive white foam may be seen with septicemia or pneumonia.
• Secretions from the nasal salt gland may dry as a fine, white powder around the nares in some species like the green iguana.
• A spectacle or clear scale overlies the cornea in some species of gecko.
• Auscultation is more difficult because of the presence of scales, but may be attempted. Placing moistened gauze between the stethoscope’s diaphragm and the lizard may enhance conduction of sound.
• The lateral skin fold will be more prominent with weight loss and/or dehydration.
• Feel over the entire lizard for evidence of lumps or bumps that are most often subcutaneous granulomas or abscesses. Also look for evidence of ectoparasites such as mites, which appear red in lizards.
• Palpate the coelom.  Lizards store fat within paired symmetrical fat bodies in the caudal coelom. Fat bodies can become huge in the obese lizard causing coelomic distension, and may even be visible on survey radiographs.
• Evaluate the vent for evidence of fecal pasting, erythema, or prolapse.
• Palpate the long bones and joints of each limb. Evaluate the legs for evidence of swelling including hard, firm swelling consistent with fibrous osteodystrophy in metabolic bone disease.

Gender identification is often fairly difficult in juvenile lizards. Secondary sex characteristics in adult male lizards may include:

• Femoral and precloacal pores (Figs 7 and 8)

Figure 7. Arrows illustrate large femoral pores on the medial surface of the thighs in a male green iguana (Iguana iguana). Image provided by C. Pollock.

Figure 8. Arrows indicate small, relatively dainty femoral pores in a female green iguana (Iguana iguana). Image provided by C. Pollock.”

• Hemipenal bulge: Dramatic swelling of the ventral tail base caudal to the vent occurs in some males due to enlargement of the hemipenes.
• Larger head and body size
• Brighter coloration
• Male iguanas often have a larger dewlap and operculum scales, and taller dorsal spines (Fig 9).
• Male chameleons often have head ornamentation.

Figure 9. Male iguanas tend to have taller spines and larger dewlaps, Image by Cy. Click image to enlarge.

References