Abstract

Hypothermic stunning is an occasionally fatal condition of sea turtles occurring when they are caught in waters that cool rapidly to around 10°C or less. Effects include decreased metabolic rate, lethargy, and positive buoyancy. Uncomplicated cases may be releasable after a short period of rehabilitation, but complications, such as bacterial and fungal infections, lytic bone lesions, and scavenger-inflicted wounds, can extend the rehabilitation period considerably. Hot spots of sea turtle hypothermic stunning are characterized by shallow estuarine waters with natural barriers restricting emigration to warmer waters in the autumn. In 2013 in North Carolina, there was a total of 254 hypothermic-stunned turtles reported (19 loggerhead turtles, 181 green turtles and 54 Kemp's ridleys. While in water, turtles are buffered somewhat from freezing air temperatures and winds, but emergent tissues could suffer a penetrating freeze. Minor differences in the depth of freezing of the carapace can have major impacts on case outcome. We present two cases of carapacial necrosis consistent with freezing of emerged portions of the carapace of hypothermic-stunned in-water sea turtles.

Green turtle Cm-EHG-140118-01 was recovered as a hypothermic stunning case and was treated at the Sea Turtle Assistance and Rehabilitation Center at the NC Aquarium on Roanoke Island. An oval patch of necrotic bone over the central dorsal-most portion of the carapace developed exposing underlying vertebrae and healing epithelium. Carapace healing proceeded well, but swimming was uncoordinated and deep pain response was questionable. A CT examination revealed severe disruption of the spinal canal in multiple locations. The turtle was euthanized and postmortem examination confirmed discontinuity of the spinal cord.

Kemp's ridley Lk-LLB-140108-02 was recovered as a hypothermic stunning case and was transferred to the Karen Beasley Sea Turtle Rescue and Rehabilitation Center. An oval patch of necrotic bone developed over the central dorsal-most portion of the carapace and began separating slowly from healthy underlying tissue. A CT examination revealed exfoliating necrotic carapacial bone with laminar healing of underlying boney structures. The spinal canal was continuous and intact, albeit within a few millimeters of necrotic or missing bone in places. Rehabilitation is expected to be prolonged, but the prognosis is guardedly optimistic.

Spinal reflexes (withdrawal reflex, spinal locomotion) and occasional subdued responses to flipper pinching, even in neurologically intact sea turtles, are challenges to evaluating neurologic function in cases of suspected spinal cord trauma. Imaging by CT can help resolve ambiguities of the neurologic examination and can inform decision making with respect to eventual release, permanent captive care, or euthanasia.

* Presenting author