An analysis is presented of records of injuries and the types of injuries to jackass penguins in Algoa Bay, South Africa, over a 10-year-period. Sharks are implicated in causing most of the injuries, but other possible agents are discussed. The types of injuries were categorized and compared to the dentition of sharks known to occur in the area. Using a life-size model of a jackass penguin and preserved jaws of sharks, bites were simulated to establish the types of injury inflicted by different species. Certain injuries indicate attack by great white sharks, while others cannot be ascribed to any particular species. Most shark injuries show single jaw involvement, and range from small cuts across the feathers to the bird being cut in two. Sharks accounted for the highest number of identifiable natural causes of death, but the significance of shark attack as a mortality factor in jackass penguins is difficult to assess.