Major organ loss from post-mortem animal predation: Issues arising from emptied body cavities

Introduction

Post-mortem animal predation refers to the process whereby animals feed on bodies after death has occurred.^1–3 It specifically excludes injuries and trauma inflicted by animals during life, although on occasion the process may be initiated ante-mortem and continue after death has occurred. ⁴ Histological sampling of damaged tissues in these cases may reveal a vital reaction. ⁵

Post-mortem predation often makes autopsy interpretations more difficult, as skin and soft-tissue removal may eliminate or disguise injuries, and loss of internal organs may preclude assessment of the possible role played by organic disease in the terminal episode. This is often compounded by changes of putrefaction and autolysis, as animal predation is often linked to decomposition, given that significant feeding often only occurs on bodies that have not been found for some time. ⁶ Artefactual damage to the eyes and anogenital region may raise the possibility of a sadistic or sexually motivated homicide, and post-mortem injuries may also simulate sharp-force wounds. ⁷ Although the range of post-mortem animal injuries has been well documented, there has not been a specific analysis of the features of cases that have involved removal of entire organs and emptying of body cavities.

The autopsy files of Forensic Science South Australia were reviewed for cases where post-mortem animal predation had resulted in loss of major organs and emptying of body cavities. Several of these cases have been selected to illustrate points raised in the Discussion.

Discussion

There is no doubt that post-mortem animal activity may occasionally provide useful information for the examining pathologist. The type of fauna colonising or feeding on a body may give an indication of the location of the scene of death and/or body storage and provide evidence that a body may have been moved. Insect activity with loss of superficial layers of skin in exposed areas, for example by ants, may outline any clothing that has been subsequently removed. ⁸ Maggot mass and insect morphology may also be useful in attempting to determine the time of death, although the many variables in individual cases make this an imprecise technique at best.^9,10 Often, the type of animal that has been feeding can be discerned in smaller, better preserved areas of trauma. For example, the paired gnaw marks from rodent incisors on the dried tips of fingers and toes is very characteristic^11,12 (Figure 1(a)).

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Figure 1.

(a) Typical post-mortem rodent gnaw marks of particularly the index finger and hand of a 74-year-old woman found deceased at her home address. (b) Separation of the skull from the body with complete removal of the anterior chest wall, thoracic cage and thoracic contents by a pet dog, with exposure of the posterior rib cage and vertebral column. The decedent was a 45-year-old woman who was found dead at her home address. (c) Defleshing of the face and removal of soft tissues from the neck and organs from the thoracic cavity (the latter through a defect in the right side of the chest) of a 69-year-old man caused by a number of domestic cats. (d) An X-ray of the chest plate in the preceding case showing loss of right-sided ribs and costal cartilages, allowing the cats access to the thoracic organs.

On occasion, however, post-mortem predation may result in extensive tissue and organ damage and loss. Determining what injuries occurred during the lethal attack and what may have occurred afterwards with post-mortem feeding may be difficult. For example, while large carnivores such as Crocodylus porosis, the estuarine or saltwater crocodile found in Northern Australia, kill by crushing, they may leave prey to decompose in order to assist with the ingestion of smaller pieces. ¹³ Thus, although death may be caused by the animal, the injuries found may be post-mortem in origin. In addition, death by drowning initially not involving crocodile activity is often impossible to exclude. ¹³

Generally, opening of the head or removal of thoracic cavity organs requires an animal of sufficient size and power to chew through the skull, sternum, clavicles and ribs. ¹⁴ This is most commonly seen in the local South Australian situation with domestic dogs living in a house with a reclusive individual. For example, removal of the brain and all thoracic organs in a 45-year-old woman after death was undertaken by her pet dog, which then precluded determination of the cause of death (Figure 1(b)). In other parts of the world, predators such as coyotes and bears may cause similar destruction. ¹⁵

It should be recognised that considerable organ and tissue damage may also occur if there are a large number of voracious animals present. For example, although cats most often remove only the soft tissues of the face, a case has been reported where loss of most of the thoracic contents had occurred due to the concerted efforts of an estimated 30 domestic cats ¹⁶ (Figure 1(c) and (d)). Thus, the number of animals at the scene is another factor to consider in the analysis of post-mortem evisceration, in addition to individual animal size.

Post-mortem insect activity is often a feature of decomposed bodies, particularly in warm summer months. Given sufficient time, fly larvae (maggots) and beetles may completely remove the brain and chest and abdominal organs, resulting in a hollow body. Again, the effect on the body is dependent on the number of post-mortem predators present rather than on their individual size.

The finding of bodies with evidence of shark-inflicted trauma in the seas off South Australia always raises the question as to whether death was due to shark attack or whether the injuries were merely inflicted by post-mortem feeding following, for example, death by drowning. The case of a 28-year-old man whose body was found at sea some days after his disappearance is a good example. There was clear evidence of evisceration of the abdominal organs, with no vital reaction to suggest that this occurred perimortem (Figure 2(a)). Characteristic ‘V’ shaped bites and gouging of the femoral shafts were very typical of shark activity^17,18 (Figure 2(b) and (c)).

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Figure 2.

(a) Loss of abdominal organs with defleshing of the legs and other injuries from post-mortem shark predation in a 28-year-old man who was missing at sea. (b) A very characteristic V-shaped wound mark from a shark bite in the preceding case. (c) Gouges of the femoral shaft typical of shark attack in the preceding case.

The post-mortem evisceration or consumption of major organs by scavenging animals may therefore raise a number of issues. Removal of organs may imply the actions of a single large animal such as a dog or shark. However, groups of smaller animals, if of sufficient size and acting in concert, may also be able to achieve the same result. Similarly, loss of organs may occur if there is enough time for the generation of significant insect activity compounding decomposition. Thus, the finding of empty body cavities at autopsy may be the result of a wide variety of animal activities involving a range of species from different locations. One of the major problems that arises in these cases is in identifying or excluding natural diseases or injuries that may have played a role in death, given the absence of significant organic material.