Fox (Vulpes vulpes) involvement identified in a series of cat carcass mutilations

Abstract

This study was designed to identify the cause of mutilation and death in 32 cats, part of a larger cohort found dead in Greater London, the United Kingdom, between 2016 and 2018. At the time, discussion in the media led to concerns of a human serial cat killer (dubbed The Croydon Cat Killer) pursuing domestic cats, causing a state of disquietude. Given the link between animal abuse and domestic violence, human intervention had to be ruled out. Using a combination of DNA testing, computed tomography imaging, and postmortem examination, no evidence was found to support any human involvement. Instead, a significant association between cat carcass mutilation and the presence of fox DNA was demonstrated. Gross examination identified shared characteristics including the pattern of mutilation, level of limb or vertebral disarticulation, wet fur, wound edges with shortened fur, and smooth or irregular contours, and marks in the skin, muscle, and bone consistent with damage from carnivore teeth. Together these findings supported the theory that the cause of mutilation was postmortem scavenging by red foxes ( Vulpes vulpes). The probable cause of death was established in 26/32 (81%) carcasses: 10 were predated, 8 died from cardiorespiratory failure, 6 from blunt force trauma, one from ethylene glycol toxicity, and another from liver failure. In 6 carcasses a cause of death was not established due to autolysis and/or extensive mutilation. In summary, this study highlights the value of a multidisciplinary approach to fully investigate cases of suspected human-inflicted mutilation of animals.

Forensic Death Investigations of Dog Bite Injuries in 31 Cats

“…The speculation of animal cruelty escalated further on social media and attracted attention. Similar phenomena on social media were also mentioned in a study on cats dismembered by coyotes and a study on cats dismembered by foxes [ 22 , 23 ]. This particular case points out the importance of performing forensic necropsy and DNA analysis in this kind of dismembered carcass, since findings suggestive of animal bite injury might be identified afterward.…”

“…These findings further support our theory that most of the attackers were dogs, because their behaviors are different from those of predators that hunt for food or scavenge prey. Predators, such as coyotes and foxes mentioned by previous studies, commonly mutilate cats and leave incomplete carcasses, and the injury patterns may vary among predators because of variations in feeding habits [ 22 , 23 ]. In contrast, stray dogs (lost or abandoned pet dogs) and roaming dogs (pet dogs who are free to roam) do not hunt for food.…”

“…First, the saliva of the attacker might be deposited on the coat, body surface, and wounds of the victim [ 21 ]. It has also been reported that the hair of the victim is sometimes stuck together by the attacker’s saliva, forming clumps or tufts of hair, which can provide DNA trace evidence for identifying the attacker [ 21 , 22 , 23 ]. Second, broken or frayed claws in animal bite events may occur when there is a violent interaction between the victim and the attacker, such as when the victim struggles to escape or defend itself, the victim is chased by the attacker, or the attacker drags the victim [ 21 ].…”

“…In a study on coyote predation on sheep, samples were taken only from puncture wounds with skin reflection to prevent collecting saliva from scavengers who consume the victims after their death [ 24 ]. Other studies emphasized the importance of avoiding contamination of the blood of victims when sampling [ 21 , 23 , 25 , 26 ], since bleeding may wash off the saliva DNA [ 21 ]. However, methods performed in previous research might not be adaptable in different situations [ 26 ].…”

“…On the other hand, mtDNA has a higher copy number per cell and is more resistant to degradation than nuclear DNA [ 21 , 27 ]. Moreover, a previous study on mutilation of cats by foxes successfully sampled fox mtDNA on cat fur [ 23 ].…”