As nature's cleanup crew faces decline, scientists warn that disappearing scavengers could leave behind not just carcasses, but a growing threat to human health. If these essential scavenger animals vanish, humans may find themselves more vulnerable to infectious diseases and costly waste problems, according to a study published this week in PNAS. Researchers examined 1,376 vertebrate species known to eat carrion and found that 36% are either threatened or declining, especially larger species. Half of the 17 species classified as obligate scavengers—animals that exclusively eat dead animals—are considered "vulnerable" or "critically endangered," per Smithsonian.
When large scavengers disappear, smaller species like rodents and feral dogs often take their place, per Science News. However, these so-called mesoscavengers are not as effective at cleaning up carcasses as sharks, bears, hyenas, and vultures, and are more likely to transmit diseases to humans, such as leptospirosis and cryptosporidiosis. The study's lead author, Stanford biologist Chinmay Sonawane points out that mesoscavengers simply can't match the carrion consumption of their larger counterparts.
Large scavengers are especially affected by human activities, including livestock production, land use changes, wildlife trade, and hunting. They may also be killed accidentally or poisoned by substances found in livestock carcasses. The research highlights the broader value of scavengers, from curbing disease spread in livestock to saving communities money on waste removal. In Spain, vultures have reportedly saved farmers up to $67 million in livestock disposal costs, per Smithsonian. (This content was created with the help of AI. Read our AI policy.)
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