Species → Feral Domestic Cat
Feral Domestic Cat
Felis catus
What if it disappeared?
Impact HighWithout free-ranging cats, the single greatest source of human-caused mortality for birds and mammals in the United States stops overnight: up to 3.7 billion birds and 20.7 billion small mammals are no longer killed each year.
DocumentedDetail
Loss, S.R., Will, T. & Marra, P.P. (2013). The impact of free-ranging domestic cats on wildlife of the United States. Nature Communications, 4, 1396.
Loss, Will and Marra's (2013) estimate combines dozens of local predation studies to size, year by year, the scale of this mortality in the United States — the country's single greatest source of human-caused mortality for birds and mammals. The day this predation stops, that yearly toll of killed animals disappears from the ledger, even though its real effect on population sizes remains less certain (see the next horizon).
On islands, where many native species never evolved defensive behavior against a mammalian predator, the end of this hunting would likely let the most threatened populations — among the 175 species recorded across at least 120 islands — begin to stabilize.
ExtrapolatedDetail
Extrapolation à partir de Medina, F.M. et al. (2011), qui documente l'ampleur de la prédation du chat sur les vertébrés insulaires menacés pendant sa présence, pas le devenir de ces populations une fois le chat disparu.
The study shows that species with no native mammalian predator — a common situation on islands — are especially vulnerable to cats, lacking evolved defensive behaviors. That vulnerability stems from the predator's presence: once it is gone, nothing should, in principle, stop these populations from starting to grow again, though no post-removal monitoring study is gathered here to confirm it.
What's missing to confirm it: Population monitoring on islands following an actual cat removal, compared to their trajectory while the cat was present, to confirm this rebound rather than assume it.
On the North American continent, a century likely wouldn't settle the question that matters most: if most of that mortality was going to happen anyway from other already-present causes — disease, competition, other predators — bird populations wouldn't have changed much; if not, they would have had plenty of time to largely recover.
HypothesisA thousand years without cats wouldn't bring back the species already lost: among the dozens of island extinctions where cats were identified as a direct factor, none would return — those islands would long since have been recolonized by other species, never quite the same as before.
ExtrapolatedDetail
Extrapolation à partir de Medina, F.M. et al. (2011), qui documente des dizaines d'extinctions insulaires où le chat est identifié comme facteur direct — l'irréversibilité d'une extinction est un principe bien établi, pas une mesure de l'étude elle-même.
Medina et al. (2011) document dozens of island extinctions where cats played a direct role, across at least 120 islands. An extinction does not reverse: whether the cat disappears one year or a thousand years later changes nothing for a species already gone. What a thousand years would change, instead, is the island's makeup itself — other species, arrived since, would have filled the vacancy.
What's missing to confirm it: An inventory of the species that recolonized these islands after the cat-caused extinction, to check whether they truly occupy the same ecological function as the species that were lost.
Documentation
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Loss, Will & Marra (2013) — The impact of free-ranging domestic cats on wildlife of the United States, Nature Communications
Accessed August 10, 2026
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Medina et al. (2011) — A global review of the impacts of invasive cats on island endangered vertebrates, Global Change Biology
Accessed August 10, 2026
Last verified: August 16, 2026