Tweety & Sylvester Down Under: two new studies exonerate cats

Birds are Still Singing in Our Suburbs and Bella & Charlie Are Not the Problem,  argue team from the University of Queensland

KENMORE,  Queensland,  Australia––Two new studies from scientists associated with the Australian Pet Welfare Foundation and the University of Queensland challenge the notion that cat predation has much of anything to do with bird population declines.

Perhaps only New Zealand is more militantly mobilized against outdoor cats,  both feral and domestic,  than Australia,  based on the long politically amplified claim that cats rather than agriculture and urban development are primarily to blame for losses of birds and endangered species.

(See Cat-haters Down Under set up rare birds for an attack of H5N1 avian flu.)

New studies deliver a one-two punch to scapegoating cats

But Birds are Still Singing in Our Suburbs:  Contemporary Hunting Data for Pet Cats in Urban Australia,  a 38-page review of data and of the presumptions behind the data,  knocks the quasi-scientific underpinnings out from beneath the theory that cat predation on birds is anywhere near as frequent as is commonly claimed.

Birds are Still Singing in Our Suburbs follows by barely a month the release of a study by an overlapping team entitled Bella & Charlie Are Not the Problem—It’s Us: The Real Causes of Wildlife Rescue in New South Wales.

“Hunting of wildlife by pet cats is an important concern in Australia,  resulting in claims pet cats are ‘sending our suburbs silent,’  begin Jacquie Rand of the Australian Pet Welfare Foundation,  who is a former University of Queensland veterinary professor,  and three University of Queensland co-authors in Birds are Still Singing in Our Suburbs.

            One of the University of Queensland co-authors,  wildlife ecologist Kate J. Dutton-Regester of the School of Veterinary Science,  also co-authored Bella & Charlie Are Not the Problem.

Challenging unsupported assumptions

“National estimates of predation by pet cats are limited and depend on assumptions about how many cats hunt,  how much prey they catch,  and how much prey is not observed by owners,”  Rand et al observe.

Countering the guesstimates,  Rand et al collected data reported by “2,405 owned and semi-owned cats from lower-income suburbs in Ipswich,  Queensland,  whose carers enrolled them in a free sterilization program and were required to complete a questionnaire” in order to receive the free spay/neuter service.

“Most cats were not reported to hunt:  77% were reported never to hunt,”  primarily because the cats were kept indoors,  “and even among cats with outdoor access,  58% were not reported to hunt,”  Rand et al found.

Not hunting,  or not hunting successfully,  might chiefly reflect a lack of vulnerable prey in the cats’ habitat during the hours when the cats are outdoors.

Insects & rodents

“Among cats reported to catch prey,  insects and rodents were most common,”  wrote Rand et al,  affirming previous studies and common belief,  “while birds were least commonly reported and were usually caught in low numbers.”

Moreover,  Rand et al suggest,  most of the cat predation that does occur in Australian suburban environments is “compensatory,”  rather than “additive.”

Only “additive” predation actually contributes to population losses among prey species.  “Additive” predation is predation on the healthy,  potentially successfully reproducing part of the prey population.

Almost all animal predation,  however,  not just by cats,  is “compensatory,”  meaning that the predators kill and eat mainly the sick and injured,  the aged and infirm,  and unattended young.

None of these victims are likely to contribute any more to the reproductive success of their species than they already have.

Cats are not killing six times more birds than exist

“When the observed hunting frequency and number of prey observed to be caught in this population were used to generate national predation estimates,”  Rand et al continued,  “the resulting totals were substantially lower than previously published Australian estimates.

“For birds,  our estimated annual mortality of 0.38 million was 161- to 311-fold lower than

the widely cited estimates of 61–118 million birds killed each year by pet cats,  and was more consistent with estimates of Australia’s total urban bird population of 11 million,”  who are obviously not extirpated by cats multiple times per year and then somehow replenished,  as would be necessary to achieve the claims of higher predation.

Actual Australian bird population turnover per year,  Rand et al mentioned,  is scientifically reported as about 3.6 million per year,  meaning that about one bird in three dies,  and about one bird in three is in his or year first year of life.

These figures are in the normal range for population studies of most birds and other wildlife.

Obsolete data

“Published estimates of predation by pet cats have led to claims that pet cats are having a devastating effect on native wildlife,”  Rand et al wrote,  “based on data collected between 32 and 37 years ago.”

The Birds are Still Singing in Our Suburbs data can perhaps best be compared to what is still the mostly widely cited study of cat predation,  and the study most often cited out of context by people who want to blame cats for vanishing birds,  published by the British-based Mammal Society in February 1998.

To produce that survey,  800 British cat owners––about a third of the Australian sample––recorded their cats’ kills for six months,  amounting to 144,000 cat-days of activity.

Missy & Kipper

Among all those cats,  the most active killer was Missy,  with 125 documented kills in 180 days,  including 28 birds.  Almost all of the rest of her known kills were mice,  voles,  and other small rodents.

The runner-up was Kipper,  with 82 known kills in 180 days,  including six birds.

Between them,  Missy and Kipper,  by far the most actively predatory cats in the British sample,  accounted for 34 bird kills in 360 cat-days.

Those two most skilled of feline killers managed to kill birds at a rate amounting to just 16% of their total prey,  and succeeded in killing a bird on only 9.4% of the days they hunted.

Jacquie Rand et al vs. John Woinarski & Sarah Legge

Concluded Birds are Still Singing in Our Suburbs co-authors Rand et al,  “previously published estimates of pet cat predation in Australia are exaggerated.

“Using the most recent published estimate of the Australian pet cat population,  5.83 million,   which is 1.5 times higher than the populations used in the previous extrapolations,”  done respectively by Charles Darwin University conservation biologist John Woinarski and Australian National University wildlife ecologist Sarah Legge,  “estimates of bird predation by pet cats would increase to 92 million (Woinarski) and 177 million (Legge),  greatly exceeding the estimated total urban bird population.”

            (Download Birds are Still Singing in Our Suburbs at https://www.preprints.org/frontend/manuscript/64e19c9833a18a7b3203d341a75aea1b/download_pub.)

Wildlife rehab records

            To produce Bella & Charlie Are Not the Problem—It’s Us: The Real Causes of Wildlife Rescue in New South Wales,  Jacquie Rand,  Kate J. Dutton-Regester,  and Antong Liang of the School of Agriculture and Food Sustainability at the University of Queensland “analyzed 11 years of records from the New South Wales Wildlife Rehabilitation Data Dashboard,”  gathered from 2013 to 2024,  covering 52,475 rescued animals from 158 threatened species,”  they reported.

“Outcomes for rescued threatened animals were often poor,”  Rand et al acknowledged.  Only 24.1% were released alive,  58.5% died in care,  and 17.5% “had another recorded outcome,”  which could include escapes.

“The most common recorded reason for rescue,”  Rand et al found,  “was Unknown,  followed by Entanglement,  Weather Event,  Abandoned or Orphaned young,  Unsuitable Environment,  and Motor-Vehicle Collisions.

Dogs harm more wildlife than cats

“Together,  these accounted for 68% of threatened species rescues.  Animal attacks made up 4.4% of recorded rescues.  Dog attacks were more than three times as common as cat attacks, while cat attacks accounted for 0.6% of threatened species rescues.”

The greater frequency of dogs injuring animals brought to wildlife rehabilitation centers has been informally reported by some U.S. rehabilitation centers,  but has been explained as a matter of cats being more selective and more efficient killers:  cats are said to not attack what they cannot quickly kill,  and though cats may play with their prey,  rarely let injured prey escape.

However,  among wildlife brought to wildlife rehabilitation centers,  neither cats nor dogs account for much that could be considered “additive” rather than “compensatory” predation.

Focus on cats ignores more effective ways of protecting wildlife

“Public discussion in Australia often presents pet cats as a major cause of wildlife decline,”  observed Rand et al.

“Cat management,”  a euphemism for extermination,  “is frequently promoted as a major conservation response.  However, this focus may draw attention away from other common and preventable recorded causes of threatened species rescue.

“Many of these claims,”  about the supposed extent of cat predation,  “are based on modeling and estimates drawn largely from non-peer-reviewed sources and from data collected 32 to 37 years ago,  including cat owners’ reports of prey brought home,”  Rand et al continued,  as they noted a month later in Birds are Still Singing in Our Suburbs.

Twice as many cats are kept indoors now

“This is important,”  Rand et al explained,  “because urban cat ownership and containment practices have changed substantially over time.  Older estimates used in influential modeling were based on approximately 29% of cats being contained,  whereas recent Australian data indicate that approximately 65% of pet cats are fully contained,  and a further 24% are contained at night.”

Cat containment at night,  however,  would much more significantly influence predation on rodents,  who are most active and vulnerable at night,  than on birds,  who except for ground-nesting species are seldom vulnerable to cats after dark.

            (Bella & Charlie Are Not the Problem may be downloaded at https://www.mdpi.com/2076-2615/16/14/2174.)

Ghost of Forbush haunts ornithology

As Rand et al found in Australia,  the most often mentioned U.S. estimates of cat predation on birds are projected from obsolete data,  some of which goes all the way back to the grossly inaccurate claims of then-Massachusetts state ornithologist Edward Howe Forbush in a 1916 tract entitled The Domestic Cat: Bird Killer, Mouser and Destroyer of Wild Life;  Means of Utilizing and Controlling It.

Among other errors,  Forbush conflated with cat predation the predation of other species including raccoons,  bobcats,  and even gulls.

(See How a birder’s mistakes incited 100 years of cat hatred.)

Loss,  Marra,  & Will

Smithsonian Conservation Biology Institute ornithologists Scott Loss and Peter Marra and U.S. Fish & Wildlife Service biologist Tom Will on January 29,  2013 used numbers almost as absurd in a much cited Nature Communications article alleging that domestic cats in the U.S. kill up to 3.7 billion birds and as many as 20.7 billion mice,  voles,  and other small mammals.

Loss,  Marra,  and Will––and the pro-cat organization Alley Cat Allies,  at the time––projected a claim that there were 80 million feral cats in the U.S.,  a claim that appears to have originated in a 1934 Nature article,  which also projected a pet cat population of about 40 million.

This was more than twice as many owned as any actual survey would find before 1950.

The combined total of 120 million cats was derived not by counting cats,  but by simply guessing that two-thirds of all cats might be feral,  and then multiplying the number of U.S. households by 1.25 to get the guesstimated number of cats per home.

The 1934 claim did not stand up even in 1934

Skeptical of the math in the Nature article,  the American Humane Association in late summer 1934 surveyed five neighborhoods in Albany,  New York,  finding just one cat per 10.7 households.

Taking over the project,  National Family Opinion Survey founders Howard and Clara Trumbull, writing as “John Marbanks,”  reported that as of 1937 the total U.S. cat population was about 35 million.

The Trumbulls continued their research in 1947-1950,  finding that by 1950 the U.S. cat population had increased to about 50 million, paralleling the post-World War II increase in the number of U.S. households.

Their surveys found about 13.2 million barn cats,  6.5 million other rural cats,  7.0 million cats in urban homes,  and 23 million ferals––at least 42 million cats outdoors.  This was more than any actual surveys of cat populations,  roadkills,  or animal control intake have projected within the past 20 years.

(See D.C. Cat Count confirms low feral cat population, lots of free-roaming pets.)

From Howard & Clara Trumbull to the D.C. Cat Count

The Trumbulls also compared their findings to six studies of cat predation done by conservation biologists between 1936 and 1951,  mostly by investigating the stomach contents of dead cats.

“All tended to indicate the same thing––cats have been badly and unjustifiably maligned,”  they wrote in the June 1953 edition of The National Humane Review.

The three-year,  $1.5 million D.C. Cat Count study,  completed in 2021,  is the most recent comprehensive cat population study.

The D.C. Cat Count finding of 3,000 bona fide feral cats in Washington D.C. projects to 1.4 million feral cats nationally.

            (See also What if your cat could kill 10 billion insects?,  Predation is nature’s disease control, including for Tweety & Sylvester,  and Who killed 2.9 billion birds since 1970? Not cats, says a look through the glass!)

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