Cats 1,100 times as deadly to wildlife as lead poisoning?

 Image from spiegel.com

The number of animals that die from lead poisoning because of lead projectiles or lead sinkers on fishing tackle, is highly disputed. The high end estimates are about 10-20 million a year in the United States. Let us put that into perspective.

Cats kill birds and small animals. Lead poisoning kills some birds and animals. Animals are killed in collisions with vehicles on our roads.  All animals die. How significant are these numbers?  In Internet wanderings I came across some numbers that show that estimates of the deaths by these various means are pretty wild.

The articles claimed a median of 15 million birds and animals killed by lead poisoning, vs. a median of 16.95 billion killed by domestic and feral cats. That is 1,130 birds and animals killed by domestic and feral housecats for each bird or animals killed by lead poisoning.  In addition, it has been claimed that 365 million birds and animals are killed in collisions with vehicles on our roads. That would be about 24 times as many killed by lead poisoning.

From abcbirds.com:

(Washington, D.C., January 29, 2013) A new peer-reviewed study published today and authored by scientists from two of the world's leading science and wildlife organizations – the Smithsonian Conservation Biology Institute and the U.S. Fish and Wildlife Service (FWS) – has found that bird and mammal mortality caused by outdoor cats is much higher than has been widely reported, with annual bird mortality now estimated to be 1.3 to 4.0 billion and mammal mortality likely 6.3 to 22.3 billion individuals.

USATODAY source 

 From abcbirds.com:

An estimated 10 million to 20 million birds and other animals die each year from lead poisoning in the United States. This occurs when animals scavenge on carcasses shot and contaminated with lead bullet fragments, or pick up and eat spent lead-shot pellets or lost fishing weights, mistaking them for food or grit. Some animals die a painful death from lead poisoning while others suffer for years from its debilitating effects.

This article claims that 1 million animals are killed every day in vehicle/animal highway collisions in the United States.

That is 365 million animals killed on the road vs. 15 million killed by lead poisoning.

But consider that there are about 10-20 billion birds alive in the U.S. at any one moment.   There are probably about 1-5 times as many mammals as birds, so a rough estimate would be 40 billion mammals, about double that for reptiles, and about the same for amphibians as reptiles. Say 80 billion reptiles and 80 billion amphibians.

This gives us a very rough estimate of animals in the United States, not counting fish, insects, arthropods, or protozoans, of about 215 billion animals living at one time.  Very, very, few of those animals will live longer than five years. Most will only live about a year (small mammals, birds, reptiles and amphibians have very short life expectancies).

For the sake of argument, let us assume an absurdly long life expectancy of five years. That would mean about 43 billion animals die every year. Almost none of them die of old age in nature. Most are killed and eaten. A great many die in accidents.

Of the 43 billion that die every year, the top end estimate for lead poisoning is 20 million.  Using that number, .047 percent of animals that die in the U.S. each year die of lead poisoning, while 39% are killed by domesticated and feral cats, and .84 percent die in vehicle collisions.

I suspect the numbers are absurd.  They only serve to make the point that the numbers of animals that die of lead poisoning are a virtually irrelevant percentage of the number of animals that die every year, whether man has anything to do with it or not. 

I do not believe that cats kill almost four of ten birds and animals that die in the U.S. every year.  I doubt if the actual figure is even a tenth of that.

The reality is that life and death are intertwined. You cannot have birds without killing other birds, fish, insects, or ungerminated innocent seeds.

The best we can hope to do is to be good stewards of the land, increasing fertility and attempting to keep animal populations from getting completely out of control.

In the United States, because of irrigation and fertilizers, there is much more productive land than ever before. Biomass has greatly increased. Some animals did not fare well, others benefited enormously. The whitetail deer and coyote populations have soared. Bison and wolf populations plummeted.  Rock Doves (domestic pigeons) are numerous. The passenger pigeon became extinct.

The small percentages that die because of the intervention of man are more than made up for by the large increase in animal population that occurs because of the incredible increase in the fertility of the land. Man's intervention has made the United States far more fertile than it would be without man.

And that is a good thing.


©2017 by Dean Weingarten: Permission to share is granted when this notice and link are included.

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