The death toll from cats

Among the perils of city life that birds and other animals share, the most uniformly serious one is the domestic cat that ventures out-of-doors. . . . [I]n the United States . . . cats kill 6.9 to 20.7 billion small mammals each year. Suddenly the slaughter of more than three hundred million vertebrates—birds, herps, and mammals—on U.S. roads seems tiny. Cats eat at least an order of magnitude more animals than we run over with our cars each year. And it is mostly a different set of animals that cats eat; Fluffy doesn't eat many deer or salamanders, but she really tears up the mice, birds, and small reptiles.

John M. Marzluff, Welcome to Subirdia: Sharing Our Neighborhoods with Wrens, Robins, Woodpeckers, and Other Wildlife (New Haven: Yale Univ. Press, 2014), p.

Cars and trucks versus wildlife: a big problem for both sides

Wings allow birds to avoid massive road mortality that culls the urban herd of mammals and herps. . . . The full magnitude of roadkill is difficult to estimate, but collisions with large animals are certainly on the rise. In a 2008 report to Congress, the Western Transportation Institute noted that in 2004, one in twenty reported vehicle collisions in the United States—some three hundred thousand—involved wildlife, most likely deer. These collisions annually kill two hundred Americans and injure twenty-six thousand, at an estimated cost of more than $8 billion. The cost to wildlife is also extreme. In the United States, between half a million and one million deer are killed each year, and twenty-one species of vertebrates are federally endangered in part because of road mortality; only three are birds. The Humane Society of the United States estimates that more than three hundred million vertebrates die annually in vehicle collisions. Worldwide, the annual death toll is staggering . . . .

John M. Marzluff, Welcome to Subirdia: Sharing Our Neighborhoods with Wrens, Robins, Woodpeckers, and Other Wildlife (New Haven: Yale Univ. Press, 2014), pp. 170-71.

Unscented fawns

Deer and elk, cervids, are graced with a natural survival trait that helps protect their offspring. Newborn deer fawns and elk calves have very little smell, so when the mother moves away from the herd to give birth, it's harder for predators to find the virtually odorless babies. But even with this protection, bears and other predators know when calving is going on and the smell of blood from the birthing process allows them to home in on the newborns.

Immediately after the calf is born, many of the mothers eat the afterbirth, the placenta, to lessen the chances for detection by predators. Then they move the calf away from the birth site, hide it in thick vegetation, and walk away. The scentless calf lies perfectly still until the mother returns, so a hungry predator can walk very, very close to the baby and pass it by without even realizing the calf is there.

Kim DeLozier & Carolyn Jourdan, Bear in the Back Seat II: Adventures of a Wildlife Ranger in the Great Smoky Mountains National Park (2014)

Multiplying pigs

Pigs are the most prolific large mammal in North America. In some ways, they're like a big, ugly rabbit, capable of having two litters a year. Research indicates that we need to remove about helf of the wild hogs every year to keep the population levels under control. If not, their numbers grow in a hurry. 

Kim DeLozier & Carolyn Jourdan, Bear in the Back Seat II: Adventures of a Wildlife Ranger in the Great Smoky Mountains National Park (2014)