A group of scientists from the epicenter of the debate on community cat colony management recently made a discovery they termed "surprising." A report in the journal Global Ecology and Biology showed that native mammals were most likely to die off on islands that had rats, but not cats, foxes, or dingoes.
I’m actually stunned that the scientists were surprised by this discovery. I only had to watch PBS shows and take high school science classes to learn how predator-prey relationships benefit prey animals. You’d think a bunch of Ph.Ds would have learned this lesson along the way, too. For those who need a refresher course, here’s how feral cats actually help prey animals to survive.
On Australian islands where feral cats were eliminated, rat populations rose exponentially. Rats are notorious for eating bird eggs, and as a result of being overrun by rats, bird populations on those islands were decimated.
By eating rodents or birds that don’t have the health and vitality to survive, or that lack the ability to camouflage themselves, feral cats help to assure that prey animal populations become stronger and more adapted to their environment.
Prey animals that learn that cats are to be avoided teach this lesson to their offspring. Those that get the clue will survive, and therefore the population as a whole will become smarter and more likely to live to reproduce.
If prey populations rise too high, the impacts on the environment can be profound. After the elimination of feral cats in Australia’s Macquarie Island, rabbit populations exploded and rabbit grazing destroyed albatross habitats. By preying on those rabbits, feral cats helped to ensure that the island’s ecosystem remained stable.
Because predators are more likely to kill animals that have a higher population, they make room for other animals that fill the same ecological niche. Shrews and birds both eat worms, for example, but if the shrew population rises high enough to threaten the birds’ ability to eat, feral cats will come to the rescue: they’re much more likely to eat shrews since there are so many more of them, therefore leaving more food for the birds.
So, the next time you see a feral cat with a rodent or a bird in its mouth, don’t assume that it just killed off the best and strongest of its species. Remember that the predator-prey relationship is a delicate dance and that in many cases, those cats are making prey stronger and smarter. Trap-neuter-vaccinate-return is the smartest way to manage feral cat populations: It keeps the predator population under control, which stabilizes the prey population at sustainable levels.
Have you seen examples of what happened when predators were eliminated from an area? Do you have anything to add about how predators help prey — or how they have destroyed prey populations in your area? Please share your thoughts in the comments.
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About JaneA Kelley: Punk-rock cat mom, science nerd, animal shelter volunteer, and all-around geek with a passion for bad puns, intelligent conversation, and role-play adventure games. She gratefully and gracefully accepts her status as chief cat slave for her family of feline bloggers, who have been writing their cat advice column, Paws and Effect, since 2003. JaneA dreams of making a great living out of her love for cats.