An abundance of suburban wildlife, mowing milkweed for monarchs and glowing platypuses
“There’s this idea that nature and humans don’t coexist,” says North Carolina State University ecologist Roland Kays. But a recent study of residential backyards conducted by Kays and colleagues from the University of Montana reveal that wildlife often is more abundant and diverse in suburban neighborhoods than in nearby wild places. “We’re finding that certain mammals actually do pretty well around people,” he says.
Working in two North Carolina metropolitan areas, Kays’ team set up cameras with motion sensors in 58 suburban yards. For comparison, they also placed cameras in local forests and other rural sites. Examining images recorded during an eight-month period, the researchers identified seven mammal species that appear more frequently in peoples’ yards than in surrounding forested areas, including gray and red (above) foxes, Virginia opossums and eastern cottontail rabbits. In a report published in Frontiers in Ecology and Evolution, they explain that bird feeders and other supplemental food sources, along with opportunities for shelter, are the key factors that attract wildlife to the suburbs. The study, says Kays, “shows how individual decisions by homeowners can have a big impact on wildlife living in the area.”
While conservationists generally advise homeowners to minimize mowing to benefit wildlife, recent studies in midwestern grasslands found that cutting back milkweed plants at key times of year actually boosts populations of declining monarch butterflies. Writing in Biological Conservation, entomologists from Michigan State University report that strategic mowing of mature milkweed benefits monarchs in part because the butterflies lay more eggs on the new growth that sprouts afterwards. Milkweed is the only host plant for monarch caterpillars (above). As a food source, the plant is “more like spinach when it’s young and comparable to cardboard as it ages,” says lead author Nate Haan. In addition, the researchers found that fewer predators visit immature milkweed, preferring to hunt on the plant’s more-developed flowering stages. Mowing small areas, the entomologists report, results in three to 10 times more eggs per stem on this new growth. They also say that gardeners who cultivate milkweed can conduct their own experiments—by mowing or trimming about a third of a milkweed patch in mid-June, when the stems are beginning to flower; cutting another third in mid-July, when the mowed stems have grown back; and leaving the rest undisturbed throughout the growing season.
When researchers from Wisconsin’s Northland College examined a museum collection of platypus specimens, they made a surprising discovery: The mammals’ drab brown fur (above, at left) glows greenish-blue (middle and right) under ultraviolet (UV) light—a phenomenon called biofluorescence that scientists have identified in only a few other mammals. A secretive egg-laying creature with webbed feet and a ducklike bill, the platypus is endemic to eastern Australia, where its numbers have declined in recent years. The species is the sole surviving member of both its genus and family. Like two other mammals whose fur glows under UV light—the opossum and flying squirrel—the platypus is most active at night. In the journal Mammalia, the researchers suggest these animals— and perhaps other mammal species—may have evolved biofluorescence as an adaptation to see and interact with one another in the dark. “Our main goal is to document this trait,” says co-author and Northland natural resources professor Erik Olson, whose team is investigating other nocturnal mammals that also may have biofluorescent fur.
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