Ecology – Page 7 – Al Cambronne

Urban Kangaroos, Urban Deer, and Finding a Balance

Last night I watched a fascinating episode of the PBS show Nature. It was titled “Kangaroo Mob.” Apparently that’s what groups of them are actually called—not herds, mobs. The episode told of how frustrated Australians are trying to cope with exploding kangaroo populations in and around Canberra. Only a decade ago, there were a few hundred. Today there are tens of thousands.

Out beyond the city limits, drought and skyrocketing kangaroo populations have caused ecological devastation and left the landscape denuded of vegetation. As hungry, thirsty kangaroos invade the suburbs, the citizens of Canberra are coping with hundreds of car crashes, increasing damage to landscaping and natural vegetation, and incredible hordes of kangaroos that are just generally making a nuisance of themselves. In several recent incidents, they’ve attacked people and pets with no apparent provocation. As sometimes happens with deer here in America, a few confused ‘roos have even crashed through windows and into suburban homes.

Local officials have reluctantly decided to stage a cull. Although most Canberrans support it as a necessary step, a few have donned kangaroo masks and staged angry protests. Two wildlife biologists we follow during the program are tracking radio-collared kangaroos in the hopes of learning more about their habits and movement patterns. Meanwhile, we also meet a couple who are working hard to rescue kangaroos that have been injured or orphaned.

Elsewhere, not far from Canberra, overabundant kangaroos have sometimes outmatched the land’s carrying capacity and starved in large numbers. In one notable 2009 example, the Royal Society for Prevention of Cruelty to Animals (RSPCA) chastised the Defence Department for not holding a cull on a nearby military base. After mowing the base’s threatened grassland preserves and leaving the ground pretty much bare, an estimated 5,000 kangaroos starved that summer.

For me, the Kangaroo Mob story was especially fascinating because of its obvious parallels with overabundant urban and suburban deer here in North America. In Deerland, I plan to include an entire chapter on the topic. Its working title: “The Invasion of the Suburban Cervids.” In some ways, deer in Connecticut aren’t all that different from kangaroos in Canberra.

Australia actually has deer problems of its own; it has six different types of deer, all of which are non-native invasives. In addition to kangaroos and deer, Australian hunters can also pursue feral cattle, goats, and camels. Which is probably a good thing, since most of these animals have at various times and places reached outrageous population levels that caused serious problems for both humans and the natural environment.

The camels are quite large; I suppose if a hunter were to shoot one in rugged terrain that could only be reached on foot, it would be a lot of work to hump it out. Sorry. Couldn’t help myself. Actually, though, feral camels are no joke. Australia currently has over a million, and that number could double by the end of the decade. In large parts of the country, they’re now causing serious environmental damage.

Australians have learned to take their invasive species seriously. The rabbit is probably the one animal that has caused the most damage there. Today the ownership of live rabbits is regulated in most of the country, and Queensland recently raised its fine for the possession of a single pet rabbit from $3,750 to $30,000.

Meanwhile, back here in North America… Deer are not, strictly speaking, an invasive species. They were here first. But they sure can be invasive. As I research Deerland, I’ve been talking with experts and learning a lot about the lethal and nonlethal control strategies being used when deer invade our cities and suburbs. I’ve learned a lot about what works and what doesn’t. The solutions aren’t simple, and implementing them isn’t always easy. But sometimes doing nothing is not a option, and sometimes letting nature take its course is no kindness.

Or, as one ecologist recently told me, “Just because you’re not shooting them doesn’t mean you’re not killing them.” Suffering. Compassion. Kangaroos. Deer. Birds. Trees. Sedges. Ferns. Humans. It’s complicated.

Silent Summer

In my last post, I introduced you to the deer of Dairymen’s and showed you an exclosure and a lollipop tree. This time, I’ll tell you more—how bad things got, why they’re getting better, and what lessons this story holds for the rest of us.

In the photo above, you can see how much of Dairymen’s still looks today. The forest understory is completely missing. Even in June, the ground is brown. Elsewhere, the scene is green and park-like, as in in the photo below. These are all plants that resist or tolerate herbivory. Everything else is gone. Still, if you don’t know you’re looking at a scene of ecological devastation, it looks lovely.

It is green. But there’s no cover for small mammals or ground-nesting birds. There’s no understory or mid-story where other songbirds would be nesting. No grouse, no turkey, no finches, no warblers, no squirrels, no chipmunks, no nothing. I was there on a still, humid day in June. Nothing moved, and the forest was strangely silent. I heard a robin off in the distance. That was about it.

(Admittedly, there were plenty of mosquitoes. So it’s not exactly true that nothing was moving. But that was it.)

This is what long-term overbrowsing looks like. Here, deer had reached densities of over 100 per square mile and stayed at that level for decades. This is unusual, but not unique. The U.S. now has over 30 million deer, a hundred times more than were here just a century ago. Their densities per square mile in America’s suburbs and parks have at times reached 100 in Chicago, 125 in Minneapolis, 182 in parts of New Jersey, 200 in Kansas City, and 400 in Washington, D.C.

Elsewhere, the effects of overabundant deer are less dramatic, but still significant. Even if we spend a fair amount of time out in the woods, most of us have never seen a forest that’s not shaped by deer. There’s no free lunch, and we trade more deer for less of everything else. But when forced to choose between whitetails and all other wildlife, we almost always choose deer.

For 70 years, the Dairymen did. But in the 90s, they stopped feeding them. (In the photo above, you can still see the rusted, abandoned half of a 55-gallon drum that was once used to feed deer.) A couple years ago, a pack of wolves moved in. Things are looking up.

Still, I’m not sure the wolves will be a popular solution in New Jersey or Kansas City.

Deer on the Right, No Deer on the Left

Exclosure.

It’s an odd word. If you’ve never seen it in print, it just looks wrong. Still, you’ve probably already guessed what it means. If an enclosure keeps deer in, then an exclosure keeps them out.

Botanists use exclosures to measure, among other things, the effects of overabundant deer on the forest ecosystem. Although the measuring and analysis can get complicated, the concept is simple: Exclude deer from a small area (or sometimes a large one covering several acres), and then watch to see what happens. But be patient. This could take a while.

Eventually, if those overabundant deer are still present on the outside of the exclosure, the areas inside and outside the fence will begin to look very different. The exclosure in the photo was built over ten years ago, and the area inside still isn’t quite back to normal. Already, however, it looks very different from what’s on the outside. That’s what a normal, healthy forest looks like—a forest, that is, with a normal, healthy number of deer.

This particular exclosure is on a 6,000-acre preserve in northeastern Wisconsin called, oddly enough, “Dairymen’s.” The club was started back in the 20s by a small group of wealthy dairy magnates who wanted a private playground in the north woods. (Yes, they were the “big cheeses” of the dairy industry.) They also wanted Dairymen’s to be a wildlife refuge where no hunting was allowed.

Deer had been almost totally eliminated from northern Wisconsin, and they pretty much had been eliminated from the southern part of the state. So back then a wildlife refuge was a great idea. By the 40s, however, Dairymen’s had a new problem. It actually had too many deer. Looking for answers, the club’s Conservation Committee invited a consultant up from the University of Madison, a professor named Aldo Leopold. He told them they had four times as many deer as the land could support, and advised them to open Dairymen’s to hunting.

They thanked him for his advice, and then ignored it. Instead, they decided to solve the problem by feeding the deer. That way, they figured, the land could support more deer. As you can imagine, this only made things worse. Eventually deer densities exceeded 100 per square mile. The deer ate everything they were fed, but they also ate every bit of vegetation they could reach. The closer to the lodge, the worse the overbrowsing.

In the 90s, members of Dairymen’s began working with Dr. Tom Rooney, a botanist from Wright University in Ohio. This sort of thing is his specialty; he’s one of the world’s leading experts on the effects of overabundant deer on the forest ecosystem.

Here, he’s standing next to an eastern hemlock that’s just outside another exclosure. This sad little sapling looks like it just hopped out of a Dr. Seuss story. It’s one long, skinny trunk with a single tuft of needles at the top. Deer have been hitting this tree hard for a long, long time. It’s finally tall enough so it’s about to break free and begin growing normally.

After a clearcut, an aspen sapling could reach this height over a single summer. But this tree is probably older than you are. The technical term botanists use to describe a tree that’s been browsed in this pattern is “lollipop tree.” (This describes its shape. Unfortunately, lollipops don’t actually grow on it.)

Here, Dr. Rooney and I are about to break into a larger exclosure down the road. He’d misplaced the key, and we didn’t want to crawl under the fence. Normally it’s a bad idea to mix botanists, beer, and boltcutters. But in this case, I made an exception.

Next time: more about the deer of Dairymen’s—how bad things got, why they’re getting better, and what lessons this story holds for the rest of us.