Deer ticks are all the rage these days. "I had mine behind my knee." "Mine didn't get past my calf, but my husband's made it all the way to his hip." This is not to make light of Lyme disease. It's no fooling matter, especially when it goes undetected for months, maybe even years. But deer ticks are part of a trophic cascade that is just coming to light, and interconnectedness among species is now the bread and butter of community ecology, a field that is experiencing a renaissance. So let's look at this a little more.

I was in Yellowstone at the end of January. It's a tough, unforgiving environment in winter, and I got the impression that almost all the big animals were just enduring. No wolves. They were off doing fun things. But their introduction out there is perhaps the grandest and most studied wildlife experiment every attempted. (Our feeding of wild birds also qualifies, but was not planned and has only been studied indirectly.)

In just a few years, wolves have changed their environment a lot. They interact directly (by eating things) and indirectly (by making food available to 12 or more vertebrate species by not eating every bit of what they kill). In 2010, Cristina Eisenberg explored one trophic cascade generated by the wolves.        

Prior to wolf reintroduction, the Yellowstone elk herd was large and getting long in the tooth. They had overgrazed much of the Park, especially the riparian (streamside) willow thickets. Healthy streamside thickets are essential for many songbirds, especially some of the warblers. With the wolves' thinning of the elk herd, the willows have come back, and with them, the birds. Here the energy goes from willows to elk to wolves, and wolves indirectly benefit some songbirds.

Another interesting cascade has come to light in coastal California, where I used to live. Santa Cruz Island is one of eight islands just off the southern Californian coast. Several of the islands harbor tiny gray foxes--about the size of a housecat. (Mammalian dwarfism is common on many marine islands.) The foxes eat mice that eat seeds, including lots of lupine seeds. Lupine plants are nitrogen fixers and thus fertilize the soil. Tragically, golden eagles have made their way to Santa Cruz (it's only 20 miles off the coast) and are eating the foxes, which has released the mice, allowing the rodents to eat more lupine seeds, thus affecting soil fertility. So energy moves from seeds to mice to foxes to eagles, and eagles may indirectly harm native vegetation, but help mice. Everything isn't really connected to everything else--it just seems that way.

OK, back to us in Vermont. We also seem to have one of these cascades that appears harmful to us. I love coyotes, but they may have a negative impact on red foxes (a common assertion that requires more experiment examination). The foxes are rodent specialists, so a reduction in foxes might result in a mouse boom. It now appears that mice, not deer, are the primary vectors of those dreaded ticks and the diseases they carry. If the links all check out, then coyotes have negative effects on both foxes and humans, but positive effects on mice and maybe some pathogenic bacteria.

You do check for ticks, don't you?