The Much Maligned Coyote

Here in Nebraska, we’ve lost most of our largest predators.  Bears and wolves are gone (excepting rare long-distance wanderers).  Mountain lions are making a slow comeback in the northern and western parts of Nebraska, but the agricultural character and fragmented nature of our state makes it difficult to imagine a much stronger presence of large predators than we have right now.  That’s not a critique – it’s just reality.  It’s difficult to know what effect the absence of those predators has on our wildlife and natural landscapes, but based on what we know from research elsewhere, it’s surely significant.  Throughout the world, and across a wide range of habitat types, major predators stimulate complex cascades of impacts far beyond simply suppressing the populations of their favored prey species.  In fact, the diversity and abundance of many plant, invertebrate, and wildlife species have been shown to decline dramatically when dominant predators disappear.

Illustration by Kim Tri

Coyote illustration by Kim Tri, one of our Hubbard Fellows and, obviously, a talented artist.

Today, in the absence of wolves and bears, coyotes have stepped into the role of top mammalian predator across much of Nebraska.  It’s hard to know if they are as effective as their larger counterparts at maintaining ecosystem function, but there is strong scientific evidence for the strong and positive impacts coyotes have on a number of other grassland species.  Much of the research on this topic was published 15-20 years ago, but few people seem to be familiar with it.  In fact, rather than being celebrated for their importance, coyotes are widely reviled, and often shot on sight, by many (most?) rural citizens across much of prairie regions of North America.

There is much unfortunate irony in the vilification of coyotes.  One common coyote narrative is that coyotes are hard on nesting birds, especially game species like pheasants, quail, turkeys, grouse, and ducks.  In reality, coyotes feed mainly on rodents, and the major predators of birds and their nests tend to be smaller animals, including foxes, raccoons, and cats (especially feral house cats).  Coyotes are large and aggressive enough to intimidate or kill those “mesopredators”, keeping their numbers low and driving them into areas where coyotes spend the least time, such as wooded draws, farmsteads, and even surburbia.  In fact, numerous studies have documented detrimental impacts to bird populations ranging from songbirds to ducks and grouse when coyote numbers are suppressed and mesopredator populations swell.

One of the most dramatic studies of coyote impacts on the structure and function of ecological communities took place on 20,000 hectares of west Texas land back in the 1990’s.  Researchers halved the number of coyotes in one portion of the study area and left the population alone elsewhere.  Within a year of coyote control, the area with fewer coyotes experienced higher populations of bobcats, badgers, and gray foxes.  Perhaps as a result, 11 of the 12 rodent species in that area disappeared, leaving only a skyrocketing population of kangaroo rats.  Jackrabbits also tripled their numbers in the coyote control area, much to the chagrin of ranchers, since jackrabbits compete with livestock for forage.

Another great coyote illustration by Kim Tri.

Another great coyote illustration by Kim Tri.

Speaking of ranchers, many tend not to be coyote fans, in large part because coyotes are sometimes hard on livestock.  Sheep ranchers can suffer big losses to coyotes if they don’t actively protect sheep with dogs, overnight enclosures, and other strategies.  Cattle ranchers can also have trouble with coyotes killing livestock, especially just-born calves.  Coyotes are very good at killing young deer fawns – a great reason for prairie enthusiasts to be coyote fans, by the way – but some transfer that skill to calves as well.  While any self-respecting cow can protect her calf from coyotes under most circumstances, even the toughest mother is weakened enough by the process of giving birth that she is vulnerable to a quick sneak attack.

Unfortunately, the response to livestock losses is often the indiscriminate killing of whatever coyotes ranchers can find.  Research has shown that kind of “coyote control” to be largely ineffective, in part because it usually fails to kill the individuals actually causing problems.  For example, a fourteen year study showed that almost every sheep killed by coyotes was taken by the “alpha pair” in the pack’s social structure.  Those alpha animals are also the wiliest and most difficult to kill.  Furthermore, of course, in the unlikely event that coyote control efforts succeed at suppressing the population in an area, the results might not turn out in favor of the rancher.  Higher numbers of raccoons and foxes, not to mention jackrabbits, along with fewer ducks, grouse, and quail, might take the thrill out of the temporary victory.

Even if coyotes gain wider recognition for their positive effects on natural systems, however, the relationship between coyote and human is bound to be complicated.  As we continue to alter their habitat, coyotes will continue to adapt and survive as best they can.  At times, that will bring them into conflict with us.  It is understandable, for example, that a rancher needs to address livestock losses, and sometimes that could mean tracking down and killing the individual coyote(s) responsible.  However, that kind of careful, targeted response is much different (and more effective) than current broad, indiscriminate campaigns against an animal whose bad reputation is largely based on innuendo and misinformation.

Ideally, seeing coyote tracks on their property would be a positive experience for landowners.

Ideally, seeing coyote tracks on a property would be a positive experience for landowners.

Coyotes and other predators play critically important roles in grassland ecosystems.  It’s easy to understand how they directly suppress populations of their primary prey species.  However, as we continue to study predators, we find more and more of the kind of indirect impacts that ripple through ecological systems in ways that are difficult to predict.  While it seems unlikely that wolves and bears will ever return to prominence in Nebraska or most other prairie regions of North America, coyotes may be able to cover at least some of the ecological roles those larger predators once played.

But only if we let them.

 

Hubbard Fellowship Post – Mother Owl

This post was written by Evan Barrientos, one of our Hubbard Fellows.  Evan is a talented writer and photographer and I encourage you to check out his personal blog.

Warning: This post contains images of fluffy, baby animals.

Along the edge of one of our prairies there is a road lined with mature cottonwood trees. Although I appreciate the wide-open prairie environment, I like to take a walk once a week in the shady security of this miniature forest. The rustling leaves are soothing, shade is a novelty, and the trees bring back memories of hiking in New York’s forests. I also happen to see a lot of interesting wildlife behavior when I go here. One morning in July I was jogging down this road when I spotted an Eastern Screech-Owl being mobbed by Baltimore Orioles and American Robins. I sprinted back to my house, grabbed my video equipment, and hurried back before the action was over.

For several minutes I filmed as the orioles and robins viciously pelted the seemingly harmless owl (click here for a previous post I wrote about this behavior). It amazed me that the owl could withstand such harassment so patiently. Despite several painful-looking beak-jabs to the back of the head, the brave little owl outlasted the assault and was finally left in peace. Only then did I realize why she had refused to leave; she had babies to look after!

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In a nearby branch I finally noticed three owl fledglings trying to sleep. In addition, there was a second adult screech-owl who seemed equally intent upon sleeping unnoticed. I don’t know which adult was which gender, but I like to imagine that it was the mother who bravely endured blows from the angry songbirds in order to let her family sleep in peace while the lazy dad took a nap. Either way, I always find it touching when I see animals put such great effort into protecting their young.

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On another subject, all three birds in this post are species that used to be much less common in Nebraska. Before Europeans arrived, trees were hard to come by in central Nebraska. Over the last century, however, trees from the East have spread into the state as people have planted them around their crops for windbreaks and around their homes for shade. With trees leading the way, many forest species from the East, such as Eastern Screech-Owls, have ventured into Nebraska and the Great Plains. The ecological effects of this tree march are more complex than I’ll go into here, but overall they’re detrimental to grassland plant and wildlife populations. Here are just a few examples:

  1. Trees provide perches for aerial predators (such as owls and hawks), which increases predation rates of prairie grouse and mammals.
  2. Tree corridors provide safehavens for woodland nest predators (such as skunks and opossums) as well as brood parasites (i.e. Brown-headed Cowbirds), who venture into the prairies for prey/hosts. Thus, wildlife in small prairies bordered by trees experience abnormally high rates of nest depredation and parasitism.
  3. If uncontrolled, trees form dense canopies that shade out prairie plants, which are adapted to full sun. This makes it harder for prairie fauna that rely on prairie plants for food and shelter to survive. The result is a positive feedback loop: the presence of trees encourages more trees to grow.
Doom on the horizon? The trees bordering this prairie are the same ones that love walking through.

Trouble on the horizon? The trees bordering this prairie are the same ones that I love walking through.

So what’s the takeaway? Our relationship to nature is complicated. Nothing is simply good or evil. On one hand, trees may seem like a existential threat to prairies, but on the other, I value them for their soothing shelter and the species they harbor. I think the key to this dilemma is diversity. Although I appreciate woodlands, I also appreciate prairies. But healthy prairies are so much more scarce in eastern Nebraska than wooded roadsides, and grassland species are generally in decline, while most woodland species are stable or even increasing.* Therefore, I would choose to cut down trees that are encroaching upon prairies. This does not mean that I think all trees in Nebraska are evil and must be destroyed, just that we need to keep them in check in order to maintain a balance between the two habitats.

*To make things even more complicated, while tree invasion is a real problem, cottonwoods are actually failing to reproduce in Nebraska. To germinate, cottonwoods need floods to scour vegetation and deposit sediment. Now that Nebraska’s rivers are regulated by dams, these floods happen much less often. As a result, we’re seeing very few young cottonwoods taking their parents’ place.