The Wildlife Professional - Spring 2010 2009

Credit: t WS

Nest in Peace

The prairie pothole region of North America, with its abundant wetlands and food sources, is duck heaven. But agricultural conversion and a loss of top predators like wolves also make it great habitat for mid-sized carnivores like coyotes (Canis latrans) and raccoons (Procyon lotor), which are limiting duck population growth. In JWM (v. 74/1), Matthew Pieron and Frank Rohwer of Louisiana State University share the results of an effort to trap predators in order to improve duck nesting success. From 2005 to 2007, the researchers hired trappers to remove mammalian predators from March until July at seven sites in North Dakota. Five other sites served as a control with no trapping. During repeated surveys for nests, the researchers recorded clutch size, nest abandonment, and other nest characteristics. Using 7,489 nests in their analysis, they found that nests on trapped sites were between 1. 4 and 1. 9 times more likely to be successful than those on untrapped sites. Trapping may therefore be a viable way of ensuring that upland nesting ducks continue to thrive, particularly as Conservation Reserve Program land protection contracts expire, freeing landowners from obligations to conserve habitat on their land.

Bats on the Forest Edge Bats living in commercially managed pine forests in the southeastern U.S. occupy a top position in the nocturnal food web. Yet their foraging habits had been little studied. Hoping to gain information about bat habitat preferences, Adam Morris of North Carolina State University and colleagues spent two summers in different areas of a Weyerhaeuser-managed pine forest in coastal North Carolina studying bat activity patterns, then detailing their results in JWM (v.74/1). They used echolocation recorders to monitor activity, trapped bats to confirm species identity, and trapped insects to measure prey abundance. Though different bat species had specific preferences for the four types of forest stands—open-canopy pine, pre-thinned (mid-aged, closed-canopy) pine, thinned pine, and unmanaged hardwood—overall, six of the seven bat species studied preferred forest edges, as did their insect prey. The authors conclude that managed pine stands with a mosaic pattern that includes hard forest edges can provide bats with ample opportunities for feeding.

Credit: t WS

Grouse Versus Ravens

In many parts of their remaining range, greater sage grouse (Centrocercus urophasianus) are in decline. Development of their habitat by people has not only cut down suitable places for the sage grouse to breed, but in some cases has made better habitat for predators like ravens (Corvus corax). At a site in northeastern Nevada, Idaho State University researchers Peter Coates and David Delehantry set out to determine first if ravens indeed impacted grouse nest survival, and next, what features of nest microhabitats increased the probability that a raven would strike. They monitored female grouse equipped with radio transmitters to identify 87 nests, which they surveyed every one to three days. At and around the nest sites, they measured shrub height, understory cover percentage, and additional habitat features, and also surveyed for ravens. They later videotaped 55 of the nests to determine which predators visited. Their study, published in JWM (74/2), confirmed that ravens posed a problem for grouse: one additional raven per 10 kilometer transect survey correlated with a 7. 4 percent increase in the chance of nest failure. In addition, nests with low shrub canopy cover were more likely to be predated by ravens. The authors recommend that raven management paired with maintaining shrub canopy could help protect nesting sage grouse.

Elk Seek Refuge

If elk (Cervus elaphus) knew what was good for them, one might think they would move out of hunting areas when elk season comes around. In fact, a new study in JWM (v. 74/2) indicates that they do try to move out of harm’s way during hunting season, to the detriment of hopeful hunters and possibly even to the elk, who may find themselves overcrowded. A team of Montana State University and Montana Fish, Wildlife, and Parks researchers led by Kelly Proffitt GPS-collared and monitored 20 female elk over one winter and 25 elk over the next winter, tracking their locations before, during, and after a January hunting season. The researchers then created models to represent how elk selected their locations, factoring in distance to hunter access points, habitat type—such as grassland flats or sagebrush steppe—and a measure of the amount of water in area snowpacks. The team found that elk avoided hunted areas in hunting season, leading to greater concentrations of animals in refuge areas, particularly open grasslands, posing a challenge to managers hoping to control populations by harvest.