Charismatic megafauna: this is current conservation jargon for big, beautiful animals such as gorillas and elephants, that capture our hearts and minds. An insect equivalent, claims landscape ecologist, Dr. Sharon Collinge, would be the Valley Elderberry Longhorn Beetle. About the size of a large earwig, it is scarlet with black spots, and sports a dramatic pair of curved antennae as long as its body. Charismatic microfauna.
In addition to being bright and beautiful, the Valley Elderberry Longhorn Beetle, known to its friends as VELB, is extremely rare. Exclusive to California's Central Valley, the beetle has highly specific requirements. It will live only in thickets of native elderberry that grow amidst other native plants along the valley's waterways.
Unfortunately, this riverside habitat, known as riparian woodland, has been hard hit by modern human activities.
Agriculture, development, and flood control practices, have reduced the valley's riparian woodland to about 10% of what it used to be 200 years ago. In those halcyon days, an adult VELB emerged from its cocoon into a rich, green world of elderberry, stretching for miles along a creek or river. Nowadays, a newly-emerged beetle could find itself on a solitary bush, surrounded by denuded levees and tomato fields. A modern map of the valley's riparian woodland shows it as small, tattered patches, few and far between.
This spells big trouble for our beetle. In 1980 it was declared threatened under the Endangered Species Act, and restoration programs were instituted. Any damage to riparian habitat in certain critical areas must be compensated for by planting elderberries somewhere else. Has this policy worked? Have the beetles colonized these new sites, and if not, why not? Collinge and her colleagues in the Department of Environmental Design at UC Davis want to answer these questions. They want to know what makes any particular patch of restored elderberry successful or unsuccessful in bringing back the VELB
This research requires that Collinge find and count beetles, which is no easy task. Not only are they rare, but for a large portion of their lives, they are invisible to humans. The female lays her eggs in the cracks of an elderberry stem. When the larvae hatch, they bore into the stem where they remain for two years, dining on pith. After pupating, the adult beetles, in all their red and black glory, emerge through a hole in the stem and live for just long enough to eat some elderberry flowers and breed. For males, that's a few days; for females, a few weeks.
During months of fieldwork , in the heart of VELB habitat, Collinge saw only two beetles the whole time. Luckily, the emerging adult leaves a distinct exit hole, and these holes can be counted instead of the bugs. Because new exit holes can be distinguished from old, the method gives Collinge a good estimate of the current beetle population.
The researchers also measured certain features of the patches where beetles were found, such as the size of stems with exit holes, and the number of elderberry plants in any one patch. In 1997, they re-surveyed several sites that had been examined in 1991, and related the changes in beetle numbers to the various features of the sites. In more sites than not, there had been a decrease in number of exit holes, which in some cases could be related to loss of habitat. Certainly in 1997, there were more isolated elderberry bushes than previously. It was also apparent that beetles were partial to stems of particular sizes and avoided the smallest.
These findings will help Collinge in her on-going study of restoration sites and their effectiveness. So far, it doesn't appear that the beetles find them wildly attractive.
Of the five sites so far examined, only one - the Katchituli Oxbow site along the Sacramento River - has been colonized by the bugs. At 124 acres, it's large and relatively close to established riparian woodland. The replanted vegetation has thrived, and there is, after many beetle-free years, a healthy population of VELBS. Collinge will continue to monitor the other sites, which beetles could be overlooking for a variety of reasons, including poor maintenance or unhealthy plants.
It's a comfort to know that someone is looking out for our Valley
Elderberry Longhorn Beetle. Too often in restoration projects,
trees are re-planted, animals are returned to the wild, and then
the money runs out and these efforts are not followed up. We need
more studies like that of Collinge and her team, providing ecological
guidelines for our penitent efforts to undo at least some of the
damage we have wrought.
Dept. of Anthropology, University of California, Davis, CA 95616.
e-mail: kjstewart@ucdavis.edu