"It is a warm, midsummer night. Two creatures find a small, dead animal and begin to bury it underground by gradually excavating soil out from under it. Once in the underground chamber, the creatures strip the fur or feathers from the carcass, roll it into a ball, and coat it with secretions, preserving it in a semi-mummified state. They mate. Later, the carcass will be food for the entire family."
A scene from Stephen King's latest novel? Not at all. The creatures are carrion beetles, also commonly known as burying beetles, and they are on of nature's most efficient and fascinating recyclers. But, like several other insect species, these beetles are nearing extinction. The American burying beetle, the largest of the North American carrion beetles, has so drastically declined in numbers and range that, in July 1989, it was added to the federal Endangered Species List.
About an inch and a half long, the American burying beetle can be identified by its striking, distinctive coloring. The body is shiny black, and on its wing covers are four scalloped, orange-red markings. Most distinctively, there is an orange-red marking on the beetle's pronotum, a large shield-like area just behind the head. The American burying beetle has orange facial markings and orange tips on the antennae. The beetles are strong fliers, moving as far as a kilometer in one night.
Historical records show that this beetle once lived in 35 states, the District of Columbia, and three Canadian provinces. Now, natural populations are known to occur in only four states: Rhode Island, Oklahoma, Arkansas, and Nebraska. Biologists are not sure what led to the disappearance of this insect from so many areas and are attempting to determine the reasons for its decline. As part of this ongoing research, and in an attempt to establish another beetle population, biologists have released laboratory-raised American burying beetles on Penikese Island in Massachusetts, historical habitat of the animal.
Burying beetles are unusual in that both the male and female take part in raising the young. Male burying beetles often locate carcasses first and then attract a mate. Beetles often fight over the carcass, with usually the largest male and female individuals winning. The victors bury the carcass, the pair mates, and the female lays her eggs in an adjacent tunnel. Within a few days, the larvae develop and both parents feed and tend their young, an unusual activity among insects. Brood size usually ranges from one to 30 young, but 12 to 15 is the average size.
The larvae spend about a week feeding off the carcass then crawl into the soil to pupate, or develop. Mature American burying beetles emerge from the soil 45 to 60 days after their parents initially bury the carcass. Adult American burying beetles live for only 12 months.
Historical records offer little insight into what type of habitat was preferred by the American burying beetle. Current information suggests that this species is a habitat generalist, or one that lives in many types of habitat, with a slight preference for grasslands and open understory oak hickory forests. However, the beetles are carrion specialists in that they need carrion the size of a dove or a chipmunk in order to reproduce. Carrion availability may be the greatest factor determining where the species can survive.
Why are they so rare?
Biologists have not unlocked the mystery why the American burying beetle has disappeared from so many areas. Widespread use of pesticides may have caused local populations to disappear. The dramatic disappearance of this insect from many areas, however, took place before widespread use of DDT. Lack of small carcasses to bury would prevent the species from reproducing, and changes in land use has reduced the quantity of small- to medium-sized birds and mammals preferred by the American burying beetle. Even the extinction of the once ubiquitous passenger pigeon may have had a ripple effect on carrion feeders like this beetle.
Biologists return each year to Penikese Island to study the survival and growth of the beetle population. Hopefully, their annual visits will provide clues about the environmental conditions American burying beetles must have to live and reproduce.
Why should we be so concerned?
Since the landing of the Pilgrims in 1620, more than 500 species, subspecies and varieties of our nation's plants and animals are known to have become extinct. This recent, catastrophic loss of biological diversity is continuing at an unprecedented rate. Each and every species has a valuable ecological role in the balance of nature, and each loss destabilizes that fragile balance. Once a species is extinct, it is gone forever. Experience has proven that many plants and animals have properties which will prove beneficial to humans as sources of food and medicine. With the loss of each species, we lose a potential resource for improving the quality of life for all humanity.
Carrion beetles, like the American burying beetle, recycle carcasses, ultimately returning valuable nutrients to the soil. In addition, this beetle might be an "indicator species," or one that tells us whether or not its environment is healthy. Understanding why its numbers have decreased so drastically may give us indications of problems with both its habitat and our environment.