Sunday, June 9, 2013

Burying the Beetles - Part I

USFWS photo of American Burying Beetle
What excites a Master Naturalist?  Holding an endangered species in your hand ranks high, and it is even better if you are doing something to help them survive.  We had the opportunity to participate in the restoration of American burying beetles (ABB) last Tuesday, which we will discuss in the next blog.  We reviewed the project in a 2010 blog, but to refresh your memory here is an update.

The American burying beetle (Nicrophorus americanus) (ABB) originally was present in 35 states.  Now it is only found in seven states and efforts are underway in several states to restore it to its native habitat.  The St. Louis Zoo's Center for American Burying Beetle Conservation has a breeding program and is actively involved in restoration efforts with the US Fish and Wildlife Service and the Missouri Department of Conservation.  Master Naturalists were invited to join the work day at Wah’Kon-Tah Prairie just north of Eldorado Springs.

The burying or sexton beetles, genus Nicrophorus, are a colorful group, shiny black with bright orange spots in patterns which identify the species.  Our ABB, N. americanus is distinguished from the other burying beetles by coloration and size.  It is the only one with an orange spot on the upper surface of its pronotum (first segment of the thorax).  It is also considerably larger that the other common burying beetles.

N. Orbicollis - Note black pronotum


The burying beetles are one of only a few groups of insects that personally nurture their young, feeding them much like a bird does.  In their case, a vulture might be a more appropriate model, as they eat a dead mammal or bird, then regurgitate it into the mouths of their emerging larvae.  Before a pair can mate they must first find a dead animal, flying up to two miles while sniffing the air with their antennae.  Just like Goldilocks, it has to be just the right size. Too big and they can't move and bury it, too small and they will run out of food. 

Mighty mites- Aussie Botanist
The Nicrophorus beetles don't do it alone.  They carry mites along, predominately on the under side of the thorax and abdomen.  Once they arrive at the animal, the mites disembark and begin eating fly eggs, larvae and other competition for the body.  Mites - don't leave home without them!  Meanwhile the beetles trim off the beak, feet and feathers or unwanted parts and bury the carcass swiftly.  Lacking refrigeration, they coat the carcass with a substance that fights off bacteria and fungus.

Click to enlarge
Why has the ABB, N. Americanus been disappearing while other Nicrophorus species have remained stable?  No one knows although there is no lack of theories.  Some include the usual suspects, habitat fragmentation and pesticide use.  The ubiquitous artificial lights may be a factor, as these beetles only fly at night, awaiting total darkness.  Another problem is finding just the right sized dead body to bury.  The loss of passenger pigeons may have eliminated a major food source of the right size, as would the loss of quail habitat.  More on quail in Burying the Beetles, part II up next.

Details on the ABB release program are in this St. Louis Zoo PDF

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