Burying the Beetles

MDC News Release, September 14, 2020

"The American burying beetle, reintroduced at two southwest Missouri prairies, has been down listed by the U.S. Fish and Wildlife Service (USFWS) from endangered to threatened on the nation’s endangered species list. "  MDC News Release

Back in 2013, several of us were involved in a project to restore the endangered American Burying Beetle which had been extirpated in 28 states of its native range.  This week we have been notified of the projects success in this news release.  In these trying times, we need all the good news we can get.  Below the photograph is the 2013 blog that describes what MDC and some MN volunteers were doing in this exciting ongoing project.

USFWS photo of American Burying Beetle

2013

 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. 

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. 

The St. Louis Zoo's Center for American Burying Beetle Conservation has an extensive program which propagates beetles, each individually identified by parents, generation, etc. The eventual goal is to reintroduce them into the wild and hopefully reestablish breeding self-sustaining populations.  Now it is time to get down and dirty.

Ben and friend

So how do we get the endangered American Burying Beetle (ABB) back into the wild?  By burying them!  You may remember we mentioned the importance of having a dead animal of the right size.  This is where the quail comes in.   Our job was to bury a mating (we hope) pair of ABB with a nice fresh...well more like slightly stinky... farm raised quail carcass.  Phew to us but home cooking to the beetle.  Ben Alleger, our young team member with experience in reintroducing ABB last year will lead us through the project in pictures.

We formed up in three teams, each headed by a member of the St. Louis Zoo team.  Each team would be responsible for 100 beetle pairs, each separately boxed and banded together.  Our leader gave out detailed, explicit instructions repeatedly, preventing any mistakes.  After all, these are federally endangered species and none of us wanted to end up in the pen!  Each step included another of his inspections, like a kinder and gentler drill sergeant without the expletives. 

Hole with quail in side chamber

The first task was digging 100 holes, evenly spaced along a straight line.  The hole had to be the right size and depth with a carefully removed lid of prairie turf, to be replaced when we were done.  Next a side chamber was dug out of the hole, all pointing to the same side so they could be found later.  (Editor's note- no volunteers were injured in this project)

Now came the fun- sort of.  A ripe quail was placed in each side chamber, being careful that it didn't stick out into the main hole.  We had to wear rubber gloves to handle the beetles.  Packing in the dead quail ensured that no one complained about wearing the gloves.

Male and female- separate quarters

For our burying project the beetles each had a pedigree and were carefully paired up, making sure that they were from separate families, no cousins or siblings allowed.  They were packaged in a pair of separate boxes.  They won't meet until the last minute when they get together on the quail, the ultimate of a blind date hookup.

The highlight was placing the beetles in the hole.  After determining that each pair was alive, we put them individually in the hole, herding them into the side chamber with the quail.  It is important to be sure that none of the valuable critters escapes for they have work to do.

Placing the beetles in their chambers, one at a time.

Release into the chamber

Aside from one which, after smelling the quail, was apparently considering becoming a vegetarian, they all scurried into the side chamber without encouragement, never to be seen again.  We were told that they might make audible squeaks as they mate, something that can take place almost immediately.  Since this was a family venture with pure of heart and mind MDC folks, we didn't watch.  What happens in quail chambers, stays in the chambers.

ABB male climbing over the quail into the chamber, looking for love.

Replacing the turf lid

Now back to work.  As soon as they were in the side chamber, we put the lid of turf back over the hole, using loose dirt to fill in the edges.  Once that was complete for 100 holes, we stretched chicken wire over the strip and tacked it down tight to prevent  marauding mammals from digging out the quail.

With three teams, we buried 302 pair of ABB in three separate plots.  Now it is up to the beetles.  What happens next is described on the St. Louis Zoo website.

"Pairs bury the carrion cooperatively. The female beetle lays her eggs near the preserved carcass. Within four days, the eggs hatch into larvae. Both parents feed their offspring by eating some of the dead flesh and regurgitating it into the larvae's mouths. This goes on for about 6 to 12 days, until the larvae begin their next stage of development, pupation. After 45 to 60 days, the new generation of beetles emerges from the carcass cavity. This process is repeated during the beetles’ one-year life span."

ABB Larvae- St. Louis Zoo

In ten days, the St. Louis Zoo team will return and assess one-third of the holes, carefully opening them to see if the larvae are present.  By this time they should be functioning and the male may have all ready escaped.  After last year's project, 1/3 of the beetle pairs were checked and found to have produced 395 offspring.  Future assessments will include looking for new adults on the prairie.  They have already seen one adult beetle from last year's class. 

The beetles we released have been notched, that is, marked by notching the elytra, the hard, modified forewings that encase the thin hind wings used in flight. The notch distinguishes captive-bred and wild beetles, and beetles are notched based on release location.

Rectangular notch on  right tip

If you look closely at the back tip of the elytra of the beetle on the right, you will see a tiny rectangular notch cut out.  This allows the team to determine if it is one we put in the ground or a member of the next graduating class.

More information on the project is at the St. Louis Zoo website.  A slide show from last year's reintroduction is here.

Team 2- we happy few   Click to enlarge

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