Can honey bees assist in landmine detection?
Jerry Bromenshenk et al
Honey bees have recently received considerable attention from the popular
press as an innovative method to detect a variety of explosives, landmines and
UXO. Many of these reports are inaccurate and may encourage individuals and
demining groups to "sell" a service that they poorly understand or
lack the experience to properly apply. As the developers of this technology, we
offer the following summary about the current status of this alternative for
landmine detection, including its strengths and limitations.
People and bees have a long and mutually beneficial history. Ancient cave
paintings in Spain depict a woman harvesting honey. The Egyptians moved bees on
barges up and down the Nile. Originating near current-day Afghanistan, one
species of honey bee, Apis mellifera, now lives all over the world, with the
exception of the Antarctic and far Arctic regions. In every community and
country, bees are kept for the honey and wax that they produce, and for the
crops that they pollinate.
More than 30 years ago, we at the University of Montana (UM) began sending
out bees to explore and sample environments of interest, as a way of collecting
and mapping data over large areas within a two-to-four-km radius of the hive. A
honey bee's body has branched hairs that develop a static electricity charge,
making them an extremely effective collector of chemical and biological
particles, including pollutants, biological warfare agents and explosives. They
also inhale large quantities of air and bring back water for evaporative cooling
of the hive. As such, bees sample all media (air, soil, water and vegetation)
and all chemical forms (gaseous, liquid and particulate). With proper colony
placement and sampling, gradient maps of the distribution of chemical or
biological materials can be produced.
This approach has been described in numerous studies and publications, with
statistical mapping of large areas first described by us in Science, 1985. Other
investigators, especially in Europe, have emulated our approach, with a
monograph covering this topic appearing in 2002. Although all of the authors
agreed upon the effectiveness and utility of bees, some had difficulty
attributing or correlating the chemicals found in or on bees, pollen, honey or
the hive with potential sources in the environment. Time of year, spatial
distribution of the colonies, and component of the hive to be sampled all must
be considered before an appropriate sampling plan can be developed and carried
out. Simply taking "grab" samples or pulling honey jars off the shelf
is not likely to show anything other than that some material of interest is or
is not present.
Given an appropriate sampling design, bees can quickly provide samples of
materials in the vicinity of each hive, since the foragers from each colony will
make tens to hundreds of thousands of foraging forays or flights each day, with
each forager returning to its home hive by nightfall. This passive collection to
determine environmental presence of chemical and biological threats can provide
an initial survey of landscapes. It generally identifies regions where materials
of concern can be found and, with appropriate re-location of hives and
re-sampling, can help narrow down the search to areas of a few hundred meters.
Active Training and Search
For more than four years, we have been refining our ability to condition or
train bees to go to "odors of interest." Bees have an acute sense of
smell and can be trained to find explosives, bombs and landmines, as well as
other chemicals of interest, including drugs and even decomposing bodies.
Begun under a contract from the Defense Advanced Research Project Agency's (DARPA's)
Controlled Biological and Biomimetic Systems Program, we developed the methods
and equipment necessary to condition bees to pass rigorous blind field trials,
conducted at Southwest Research Institute in San Antonio, Texas. Sandia National
Laboratories (SNL) and the Air Force Research Laboratory (AFRL) collaborated in
our work, providing specific expertise in explosives and signal processing,
Through a series of repeated trials conducted in 2001 and 2002, we observed
that bees behaved like a very fine-tuned, nearly ideal detector at vapor levels
higher than 10 pptr from 2.4-dinitrotoulene (2.4-DNT) mixed in sand. In 2001,
AFRL and we calculated a detection probability of 97-99 percent at parts per
billion (ppb) and parts per trillion (pptr) vapor concentrations, with a 1.0-2.5
percent probability of false positive and less than one percent false
probability of false negative. In the 2002 tests, bees consistently detected DNT
targets generating 50-80 pptr vapor. Under moist conditions, this dropped to
about 30 pptr. AFRL predicted that with sufficient numbers of bees, the
detection threshold could go even lower.
Bees are trained in much the same way as dogs, using traditional operant
conditioning methods. The reward is food, which is associated with the odor of
the chemical of interest. Like dogs, bees can detect suites of chemicals, such
as 2.4-DNT, 2.6-DNT, TNT, and RDX over a wide range of concentrations. Bees
indicate the presence of an odor by the numbers of bees following vapor plumes
toward and over the source or target. We have observed that bees detect the
vapor plume several meters from the source, then navigate up the plume to the
source. Numbers of bees over odor sources are integrated over time and compared
to those over the rest of the area. In other words, we map the density of bees
over an area, using visual, camera or laser-assisted counts.
By the end of our DARPA contract in August 2002, we had convincing evidence
that bees could reliably find explosives' vapors at levels reported to occur in
landmine fields. However, we still had to demonstrate that honey bees could
detect real landmines at a well-characterized minefield. Furthermore, in order
to demonstrate that the bee concept was useful, we also had to show that we had
a means of detecting or tracking bees at a distance from the hive and over the
We were concerned that bees might have problems when faced with multiple
chemical sources in an area. Would the bees go to the highest vapor sources and
ignore others? We also needed to be able to find bees at distances consistent
with their long-range flight ability. Visual observations and cameras were
suitable only for short-range trials or for simulated trials where the observer
could readily walk out into the field.
Since bees can easily fly up to three to five km, it was highly desirable to
have a bee detection system that could cover that same range, both from the
standpoint of realizing the full potential of bees for dramatically reducing the
time required to survey an area and from the aspect of personnel safety.
Ft. Leonard Wood Landmine Trial, Summer 2003
S&K Electronics (SKE), UM and Montana State University (MSU), in
collaboration with the National Oceanic and Atmospheric Administration's (NOAA's)
Environmental Technology Laboratory and SNL, funded and conducted a blind field
test at the Ft. Leonard Wood minefield from July 25-August 5, 2003. Tests were
conducted to determine whether conditioned honey bees can be used to locate
buried landmines and explosives. MSU and NOAA joined in with the Light Detection
and Ranging (LIDAR) technology for this demonstration.
UM's earlier trials had demonstrated that honey bees can be trained to
efficiently and accurately locate explosives signatures in the environment.
However, it was difficult to track bees and determine precisely where the
targets are located. Video equipment is not practical due to its limited
resolution and range. In addition, it is often unsafe to set up cameras within a
Earlier tests by SNL had demonstrated that a LIDAR system could see bees
(patent pending), but did not show that a LIDAR could track bees. Nor did the
tests make scanning LIDAR measurements.
LIDAR is a remote sensing technique that uses laser light in much the same
way that sonar uses sound or radar uses radio waves. Laser light pulses are
transmitted over the area where bees are trained to fly. Some of the laser light
that strikes the bees is scattered back to a detector collocated with the laser.
The time between the outgoing laser pulse and the return signal is used to
measure the distance from the bees to the LIDAR. By using a narrow laser beam
and scanning this beam over time, one can produce an accurate map of the
location of the bees. Since LIDAR can provide both the range and the coordinates
of the bees over targets, the location of buried munitions can be mapped for
Chemical map of a minefield
Bees, dust and hard objects produce a back-scatter signal that is larger than
the typical atmosphere. Whereas it is possible to discriminate different objects
with fluorescence LIDAR, for this test we simply compared the density of bees
over the minefield and an adjacent control area. Other insects may have been
detected, but their numbers were small compared to those of the bees.
SNL also conducted vapor plume and soil sampling, followed by chemical
analysis for explosives, to verify bee localization of mined areas. All results
were submitted to the Army's Night Vision Laboratory for final assessment of bee
Results of Ft. Leonard Wood Bee Trials
All of the data forms (LIDAR, video, visual counts) indicate that area
reduction, identification, and ranking (strength of the plume source) could be
determined using bees. The following are some results of the trials:
LIDAR was able to detect individual bees at long ranges of hundreds of
meters. Fixed and scan modes were tested and proved capable of providing bee
location and range data within a few centimeters' resolution.
Video and visual counts showed that bees found both individual mines and
clusters of mines within the test area.
Preliminary chemical analyses results indicate that numbers of bees correlate
with plume concentrations. Ten of 12 vapor sources identified by the initial
chemical analysis have already been detected by a partial data set of bee counts
(based on only four days of the data). The contour maps of the landmine field,
based on the visual and partial video counts of bees and on the cumulative
results of three different chemical sampling methods illustrate the degree of
localization that was achieved.
In the designated, unmined, blank or control area, the LIDAR detected a
concentration of bees over a spot in front of the minefield. When that spot was
later sampled, it was found to be contaminated with TNT, 2.4-DNT and 4-amino DNT.
The pressurized conditioning system worked flawlessly, and Missouri bees
conditioned as readily as any of the bees that we have previously worked with in
Montana and Texas.
The bees also made a surprise detection of a contaminated site where none was
expected. This example proves the importance of combining a high-resolution
tracking system such as LIDAR with properly conditioned bees as a system for
detecting explosives or residues.
The Ft. Leonard Wood trials demonstrated both area reduction and localization
of vapor plume sources within the mined area. The deployment of a field-capable,
stand-alone conditioning system also was successfully demonstrated. When used in
accordance with specific protocols, active conditioning and target detection
were maintained for several days with a small, static set of colonies,
demonstrating the proficiency of this system. Some work remains in optimization
of the conditioning protocols and for designing a portable tracking system.
LIDAR tracking and mapping of bee densities or distributions not only worked,
but also located bees over a heretofore unknown source of explosives in the
supposedly control area. The LIDAR used for these trials was developed for
surveying fish, not bees. MSU's goal is to produce a low-cost, light-weight,
suitcase-sized, field-portable optimized LIDAR system for bee detection.
With appropriate funding, we should be able to field proof a readily
deployable system at minefield and UXO locations in the United States, in Canada
and overseas in 18 months. Following the experience and fine-tuning of the
system through field trials at other locations, deployment could rapidly occur.
We do not expect bees to replace dogs. Rather, we anticipate that bees, in
passive and active modes, could be used in concert with dogs and other methods
to reduce the time and expense of area reduction and landmine field surveys.
Like dogs, bees are able to recognize multiple substances concurrently at
very low concentrations. To date, we have trained bees on the odors of the main
charge explosive, but we could also include casing materials (plastic, rubber,
cardboard, wood, paint). Including other materials might improve performance,
especially if there is no odor from the main charge. As with any vapor sensing
system, bees cannot find a mine that is not leaking. We also see the need for
additional research to define the performance of mine-detecting bees, taking
into consideration environmental factors that influence the amount of chemical
Of great concern to us is the need to properly train and certify anyone who
intends to use bees in minefields. We believe that training, certification and
licensing (similar to that of the Geneva International Center for Humanitarian
Demining for dogs) is essential. Toward that end, Bee Alert Technology, Inc. in
cooperation with the College of Technology of UM has established programs to
provide the necessary training and certifications.
Bee-generated map of a minefield.
Limitations and Agricultural Benefits
Bees do not fly at night, during heavy rain or wind, or when temperatures
drop to near or below freezing. As such, the use of bees is seasonal in
temperate climates. Bees are active year-round in tropical regions. These
limitations are not unique. Dogs do not perform well in wind, rain or frozen
ground, and dogs and handlers usually do not work in the dark. Unlike a dog,
bees do not need to bond to their handlers, and they work whenever weather
conditions permit. At a weight of one-tenth of a gram, bees are not going to
trip wires or set any mines off. Their wide foraging range offers the possibly
of greatly speeding up survey times, while also increasing handler safety. Bee
colonies can be established along the perimeter of the minefield, not in the
minefield. With no leash to hold, the beekeepers can stay well clear of the
Article by Jerry J. Bromenshenk, Colin B. Henderson, Robert A. Seccomb,
Steven D. Rice and Robert T. Etter, Bee Alert Technology, Inc. and UM; Susan F.A.
Bender and Philip J. Rodacy, SNL; Joseph A. Shaw, Nathan L. Seldomridge and Lee
H. Spangler, MSU; and James J. Wilson, NOAA
Article courtesy of the Journal
of Mine Action
"Pollution Monitoring of Puget Sound with Honey Bees." Science.
"Honey Bees: Estimating the Environmental Impact of Chemicals." Taylor
and Francis, New York, 2002.
"Vehicle Bomb Detection Video." Online video: http://beekeeper.dbs.umt.edu/bees/videos.
"Alternatives for Landmine Detection." MacDonald, et al. Online
Mr. Jerry Bromenshenk
Division of Biological Sciences
University of Montana
Missoula, MT 59812