Detector Dogs and Scent Movement

How Weather, Terrain, and Vegetation Influence Search Strategies

Tom Osterkamp

• Publisher: CRC Press
• Year: 2020
• Print ISBN: 9780367074296
• eBook ISBN: 9780429665295
• Edition: 1
• Topic: Politics & International Relations
• Subtopic: Middle Eastern History
• Index: Politics & International Relations

Dogs detect scent from a source that is carried to them in a plume by the wind. The most important tool for a detector dog handler to have on searches is a knowledge of scent plume movement or "scent dynamics" (the science of scent movement). Such knowledge resides primarily in scientific journals that are largely inaccessible to detector dog handlers and written in language that is difficult to understand. Detector Dogs and the Science of Scent Movement: A Handler's Guide to Environments and Procedures retrieves, reviews, and interprets the results of pertinent scientific research on scent dynamics and presents these results in terms that are easier for handlers to understand.

Information on the physiology of the dog's nose, their sense of smell, and the properties of scent provide the essential information on the process of scenting. The composition of training aids for explosives, narcotics, human remains and other sources is discussed. Recommendations are made on the use of training aids, their placement during training, and the resulting availability of scent. Potential problems and handler errors in the use of training aids are also examined.

The characteristics of scent plumes and how wind influences their movement are a key focus of the book. The primary task for the handler is to get the dog into the scent plume so that the dog can detect the scent and follow it to the source the handler seeks. As such, a knowledge of scent and scent plume movement will vastly improve the ability of the handler to accomplish this task.

The influence of weather and physical settings such as terrain, vegetation, ground cover, soil and water on scent movement are examined in detail. Strategies for searching, detecting, and locating sources in all physical settings are presented. Specific effects associated with hills and mountains, fields and forests, bare soils and soils covered by vegetation, different soil types, and lakes and rivers are examined in detail. This includes specific recommendations are made about weather and physical settings that result in higher probability of success on searches.

Detector Dogs and the Science of Scent Movement will be a vital resource for K9 handles in the private and public sectors—including in Homeland Security, law enforcement, and military settings—as well as a useful guide for lawyers, forensic, and investigative professionals who need to better understand K9 operations.

1

Introduction

1.1 History

Genetic evidence indicates that dogs evolved gradually from wolves beginning about 100,000 years ago. The oldest dog fossils date from about 14,000 years ago. It is likely that ancient hunters used dogs to secure animals for food and as sentry dogs around their camps in a symbiotic relationship. This relationship has evolved and strengthened to the point where dogs and humans enjoy the closest interactions of all species in the animal world.

The evidence of human and canine interactions is well documented (Thurston 1996; Schoon and Haak 2002). Egyptian paintings prior to 3,000 B.C. show dogs being used for hunting, and many mummified dogs have been found in Egyptian tombs, indicating that dogs occupied a special place in their society. Writings and pictures that predate the Roman Empire illustrate the use of dogs for scent detection. Sophocles (496–406 B.C.) wrote a satire about the gods called “The Tracking Dogs,” indicating that dogs were used for tracking at that time.

The role of dogs continued to flourish in Roman society. Plinius (A.D. 23–79) described six classifications of dogs: guard dogs, shepherd dogs, hunting dogs, war dogs, sight hounds, and tracker dogs. Roman legions sent packs of armored attack dogs into battle, and Attila the Hun used them as sentries. Worldwide, dogs were used as sentries, guards, messengers, scouts, and fighters by armies and as hunting, herding, tracking, and draft animals by the populace. Except for hunting, a full appreciation of their scenting ability was slow to develop.

During the French and Indian Wars in 1775, Benjamin Franklin recommended the use of dogs by the Army to search for marauders who were attacking and killing colonists near Boston. In 1779, William McClay suggested using dogs to search for scalping parties in Pennsylvania. The first documented air scenting search dog (SD) (Barry, 1800–1812) lived with monks in a hospice in Saint Bernard Pass in the Alps at an altitude of over 8,000 feet. Barry used his scenting abilities to help rescue more than 40 persons during his lifetime. Bloodhounds and their handlers from Cuba were employed by the Army as man trackers in the swamps of western Florida and Louisiana in 1835.

The modern use of dogs for scent detection dates from the late 1800s and early 1900s. In 1888, Scotland Yard used bloodhounds for scent detection work in the infamous “Jack the Ripper” case. Many documented cases exist of the use of dogs in Europe for police work, which involved trailing and scent discrimination in the early 1900s (Schoon and Haak 2002). The British police and military explored the use of dogs in scent work and trained dogs to detect land mines in WWI. In the 1930s, police and military units began extensive training of canine units and the Swiss Army began training SDs to find avalanche victims. Germany had an estimated 30,000 trained dogs at the start of WWII, and Russia had a canine force of over a million animals that included explosive dogs (EDs) trained to detect explosives. The German Army used trailing dogs (TDs) to silently follow British Special Air Service officers who parachuted into Germany to collect intelligence prior to WWII. The dogs were trained to follow a given ground scent (scent discriminating) from a scent article or a footprint and to attack the subject at the end of the trail. The British Army adopted the idea of using silent TDs to find but not attack the enemy hiding on islands in the Pacific theater.

The USA did not have a canine unit in WWI although individual dogs did serve. Scent training in the USA began in earnest in WWII. At the start of the war, the only military dogs to be found within the Army were about 50 sled dogs in Alaska. The Army formed an official K-9 Corps but had to turn to the public to obtain dogs. A civilian organization called Dogs for Defense was established in 1942 to promote a national recruiting drive for canines. In 1944, the Army deployed over 100 dogs with a mine detection unit although the dogs were initially unsuccessful in locating nonmetal mines in Algeria and Italy. Dogs continued to be used in the Korean War, but in 1958 the K-9 Corps was terminated and responsibility for military working dogs was transferred to the Air Force where it remains.

The Vietnam War saw a dramatic increase in the US military canine presence. These four-footed soldiers were used to detect explosives, booby traps, trip wires, underwater enemy swimmers, stockpiles of enemy food, and to trail the enemy. They were credited with finding over a million pounds of stockpiled corn which caused the enemy considerable hardship. The enemy’s efforts to distract the dogs with bait and perfumes were not successful, and they offered rewards to anyone who killed a military dog.

Tragically, at the end of the war, the military command left the dogs which had faithfully served them to a culture that considered them food and an enemy who hated them. Some were transferred to the South Vietnamese, some turned loose, many were euthanized, and a few were returned to the USA. This was their fate despite saving an estimated 10,000 American soldiers’ lives and preventing many more soldiers from being injured. Military dog handlers are still suffering from the traumatic effects of leaving their dogs behind.

During this same period in the 1960s and early 1970s, the US expanded its detector dog programs with an emphasis on drugs and explosives. A Military Working Dog Program was established in 1968 at Lackland Air Force Base in San Antonio, Texas, that is still in operation. By 1971, they were training drug dogs (DDs) for use on ships and aircraft and had conducted a drug detection program for the Customs Service which showed that dogs could be trained to detect at least four odors. At about the same time, the British began training its military dogs to detect drugs and followed this program with training for explosives detection work to assist in the fighting in Northern Ireland. The US began training and deploying EDs in 1973, and, by the mid-1970s, government agencies in many countries were using SDs for various specialized tasks.

Several reports described the programs and methods used to train the dogs, and these were known to law enforcement and civilian trainers. In 1974, the New York State Police had a trooper handler and a yellow Labrador named Pearl trained for cadaver search by Southwest Research Institute. Law enforcement trainers in the northeast soon developed their own programs. These programs spread rapidly to other parts of the country and to civilian trainers. By the end of the century, it is estimated that there were over 100 volunteer search dog units that performed cadaver searches.

Today, SDs are used for an incredible variety of tasks. The expanding use of SDs in war (Frankel 2014) includes searching for improvised explosive devices (IEDs), body parts after explosions, and clandestine graves of soldiers and civilians, as well as trailing the enemy. Dogs are employed by government agencies to search for all manner of contraband including agricultural products, weapons, ammunition, accelerants, drug money, wildlife and wildlife parts, exotic plants and animals, sewage, bacteria, and people being smuggled into the country in ships, trains, and vehicles. Law enforcement uses SDs at crime scenes to search for evidence, blood, weapons, and clandestine graves. Dogs have been shown to be capable of detecting the scent associated with various diseases including cancer. Other uses include the detection of cows in estrus, poached abalone, termites, indoor air pollution, gas line leaks, rusted pipes, seal and polar bear dens, duck nests, animal scats, noxious weeds, contaminated water, mold, bed bugs, and historical graves—anything that emits scent molecules. The searches are conducted in airplanes, airports, ships, trains, trucks, cars, warehouses, businesses, schools, cities, suburbs, houses, backyards, cemeteries, archaeological sites, fields, forests, deserts, and wilderness.

The ability of SDs to detect and locate faint scent sources continues to amaze. The US Department of Defense has reportedly spent almost $20 billion to develop scent-detecting devices but found that EDs are better than instruments at detecting buried land mines and explosive devices. Dogs are still the gold standard for detection work. They are successful at these searches primarily because of their sensitive noses, but also have other capabilities which support the use of their noses. Dogs are highly mobile and can operate in challenging terrain even at night. They apply efficient search strategies for detecting scent, can actively extract scent from sources, use their wet noses to determine wind direction and the direction to a scent source, and use the wind to follow a discontinuous scent plume to the source. Importantly, because of their long association with humans, they have a special intelligence and bond with humans which exceeds that of other animals.

1.2 Purpose

This book reviews the scientific literature on scent and scent movement which is concerned with the movement or transport of scent from a source to the dog’s nose. The emphasis is on scent movement in outdoor environments. The primary goals are to translate the scientific information into less technical terms, to provide it to SD trainers and handlers, and to show how it can be used to improve their skills in training and deploying their dogs on searches.

There are several reasons why SD trainers and handlers need to have information on scent movement.

• First, the primary task of the handler is to place the dog in a position where it can access scent from the search object. The more handlers know about scent movement the more likely they will be successful.
• Second, problems inevitably arise that the dog cannot solve. When this occurs, the handler must understand their behavior and be able to devise a search plan on how to help them. Scent movement will be a critical part of that plan.
• Third, in training and searches it is desirable to maximize the success of the canine team by continually adapting to changing winds and scenting conditions. Careful attention to the wind during training and searching can make the difference between success and failure.
• Fourth, there has been a dramatic increase in the research on scent during the past two decades, and new information on scent and scent movement in training and deploying SDs is available. Trainers and handlers who improve their knowledge of scent and scent movement will improve their success in training and on searches.

1.3 Terminology

While there is no standardized method for naming SDs, a common method that we will use is to name them after the source they are trained to detect. Examples are explosive dogs (EDs) and cadaver dogs (CDs). The terminology for CDs and human remains dogs (HRDs) is confusing and varies with locations and organizations. CDs have been defined as dogs that are specially trained to detect the scent of human decomposition and show their handlers its location. The sources of this scent include complete human cadavers, body parts including bones, tissue, decomposition fluids, blood, and residual scent on anything that comes in physical contact with these sources. Physical contact may not be required for the dogs to alert when objects such as grass, shrubs, trees, leaves, soil, rocks, etc. are in contact with the air flow which contains the decomposition scent. These objects may collect scent on their surfaces and in dead air spaces and may exchange scent molecules with air under favorable conditions.

In the last few decades, there has been a shift in terminology from CDs to HRDs, especially by some certifying agencies. There has also been an attempt to differentiate between CDs, HRDs, and historical human remains dogs (HHRDs). The proposed distinctions are that CDs would be those used to locate recently deceased human remains, whole bodies, and recently disarticulated bodies on the surface of the ground or hanging above the ground. HRDs (also called forensic search dogs) would be those used to locate human remains that range in age from recently deceased through all stages of decomposition, including disarticulated and skeletal remains both above and below ground. They would be trained to locate trace evidence, blood splatters, and residual scent but should not alert on human urine, feces, semen, and items with live human scent on them since this could confuse the investigation. HHRDs would be those used to locate human remains that are very old, most often bones, both above and below ground.

Currently, there is little or no distinction between CDs and HRDs. Agency standards for certification of CDs and HRDs do not include testing to ensure that the dogs do not alert on human urine, feces, semen, and articles with live human scent on them. An example of a potential problem would be when they alert on the back seat of a car or in a bedroom and this is taken as evidence that a body has been there. However, the alert may have been caused by the presence of semen. Another example would be when they alert in a shed, barn, or outdoor setting and this is taken as evidence that a body has been there, or a crime has been committed there. The alert in these cases may have been caused by someone having urinated or defecated there.

It has been shown (Riezzo et al. 2014) that two dogs specially trained only on cadaver blood can detect this blood diluted to 1 ppm (part per million) with urine. This suggests that microscopic quantities of blood potentially present in urine, feces, and semen could cause the dogs to alert. Also, semen contains putrescine and cadaverine, two decomposition compounds that are partly responsible for its smell and flavor, which have been used to train CDs. CDs should not alert on urine, feces, and semen that do not contain blood but may, in fact, alert on these sources if they do contain blood. When a CD alerts on what may be one of these sources, it is desirable to inform law enforcement about whether the dog will alert on urine, feces, and semen that contain blood so that laboratory testing can be used to eliminate these potential sources.

Detector dogs usually refer to dogs trained to find scent from a source while search dogs include detector dogs and dogs trained to follow a scent trail on the ground. The rest of the book will use search dogs to refer to detector dogs and trailing dogs.

1.4 Using Search Dogs

Well-trained SDs should:

• Search independently for an odor using a thorough free search strategy or on lead.
• Be responsive to the handler’s directions while searching. Some SDs require control at a distance using voice and/or hand commands.
• Discriminate between sources which have common scents in the presence of distracting odors and environments.
• Detect very faint scents as well as variable and high levels of scent.
• Find the source of the scent once it is detected.
• Communicate the location of the source to the handler.
• Be capable of learning and generalizing from past experiences.

SD searches vary greatly in type, area, and difficulty, which lead to a wide range of requirements for the dog and handler. For example, searches for missing persons who may be alive or deceased in large areas (10s to 1000s of acres) a...

Table of contents

• Cover
• Half-Title
• Title
• Copyright
• Dedication
• Contents
• Preface
• Acknowledgments
• 1 Introduction
• 2 The Dog’s Nose and Scent
• 3 Scent and Wind
• 4 Above-Ground Searches
• 5 Buried Sources
• 6 Water Searches
• 7 Trails and Trailing
• Appendix 1: Abbreviations
• Appendix 2: Acronyms
• Appendix 3: Questions and Needs for SD Training and Deployment
• References
• Index