|Fielding Water Search Dog Teams|
by Mark Polakoff
The use of trained search dogs to detect scent originating from submerged drowning victims has become commonplace over the past decade and is now an accepted part of water search practice. The seemingly magical ability of dogs to scent "through" the water continues to cause confusion and skepticism in some quarters of the search and rescue community. This paper will attempt to demystify this ability; the benefits that dogs bring to a water search; discuss some methods of deploying dog teams in several situations; and clarify what an incident commander can expect of Absaroka Search Dogs teams when their assistance is requested in the search effort.
Most SAR personnel are familiar with the ability of air scenting search dogs to locate human scent, follow the scent to its source, indicate to their human partner that they have located the person who is the source, and then lead the dog handler to the lost person. A trained water search dog team will follow most of these steps in locating the body of a drowning victim.
How Water Search Dogs Work
A brief explanation of the makeup of human scent will assist in the understanding of how a dog's nose can penetrate the surface of water. Remember that human scent is composed of numerous chemicals, some produced by the human body and others applied to the body and clothing in the form of various hygiene products (soap, deodorant, shampoo, laundry detergent, etc.). While many of the hygiene products are readily water soluble, many of those produced by the body are not. A number of those are volatile oils and other substances that do not readily dissolve in water and are in fact lighter than water. When these molecules are released into the water they float to the surface. Upon contact with air they "dissolve" in the air as gaseous vapor that is carried on the wind to the dog's nose. (An analogy would be our ability to smell gasoline released into the water which floats to the surface and produces an odor we can detect. Since a dog's scenting ability is up to 100 million times more sensitive than a human's, it stands to reason that we would be unaware of what the dog is detecting.)
So in reality the dog is detecting the point at which the scent has risen to the water surface, rather than the actual underwater source of the scent. This is an important point to remember, and we will come back to it later when discussing the human part of the dog team.
Advantages of Using Dogs
With the understanding of how dogs are able to detect scent, it becomes easier to answer the question of when and how to use them in the search effort. Some other common methods of searching water include visual searches from shore, boats, bridges, and airplanes, draglines, pike poles, underwater sonar and of course divers. It must be emphasized that dogs are not a substitute for these other methods, but rather a complementary resource to improve the efficiency of any of them.
Most if not all drowning victims, if not recovered soon after death, will submerge for a period of time before resurfacing. The body may submerge at the time of death if enough water is swallowed and/or inhaled (often referred to as a wet drowning). If the airway spasms shut during the person's struggle in the water (a dry drowning), the lungs may not fill with water and resubmerge the body until sometime after death. Other factors that will affect how rapidly the body submerges will be the amount and type of clothing worn, and body composition (muscle has less buoyancy than fat tissue). A body may exhibit three states of buoyancy:
Once a body submerges, a number of additional factors will affect how much time passes before resurfacing. A primary influence is water temperature. At warmer temperatures, decomposition of the body and fermentation of stomach contents will form gases which will eventually refloat the body. (This process will also continue to produce detectable scent for the dog, distinguishable by the dog as cadaver scent). As water temperatures drop, the decay process slows, and at 38o F it stops and there is preservation by refrigeration. The following chart gives approximate times for a body to refloat, taking only water temperature into account:
Water Temp. (F) Time
70..................................... 1 day
60..................................... 2-3 days
50..................................... 3-4 days
40..................................... 6+ days
38.................................... Will not resurface until temp. increases
Other factors that may influence this process include water depth (at 200 feet it is unlikely for a body to refloat due to the increased pressure on the body. Shallower depths may act to slow the rise of the body.), underwater structures that may snag the body, thermal layering of lakes that occurs during the summer, as well as other conditions. The success of above water visual searching will be affected by these processes, as well as visual clarity of the water. Search dogs can be of great benefit when the body is not likely to be found immediately using visual search methods.
In searches involving large bodies of water or large, swift moving rivers, dogs can be used to eliminate large segments of the search area. Just as in missing person searches, if you can determine where the victim is not, you have positive information to use in revising search strategy. This is particularly useful when combining the use of dogs and divers. Anytime divers are placed in the water for body search, the safety vs. risk factor is a critical decision for the incident commander to make. Using dogs to aid in the placement of divers can reduce the need for dives into risky terrain, reduce dive time, and speed recovery; thereby increasing safety and saving both time and money.
Water Search Strategies for Dogs
Dog teams can be deployed to search from shore, from a boat, or in certain circumstances a dog may search by swimming. Factors to consider in determining search strategy will include the following:
If terrain permits, a shoreline search is often safe and effective. This may work on smaller bodies of water when the wind speed and direction carry scent towards shore. When these conditions don't exist, or to pinpoint the source of a shoreline alert, searching from a boat can be a valuable method.
The ideal boat for use with search dogs would have a non-slip deck at the bow, low enough to the water that the dog could check for scent lingering at the water surface (cool air will keep the scent right at the surface, not allowing it to rise up and be dispersed on air currents). It would be a stable platform to allow the dog and handler to move from side to side without tipping, and be seaworthy for the type of water being searched. The boat would be propelled by a powerful electric motor. (Gas engine exhaust fumes can interfere with the dog's scenting, as can the oil that is released into the water. The noise of a gas engine can interfere with on board communication) It would be maneuverable at low speeds and have an expert operator. Obviously, the ideal boat for all types of water search doesn't exist. Therefore a compromise must be reached. The two most important factors will be the ability of the dog to work within one to two feet of the water surface (the lower the better), and a skilled operator who can handle the boat on the type of water being searched and can maneuver the boat at low speeds.
For boat based searches, a GPS unit can be very useful for pinpointing the location of alerts and search area boundaries. Alternately, buoys can be used to mark locations. These can be commercially available buoys, or homemade from milk jugs painted a high visibility color with enough line and an anchor. Buoys should be placed after dogs are finished searching, so the human scent on the buoys doesn't cause any confusion for the dogs.
Larger bodies of water may be grid searched from a boat. The spacing of the grids will be affected by both air and water temperature, as well as water depth. Rivers with a substantial current may need to be searched quite a distance downstream, taking into account the time since the drowning occurred, the speed of the current and likelihood of the body to be snagged on logjams, debris piles, in deep holes, beneath undercut banks, etc. Gravel bars and shorelines should be searched if water levels are fluctuating.
Occasionally a swimming search is appropriate if the water is calm, warm and free of snags or other hazards. In the experience of Absaroka Search Dogs, this is not a commonly used technique in Montana, due to cold water temperatures for most of the year, and the fact that the majority of water searches have been on rivers during high water runoff.
What to Expect from Qualified Search Dog Teams
This discussion will focus on what to expect from Absaroka Search Dogs teams that respond to water search requests, although it may be generalized to other bona fide SAR dog teams in the area, as most train to similar standards.
In terms of basics, the arriving dog team will be cross trained and qualified in air scenting and trailing . This means that the dog will understand the concept of locating scent and it's source as discussed earlier. It will also be motivated to do it's job and will be enthusiastic to begin. The handler will understand concepts of scent theory, search strategy, incident command, and the various other skills that go alone with being a qualified SAR responder.
Specifically, the team will have trained for water search on a variety of types of water, in numerous kinds of watercraft including jet boats, canoes, inflatable rafts and johnboats, among others. The dog will understand the concept that scent emanates from "underneath". The handler will understand the dynamics of water movement, and its effects on safety in and around moving water; both swiftwater currents and open water swells.
Earlier in this discussion it was pointed out that the dog often does not actually find the specific location of the victim's body, but rather indicates on the point where the scent has risen to the water surface. If the body cannot readily be seen from this indication, it remains up to the handler to interpret the dog's alert. The handler can be expected to give an estimation of where the body is located, based on the location of the dog's alert and the interplay of various factors influencing scent movement such as water and air temperatures, currents, water depth, etc. This important skill is developed out of the realization that just as in missing person searches, the dog is only half of the team. If the dog finds the missing person but the handler is unable to follow up on the alert, the person is still missing. In water search, if the dog locates the scent, but the handler cannot properly interpret where the scent is coming from, the victim remains missing.
The team will arrive equipped for water search with a personal flotation device (PFD), appropriate water clothing and footwear for the search conditions. And as always, there is no cost to the requesting agency or the victim's family. Absaroka Search Dogs teams are volunteers that do not charge for services, although donations to offset expenses are always greatly appreciated.
Search dogs can be a useful tool to complement and increase the efficiency of various search resources in water searches, reducing time and expense, and most significantly adding a margin of safety for other searchers. There is no magic in what our canine partners do, although their unique abilities may at times appear so. An astute and resourceful search manager will utilize dogs as part of the search team, relying on their abilities to augment the strengths of other search methods.
Water searches are always tragedies, and the final outcome is never a joyous occasion as often occurs on missing person searches. The faster the situation can be resolved by locating the body, the easier the situation will be for the friends and family of the person who drowned. Therefore, Absaroka Search Dogs always appreciates being notified of a request to search as early in the mission as possible.