Telling Tigers Apart: Scent Lineups Identify Individual Tigers from Scat

Dogs have been used to monitor the status of endangered species for some time, and a number of examples have been mentioned in prior blogs. (See Certification of Tortoise Detector dogs? May 20, 2009; Types of Detection Dogs—How Many Can You Name? March 5, 2010) In all cases I know of, however, the dogs were not trained to distinguish between individual bears, tortoises, ferrets, or whatever. Like drug dogs or cadaver dogs, they are trained to recognize any scent that belongs to the target category. An exception involves dogs that are being used to monitor the status of the Amur, or Siberian tiger (Panthera tigris altaica), found in the Russian far east. This involves training dogs under procedures similar to those used for scent lineups in criminal investigations where the dog is asked if there is a match to a scent from the crime in a lineup of scents from foils and a suspect in the crime.

Monitoring tigers has involved track size measurements, camera traps, and genetic analysis of hair and scat. Genetic analysis has been largely ineffective because of the low genetic variability of the remaining Amur tiger population. Camera traps often malfunction in cold temperatures, though winter may be the best time to survey these animals.

Two researchers from the Lazovsky State Nature Zapovednik (preserve) began training five dogs to develop the ability to distinguish tigers by scat. The training followed Dutch forensic practices, but the dogs were rewarded with food, not play. Dogs were selected at six to eight weeks based on observed play and food drive, and training began at four to six months of age. Dogs were trained to sniff the scat of one tiger, then alert to a match in a scent lineup of seven scat jars.

Dogs were first trained to smell jars by being presented with a row of 15 to 20 jars filled to the top with wadded paper on some of which was a small piece of hot dog. The dogs walked in front of the handler and were taught to smell each jar for the possible treat. After this was learned, treats were removed and jars were placed further apart and covered with scent boxes. A passive alert, a sit, was taught as the alert. The test jar, containing the scat the dog was supposed to match from the lineup, was placed on a 15 cm high stool. (See diagram.) Dogs were taught to smell the test jar first and received a reward from the handler on sitting at the matching jar. First this was done with a command but the command was soon removed so that the handler could remain blind to the correct target jar. Also, scat from different tigers was slowly introduced into every jar in the lineup but only one was a match.

When a dog chose the correct jar more than 70% of the time, more matching jars were introduced so that a dog might make one, two, or three matches in every trial (see diagram). Training was completed in two to four months, and performance usually continued to improve for four to six weeks after training was completed. Each trial took 10 to 15 minutes and dogs performed three to seven trials each day. Dogs that turned out to be unmotivated to work more than 10% of the time were retired.

Scat was obtained from tigers in zoos, circuses, and wild Amur tigers. Scats from known wild tigers (some of which were radio-collared) could be collected when there was a single set of tracks. The diet of wild tigers consists of red deer, wild boar, sika deer, and other animals, including dogs. Care had to be taken that collected scat did not grow mold, which could interfere with a dog’s ability to detect individual scent. Scats were aged about two days. Researchers found that dogs are attracted to some scats, as has been found by Adee Schoon and Tadeusz Jezierski with dogs used in forensic scent lineups. Of 58 scats, dogs were determined to be attracted to three for no apparent reason.

In 521 trails, dogs correctly chose one of seven scats with an average rate of 87% (individually varying from 79% correct up to 89% correct). When trials were repeated with different dogs, accuracy increased to 98%. Where two samples in the lineup matched the trial scent, dogs were accurate 84% of the time. Dogs were more accurate in identifying wild tigers than with captive tigers, perhaps reflecting the nearly identical diets of some of the captive tigers.

The researchers recommended that identifications be based on repeated tests of two or three dogs. They also recommended that scent identification be combined with other methods of following tigers.

Linda L. Kerley and Galina P. Salkina, Using Scent-Matching Dogs to Identify Individual Amur Tigers from Scats. Journal of Wildlife Management, 71(4), 1349-1356 (2007).  See also, Linda L. Kerley, Using Dogs for Tiger Conservation and Research.  Integrative Zoology, 5(4), 390-396.

Scent Lineup Admitted into Evidence by California Court Despite Numerous Deficiencies

A recent California case demonstrates why scent lineups continue to be attacked as “junk science” by the defense bar, and why better procedures must be imposed by courts and law enforcement agencies to overcome such criticisms. People v. White, 2009 WL 3111677 (Cal.App. 2Dist. 2009)

The crime occurred on June 7, 2006, in the early evening in Compton, California. Five teenagers were skateboarding when two of them were shot by an assailant. One died. Shell casings were recovered from the crime scene and placed in manila envelopes. Problem one: manila envelopes, as noted by an expert witness for the defense, Lawrence Myers (Auburn University College of Veterinary Medicine), are porous, which allows for the possibility of contamination. Scent pads were later wrapped around the casings for about 10 minutes and the pads were stored in Ziploc bags. Problem two (minor): glass containers would have been better. (See Hudson, D.T., Curran, A.M., and Furton, K.G., The Stability of Collected Human Scent under Various Environmental Conditions. Journal of Forensic Sciences, 2009, vol. 54(6): 1270-1277, noting glass containers were preferable to plastic.) The Ziploc bags were put in an evidence locker for two days. Problem three: The scent samples should have been refrigerated, as noted by the defense expert.

Two officers collected scent from four individuals, including the arms of the defendant, put the scents in boxes and arranged the boxes in a diamond format. Problem four (perhaps minor): If by collecting scent from the arm of the defendant, the court means that it was collected by some means such as rubbing a scent pad along the arm, this would mean that scent was collected from a slightly different body part that the fingers that probably handled the casings collected at the crime scene (while the weapon was being loaded). Some evidence has suggested that scent from different parts of the body may be difficult for a dog to distinguish. (See Brisbin, I.L. and Austad, S.N., Testing the Individual Odour Theory of Canine Olfaction. Animal Behaviour, 1991, vol. 42, 63-69.) Another study contradicted this result, however. (See Schoon, G.A.A., and de Bruin, J.C. The Ability of Dogs to Recognize and Cross-Match Human Odours. Forensic Science International, 1994, vol. 69: 111-118.)

The dog was taken into the middle of the diamond and scented to a pad that had been wrapped around a shell casing. The dog lay down next to the box containing the defendant’s scent. Problem five: There was no discussion of any control trials. European protocols generally call for several control trials to determine if the dog is willing to work on the day of the tests and to verify that the dog is alerting correctly where the “perpetrator” and the target are known to be the same. Also, it may be necessary to determine if the dog has an “attraction” to the scent of a suspect. Problem six: Almost all protocols developed in the Netherlands, Poland, and other law enforcement centers in recent years provide a dog with at least five, and often six or seven choices, sometimes in two lineups simultaneously (See Schoon G.A.A. Scent identification lineups by dogs (Canis familiaris): experimental design and forensic application. Applied Animal Behaviour Science, 1999, vol. 49, 257-267; Schoon G.A.A. A first assessment of the reliability of an improved scent identification line-up. Journal of Forensic Sciences, 1998, vol. 43, 1, 70-75.) In some control lineups, it is often advisable to include “zero trials” where the correct response of the dog is not to alert at all because the item the dog is scented to does not correlate with any of the scents in the lineup.

The handler was unaware of which box contained the scent of the defendant, but while the lineup was being conducted, the two officers who set it up watched from a picnic table 40 to 50 feet away from the diamond formation. Problem seven: No responsible lineup procedure allows the handler to see an experimenter or anyone who knows the location of the target or the suspect’s scent. The “clever Hans” effect can arise even if the handler is blind to the location of the target. This issue was raised by the defense expert (Myers) but dismissed

The defense expert could not interpret the handler’s training logs and could therefore not assess the dog’s reliability. Problem eight: It is the author’s opinion that training logs should always be available to counsel for the defense (or the prosecution in the case of an exonerating scent lineup). The court found this problem was irrelevant because the handler testified as to the dog’s training and was subject to cross-examination. The handler testified that he was not aware that his dog had made any mistakes in 171 criminal lineups. Courts should cease allowing handlers to be the sole means by which major foundational requirements are satisfied in scent lineups. (See the records procedures recommended by the Scientific Working Group on Dog and Orthological Detector Guidelines (SWGDOG), Human Scent Dogs: Scent Identification Lineups (posted at www.swgdog.org). SWGDOG is a forum, with participants from the FBI, other law enforcement agencies, and research facilities involved in canine forensic research.)

The court concluded that the defense expert had done no more than make suggestions for improving the lineup procedure that was used, but that his testimony had not shown the evidence to be unreliable. There was, admittedly, good corroborating evidence here, including the testimony of two eyewitnesses. Part of the case concerned the reliability of visual lineups for eyewitnesses, another area that is not as simple as it once seemed to be. (See, e.g., Wright, D.B. and McDaid, A.T. Comparing System and Estimator Variables Using Data from Real Line-ups. Applied Cognitive Psychology, 1996, vol. 10(1), 75-84.)

Twenty years ago, Professor Andrew Taslitz argued that scent lineups should not be admitted as evidence of guilt in a criminal trial. He noted that research being conducted by Jan de Bruin of the Dutch police might reach a level to be satisfactory for judicial use but noted the research had not yet been published. Adee Schoon, cited in several parentheses above, continued that work. Some convictions obtained in part by scent lineup results have been overturned, and it is not clear if the public still has a “mythic belief” in the scenting powers of dogs. (Taslitz, A. Does the Cold Nose Know? The Unscientific Myth of the Dog Scent Lineup. Hastings Law Journal,1990, vol 42, 15-134.)

The problem with cases like People v. White is that they risk opening use of a poorly conducted scent lineup to the charge of “junk science.” Almost all of the defects of this lineup would be obvious to the researchers in this area, and most of them could have been easily cured. Some might require that additional dogs be available to confirm the result. Protocols developed in Polish research have demonstrated that requiring at least two dogs—ideally three dogs—to identify the suspect in a scent lineup substantially diminishes the possibility of a misidentification. (Jezierski, T., personal communication, 2010) A proper testing environment and equipment might require additional expense. Nevertheless, in cases where witnesses are fearful or disappear, the scent lineup, if properly conducted at the levels required by the more advanced forensic research centers, may be an appropriate link in the case.

Types of Detection Dogs--How Many Can You Name?

When I began working on Service and Therapy Dogs in American Society, I was soon struck by the proliferation of service dog types, including the fairly recent category of hypoglycemia alert dogs and the still anecdotal migraine-alert dog category. This is nothing compared to the list of scenting dogs that were assembled by a group of chemists in 2004. They came up with 30 scent detection dog categories. Some of these categories probably only represent a few dozen dogs, but many of them are essential to law enforcement and are found throughout the world. The categories are:

1. Abalone (endangered mollusk poaching) detector dog
2. Agricultural product (importation) detector dog
3. Arson (accelerant) detector dog
4. Brown tree snake (pest species) detector dog
5. Airport/runway detector dog
6. Cadaver (human remains) detector dog
7. Chemical weapon detector dog
8. Citrus canker detector dog
9. Concealed person detector dog
10. Currency detector dog
11. Drug (narcotic) detector dog
12. Explosives (bomb) detector dog
13. Gas leak detector dog
14. Gold ore detector dog
15. Gun/ammunition detector dog
16. GYPSY moth larvae detector dog
17. Land mine trip wire detector dog
18. Melanoma detector dog
19. Missing person detector dog
20. Rotten power pole detector dog
21. Scent line-up detector dog
22. Screw worm detector dog
23. Seal detector dog
24. Search and rescue (warm blood) detector dog
25. Syringe needle (dried blood) detector dog
26. Termite detector dog
27. Tracking (fleeing suspect) detector dog
28. Truffles detector dog
29. Water search detector dog
30. Wildlife detector dog

The list was compiled for an article in the Journal of Analytical and Bioanalytical Chemistry. Lorenzo, N., Wan, T.L., Harper, R.J., Hsu, Y.L., Chow, M., Rose, S., and Furton, K.G. (2004). Laboratory and Field Experiments Used to Identify Canis lupus var. familiaris Active Odor Signature Chemicals from Drugs, Explosives, and Humans. Analytical and Bioanalytical Chemistry, 376: 1212-1224.

For more on the use of detection dogs in conservation projects, see Brown, C., Stafford, K., and Fordham, R. (2006). The Use of Scent-Detection Dogs. Irish Veterinary Journal, 59(2), 97-104. dogs have been used to find dead bats at wind farms. Arnett, E.B. (2006). A Preliminary Evaluation on the Use of Dogs to Recover Bat Fatalities at Wind Energy Facilities. Wildlife Society Bulletin, 34(5), 1440-1445. They have also been trained to detect microbial growth in buildings, which can cause respiratory and other symptoms in occupants. Kauhanen, E., Harri, M., Nevalainen, A., and Nevalainen, T. (2002). Validity of Detection of Microbial Growth in Buildings by Trained Dogs. Environmental International, 28, 153-7. A master's thesis filed with South Dakota State University studied dogs trained to find ferrets. The thesis was adapted into an article Reindl, S.A. et al. (2006). Efficacy of Scent Dogs in Detecting Black-Footed Ferrets at a Reintroduction Site in South Dakota. USDA National Wildlife Research Center Staff Publications; Kerley, L.L. and Salkina, G.P. (2006). Using Scent-Matching Dogs to Identify Individual Amur Tigers from Scats. Journal of Wildlife Management, 71(4), 1349-1356 (a unique study in that the dogs were not trained just to recognize tigers, but also to identify individual tigers).

In the Federal Register of October 2, 2013, the Fish and Wildlife Service reported that dogs had been used in an attempt to identify and locate potential natural roosts of the bonneted bat in Florida. 78 Fed. Reg. 61004 (October 2, 2013), at 61007 and 61018.  The dogs were obtained from Auburn University's EcoDogs. 

Dogs Identify Murder Suspect from Manure on Shoe

Something of a precursor to the modern scent lineup is described by Adee Schoon and Ruud Haak in their book, K9 Suspect Discrimination. In 1918, a farmer was murdered near the town of Breezand in Holland. Fingerprints taken from the crime scene were found to belong to one suspect, who confessed and implicated two other men, one of whom was also apprehended. This second suspect had slipped when climbing through a barn window and his right foot went into a manure gutter. When asked about the manure still on his shoes, the suspect said that he had recently gone to a cattle market in the town of Purmerend, where he had stepped in manure. The investigator in the case, Van Ledden Hulsebosch, wondered if a dog could distinguish between manure obtained from different locations. He asked the gendarme from Breezand to bring him cow manure from 12 different locations, including the place where the murder had occurred. The manure from the different locations was put into 12 clean jam jars, which were numbered and labeled indicating the cowshed from which the manure was obtained. Hulsebosch took 72 pieces of paper and divided them into six groups of 12, labeling each of the 12 sheets according to the numbers on the jam jars holding the manure. Manure was then spread on the papers, which were then laid out in the courtyard of the police headquarters. The inspector let dogs sniff the manure from one barn, then released them in the courtyard to find the sheet with manure from the same source. The dogs alerted to the correct piece of paper. The experiment was repeated a number of times, with the correct paper identified every time. The next phase involved the shoes of the suspect. The suspect’s left shoe had no manure on it and the dogs did not react to it. When they were presented with the right shoe, the one with manure on it, they began searching until they found the piece of paper in the courtyard with the same scent on it. That piece of paper held manure taken from the barn where the farmer had been killed. The dogs had identified a second participant in the crime. Adee Schoon and Ruud Haak, K9 Suspect Discrimination, 27-28 (Detselig Enterprizes 2002).