Februari 7th, 2017
Missing persons and what rats possibly can contribute to find them.

Every year millions of people are reported missing worldwide. Statistics give a staggering amount of people that are never found or heard of again. Each individual case of a missing person has a devastating impact on the lives of the people left behind. The uncertainty if a beloved one is still alive or not is unbearable. Many organisations put a lot of effort in finding missing persons.

Unknown graves
Investigators of the police sometimes receive information about locations where missing persons could be buried or by coincidence stumble across a grave during research in the field. Also the re-opening of cold cases can retrieve information about possible locations of graves.
The location of such graves are often not very precise and having a method available to find out quickly if human remains are buried in a specific area is important.

Researchers of the Dutch police are testing a method which uses brown rats to indicate if samples of soil contain the scent of human remains. Results of the research so far shows a 93% of correct triggers by the rat on known positive samples.

Cute little white rat © The Rat Gazette - Photo: Arjan Schuitman

Soil samples
Rats don't like new environments. Instead of bringing the rats to the locations of the possible graves, soil is extracted and brought to the rats. Together with known soil samples (both positive and negative) the rats are offered the unknown samples and must indicate the sample with the scent of the human remains.

Soil put in small numbered cups as samples for rats © The Rat Gazette - Photo: Arjan Schuitman

Work space
During the sample detection the rat is placed in a cage made of glass situated in a quiet environment. The cage has three holes in the bottom. Each time three samples are offered to the rat. The rat has learned to walk in circles around the sample hole with the positive sample with his nose still above the sample. The researcher will note the result on the chart. Each sample is offered twice to the rats to ensure the reliability of the results.

Rat runs around hole after positive identification of sample © The Rat Gazette - Photo: Arjan Schuitman

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