The Nose Knows: New Discoveries in Otter Odor Dialects


Researchers have found that there are both sex specific and age specific differences in the scent of spraints, though this has been heavily supported by previous research. The most interesting discovery is that each genetic population had a unique makeup of spraint not cause my geographical distance as was originally thought but by genetic differences.


Source: Wikimedia Commons

Otters are unique in their ability to communicate through odor detection as it has not been found in other aquatic mammals. This is likely due to the fact that transmitting odors, or leaving behind markings is very difficult in an aquatic environment. They are not, however, the only species known to communicate through scent. Mice, badgers, primates, and countless other species have been known to use these pathways to communicate non-verbally.

Humans are no exception to this rule. Scientists discovered this when they conducted the infamous “Sweaty T-Shirt Experiment”. Women lined up to sniff a line of sweaty T-shirts to see if they found any of the scents attractive. The study found that most people were attracted to the scent of individuals with a different genetic makeup to their own. Some people were even repulsed by scent of T-shirts belonging to individuals with a similar genetic makeup.


Source: Wikimedia Commons

The puzzle of non-vocal communication has perplexed scientists for decades. It was first discovered that otters performed scent marking by leaving small deposits of fecal matter throughout their territory. This behavior, known as “sprainting” has been associated with several other species and is a well-studied behavior.  Female otter territories consist of a large range which is inhabited by but multiple females who live individually. Male territories overlap with the female ranges and are inhabited by multiple males. Since these ranges are so large and otters live by themselves, there is limited opportunity for face-to-face communication.

There is much debate about what kinds of information are being communicated through these spraints. The most popular theory has been that sprainting allows individuals to mark territory or resources as a way to avoid fighting with non-related or intrusive individuals. Fights over territories or resources are costly for both individuals and it is beneficial for all members of the species to communicate this way. Other theories suggest communication of sex and age in order to attract mates, or to alert related otters that a food resource had recently been exploited and would therefore be less likely to yield food for the next visitor. Several studies have been conducted to explore the likelihood of these theories. They have yielded a mix of positive results which makes it difficult to understand how spraints are used to communicate.

In the most recent studies, researchers found that there are both sex specific and age specific differences in the scent of spraints, though this has been heavily supported by the previous research. Researchers have also discovered that pregnant females have a unique spraint compared to other mature females. The most interesting discovery, however, was that each population had a unique makeup of spraint not cause by geographical distance as was originally thought, but by genetic differences in the populations.

Thanks to the continual development of new research tools and technologies, scientists have been able to explore the chemicals at play in sprainting communication. Additionally, they have been able to study the genes of several individuals to see if there is communication between genetically distinct populations. The studies recently conducted in the UK found there are four groups of genetically distinct populations. It is important to note that this is a rare case where the populations have become separated genetically due to re-colonization and the severe declines in otter population throughout the country. It is not unlikely that similar situations are affecting other populations and species throughout the world, but not all populations will have such clear cut genetic separation. As the spraints were studied, researchers found that each genetic population had its own unique identifiers, meaning otters are able to identify when an otter is not from their range and where they have come from.



Current Eurasian Otter Range

Source: WikeMedia Commons

Over the past decade populations of the Eurasian otter have been steadily declining and are currently listed as “Near Threatened” by the IUCN Red List. The understanding of different pathways of communication has an important impact on the way we approach conservation and repopulation efforts. Since otters are able to identify distinct odor profiles they may, as with the women in the T-shirt test, reject potential mates based off of their genetic makeup making repopulation efforts more difficult. Understanding these odor dialects will be especially helpful for conservation efforts for more endangered species such as the endangered sea otter.

There is still so much we do not know about the intricacies of communication through odor. With the rapid development in genetics studies and new research on the microbiome beginning to develop we are certain to discover more than we could imagine about communication pathways. We are on the brink of a deeper understand of how animals, ourselves included, communicate. However, these studies will not be possible if we lose the valuable populations being monitored. There are plenty of ways to get involved with this exciting research such as citizen science, volunteering at your local zoo or aquarium, or taking part in active conservation efforts.





Almeida, D., Barrientos, R., Merino-Aguirre, R., Angeler, D. The role of prey abundance and flow regulation in the marking behaviour of Eurasian otters in a Mediterranean catchment. Animal Behaviour. 84 1475-1482 (2012)

Kean, E. F., Chadwick, E. A. & Müller, C. T. Scent signals individual identity and country of origin in otters. Mamm. Biol. 80(2), 99–105 (2015).

Kean, E. F., Müller, C. T. & Chadwick, E. A. Otter scent signals age, sex and reproductive status. Chem Senses 36(6), 555–564 (2011).

Kean, E.F, Bruford, M.W., Russon, I.., Muller, C.T., Chadwick, E.A. Odour dialects among wild mammals. Nature. (2017)

Kruuk, H. Scent marking by otters (Lutra lutra) – signalling the use of resources. Behav. Ecol. 3(2), 133–140 (1992)


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