The Incredible Sense of Smell in Ants
How Ant Olfaction Triumphs Over the Audiovisual System in Recognizing Friend or Foe
Aiden Salk | November 15th, 2023
Why can’t humans sense their own body odors? Why do some humans tolerate certain smells better than others? Why do people like certain smells that others do not?
The answer to these questions is the habituation of smells or odorants. From a neurological perspective, habituation refers to less signals being fired to the brain by sensory neurons after frequent exposure to the same olfactory stimuli. Interestingly, humans, like many other animals, have an olfactory memory. There are plenty of other fun facts about the human sense of smell. Nonetheless, the sense of smell–called olfaction–is often overlooked. After all, being able to detect and discriminate between odorants is no longer essential to survival in modern day. Though there is evidence of humans being able to detect pheromones–chemical signals released to induce a specific behavioral or psychological response–olfaction appears to be more significant for other animals, in particular ants.
Ants are eusocial animals, meaning their colony has social organization. The primary goals of the colony are survival and reproduction, and the group will strive towards these goals together. An ant colony will likely be made up of thousands of ants, which differentiates them from some other animals that rely heavily on olfaction, such as a domesticated dog that may only interact with a few dogs at the park each week. Different ant colonies will clash with one another for resources, as ants have been shown to exhibit aggression towards non-nestmates. Due to passing by thousands of ants every day, ants must have a way to distinguish between friend and foe. Laurence Zweibel, Stephen Ferguson, and others from the Zwiebel Lab at Vanderbilt University investigated this process by studying nine colonies of Camponotus floridanus, an ant species common in Florida.
How Does Ant Olfaction Work?
The way ants discriminate non-nestmates from nestmates involves odorant cues from cuticular hydrocarbons, which are found in the cuticles of many insects. Ants can detect small changes in the profile of another ant’s cuticular hydrocarbons by the odors the ant gives off. If the profile does not match the cuticular hydrocarbon profile of their own nestmates, the ant may exhibit an aggression response, physically fighting the other ant. An experiment was performed by placing two ants from the same or different colonies in “distinct bioassay arenas for behavioral traits.” The ants were placed in one of two separated halves of the arena and given time to acclimate to the new environment. Subsequently, the ants were exposed to each other, and their aggression behavior was monitored. The previously mentioned pattern of aggression was observed.
Further trials were conducted where the antennae olfactory organs of the ants were ablated. The antennae are where the odorant receptors and odorant receptor co-receptors are located, so having ablated antennae will prevent the odorants from binding to these receptors. While ants that had wildtype (normal) antennae attacked non-nestmates, ants with an ablated antennae or over-activated receptors now showed dramatically lower aggression. Interestingly, Ferguson states that the “study finds that unless there is a clear and unambiguous threat, ants are more likely to be accepting than they are to be aggressive.”
There is a lot to learn from the ant behavior studied by the Zwiebel lab. These insights from C. floridanus may make them a model system for smell-related aggression. There is also much research being done on the sense of olfaction in many other species of animals. Evidence suggests that individuals with Alzheimer’s disease or dementia have deficits in their olfactory memory, and that these individuals lose the ability to discriminate smells as the disease worsens. We certainly still have much to learn about the incredible sense of smell.
Ferguson, Stephen T., et al. “Odor coding of nestmate recognition in the eusocial ant camponotus floridanus.” Journal of Experimental Biology, vol. 223, no. 2, 2020, https://doi.org/10.1242/jeb.215400.
Verhaeghe, J et al. “Pheromones and their effect on women’s mood and sexuality.” Facts, views & vision in ObGyn vol. 5,3 (2013): 189-95.
Turney, Spencer. “How Ants Get Angry: Precise ‘Lock and Key’ Process Regulates Aggression, Acceptance.” Vanderbilt University, Vanderbilt University, 3 Feb. 2020, news.vanderbilt.edu/2020/02/03/how-ants-get-angry-precise-lock-and-key-process-regulates-aggression-acceptance/.
Wikipedia contributors. “Olfactory memory.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 18 Aug. 2023. Web. 17 Oct. 2023.
Digital Strategies (Div of. “The Zwiebel Lab.” Comm) Vanderbilt University, Vanderbilt University, lab.vanderbilt.edu/zwiebel-lab/. Accessed 12 Oct. 2023.