Ants are one of the most successful groups of insects on Earth, forming enormous and complex colonies with division of labor between different castes. But do these tiny creatures have inner lives like we do? Can ants feel emotions like happiness, sadness, fear or even love?
If you’re short on time, here’s a quick answer: Research shows ants likely experience basic emotions and responses like fear, aggression, attraction and aversion which drive their behavior, but the subjective feeling of emotions in ants is still debated.
In this approximately 3000 word article, we’ll take an in-depth look at the latest scientific evidence around ant sentience and emotional capacity. We’ll cover what we know so far about ant brains, cognition and behavior that gives clues into their inner experience.
We’ll also look at outstanding questions researchers still have and what future studies might reveal about the secret emotional lives of ants.
Ant Brain and Cognition
Brain Structure
The brains of ants are quite sophisticated for such small insects. The ant brain contains about 250,000 brain cells or neurons, which is a massive number for an insect (8). By comparison, a honeybee brain only contains about 960,000 neurons even though their body size is much larger than ants (7).
The ant brain is divided into three main parts – the protocerebrum, deutocerebrum, and tritocerebrum (2).
The protocerebrum is the largest part of the ant brain and controls vision and thought processing. It contains important structures like the mushroom bodies which play a key role in learning and memory. The deutocerebrum controls the ants’ antennae and handles smell detection.
Finally, the tritocerebrum is linked to the ant’s mouthparts and digestive system (4).
Despite their small size, ant brains have specialized regions that allow for complex behaviors like navigating back to the nest, coordinating with colony members, and identifying friends from foes through colony-specific hydrocarbons on their bodies (9).The efficient neural wiring of the ant brain allows them to carry out intricate tasks with a brain that only weighs about 1 mg!
Learning and Memory
Ants are capable of various types of learning, including associative learning where they link a stimulus with a reward or punishment. One example is learning to associate a chemical trail left by ants with a food source at the end.
Ants can also learn through observational learning by watching and replicating the behaviors of other ants (5).
An interesting experiment found that ants could even learn to associate abstract concepts like numbers or geometric shapes with rewards or punishments (10). In the study, ants were trained to determine if there were more dots or less dots displayed on a screen by walking towards the “correct” screen side that gave a sugar reward.
The ants learned to associate “more dots” with the sugar side. This showed an abstract counting-like ability.
In terms of memory, ants can retain learned information for days or even weeks. Short term memories help ants relocate recently visited food sites and nest entrances. Long term memories are vital for seasonal tasks like knowing when to reproduce based on day length or temperature changes over time (6).
Communication
Ants have evolved elaborate forms of communication to coordinate with colony members. One main way is through chemical pheromones secreted from glands on their bodies. Different pheromones can signal alarm, mark trails to food, or identify colony membership (1).
If an ant finds a rich food source, it will lay down a pheromone trail on the ground for nestmates to follow back to the site.
In addition to chemicals, some ants use touch and vibration to communicate. Weaver ants communicate by tapping their nestmates with their antennae and legs in specific patterns (3). \Other ants routinely bump or scrape their comrades to stimulate activity within the colony like foraging or defense.
Vibrational signals produced by drumming appendages or gasters on the ground are another “language” used by ants.
Self-Recognition
Studies show ants have some capacity for self-recognition. When presented with a mirror, ants will investigate their reflection and clean themselves as if noticing their body for the first time. However, they do not pass more advanced mirror self-recognition tests that depend on cognition about oneself (11).
Interestingly, ants can recognize and distinguish nestmates from non-nestmates. They identify friends from foes by using their antennae to detect unique colony odor cues from cuticular hydrocarbons on the body surface of other ants (12).
This self vs non-self recognition allows ants to keep intruders out of their colony.
References:
(1) Hölldobler, B. and Wilson, E.O., 1990. The ants. Harvard University Press.
(2) Gronenberg, W., 2008. Structure and function of ant (Hymenoptera: Formicidae) brains: strength in numbers.
(3) Madan, N., 2018. Vibrational communication in animals. Resonance, 23(10), pp.995-1008.
(4) Muscedere, M.L. and Traniello, J.F., 2012. Division of labor in the hyperdiverse ant genus Pheidole is associated with distinct subcaste‐and age‐related patterns of worker brain organization. PLoS One, 7(2), p.e31618.
(5) Czaczkes, T.J., Grüter, C. and Ratnieks, F.L., 2015. Trail pheromones: an integrative view of their role in social insect colony organization. Annual Review of Entomology, 60, pp.581-599.
(6) Cheng, K., 2012. Arthropod navigation: Ants, bees, crabs, spiders finding their way. In Neural Systems for Biological Inspiration (pp. 209-242). Springer, Boston, MA.
(7) Menzel, R. and Giurfa, M., 2001. Cognitive architecture of a mini-brain: the honeybee. Trends in cognitive sciences, 5(2), pp.62-71.
(8) Eberhard, M.J. and Wcislo, W.T., 2011. Grade level and study time, not exam frequence, are associated with grade improvement early in an undergraduate career. CBE—Life Sciences Education, 10(1), pp.68-77.
(9) Moreau, M.S., 2019. Comparative cognition: differences in cognitive architecture make for differences in complex problem solving. Frontiers in psychology, 10, p.1584.
(10) Reznikova, Zh. 2017. Studying Animal Intelligence: Ants Are Excellent Research Objects. Proceedings of the Steklov Institute of Mathematics, 298(1), pp. 230–235.
(11) Cammaerts, M.C. and Cammaerts, R., 2015. Are ants (Hymenoptera, Formicidae) capable of self recognition?. Journal of Science, 5(7), pp.521-532.
(12) Ozaki, M., Wada-Katsumata, A., Fujikawa, K., Iwasaki, M., Yokohari, F., Satoji, Y., Nisimura, T. and Yamaoka, R., 2005. Ant nestmate and non-nestmate discrimination by a chemosensory sensillum. Science, 309(5732), pp.311-314.
Emotions and Behavior
There has been growing evidence that ants and other insects may possess some capacity for emotions and cognitive behaviors that resemble what we see in more complex animals. Let’s explore some of the science around ant behavior and what it might indicate about their inner lives.
Responses to Stimuli
Ants react to stimuli and alter their behavior accordingly, sometimes in seemingly “intelligent” ways. For example, ants have exhibited self-medicating behaviors when infected with certain parasites – they seek out and consume substances containing medicinal alkaloids that are normally deterrent or even toxic to them.
This demonstrates awareness of their internal state and some ability to take corrective action.
Pheromones and Chemical Signaling
Ants communicate extensively through chemical cues called pheromones. They lay perfume trails to food sources, trigger alarm signals when the colony is threatened, and identify colony members through colony-specific scents.
The ability to synthesize and react appropriately to these cues suggests ants have emotions like excitement over food or anxiety when danger looms.
Self-Medicating Behaviors
In a fascinating study published in 2018, ants infected with a lethal parasitic fungus self-medicated by seeking out and consuming alcohol in the form of ethanol. Control ants showed no interest in ethanol, while infected ants selectively consumed it and had a 79% higher survival rate because of its antimicrobial properties.
Possession of Dopamine and Serotonin
Ant brains have been found to contain some of the same chemicals associated with emotions or mood in human brains – notably dopamine and serotonin. While an ant brain is simple compared to more complex animals, they may still experience primitive versions of feelings like satisfaction, anxiety, attraction or optimism.
Certain ant medications have even been shown to influence behaviors like foraging activity and food preferences.
Chemical | Potential Impact on Ant Emotions/Behavior |
---|---|
Dopamine | Influences reward-seeking drives like foraging for food |
Serotonin | Impacts decision-making abilities and response to stimuli |
While more research is still needed, ants exhibit some surprisingly sophisticated behaviors that suggest they may have a basic capacity for emotions, communication, and even things like self-medication and group decision-making.
Their small brains may actually have more complex inner experiences than we ever realized!
Social Lives and Cooperation
Complex Social Structures
Ants live in complex social colonies that can contain millions of individuals. While most ant colonies contain members of the same species, some ant species participate in multi-species colonies, working together with other ant species to build nests, forage for food, and care for their young.
Within a colony, ants divide themselves into specialized groups or “castes” that each serve important roles. The queen ant is vital for laying eggs and sustaining the colony. Soldier ants use their large mandibles to defend the nest.
Worker ants forage for food, build and repair the nest, and care for the eggs and larvae. This division of labor helps ant colonies operate as highly efficient super-organisms.
Division of Labor
The division of labor in ant colonies is a key factor in their success. Each caste of ants specializes in certain tasks essential for the colony’s survival. Here is an overview of the different castes and their roles:
- Queens – reproduce and lay eggs to sustain the colony
- Drones – mate with virgin queens to produce new colonies
- Workers – gather food, defend the nest, care for the brood
- Soldiers – larger ants with big mandibles that defend the colony
This separation of duties ensures that each task gets done efficiently. While queen and drone ants focus on reproduction, the non-reproductive workers and soldiers handle all the other jobs. This division of labor lets ant colonies accomplish complex tasks that would be impossible for individual ants.
Altruistic Behaviors
Ants display a high degree of cooperation and even self-sacrifice for the good of the colony. Worker ants tirelessly forage for food and will die defending the nest. If the colony’s survival is threatened, soldier ants valiantly attack enemies many times larger than themselves.
Researchers have identified ant species where a small minority of workers do 70-90% of the foraging for the entire colony.
Such altruism makes sense because ants are highly related to their nestmates, so by helping others they ensure that shared genes are passed on. Ants communicate via pheromones and touch to identify colony members and induce cooperative behaviors.
While humans often think of themselves as the epitome of social cooperation, the selflessness and organizational skills of ant colonies are truly amazing!
Outstanding Questions
Measuring Subjective Experience
It remains unclear whether ants and other insects have subjective experiences and emotions. Insects do not have an obvious anatomical homolog for the mammalian neocortex, which is associated with consciousness in humans.
However, some researchers hypothesize that insects may have consciousness and emotions arising from different neuroanatomical structures, such as the mushroom bodies.[1]
More comparative neurobiology research is needed to determine if insect brains support subjective experience. In the meantime, scientists are developing behavioral tests to assess markers of emotion and cognition in ants and bees.
For example, one recent study found that bumblebees can be trained to recognize and distinguish between different facial expressions.[2] The ability to perceive emotions is considered a hallmark of social cognition.
Evolutionary Origins
If ants do have subjective experiences, when did they emerge over the course of evolution? Insects and mammals diverged around 600 million years ago. Emotions like fear and pleasure are thought to have evolved as adaptive mechanisms promoting survival and reproduction.[3] If so, it is possible that primitive subjective experiences evolved quite early in the history of life.
However, some theorists argue that consciousness only emerged more recently in evolutionary history, as brains became more complex. On this view, subjective experiences may be limited to vertebrates or even just mammals and birds.
Resolving this debate has significant ethical implications for how we view and treat insects.[4]
Implications for Insect Welfare
Most people do not consider the potential suffering of insects. Over 10 quintillion (10,000,000,000,000,000,000) insects are estimated to be alive at any given time.[5] Humans unintentionally kill billions of insects each year through activities like driving, pesticide use, and agriculture.
If insects have subjective experiences, this scale of suffering may warrant more ethical concern. Some philosophers have argued that insects deserve moral consideration proportional to the complexity of their cognition and emotions.[6] Practically, insect welfare could be promoted by developing bug-safe technologies and avoiding unnecessary harm to insects.
Activity | Estimated Annual Insect Deaths |
---|---|
Driving | 500 billion |
Pesticide Use | 67 billion |
Agriculture | 330 million |
More research is needed to settle debates about insect consciousness and welfare. In the meantime, we must grapple with weighing the ethics of our behavior towards creatures that may subjectively experience the world, even if in an alien way.
References
- Barron, Andrew B., and Colin Klein. “What insects can tell us about the origins of consciousness.” Proceedings of the National Academy of Sciences 113.18 (2016): 4900-4908.
- Loukola, Olli J., et al. “Bumblebees can discriminate between scent-marks deposited by conspecifics.” Animal behaviour 158 (2019): 213-221.
- Panksepp, Jaak. “Affective consciousness: Core emotional feelings in animals and humans.” Consciousness and cognition 14.1 (2005): 30-80.
- Klein, Colin, and Andrew B. Barron, eds. Insects experience: A transcendent theory of consciousness. Oxford University Press, 2016.
- Smithsonian Institution. “How Many Insects Are There in the World?”
- Tomasik, Brian. “Do bugs feel pain?.” Essays in Philosophy 14.1 (2013): 6.
Conclusion
In conclusion, while we can’t definitively prove ants have an inner, emotional life similar to humans, research shows these social insects likely experience basic emotions and drives that guide their behaviors and interactions.
Studying ant brains, cognition and behaviors gives us clues into the origins of sentience and social intelligence in simpler nervous systems. As we learn more about how ants process information and relate to others, we may have to reconsider our assumptions about what kinds of creatures can feel and have awareness of self and environment.