Dolphins are some of the most intelligent creatures on our planet, yet we still don’t know a lot about them. One question many biologists, or just average marine enthusiasts, have is whether dolphins can smell. This blog post aims to answer this question and provide readers and scientists alike with a deeper understanding of these majestic sea creatures.
Sensory Adaptations for Marine Animals and Their Use
Marine animals have many types of sensory systems that vary between species and are crucial to their survival success. Some sensory receptors present in aquatic animals include passive listening, haptosence, and the lateral line system. Echolocation is also a significant sensory adaptation in odontocete cetaceans.
Variability in Sensory Adaptations Across Habitats
The degree to which each species relies on each sensory adaptation depends on its general life strategy. Additionally, the habitat they tend to live in, such as open ocean versus coastal waters, plays a significant role. The differences between shallow and deep water, and between clear and turbid water, also influence their sensory adaptations.
Sensory perception helps an individual detect objects in their physical environment, including food, prey, and predators. It also helps identify communication signals and discern social partners. For example, auditory senses are relatively well-developed in dolphins and whales so that they
can listen for signals from other members of their pod or potential mates, as well as potential prey. Further, seals and sea lions have a very well-developed haptosense. This is inferred via long, sensitive “whiskers” on their face, which allow them to detect disturbances in the water.
Echolocation is also a well-known and widely appreciated adaptation that many animals use to detect prey and navigate their environment. This form of sensory reception is highly fascinating. It demonstrates one of the many inconceivable evolutionary adaptations mammals have undergone over the millions of years since they re-entered the aquatic environments. Echolocation involves the emission of brief sound pulses, or clicks, and then listening for the echoes that bounce back to create an auditory map of their environment.
Olfactory of Marine Mammals
So, how do marine animals smell? Well, it is a bit different for aquatic animals than it is for terrestrial organisms. In terrestrial organisms, airborne odors dissolve in the mucus lining the nasal cavity and bind to specialized proteins that transmit signals to the brain via Cranial Nerve I (CN I). This allows for smelling. However, CN I also appears to be active in response to waterborne stimuli, demonstrating that the sensation of smell is possible underwater for some species. Since water is denser than air, it can carry chemicals farther than air can, allowing chemical stimuli (smells) to travel over great distances.
Some examples of marine animals capable of smell include porpoises, mysticetes, cartilaginous fishes, and many other organisms we may not have even discovered yet! However, mysticetes are interested in the fact that they can detect smell only in the air, not in the water. This means their olfactory systems are not very useful during daily activities, but they must be used if they wish to smell.
And of course, sharks have a very acute sense of smell, enabling them to track down prey from hundreds of meters away. The chemicals released by decomposing whale carcasses or by fish chum can therefore be detected by sharks, indicating that a meal is available. Cartilaginous fish have two special organs on their head that can sense chemicals in the water, where water flows into the fish’s nose.
As the fish moves forward, the water passing through its nose creates a difference in pressure,
which helps it detect smells in the water.
Chemo-sensory in Dolphins: Do Dolphins Actually Smell?
Cetaceans have lost a significant number of their olfactory receptors over the course of evolution, and odontocetes in particular have seen the most critical loss of these sense organs, including the olfactory tract, bulb, and CN I. So, to put it simply, dolphins can’t smell in the same capacity that cartilaginous fish can smell waterborne odors, but they do have their own mechanism for interpreting these smells.
Gustation in Dolphins: How Dolphins Taste
Dolphins have a third chemical sense, the vomeronasal organ, located at the base of the nose. Although its ducts open behind the incisors in the mouth, the organ can sense stimuli on the palate and essentially “taste” these smells via impulses transmitted via CN V from the oral cavity to the brain. This perception is now referred to as quasi-olfaction and may offer the missing link researchers have been seeking in dolphin chemosensory reception.
Research has shown that dolphins can interpret (or taste) sour, bitter, and salty flavors, enabling them to detect various chemicals in the water released by their prey, predators, or companions.
(such as urine and feces). Further, dolphins have been shown to be capable of discriminating between different flavors and approaching a preferred food source, which is another example of “tasting the smells”. It is also probable that dolphins can detect such chemicals and flavors only at short range, making them useful only in close-range situations rather than at longer distances.
Conclusion
In conclusion, the answer to whether dolphins can smell is not a clear-cut, definitive yes or no. Instead, it is a highly complex and poorly understood area of marine research that requires further investigation to obtain solid data. What we do know is that where dolphins lack in their olfactory senses, they make up for it in their oral senses. The sensory system of these majestic creatures continues to fascinate us, and as technology and research advance, we hope to uncover more answers about our aquatic friends.
References
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- Can sharks really smell a drop of blood a mile away? Ocean First Institute. (2023). Retrieved on May 8, 2023, from https://www.oceanfirstinstitute.org/what-we-do/research/citizen-science-project/
- Clark, S. (2016, August 21). The Beach Bums of the Galapagos. In Darwin’s footsteps. Retrieved on May 8, 2023, from http://darwinsfootsteps.com/the-beach-bums-of-the-galapagos/#prettyPhoto
- Kishida, T., Thewissen, J. G. M., Hayakawa, T., Imai, H., & Agata, K. (2015). Aquatic adaptation and the evolution of smell and taste in whales. Zoological Letters, 1(1). https://doi.org/10.1186/s40851-014-0002-z
- Klimley, A. P. (2012). Genetics of sharks, Skates, and Rays. Biology of Sharks and Their Relatives, 503–520. https://doi.org/10.1201/b11867-25
- Kremers, D., Célérier, A., Schaal, B., Campagna, S., Trabalon, M., Böye, M., Hausberger, M., & Lemasson, A. (2016). Sensory perception in cetaceans: Part II—promising experimental approaches to study chemoreception in dolphins. Frontiers in Ecology and Evolution, 4. https://doi.org/10.3389/fevo.2016.00050
- Kremers, D., Célérier, A., Schaal, B., Campagna, S., Trabalon, M., Böye, M., Hausberger, M., & Lemasson, A. (2016). Sensory perception in cetaceans: Part I—current knowledge about dolphin senses as a representative species. Frontiers in Ecology and Evolution, 4. https://doi.org/10.3389/fevo.2016.00049
- Lubis , M. Z. (2016). Behavior and Echolocation of Male Indo-Pacific Bottlenose Dolphins (pp. 21-27). LAP LAMBERT Academic Publishing. https://doi.org/10.13140/RG.2.1.4603.7520
- Perrin, W. F., Würsig Bernd G., & Thewissen, J. G. M. (2002). Encyclopedia of Marine Mammals (second). Academic Press.
- What do bottlenose dolphins eat? American Oceans. (2021, February 18). Retrieved on May 8, 2023, from https://www.americanoceans.org/facts/what-do-bottlenose-dolphins-eat/
