Graduate Research Course
Cetacean Biophysics
Dolphins, whales, and porpoises — from hydrodynamic superefficiency to 170-decibel sonar, from deep diving physiology to the sophisticated cognition of Earth's largest brains.
Key Equations of Cetacean Biophysics
Hydrodynamic Drag
\( D = \tfrac{1}{2}\rho v^2 C_D A \)
Diving Bradycardia
\( HR(t) = HR_0 \, e^{-t/\tau_{dive}} \)
Click Rate (Echo Timing)
\( f_{click} = c/(2\, d_{target}) \)
Bottlenose Sonar Band
\( f \sim 120\,\text{kHz},\ \lambda \sim 1.25\,\text{cm} \)
Sound Speed (Seawater)
\( c = \sqrt{B/\rho} \approx 1500\,\text{m/s} \)
Whale Song SPL
\( \text{SPL} = 20\,\log_{10}(p/p_{ref}) \)
Strouhal Number
\( St = fA/U,\ \ St^* \approx 0.25\text{\u2013}0.35 \)
Encephalization Quotient
\( EQ = M_{brain}/(0.12\, M_{body}^{0.67}) \)
About This Course
Cetaceans — dolphins, porpoises, and whales — are mammals that returned to the sea roughly 50 million years ago. In that reversal they reinvented almost every feature of tetrapod biology: limbs became flippers and flukes, the nose migrated to the top of the head, the skin shed its hair and thickened into blubber, and the respiratory and cardiovascular systems were re-engineered for breath-hold diving to nearly 3 kilometers depth. They are also the only group of non-primates with brains rivaling our own, and the only group to have independently evolved a biological sonar system of extraordinary sophistication.
This course treats cetacean biology as physics. We derive the drag coefficients of dolphins from first-principles boundary-layer theory, compute the energetics of lunge-feeding blue whales, simulate the acoustic focusing of the sperm whale melon, and analyze the population dynamics of endangered right whales. Along the way we touch on bioacoustics, fluid dynamics, diving physiology, cognitive neuroscience, and conservation biology.
Cross-links to our Ocean Biodiversity, Avian Biophysics, Feline Biophysics, and Bee Biophysics courses connect comparative bioacoustics, locomotion, cognition, and conservation across the animal kingdom.
Nine Modules
M0
Evolution & Anatomy
From artiodactyl ancestors (Pakicetus) to modern Odontoceti and Mysticeti. Body plan, melon, blowhole, and the largest brain on Earth.
M1
Hydrodynamics & Swimming
Gray’s Paradox, compliant skin, lunate fluke propulsion, Strouhal optimum 0.25–0.35, and Lighthill’s elongated body theory.
M2
Deep Diving Physiology
Sperm whale 2,250 m dives, mammalian dive response, bradycardia, lung collapse, myoglobin stores, and aerobic dive limits.
M3
Echolocation & Sonar
Phonic lips, melon acoustic focusing, 230 dB sperm whale clicks, target strength, inter-click intervals, and the buzz phase.
M4
Whale Song & Communication
Humpback song structure, cultural transmission, SOFAR channel propagation, signature whistles, and noise pollution impacts.
M5
Baleen & Filter Feeding
Keratin plates, lunge feeding energetics, 80,000 L engulfment, filtration scaling, and why blue whales are Earth’s largest animals.
M6
Cognition & Social Behavior
Mirror self-recognition, tool use, orca dialects, matrilineal pods, unihemispheric sleep, and spindle neurons.
M7
Migration & Navigation
Gray whale 22,000 km round trip, magnetic sensing, acoustic landmarks, energetic costs, and mass-stranding phenomena.
M8
Conservation & Threats
Historical whaling, right whale critical status, vaquita crisis, sonar trauma, ship strikes, and population viability analysis.
Recommended Textbooks
- [1] Reynolds, J.E. & Rommel, S.A. (eds.) (1999). Biology of Marine Mammals. Smithsonian Institution Press.
- [2] Berta, A., Sumich, J.L. & Kovacs, K.M. (2015). Marine Mammals: Evolutionary Biology, 3rd ed. Academic Press.
- [3] Würsig, B., Thewissen, J.G.M. & Kovacs, K.M. (eds.) (2018). Encyclopedia of Marine Mammals, 3rd ed. Academic Press.
- [4] Au, W.W.L. (1993). The Sonar of Dolphins. Springer.
- [5] Kooyman, G.L. (1989). Diverse Divers: Physiology and Behavior. Springer-Verlag.
- [6] Thewissen, J.G.M. (2014). The Walking Whales: From Land to Water in Eight Million Years. University of California Press.
- [7] Whitehead, H. & Rendell, L. (2015). The Cultural Lives of Whales and Dolphins. University of Chicago Press.