Don’t flip out: whales jump for more than one porpoise

Have you ever asked, “Why do whales jump?” Well, there’s not a precise answer, but we will try to answer it in this post, so keep reading.

If you’ve ever played in shallow water, you might have used your feet to push off the bottom and pretend to jump out of the water like a whale or dolphin. While doing so, you may have noticed that it’s difficult to get your entire body out of the water. Why is this? For one, just like when you jump on land, gravity is working against you. Secondly, water is 800 times denser than air, causing a lot of drag. You have to put in a lot of effort to work against these forces and break the water’s surface. Now imagine how much effort it takes for a whale weighing several thousand pounds to jump out of the water. Why would they perform such energetically expensive activities?

Jumping with purpose – or should I say porpoise.

Small toothed whales, like dolphins, are more likely to porpoise. Porpoising is a form of jumping defined as high-speed jumping alternated with periods of swimming close to the surface. Because air is less dense than water, the act of jumping while traveling at high speeds expends less energy than staying in the water. Porpoising is most often connected to acts of hunting when the rate is of the essence. Check out this video of a pod porpoising.

Breaching for the stars

On the other hand, large whales – like a humpback – are more likely to breach. A breach occurs when most or all of a whale’s body emerges from the water. Whales do this by diving down to a sufficient depth, and then, using only their flukes (or tails), they swim toward the surface. While doing so, they need to gather enough speed to propel themselves out of the water. A humpback whale may reach up to 28 km/hr (~17 miles/hr) to fully emerge from the water.

You can imagine such a feat requires a lot of effort to achieve. Researchers found that a single complete breach (a jump where greater than 40% of the whale was above water) can cost the equivalent energy required for a 60 kg (132 lb.) runner to complete a marathon. So why do it?

Communication is key

There are many reasons why a whale might breach. One is to pass information between conspecifics (members of the same species). Humpbacks have notably been seen breaching more often when groups of whales are coming together or separating. We cannot be sure what they are communicating exactly – a salutation or display of social status.

Despite how peaceful many find the ocean, it is a bustling and loud environment. The sea becomes even louder in times of storms. Therefore, it is essential to have inventive strategies to communicate with others. Though whales can make vocal sounds to communicate, those sounds can be lost during times of louder ambient noise. Like trying to call your friend across a crowded room. Instead of continuing to yell, you might try a new strategy. Maybe even jumping up and down. Scientists have observed whales breaching more frequently during times of increased surface wind compared to calmer weather. The sound created when their bodies smash back onto the surface might break through the noise of waves crashing or boat propellers.

Jumping for love

As stated previously, breaching is an energetically costly activity. Scientists have noticed that breaching frequency increases when migratory whales (such as humpbacks, grey, and right whales) reach their winter breeding grounds. Breaching is particularly costly at breeding grounds as whales are not feeding for months at a time. Additionally, the energy expended increases dramatically as a whale’s size increases. A single 8.5-second breach by a 46,000 kg (101,000 lb.) whale can produce power equivalent to the maximum pulling power of 25 draft horses. For reference, a single draft horse can pull 4,000kg (8,000 lbs).

So, again, why do it? As these breaches are occurring more often in the breeding grounds, they could be displays of fitness. Fitness refers to the ability to survive, find a mate, and produce offspring. During courtship, male fitness is evaluated by females, also referred to as mate choice. One way to showcase fitness, often, is extravagant mating displays. In this case, only those with high fitness could expend the energy required to breach. That’s how you get the ladies in whales’ societies…

Pest Control

You’d think being a nomad without a home would allow whales the peace of not dealing with pests. Instead, some ocean animals have made the whale’s body their home. Whale lice are one such common pest; they are not actual lice but rather small crustaceans. They live in the eyes, nostrils, and skin lesions of whales — fun fact: a louse spends its whole life cycle attached to a single whale. The species of lice found on a whale can be species-dependent or even sex-dependent. They feed primarily on algae that may grow on the whale and flaking skin. One whale can have several thousand lice living on them. The lice do not hurt the whale but may cause irritation or discomfort. In this case, breaching and the impact of hitting the water’s surface again could dislodge some whale lice.

In addition to lice, whales have often seen sporting barnacles. Unlike barnacles, you may see while tide-pooling onshore, these barnacles are specific to whales. Their lifestyle is similar to other barnacles. They start their life drifting through the ocean (planktonic phase). Eventually, a chemical cue produced by the host substrate (in this case, a whale) begins the barnacle’s transformation into its sessile phase. Once it has settled on the whale, it secures itself and spends the rest of its life using cirri to catch food that flows past the whale.

This relationship between whale and barnacle is generally commensal. There is no cost to the whale while the barnacle benefits. It can become parasitic if too many barnacles settle on an individual and increase the drag the host experiences. Therefore, the act of breaching could also aid in dislodging a few unwanted barnacles as well.

In the end, why do whales jump?

So, the answer to “Why do whales jump?” is that it’s situational. As discussed, it depends on the type of whale. Smaller whales tend to porpoise to aid in hunting. Larger, social whales tend to jump to communicate. Then, some whales may jump to rid themselves of pesky freeloaders. There is, however, the last possibility that hasn’t been covered. The definitive answer to the question is… we don’t know – yet!

Scientists have come up with these hypotheses and found evidence to support them. But there’s always the possibility there’s another reason entirely. We cannot fully understand the importance of jumping until we fully explore why whales do it. Therefore, further research and new voices in the field of marine mammal science are a necessity.  

Citations and further reading

• D. Weihs, Dynamics of Dolphin Porpoising Revisited, Integrative and Comparative Biology, Volume 42, Issue 5, November 2002, Pages 1071–1078, https://doi.org/10.1093/icb/42.5.1071
• Dunlop Rebecca A., Cato Douglas H., and Noad Michael J. 2010. Your attention please: increasing ambient noise levels elicits a change in communication behaviour in humpback whales (Megaptera novaeangliae)Proc. R. Soc. B.2772521–2529, http://doi.org/10.1098/rspb.2009.2319
• Margolis, L., 1955. Notes on the morphology, taxonomy and synonymy of several species of whale-lice (Cyamidae: Amphipoda). Journal of the Fisheries Board of Canada, 12(1), pp.121-133.
• Segre, Paolo S et al. “Energetic and physical limitations on the breaching performance of large whales.” eLife vol. 9 e51760. 11 Mar. 2020, doi:10.7554/eLife.51760
• http://whitelab.biology.dal.ca/hw/scientificamerican0385-84.pdf
  https://www.mikesevernsdiving.com/the-life-and-times-of-a-humpback-whale-barnacle/

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