An Incredible Journey: The Gray Whale

Key Vocab:

• Migration- Seasonal movement of animals from one location to another

• Stranding- When a marine animal is found  dead, either on the beach or floating in the water, or are found alive on the beach and are unable to return to the water.

• Emaciation - The state of being abnormally thin or weak.

• Metabolic- chemical reactions in the body's cells that change food into energy

Every year gray whales migrate an average of 10,000 miles from the waters of the Arctic to the warm waters of Baja California, Mexico (Oceanic Society, n.d.).

Their migration is one of the largest movements of mammals that is currently known (Stone et al., 1990)!

One of the main threats that gray whales face during migration is from vessels and ships. Vessel strikes (when a ship hits a whale) are dangerous to gray whales because often times ship captains do not see gray whales resting at the surface. Gray whales can also appear out of no where when they are feeding or traveling. If ships/vessels are going too fast, a strike can seriously injure or kill a gray whale (Sumich, 2014).

Climate change poses a threat to gray whales as well. Gray whales are traveling farther and farther north to reach proper feeding grounds (Scripps Institution of Oceanography, 2009). With these longer migration routes, gray whales are finding more locations along their path to feed (Sumich, 2014). Often times this draws gray whales closer to shore and into the path of fishing equipment. Entanglement in fishing gear is a threat to gray whales because as they become entangled they use more energy for their every day life activities (feeding, traveling, etc.), until they eventually die of exhaustion or drown.

Migration not only comes at a high metabolic cost (Corkeron, 1999), but it also exposes gray whales to threats that they otherwise may not face. So if they face many so threats along the way, why migrate?

Rich Seas Up North

The reason gray whales spend their time and energy getting to the Artic is clear- they feed on the nutrient rich waters of the Artic. Their diet primarily consists of amphipods, phyto and zoo plankton (Corkeron, 1999).

The warming waters of the Arctic affects not only the animals that reside year round in the Arctic, but also animals that travel to there for feeding and depend on the ocean food webs supported by the cold water and ice. With climbing temperatures, polar ice has begun melting ice that in the past has been impassible, this increases the competition for food, including the crustaceans, plankton, and mollusks that gray whales commonly feed on (Scripps Institution of Oceanography, 2009). Gray whales depend on the dense beds of prey that are exposed when sea ice melts in the summer. The ice essentially protects the prey from other whale and marine species while it is frozen and impassible (Sumich, 2014). When the sea ice melting patterns are altered, this causes the gray whale to have more competition for that food. In turn, the gray whales are forced to travel farther north or stay in the Arctic longer than usual to get the nutrients that are needed for their survival as they prepare to make the 10,000 mile travel down south (Sumich, 2014).

Calm Waters Down South

The Gray Whale's evolutionary reasoning for traveling so far to breed/calve in the southern waters is less clear, as these waters tend to be nutrient poor compared to the waters of the arctic. Corkeron (1999) proposes the theory of a need for calm waters to feed the calves during the sensitive first few weeks of life and avoidance of predators such as killer whales that tend to go after young calves. Watch the video to see a mother with her calf in the calm waters of Baja California.

Interesting fact: A 2022 study found elevated levels of cortisol (stress hormone) in the blubber of lactating (milking) mother gray whales and their calves. This could indicate that mother gray whales and their calves are more susceptible to stressors than other marine animals. These stressors include natural stressors such as predators, but also include human stressors such as increased ship traffic (Melica et al., 2022). Could future reproductive success be in jeopardy if stressors continue to increase?

Gray whales are the most common species of whale that become stranded on the West Coast (King 5 Staff, 2023). Since 2019, there has been a greater number of gray whale strandings on the west coast along the gray whale migration route, which has been officially declared an Unusual Mortality Event. An Unusual Mortality Event is defined by the Marine Mammal Protection Act as “a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response” (NOAA Fisheries, N.D.).

The reasoning for these increased strandings is not immediately clear, however it is found that  emaciation  is often a factor. Gray whales that are suffering emaciation are more likely to hang out at the surface resting, which increases their likelihood of a ship strike. Explore the map below to find your home and the whale strandings that have occurred since 2019. Then explore the live ship map to see the density of vessels in your area.

A study done by Silber et al. (2021) found that gray whales are exposed to vessel strikes throughout their migration journey north bound and south bound, specifically along inter-continental trade routes and in areas of high commercial fishing. They also found that the West coast of the United States, along with areas in Russia, the Bering Sea, and Gulf of Alaska, were at an elevated vessel strike risk due to whale migration patterns and vessel traffic patterns coinciding compared to other areas.

There are several measures that can be taken in order to reduce vessel strikes of whales. NOAA Fisheries recommends the following:

• Vessel speed restrictions, especially at times of the year when gray whales are known to be in the area.
• Establishing recommended vessel routes and entries to ports that reduce time in high density gray whale areas.
• Creating awareness among vessel and watercraft operators of the dangers of whale strikes and alert operators to safe boating practices when whales are present.
• Creating a reporting system for ships when they enter high whale density zones, ships could receive current information of current whale sightings in the area before entering and alerted to whale-safe boating practices

What can you do to help gray Whales? Why do you think helping Gray Whales is important?

Choose a person from the list below, write a letter describing three things they can do to help gray whales?

-Your local congressman -A ship captain -A community member

Having trouble getting started?

 Click here  for an organizer to help you plan your writing and sentence stems to get you started.

See examples from real 4th graders here: A local congressman,  a ship captain , a community member.

References:

Corkeron, P. J. (1999). Why do baleen whales migrate? Marine Mammal Science, 15(4), 1228-1245

Melica, V., Atkinson, S., Calambokidis, J., Gendron, D., Lang, A., & Scordino, J. (2022). Naturally stressed? Glucocorticoid profiles in blubber of blue and gray whales in response to life history parameters. Marine Mammal Science. 

NOAA Fisheries. (n.d.). Understanding marine wildlife stranding and response. https://www.fisheries.noaa.gov/insight/understanding-marine-wildlife-stranding-and-response

NOAA Fisheries. (n.d.). Understanding vessel strikes.  https://www.fisheries.noaa.gov/insight/understanding-vessel-strikes 

Scripps Institution of Oceanography. (2009, February 1). Climate change and Gray Whales. https://scripps.ucsd.edu/news/climate-change-and-gray-whales#:~:text=As%20a%20result%2C%20gray%20whales,in%20polar%20waters%20during%20winter.

Silber, G. K., Weller, D. W., Reeves, R. R., Adams, J. D., & Moores, T. J. (2021). Co-occurrence of gray whales and vessel traffic in the North Pacific Ocean. Endangered Species Research, 44, 177–201. 

Sumich, J. (2014) E. robustus: The biology and human history of grey whales. Whale Cove Marine Education

Townsel, A. (2022, March 1). The Gray Whale Migration in California and beyond. Oceanic Society. https://www.oceanicsociety.org/resources/the-gray-whale-migration-in-california-and-beyond/