Gray Whale Population Abundance

To understand how the eastern North Pacific gray whales population is thriving – having recovered from low numbers – and is responding to changes in the environment, we study the abundance of the over time.

West Coast

Gray whale breaching.

What We Do

Monitoring gray whale population abundance is one of two focus areas for gray whale research at NOAA Fisheries. We estimate the abundance (i.e. the number of whales) of the eastern North Pacific gray whale population by conducting shore-based surveys overlapping with the timing of the southward migration from the Arctic to Mexico. Surveys of this type began in 1967 and take place at our Granite Canyon field station south of Monterrey, California. Since the mid-2000s we have conducted surveys for two consecutive years in every five year period.

We combine new and established methods to count southbound gray whales passing Granite Canyon from December through February. Combining multiple observation methods increases the precision and accuracy of our estimates.

Visual Surveys: The most common marine mammal survey method is also one of the best. Taking three-hour shifts, visual observers watch through high-powered binoculars for the telltale “blows” of gray whales. After spotting whales and recording their coordinates, the observers are then able to track the whales as they migrate south using a custom-built computer program.

Observers on watch for gray whales at Granite Canyon study site. Photo: NOAA Fisheries

Infrared Cameras: We have also used infrared video cameras to count and track whales at Granite Canyon. These cameras point at the ocean, recording the view in terms of temperature. The warm breath of a gray whale exhalation stands out against the cold ocean surface. The thermal contrasts are distinctive enough that computers can scan the video and count the exhalations automatically. These cameras can detect whales passing at night, when the visual observers cannot.

Thermal imaging cameras used for gray whale abundance survey at Granite Canyon, CA. Photo: NOAA Fisheries

The eastern North Pacific gray whale population migrates south from summer feeding areas in high latitudes to protected lagoons on the coast of Northern Baja Mexico between November and February. The migration past the Granite Canyon field station generally peaks in mid-January. Some pregnant females give birth after arriving at their winter areas in Mexico, whereas others give birth during the migration south. The whales do most of their feeding for the year in the summer, and feed only opportunistically during the migration or while overwintering.

Current Population Size

In 2016 we estimated the size of the eastern North Pacific gray whale population to be nearly 27,000. We conducted our most recent population abundance survey in winter 2019/2020, and we are currently analyzing the data.

Population abundance estimates for the eastern North Pacific gray whale population from 1994 to 2016 (the most recently published estimate).

New Technology: Drones

In 2020 we began testing the feasibility of using fixed-wing drones to enhance our ability to count migrating gray whales. During the winter migration, we launched a small drone from Granite Canyon. The drone flies a pre-programmed pattern, continuously collecting photographs over a roughly 300-meter-wide swath of ocean surface. Computer-based artificial intelligence is being developed to efficiently detect whales in the hundreds of images typically collected during a single drone flight.

The small drone, or unmanned aerial vehicle, is called the FireFly 6 Pro. It can sample large areas by flying up to 34 mph. NOAA’s Unmanned Aerial Systems Program office supports this research.

Potential applications for this new technology include:

Estimating densities of whales in sensitive areas such as shipping lanes and in proximity to marine energy development areas.
Matching estimates of the number of passing whales with measurements of fishing gear to assess the risk of entanglement.

About Our Team

This project is spearheaded by Dave Weller, a research wildlife biologist. He leads our studies on gray whales and also works with the International Whaling Commission and the International Union for Conservation of Nature (IUCN) on the conservation of whale populations world-wide.

Publications

Sullivan, K., Fennell, M., Perryman, W. and Weller, D. 2020. Automated detection, tracking, and counting of gray whales. Proc. SPIE 11409. Thermosense: Thermal Infrared Applications XLII, 1140906 (23 April 2020); doi: 10.1117/12.2567187

Guazzo, R.A., Weller, D.W., Europe, H.M. et al. 2019. Migrating eastern North Pacific gray whale call and blow rates estimated from acoustic recordings, infrared camera video, and visual sightings. Scientific Reports 9, 12617.

Durban, J.W., Weller, D.W. and Perryman, W.L. 2017. Gray whale abundance estimates from shore-based counts off California in 2014/2015 and 2015/2016. Paper SC/A17/GW06 presented to the Scientific Committee of the International Whaling Commission, May 2017

Durban, J.W., D.W. Weller, A.R. Lang, and W.L. Perryman. 2015. Estimating gray whale abundance from shore-based counts using a multilevel Bayesian model. Journal of Cetacean Research and Management 15:61-68.

Laake, J.L., Punt, A.E., Hobbs, R., Ferguson, M., Rugh, D. and Breiwick, J. 2012. Gray whale southbound migration surveys 1967-2006: An integrated re-analysis. J. Cetacean Res. Manage. 12:287-306.

Durban, J., D. Weller, A. Lang, and W. Perryman. 2011. Abundance indices of eastern North Pacific gray whales from southbound migration counts, 2007-2011. Paper SC/63/BRG7 presented to the International Whaling Commission, Scientific Committee (SC63 meeting, Tromso, Norway, 2011). 4 p.

Durban, J., A. Lang, D. Weller, D. Rugh, R. Hobbs, and W. Perryman. 2010. Comparing two methods of shore-based counts of eastern North Pacific gray whales. Paper SC/62/BRG8 presented to the International Whaling Commission, Scientific Committee (SC62 meeting, Agadir, Morocco, 2010). 6 p.