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Understanding the Best Conditions for Rice’s Whales

May 09, 2024

NOAA Fisheries research identifies what makes the best conditions for Rice’s whale habitat, and predicts where else these whales occur.

Rice’s whale at the surface. A Rice’s whale in the Gulf of Mexico. Permit #14450. Credit: NOAA Fisheries/Laura Dias

NOAA Fisheries has been on a quest to find what conditions make the best habitat for the endangered Rice’s whale. A team of scientists from the Southeast Fisheries Science Center published research findings in the journal Endangered Species Research that characterize their habitat. The findings were based on whale surveys and oceanographic data.

The study found the oceanographic conditions important for Rice’s whale habitat are primarily located along the outer edge of the continental shelf around the Gulf of Mexico. Here, conditions promote high food productivity and likely support optimal feeding habitat for the whales.

What Is the Optimal Habitat for Rice’s Whale?

First, the team analyzed the oceanographic features of locations where Rice’s whales have been seen over 16 years to identify their habitat characteristics. The whales have been primarily observed in the northern Gulf of Mexico in areas with:

  • Water depth between 188 to 326 meters
  • Chlorophyll-a concentrations (a proxy for primary production) greater than 0.1 milligrams per cubic meter
  • Bottom temperature between 12.4 to 16.7 degrees Celsius
  • Bottom salinity between 35.67 to 36.23 practical salinity units

These features coincide in areas where cold, salty water is driven up along the continental shelf break (a process called “upwelling”). These areas are also influenced by seasonal inputs of high-productivity surface water from coastal sources, particularly fresh water at the surface from the Mississippi River. These conditions may offer optimal feeding opportunities for Rice’s whales to survive and reproduce. 

The fin of a known Rice's whale in the photo catalog.
A Rice’s whale dorsal fin observed in the Gulf of Mexico. Permit #21938. Credit: NOAA Fisheries/Laura Dias

Where Else Could They Be?

The team then used this information to develop a map of where these conditions overlap, and where else Rice’s whales would also be predicted to be.

The model indicated that areas in Mexican waters of the Gulf of Mexico might also have habitat for Rice’s whales. This prediction is also supported by recent detections of Rice’s whale calls in the area. The predicted habitat also includes areas where we know Rice’s whales occur. This includes areas off the coasts of Louisiana and Texas where a Rice’s whale sighting has been confirmed, and where Rice’s whale calls have been detected year-round with acoustic instruments. This is in addition to the known core habitat in the northeastern Gulf of Mexico where Rice’s whales have been observed most frequently. 

“These results, along with other recent research, provide additional evidence that these whales are living in a much broader geographic area than previously thought,” said Lance Garrison, senior researcher, and lead author. “These kinds of studies are especially important for understanding the distribution of cryptic species like Rice’s whales that are challenging to observe visually.”

Based on visual observations and the predictive model, the study indicates that Rice’s whale densities across the core habitat may shift seasonally with changes in productivity and food sources. In spring, Rice’s whales tend to be more concentrated in the northern portion of the core habitat and distributed farther south in the summer and fall.

A map of the Gulf of Mexico shows colored areas indicating Rice's whale average density, concentrated around the shelf break with highest densities in the northeastern Gulf of Mexico
Predicted average Rice’s whale density (whales/cell) for years 2015-2019 (Garrison et al. 2024). Credit: NOAA Fisheries

What This Means for Rice’s Whales and Critical Habitat

The Rice’s whale is listed as an endangered species under the Endangered Species Act and is protected under the Marine Mammal Protection Act. They are also a part of NOAA Fisheries’ Species in the Spotlight initiative, which brings greater attention and leverages partnerships and resources to save this highly at-risk species. These findings further inform the identification of Rice’s whale critical habitat. NOAA Fisheries proposed critical habitat for Rice’s whales in July 2023. The specific area proposed for designation as critical habitat encompasses approximately 28,270 square miles of continental shelf and slope-associated waters between the 100- and 400-meter isobaths in the Gulf of Mexico. 

This study also highlights the importance of continuing research to better understand Rice’s whale reproductive and foraging habitat and needs. We continue to investigate different aspects of the ecology and behavior of the whales to aid population recovery. This research focuses on:

  • Studying their trophic interactions and habitat requirements
  • Conducting stock assessments
  • Observing whales on vessel-based visual surveys
  • Leading acoustic studies to better understand Rice’s whale distribution, movement, and behavior
  • Testing environmental DNA (eDNA) as a new method to detect Rice’s whales 

“These findings are really exciting and add to the increasing body of knowledge we have on this endangered species and will help guide future research,” added Garrison. “We still have a lot more work to do to get a good handle on what this means for the population and their recovery.”

Help Keep Whales Safe

Boaters, anglers, and others should report all suspected sightings of Rice’s whales by calling (877) WHALE-HELP (877-942-5343). This information is valuable for helping us learn more about this endangered species. You can also use this same number to report any marine mammal that is in distress, injured or dead.

Harassing, harming, pursuing, wounding, killing, capturing, or collecting protected marine mammals is prohibited by the Endangered Species Act and Marine Mammal Protection Act. Observe marine animals from a safe and respectful distance—at least 100 yards (the length of a football field)—and never approach or touch them.

Last updated by Southeast Fisheries Science Center on May 13, 2024