Underwater mics and machine learning aid right whale conservation
Cornell University
ITHACA, N.Y. –Using underwater microphones and machine learning (ML), Cornell University researchers have developed a new method to estimate North Atlantic right whale numbers — offering a potentially safer and more cost-effective way to monitor this critically endangered species.
Their study, published in Endangered Species Research, demonstrates how microphones combined with ML and traditional aerial survey methods can help track right whale populations in Cape Cod Bay, a crucial feeding ground where the whales gather each spring.
To track this endangered species, researchers rely on costly and dangerous surveys by airplanes, or use sound recordings to identify their presence, or absence.
“Using sound recordings to monitor whale populations isn’t new,” said lead author Marissa Garcia of the Cornell Lab of Ornithology’s K. Lisa Yang Center for Conservation Bioacoustics. “What makes our study unique is that we were able to take those recordings and go beyond getting information on the presence or absence of whales to getting an approximate number of whales in an area.”
The team set out an array of marine autonomous recording units (MARU) across Cape Cod Bay to capture right whale sounds.
Following deployment of the MARUs, the team trained, validated and applied a deep-learning model that could automatically detect right whale sounds with 86% precision.
“By analyzing their distinctive upcall vocalizations, we can detect their presence continuously, day and night,” Garcia said. “This kind of round-the-clock monitoring that results from passive acoustic monitoring just isn’t possible with traditional aerial surveys, which can only happen in daylight hours and in good weather.”
Garcia says there’s still some uncertainty in the counts that the team needs to address in future research, but the team is optimistic that monitoring whale vocalizations holds promise for estimating the abundance of right whales to aid in conservation and management efforts.
Having the ability to expand monitoring efforts across larger areas of the ocean will help scientists better assess the species’ population numbers across the full extent of its range. Garcia said right whales have been traditionally thought of as a conservation challenge in New England, but right whales are found all along the East Coast.
“Using passive acoustic data and deep-learning tools, we can expand the area we can safely monitor and keep track of this critically endangered species,” Garcia said.
The work comes at a critical time for North Atlantic right whales, whose population has declined to fewer than 370 individuals due to ship strikes, fishing gear entanglement and changing ocean conditions affecting their food sources.
For additional information, see this Cornell Chronicle story.
Journal
Endangered Species Research
Method of Research
Computational simulation/modeling
Subject of Research
Animals
Article Title
Acoustic abundance estimation for Critically Endangered North Atlantic right whales in Cape Cod Bay, Massachusetts, USA
Article Publication Date
21-Feb-2025
Unraveling the mystery of the missing blue whale calves
University of Washington
image:
A blue whale mother and calf are swimming together in the Gulf of California in Baja, Mexico, one of the warm-water places blue whales spend their winter months.
view moreCredit: Diane Gendron/Centro Interdisciplinario de Ciencias Marinas - Instituto Politécnico Nacional
Only two blue whale births have ever been recorded in human history, both decades ago. This remains an extraordinary mystery given there used to be hundreds of thousands of blue whales before whaling started — even today blue whales number around 10,000 to 25,000 — and they give birth every two to three years.
Not only are births very stealthy, but calves are also only rarely sighted — far less than would be expected from their pregnancy rates. Calves closely follow their moms and are sighted as mother-calf pairs, but why are so few detected?
A new University of Washington study, published Feb. 20 in Endangered Species Research, proposes why. Its explanation hints at when and where the unseen births are happening and where blue whale calves spend their earliest months. The findings offer some hope for the health of the population.
Trevor Branch, a UW professor of aquatic and fishery sciences who studies blue whales, set out to unravel this mystery by looking at a range of hypotheses. He proposes that one in particular is the best explanation: It’s mostly because researchers prefer summertime research on feeding congregations of blue whales, but calves are born in fall and winter, and are weaned before they return to feeding areas.
In summer, blue whales migrate to feed in colder regions where krill is plentiful: for example, off California. In winter, when ready to give birth, they return to warmer regions like the Gulf of California and the eastern tropical Pacific. Around seven months after being born, and already at a whopping 52 feet (16 meters) long, the calves are weaned and stop associating with their mothers.
But across various blue whale populations, high pregnancy rates of 33-50% annually seem to contradict the average 3.1% rate of sightings of blue whales involving mother-calf pairs.
When compared with other hypotheses to explain the mystery of why so few calves are observed, such as low fetal survival, low calf survival, low birth rates, or calf separation from mother, Branch discovered that the timing hypothesis best explained observed patterns.
“My conceptual model can explain the mystery of the missing calves: Blue whales produce calves, or give birth, shortly after departing their summer feeding grounds, and wean their calves seven months later, just before they return”, Branch said.
This would explain why researchers – most of whom conduct blue whale field studies in summer months – seldom sight mothers with calves.
Branch compiled data from long-term field studies and combined this with biological information from historical whaling records to come up with this hypothesis, finding higher proportions of calves in winter regions, and lower proportions in summer regions. He is now coordinating a large collaboration to test the idea with field data by month in each region, combined with estimates of the size of calves by month.
One concern about low calf sighting rates was that this might be a warning signal of low birth rates or low survival of calves. Instead, the new hypothesis offers up some hope that higher number of calves could be sighted from field studies concentrated in regions that blue whales travel to in winter and spring.
"This new idea provides an alternative explanation for why some blue whale populations appear to produce very few calves: It's not a failure of calf production, it's because fieldwork in those populations is understandably concentrated in easily accessible summer feeding areas," Branch said.
The research was funded in part by the International Whaling Commission’s Southern Ocean Research Partnership.
For more information, contact Trevor Branch at tbranch@uw.edu.
Journal
Endangered Species Research
Method of Research
Observational study
Subject of Research
Animals
Article Title
Timing hypothesis explains the mystery of the missing blue whale calves
Article Publication Date
21-Feb-2025
A blue whale mother and calf swimming together in the South Taranaki Bight, New Zealand, a rare summer feeding region with many mother-calf pairs.
Credit
Leigh Torres/Geospatial Ecology of Marine Megafauna Laboratory (GEMM) Lab, Marine Mammal Institute, Oregon State Univers
Aerial footage showing the close association between blue whale mother and calf, in the South Taranaki Bight, New Zealand.
Credit
Leigh Torres/ Geospatial Ecology of Marine Megafauna Laboratory (GEMM) Lab, Marine Mammal Institute, Oregon State University
