{"id":137507,"date":"2021-03-21T09:00:02","date_gmt":"2021-03-21T19:00:02","guid":{"rendered":"https:\/\/www.hawaii.edu\/news\/?p=137507"},"modified":"2021-03-19T13:18:26","modified_gmt":"2021-03-19T23:18:26","slug":"false-killer-whale-dietary-first","status":"publish","type":"post","link":"https:\/\/www.hawaii.edu\/news\/2021\/03\/21\/false-killer-whale-dietary-first\/","title":{"rendered":"Stranded endangered false killer whale divulges a dietary first"},"content":{"rendered":"Reading time: <\/span> 3<\/span> minutes<\/span><\/span>
\"whale
Endangered false killer whale. (Photo credit: Cascadia Research Collective; NOAA<\/abbr> permit 20605)<\/figcaption><\/figure>\n

Researchers found something unexpected inside a rare false killer whale that stranded dead on Maui in February 2021, and it could ultimately help the endangered species. The whale was an insular false killer whale, the most critically endangered species of dolphins and whales in Hawaiian waters. While investigating it\u2019s cause of death, the University of Â鶹´«Ã½<\/span> Marine Mammal Health and Stranding Lab found the remains of octopuses in its stomach, which was previously an unknown part of the species\u2019 diet.<\/p>\n

“Understanding their food habits is foundational to their biology and ecology and has relevance to fishery interactions (an identified threat to the population) and in defining critical habitat for this endangered species,” said Kristi West<\/strong>, lab director and an associate researcher at UH<\/abbr> Mānoa\u2019s Â鶹´«Ã½<\/span> Institute of Marine Biology<\/a>.<\/p>\n

The UH<\/abbr> lab conducted a necropsy, an animal autopsy, in cooperation with National Oceanic and Atmospheric Administration (NOAA<\/abbr>) Fisheries Service<\/a>, to obtain biological samples and examine the individual for signs of cause of death and evidence of fishery interactions. Examining an insular false killer whale in Â鶹´«Ã½<\/span> is a rare opportunity for the UH<\/abbr> lab, as the last stranding occurred in 2016.<\/p>\n

\"dead
(Photo credit: UH<\/abbr> Health and Stranding Lab; NOAA<\/abbr> permit 18786)<\/figcaption><\/figure>\n

The stomach contents in the recent stranding revealed the importance of a new food item, the pelagic octopus, to false killer whales in Â鶹´«Ã½.<\/span> The remains from 25 individual pelagic octopuses were identified among the stomach contents of this individual.<\/p>\n

This effort is an example of UH<\/abbr> Mānoa\u2019s goal of Excellence in Research: Advancing the Research and Creative Work Enterprise<\/a> (PDF<\/abbr><\/span>), one of four goals identified in the 2015\u201325 Â鶹´«Ã½<\/a> (PDF<\/abbr><\/span>), updated in December 2020.<\/p>\n

Population threats<\/h2>\n

There are three distinct populations of false killer whales that call Hawaiian water homes with one that is endangered.<\/p>\n

The best estimate is that there are approximately 170 individual false killer whales remaining in the endangered insular main Hawaiian islands population. Fishery interactions and high pollutant loads have been identified as population threats. Most of the remaining individuals have been individually identified by their dorsal fin profile with sightings catalogued by Cascadia Research Collective<\/a>. The stranded whale was matched to the catalog and represents a known individual first sighted off Maui in 2000.<\/p>\n

“This work is only possible because of an extremely dedicated team of graduate students, undergraduate students and other program volunteers,” said West. “UH<\/abbr> partners with collaborators such as Cascadia Research Collective, the Â鶹´«Ã½<\/span> Department of Land and Natural Resources (DLNR<\/abbr>) and NOAA<\/abbr> Fisheries to maximize the information that can be obtained on false killer whales and the threats that they face.”<\/p>\n

Examining stomach contents<\/h2>\n
\"octopus
Cephalopod beaks recovered from the stomach of a stranded false killer whale. (Photo credit: UH<\/abbr> Health and Stranding Lab)<\/figcaption><\/figure>\n

The diet composition of endangered false killer whales is known from the stomach contents of previously stranded individuals and observations of live animals in the wild. Live false killer whales are most commonly observed by Cascadia Research Collective foraging on gamefish, including mahi-mahi, ono, aku and ʻahi.<\/span> Prior stomach content analyses have identified gamefish such as ʻahi,<\/span> mahi-mahi and the large diamondback squid as important to the species\u2019 diet.<\/p>\n

Future research on this animal will include stable isotope analysis, contaminant analysis and body condition assessment at the time of stranding through blubber examination. This is anticipated to provide further information to assess diet and predator prey relationships in the species, and to better understand the threat of pollutants and nutritional stress.<\/p>\n