Orca

The Salish Sea is home to two unique populations of orcas: the northern and southern residents. While the northern population has slowly rebounded to over 300 individuals, the southern residents remain critically endangered, with their numbers stuck at around seventy-five.

The reasons behind the southern orcas' struggle to recover have been well-documented—reduced salmon runs, pollution, and past capture for entertainment purposes. Now, new research suggests another key culprit: human-made underwater noise.

Orcas have long been considered a single global species, with different forms in different regions, known as “ecotypes.”

However, scientists have long recognised the differences between resident and transient orcas, known as Bigg's killer whales, in the North Pacific. Resident orcas maintain close-knit family pods and prey on salmon and other marine fish, while Bigg’s orcas roam in smaller groups and hunt other marine mammals such as seals and whales.

Researchers from the University of British Columbia (UBC) have uncovered compelling evidence of a potentially new population of killer whales in the Northeastern Pacific, distinct from known orca ecotypes. 

This discovery, documented in a recent study published in Aquatic Mammals, is based on observations of 49 orcas exhibiting unique hunting behaviours, including predation on sperm whales and sea turtles, off the coasts of California and Oregon.

Miami-Dade County Mayor Daniella Levine Cava addressed the issue in a statement posted on social media platform X, revealing that The Dolphin Company had consistently fallen short in maintaining the premises and ensuring the safety and well-being of the animals under their care. She emphasized that the current state of the Miami Seaquarium is deemed unsustainable and unsafe.

A comprehensive study published in the journal Marine Mammal Science analysed over 60 years of recorded interactions between Southern Resident killer whales (SRKW) and porpoises in the Salish Sea. This endangered population of orcas, known for their fish-based diet, particularly Chinook salmon, has been involved in numerous incidents of porpoise harassment, leading to the deaths of many porpoises.

Possible explanations

The study proposes three main reasons for this behaviour:

A study in the Marine Mammal Science journal examines the question of why Southern Resident orcas in the Pacific Northwest harass and sometimes kill porpoises without eating them.

Such behaviour has been passed down through the generations and across social groupings, and has been recorded as far back as 1962.

The question of why comes to mind.

Not on the menu

Certainly not to eat them. Southern Resident orcas do not harass the porpoises to consume them.

Scientists studying endangered southern resident orcas have noticed a steady increase of mysterious gray patches and gray targets (circular lesions which may appear on concentric rings – ed.) on the whales’ skin from 2004 to 2016. 

To date, researchers managed to identify six distinct types of lesions, with the two most common types being gray patches or targets. Some resemble tattooed skin.

They do not know the cause of the lesions and are worried that they could be due to underlying health problems in the struggling population.

The photo on top:  "A pod of Orcas off Point Reyes" by Gunn Shots ! is licensed under CC BY 2.0.

So far this year, dozens of orca attacks on vessels have been recorded on Spanish and Portuguese coasts. In most reported cases, orcas are biting, bending and breaking off the rudders of sailboats.

It turns out that raising sons takes a higher toll on southern resident orca mothers, when compared to raising daughters. So much so that the mother’s annual likelihood of successfully breeding is reduced by about half.

This is because the mothers share the fish they catch with their sons even after the latter become adults. The mothers would bite the fish they catch into two, consume one half and give the other half to their sons.

(In the case of their daughters, the mothers also share their food, but stop doing so when the daughters reach reproductive age.)