Southern Killer Whale has not recovered after experiencing hunts in the 1960s.
Orca , also known as the orca, is the largest and probably the easiest species in the Dolphin family. These creatures are very smart and are even observed to learn to communicate like other species of dolphin .
Despite how iconic these large mammals are, it is very different to study orcas in the wild. IUCN classifies them as “insufficient data,” meaning there is not enough information about their number or distribution to accurately assess their conservation status (the only exception is a small group of killer whales living in Gibraltar ; they are listed as “critical endangered species” by IUCN .
Here we explore whether killer whales are endangered and the threat they face.
Protection against killer whales
As marine mammals, all orcas are protected by the Marine Mammal Protection Act. Although all orcas are generally considered to belong to a species, several populations (or “ecological types”) have independent prey preferences and different behaviors in size and appearance. Although ecological types usually share overlapping habitats, there is no hybridization or even affinity between them. Interaction.
According to a 2006 survey, the global number of wild killer whales is estimated to be about 50,000.
Southern permanent population
A late extinction southern killer whales near the coast of Vancouver, British Columbia.
2001, requested the federal government to After the ecological types of killer whales were reviewed, the southern permanent population of the killer whales was first proposed as a supplement to the Endangered Species Act. Historically, between the 1960s and 1974, an estimated 69 marine mammals were captured in marine mammal parks. This reduced the number from about 140 to 71.
Initially, the biological audit team determined that the southern killer whales were "threatened" but later changed it to "endangered" during the peer review process in 2015. Last time The determination of population size occurred in 2017, when biologists recorded 76 killer whales.
threat
In the 2013 assessment, the IUCN estimated that the combination of prey reduction and marine pollution could lead to a 30% reduction in the number of killer whales in the next three generations. These groups may be designated as individual species in the future before more scientific research is conducted.
Although chemical pollution and prey consumption are the biggest threats to killer whales, other factors, such as noise pollution, capture and hunting, have also caused the number of killer whales to drop.
Chemical pollution
In the "Deepwater Horizon" oil spill, two ships are skipping oil from the Gulf of Mexico.
from sewage treatment plants, sewers or pesticide tracks Pollutants flowing into the ocean can affect orcas in a variety of ways. When they enter the environment, these chemicals directly harm the immune and reproductive systems of the orcas, but also contaminate their prey source. Considering the lifespan of orcas (wild from 30 to 90), chemical pollution can affect these animals for decades.
For example, the Exxon Valdez oil spill in 1989 is still related to the massive deaths of orcas. A study in the Marine Ecological Advances Series found that Alaska The orcas in Prince William Bay (the center of the oil spill) still did not recover after 16 years. One group lost 33 individuals during this time, and the other group lost 41% of the number.
PCB2, or chemicals in industrial waste, continue to threaten the long-term viability of more than half of the world’s killer populations. Although PCBBs were banned in 1979, the harmful chemicals are constantly being found in seawater and in orca tissue samples.
Worse, female orcas contaminated with PCBs transfer pollutants to their young whales, which are harmful to their development and put them at greater risk of health deficiencies. The southern population of permanent and temporary orcas have the highest PCB content of all cetacean animals.
Noise pollution
Killer whales use sound to communicate, travel and eat. Noise from marine vessels can interrupt these abilities or force them to make louder calls, causing them to consume more energy. If the whale watcher is too close, it may interfere with the foraging and rest of whale , while fast moving ships are at risk of touching the ship.
A study of free-range killer whales along the coast of Puget Sound found that for every 1 decibel increase in background noise on motorized ships, the sound adjustment is related to an increase in pressure levels and a decrease in communication between members of other groups.
Prey loss
In Norway, killer whales and seagulls feed on herring trapped in nets of trawlers.
As predators at the top of the food chain, overfishing and habitat loss can lead to a severe decline in the amount of food available to orcas. More importantly, many killer populations have highly specialized diets, such as the southern killer, which feeds mainly on endangered Chinook salmon. The effects of food depletion are not limited to hunger, because when the number of salmon is small, the probability of female salmon giving birth in the south is 50% lower than that of
Similarly, orcas home to the Strait of Gibraltar feed on the endangered bluefin tuna , they follow the migration pattern of bluefin tuna and even interact with the vertical fishery to find food. Like Chinook salmon, bluefin tuna has high commercial value for the fishery.
Catch and hunt
In the United States, it is no longer legal to catch killer whales for aquarium displays or marine parks, but this still happens elsewhere in the world. According to the IUCN data, at least 65 killer whales were captured between British Columbia and Washington from 1962 to 1977, and 59 killed in the Iceland waters between 1976 and 1988.
Kill whales are also deliberately hunted, and sometimes fishermen see them as competitors of fishing, or even food. From the late 1930s to 1981, whalers in Japan hunted an average of 43 orcas per year, while whalers in Norway hunted an average of 56 orcas per year.
The ethical issues of captive orca whales have received a lot of attention in the past few years, and just in 2020, the Journal of Veterinary Behavior explored its harmful effects. The study followed a male wild-born killer whale 24 hours a day at SeaWorld Florida for 7 consecutive days, noting that it had an average of more than 69% (16.7 hours) of inactivity per day. By contrast, wild orcas move 99% of their life.
The orcas born in captivity are prematurely separated from their mothers, and they also show social structural disorders, such as inbreeding and reproductive defects. At the Loro Park Zoo in Spain, killer whales give birth to cubs much younger than in the wild, less than 8 years old, while the average age is 11 to 17 years old. A female orca whale is conceived again only four months after delivery, while 90% of female orca whales in the wild will give birth every 3 to 7 years.
protection work
Due to the long lifespan, wide range of activities, location on the food chain and sensitivity to pollution, scientists regard it as an indicator species representing the health of the entire marine ecosystem.
As the IUCN lists killer whales as a “data defect”, further study of the biology and behavior of killer whales is necessary to better understand these behemoths. The National Oceanic and Atmospheric Administration currently underway projects include satellite marking, tracking, biological samples and measuring pollutants, etc., to understand and determine which salmon or tuna populations overlap with orcas, so that corresponding protection measures are also important.
The protection of killer whales should not only emphasize the protection of the species itself, but also the protection of prey and habitat.
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