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Orca Low Pregnancy Rates Largely Blamed On Scarce Food: What Can Be Done To Save The Endangered Killer Whales?

1 July 2017, 5:04 am EDT By Athena Chan Tech Times
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Killer whales have been on the endangered species list for over a decade, and yet researchers find that 69 percent of their pregnancies are unsuccessful due to food shortage. How can the problem be solved when the prey is endangered as well?   ( Pixabay )

Recent research found food scarcity as the main reason for many Southern Resident Killer Whale (SRKW) pregnancies failure. However, there are other man-made factors that can also be solved with man-made solutions.

Orca Pregnancy Failures

Since 2005, the killer whales of the U.S. West Coast have been in the endangered list. Unfortunately, their numbers have dwindled down further, and failed orca pregnancies are doing little to help boost their population.

A study published in the journal PLOS ONE highlights the large number of failed orca pregnancies and a big reason for such occurrences. Based on their findings, which they gathered by studying the feces of orcas, 69 percent or orca pregnancies were unsuccessful, 33 percent of which failed late in gestation.

One significant stressor linked to the failed pregnancies is a lack of food resources, as the female orcas that have experienced failed pregnancies had high levels of hormones that indicate nutritional stress. As it happens, the killer whales' main prey, the Chinook salmon, is also an endangered species.

In the case of Chinook salmons, their endangerment comes from factors such as urban development, pollution, and dams. Hence, in their food chain, the fall in prey population corresponds to a fall in the predator's population as well.

Vessel Disturbance

Though not extensively discussed in the study, researchers point out that the noise from passing vessels may have also contributed to this problem.

In 2015, a study published in the same journal presented the impacts of vessel activity with regard to its impacts to the natural wildlife. Marine mammals are especially vulnerable to this problem, as it is difficult for man to see what happens below the water in response to what is happening above the surface.

Aside from vessel collisions with large mammals, the degradation of their habitats as well as the lasting effects of underwater noise pollution have a large impact on animals that depend on echolocation to navigate through the waters. This is even more problematic, as sound travels much further in water, hence leading to a larger extent of underwater noise pollution.

Apart from having to physically survive the passing vessels, researchers also found that such stressors lead to negative impacts on marine mammals' reproduction.

Exposure To Toxic Chemicals

Another factor that could possibly have contributed to the orcas' breeding problems is their exposure to toxic chemicals. Last May, the results of the autopsy of Lulu, a 20-year-old killer whale found dead in Scotland, was found to have 80 times the accepted toxicity levels for killer whales.

Due to the high levels of polychlorinated biphenyl (PCB) levels in her body, Lulu's health was likely compromised with a higher susceptibility for cancers and infertility. In fact, an analysis of her ovaries showed that despite being past the prime age for reproduction, Lulu was not able to reproduce in her life span.

PCBs, just like persistent organic pollutants (POPs) are man-made pollutants that endanger the health of both man and wildlife. Though POPs have been banned in the 1980s, its persistence remains to affect the health of wildlife such as marine mammals.

What Can Be Done?

It's quite noticeable that many of the killer whales' problems are, in a way, man-made. Though it's difficult to determine exactly what causes the decline in killer whale numbers, as well as their failed pregnancies, the study calls to mind the importance of coexisting with other creatures.

In the case of the Chinook salmons, researchers stress the importance of strengthening the fish's population, not just for the species' own sake but for the whales as well.

As for the problems with vessel activity and POPs, the case of Lulu is a good example of how these actions can affect wildlife even years after the realization of its ill effects. It has been decades since POPs have been banned, and yet its effects can still be experienced today.

It is difficult to tell how the problem with POPs can be solved when the ban clearly wasn't as effective as expected, but perhaps taking a little step of caution to think of how certain human actions and developments may affect wildlife may prevent actions that are harmful to both man and wildlife.

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