Every ecosystem has an indicator species whose existence and population indicate the health of an ecosystem. A member of the Delphinidae family, the orca, is considered an indicator species for assessing the health of marine ecosystems. As an apex predator in the marine food chain, the orca can camouflage itself because of its characteristic dark and light coloring on the top and underside. Orca, also known as the killer whale, is not only a social mammal but also an intelligent one that hunts in pods using coordinated attacks of complex nature. They have earned the name killer whales because their attacks can harm even blue whales.

Carnivorous in nature, orca populations are divided into different pods based on their feeding habits. Transient pods are usually small, less closely bound, and feed on sea lions, seals, etc. On the other hand, resident pods are comparatively large and feed on fish. Most likely, orcas evolved to feed on different species to prevent competition for the same prey. 'Ecotypes' are kinds of orca populations. A population belongs to a particular ecotype based on its feeding nature, size, dialect, and hunting method. The fact that each ecotype has a different prey species, and a specific one, makes them vulnerable to changes in their environment.

The lifespan of orcas ranges from 30 to 90 years, with the female orca reproducing only once every four or five years up to twenty-five years. Being at the top of the food chain, the existence of the orca itself is vital for all marine organisms. Orcas are, therefore, an umbrella species. Their protection and well-being ensure positive effects on the marine ecosystem and the food web. However, over the years, the increase in human population, the consequent increased demand for food, accompanying pollution, and traffic in the waters have not come without consequences for the species. Human activities threaten orcas; when they do not even have any natural predators in the oceans. 

Overfishing, entanglement, contamination and pollution, frequent oil spills, and the presence of vessels in water are some factors that affect orcas in various ways. The exploding human population has to overfish to meet its food demands. Overfishing can particularly threaten orcas that prey on endangered fish. Similarly, fishing gear employed in the process may trap the whales in one place, injuring them and preventing them from feeding properly. Besides overfishing, oil spills are another reason that causes a loss of prey for the whales. Many chemicals discharged into the marine environment are known to be persistent, tend to accumulate, and magnify as they transfer onto the top levels of the food web. Such conditions can seriously affect the reproduction and immune response of orcas, the largest predators in the oceans. 

Killer whales use echolocation to communicate with members of their pod. They use the same sounding method to locate prey. But traffic in the water interrupts and disturbs their communication and hunting. As a result, the whales have to spend more energy to travel further where it is calmer and communicate with louder sounds. Exploration and industrial activities lead to the whales displaying altered behavior patterns. A more terrifying situation for the orcas is in captivity. An orca can be captured from the wild and kept in an artificial environment or marine parks for the sake of performances. As a social animal that lives in groups, orcas do not do very well in isolation. Instances recorded show orcas exhibiting aggressive behavior towards their trainers when in captivity.

Given their importance to the marine ecosystem, orcas need protection because their thriving populations indicate a healthy marine ecosystem. To celebrate this fascinating species and highlight its significance, World Orca Day, is observed on July 14th every year since 2014. Each year, the number of individuals and NGOs supporting the purpose of this day and promoting it has been growing. The reason for choosing the month of July to observe World Orca Day was because of some successful orca rescues completed in July of the previous years. Many research teams work to manage and rebuild affected orca populations around the world. Primary steps include protecting their habitat and recovering their prey populations. Preventing water contamination, bringing about a quick response in case of oil spills, and lessening the impact that vessels have on their behavior are some of the other steps to take for the conservation of orcas.

About the Author: Zainab Imran finds her interest in writing about environment and climate, particularly highlighting the issues faced today.