Hunting down the truth about killer whales

Hearing that killer whales are in the area is sure to strike fear in the heart of anyone at sea. The thought of coming across a creature with a menacing name like that is a surefire sign you are on a path to destruction. As it turns out, killer whales, orcas, are actually highly sophisticated creatures that are usually harmless to humans.

The title “killer whale” may actually be a mistranslation of the Spanish term “ballena asesina”, which means assassin whale. Orcas were nicknamed this due to their well-coordinated attacks on marine life, not for the danger they pose to humans. At nearly five to seven metres in length and a weight of over six tons, orcas are one of the largest creatures on the Earth. There are about 50,000 orcas worldwide that are spread out in several oceans. Orcas are classified as an Apex predator, which means no other creature hunt them for food.

Scientists believe that there are between three to five different types of orca and they are all quite distinctive. The most frequently seen of these are Residents. They live in close-knit family units called pods, which can contain over 50 members, and their diet consists mainly of fish. Transient whales, however, prefer to travel in smaller groups of two to six whales. Meanwhile, Offshore whales were only recently discovered in 1988. They prefer to swim farther away from land than the others and several pods may come together to form groups as large as 200 whales. Although these orca groups may seem similar to the naked eye, they are extremely different in many ways, and scientists believe they haven’t interbred in thousands of years. Researchers also acknowledge that their knowledge of orcas is limited, and even more groups may exist.

Male orcas have an average lifespan of about 30 years, while the average age for females is 50. However, there have been cases of females living up to 90 years. Yet when kept in captivity at marine entertainment parks, their life expectancies drop dramatically. In fact, it seems that the biggest threat to orcas these days is humans. Between the practices of hunting orcas, polluting their environments, and capturing them for entertainment purposes, we are making it very difficult for them to survive. Perhaps the killer whales aren’t the real killer after all.

What does the sentence "Although these orca groups may seem similar to the naked eye, they are extremely different in many ways" 1 in paragraph 3 mean?