New recordings reveal that newborn baby humpback whales and their mothers whisper to each other to avoid predators.
Humpback whales are famous for their whale songs. Observers have never heard female humpback sing, but males vocalize when mating season rolls around. Their vocalizations can be heard in an area that stretches up to several kilometers. Suffice it to say, whales aren't exactly quiet.
However, whale calves need to keep their indoor voice if they want to survive. Calves typically stay with their mothers and nurse for up to a year. Calves need to stay with their mothers at this crucial time in their lives in order to survive the 5,000-kilometer migratory journey from their nursery grounds. If adult male whales want to mate with a female nursing a calf, however, the male will try to separate the calf from its mother. Loud calf voices can attract the unwanted attention of adult males.
Another possibility that calves need to watch out for is falling prey to killer whales. Killer whales, being apex predators, have a wide diet that includes baby humpback whales.
Researchers discovered this form of communication between calves and their mothers as they tracked a group of humpback whales for 24 hours. This group consisted of eight calves and two mothers. They were in the Exmouth Gulf in western Australia, where humpback whales mate and give birth.
The researchers attached tags to the whales and listened to the whale vocalizations. They found that when mothers and calves converse, they do so more softly than adult whales. Calls between a mother and calf were 40 decibels lower than the calls adult males make.
The mother and baby humpback whales communicated with each other in soft grunts and squeaks. Other sea animals would have to be in close range in order to hear these vocalizations.
A lot of the time when human babies cry, they do so because they're hungry. This apparently isn't the case with baby humpback whales. The researchers detected the vocalizations while the mothers and calves were swimming. This indicated that perhaps the soft calls helped the whales stay together. The waters were teeming with killer whales, and a stray calf is easy prey.
Also, when the calves need to suckle, they don't call out to their mother. Instead, they rub against their mothers to initiate suckling.
The soft calls may keep the baby humpback whales safe from predators and interloping adult males, but it can be problematic. Ocean noise pollution from large sea vessels can be somewhat deafening to whales. This noise pollution can prevent mothers and their calves from hearing each other.
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