More Moms with calves are showing up here in the Salish Sea this season – 6 pairs sighted so far. Judging by their playful acrobatics and assertive blows the young ones are thriving. The mothers seem to be in good shape as well considering they lose 1/3 of their body weight during the >10,000km (6,000 mile) round trip migrations to Mexico, Central America or Hawaii and back. Add in the previous 4 months of nursing her hungry baby and it’s no surprise that a mother whale’s prime directive once she reaches the feeding waters is to feed.
“It’s Big Mama” “And she’s got a calf!” Terry is jubilant. Big Mama is one of the whales we have met several times during the years we’ve been on the water. She is a prolific mother and veteran of the humpback comeback to the Salish Sea. Big Mama was the first whale to return to these waters in 1997. Since then she has brought each of her new calves back with her.
Big Mama and her new baby are accompanied by another adult whale. We couldn’t tell who it was because we couldn’t see the whale’s flukes or whether (s)he was female or male. If the companion whale migrated together with Big Mama and her calf from their southern mating/birthing area then this whale is probably a male who is interested in Big Mama as a potential mate. This “escort” can be an asset to Big Mama and her calf if a pod of killer whales attempts an attack on the young one as he will protect the calf with Big Mama. However, he can also be a nuisance if he attempts to mate with her and interferes with nursing.
Mother humpback whales nurse their babies for the first year even though the baby is already learning to fish as soon as she reaches the feeding area. The baby thrives on mother’s rich milk, which is between 45-60% fat How do whales (and dolphins) nurse in their underwater environment? Terrestrial mammals like humans have nipples which are exposed and easy to suckle. But the mammary glands of cetaceans (whales and dolphins) are concealed inside 2 slits on either side of their genital slit low on the abdomen. The nipples are inverted inside these mammary slits. A whale calf must dive underneath the mother and nudge the mammary slits with her rostrum to release the nipple from the slit. Whale calves might be able to roll their tongues into a tube shape and press their rolled tongue around the nipple to channel milk. The mother could then squirt milk into the calf’s mouth using muscles around her mammary glands. Because of the high fat content the consistency of Mom’s milk is thick and doesn’t easily dissolve in water if some leaks out.
Mom and calf stay in close physical contact in the first months of the baby’s life. So much of what transpires between moms and babies is speculation because it happens underwater out of our visual range. Their vocal communication also happens outside of our human hearing range. Mother and baby communicate through touch and very quiet low frequency grunts, barks and groans. They “whisper” so their sounds don’t attract killer whales. Because these “whispers” are so quiet Jude can only pick up a signal on her hydrophone within about 200m of the whales. However, since the whale whispers are too low for humans to hear it’s impossible in realtime to know whether any whale conversations are actually occurring. This can be very frustrating! It is only after recording in the vicinity of whales and afterwards importing the recordings into a software program called a spectograph which translates the sound waves into a visual representation that we can see whether we recorded something. It’s also possible to speed up the slow low frequency sound waves 2 or 3 times within the program so they can be heard in our human hearing range. Unfortunately there is no room in Blue P’s small cockpit for any more audiovisual or computer equipment and no budget for expensive hardware and software. All this has to be done later on our home system.
We learn that the whales are communicating all the time, which is obvious with any amount of time observing their interactions. In the plankton filled waters of the summer Salish Sea it is vibration and sound that carry myriad whale messages through the water. Once on the feeding grounds Big Mama and her calf may associate with various other whales through the season and even during one day. We watch them form a group, separate for a while and come back together obviously communicating with each other. Since all Big Mama’s children return to their mother’s feeding area some of these whale companions may be the new calf’s older brothers and sisters. So many intriguing questions…….
