Female Humpback whales are thought to reach sexual maturity between 4-6 years of age. They typically breed every two or three years, while they congregate in the breeding grounds at low latitudes. The gestation period lasts for about 11-12 months. The peak months for birth in the Northern Hemisphere are January and February, where females will give birth in the warm, coastal waters to one calf at the time. At birth, calves measure 13 to 16 ft (4 to 5 m),which is about one third of the mother´s body length. They grow quickly however from the highly nutritious milk of their mothers. Humpback whale milk is some of the richest milk in the world, with close to 50% fat, and has the consistency of cottage cheese. A calf consumes around 240 liters of milk per day. It has to gain strength and body size before making the long migration to the feedings grounds at higher latitudes. Mothers are protective and affectionate towards their calves, swimming close and frequently touching them with their flippers. Weaning occurs between 6 and 10 months after birth, but calves may stay with the mother for up to a year after which they will separate. By this time the calf will have doubled in size.
The tropical waters off the west coast of Mexico are an important breeding and calving ground for the North Pacific population of Humpback whales. While the peak season for calving is January and February, Onca´s crew has already started seeing Humpback whale mother and calf pairs as early as December 12during this whale watching season. This is relatively early and could possibly be explained by the occurrence of relatively warm surface temperature conditions this winter. Both on the 12th and the 13thof December we encountered the same pair, the calf most likely a few weeks old already, considering the size of the animal. Christmas Day delighted us with an encounter of a new mother and calf pair, and a third couple was seen on the 07th of January.
Our most recent sighting was on January 18 of a female with a very small calf, most possibly only a few days old. Everyone was relieved to get out on the water again after a full week of staying home due to strong northerly winds. We left the dock on 2 vessels, on our quest to find whales and dolphins. After following a couple of whales in transit, one of the boats, decided to return to the marina due to one of the passengers feeling unwell. On the way in, the boat was radioed by another vessel close by who repeatedly witnessed an animal breach only about a mile offshore. Keeping our eyes scanned on the horizon we noticed a small blow approximately 400 meters off our bow. It was a very small Humpback whale calf swimming alone at the surface. The mother was nowhere to be seen, yet, so we followed the calf at a safe distance to make sure the mother would be around. She surfaced approximately 4 minutes later, with the calf right by her side. This time, with our boat following, both animals would go for very shallow dives, as we could clearly follow their set of footprints on the surface marking their path. Swimming around in circles, moving very erratically and showing signs of avoidance it seemed clear that the mother tried to shield her calf away from any possible threat or danger. This seemed the case in all mother/calf encounters so far. Often we would find the calves alone at the surface or breaching, which could indicate a way of staying in contact with the mother. As soon as the female would come up to the surface the calfwould always be directly at her side, indicating the protective and close connection between the pair. For this same reason our boats always try to maximize the distance and minimize the amount of time spent with a Humpback whale mother and calf. For all of us, both crew and passengers, the first mom and calf encounter of the season It is always a very exciting moment and we are happy to share with the world.
Photos by Oscar Guzón, Hella Martens & Saul Herrera.
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