The first humpback whales of the season have been sighted in the waters off Maui!
by Deb Caswell, Whale Trust Board Member
Over the winter months, approximately 10,000 to 12,000 whales are expected to arrive in the Hawaiian Islands after a 4-6 week migration from their feeding grounds in the north Pacific. Humpback whales do not all arrive at the same time. Instead, their arrival is staggered and their length of stay depends on several factors including age and sex. Research has shown that adult males tend to stay the longest and females without calves the shortest. While humpbacks in Hawaii have been reported in every month of the year, they are rarely sighted before the beginning of the breeding/calving season in early fall (September/October). Their numbers reach a peak in mid-winter and taper off by late spring.
Most humpback whales summering in the northern waters of the Pacific Ocean head south to warmer sub-tropical waters during winter months. Breeding and birthing are thought to occur while in the warmer waters. Most of the these migrating humpbacks seem to come to the waters around the Hawaiian Islands (estimates of just over 50%). Since most were born in Hawaiian waters, they are coming “home” for the season. Their arrival is continuous over the winter months with peak populations occurring mid-January to mid-March. Certain groups seem to arrive at different times with young juveniles being the among the first. Overall, humpback whales have been sighted as early as late August and as late as July. It is estimated that males may stay in warmer waters about three months, a female who becomes pregnant may head north more quickly, and moms who calve may stay about six weeks, until their calf is strong enough to begin the journey north.
Over the past few years, our researchers have observed changes in migration patterns, with noticeably fewer whales and a breeding season that started later and ended earlier. Whales are an indicator of the health of the oceans. As such, it is imperative that scientists study these apparent changing trends. What might these changes be telling us?