DATA Series

Summary
Using whale count data from the Hawaiian Islands Humpback Whale National Marine Sanctuary, compare whale counts in relation to environmental factors.

Objectives

• Recall at least 4 biological facts about the humpback whale.
• Calculate the average number of whales counted.
• Compare whale count data while interpreting environmental factors such as waves and bathymetry.

Introduction
This data tip focuses on the Pacific islands, and includes the Hawaiian Islands Humpback Whale and the Fagatele Bay National Marine Sanctuaries. The Bridge wishes to acknowledge the significant efforts of folks from the Hawaiian Islands Humpback Whale National Marine Sanctuary in creating this special feature.

Like rare jewels lying on a bed of blue silk, the islands of Hawai`i lie isolated in the vast Pacific. Lush greenery first greets the visitor, but the lives of Hawai`i’s inhabitants are undeniably shaped by the ocean; its beauty, its power, its bounty, and the life beneath its waves. The Hawaiian Islands Humpback Whale National Marine Sanctuary was established in 1997 to protect marine life, most notably the North Pacific population of the endangered humpback whale, and its habitat. The sanctuary is comprised of five separate areas abutting six of the major islands of the State of Hawai`i. The five areas of the sanctuary cover relatively shallow offshore areas which, although underwater, actually lie near the summit of the massive undersea volcanic mountain range that formed the Hawaiian Islands chain.

An even more remote sanctuary also visited by humpback whales is the Fagatele Bay National Marine Sanctuary in American Samoa. Located on the largest island of American Samoa, over 2200 miles from Honolulu, Fagatele Bay is the smallest national marine sanctuary (0.25 square miles) and the only true tropical coral reef in the sanctuary system. During parts of the year, the Bay’s sheltered waters are host to threatened or endangered species such as humpback and sperm whales, as well as hawksbill and green sea turtles. Fagatele Bay is a complex ecosystem with an exceptionally high level of biological productivity, providing habitats for numerous species of tropical fish, invertebrates and algae. The sanctuary’s research and monitoring programs supply information needed to make critical resource protection decisions, allowing the preservation of this unique habitat.

Humpback whales are mammals, just like humans. They are warm-blooded, they breathe air, and they bear live young and nurse them with milk. Calves typically measure 13 feet and weigh 2 tons at birth. They grow rapidly, and eventually as adults, reach sizes of 35 to 48 feet, weighing about one ton per foot. Their scientific name, Megaptera novaengliae, means “giant wings”, an apt description of their large front flippers that can reach a length of 15 feet – about one-third of the animal’s entire body length. The humpback whale’s average lifespan is unknown, but is believed to be between 30 and 40 years. During the spring and summer, these giants feed over the contintental shelf of the Pacific rim, from the coast of California north to the Bering Sea. They feed on krill and small schooling fish, such as capelin and herring. They are building up their blubber for the long migratory journey to the southern waters where they bear their young. The food supply there is scarce, but whales must give birth in warmer waters because their calves’ blubber is not sufficient to insulate them from the colder waters.

North Pacific humpback whales winter in three nearshore lower latitude mating and calving areas: Hawai`i, western Mexico, and the islands of southern Japan. The main Hawaiian Islands may contain the largest seasonal population in the world. Scientists estimate that their pre-whaling population was approximately 15,000 whales. Estimates of the current population have been made at roughly 3,700-5,000 whales. It is believed that about two-thirds of this population migrates to Hawai`i each year. While visiting the islands, humpbacks are known for their various spectacular acrobatic displays. In fact, the common name “humpback” refers to the high arch of their backs when they dive.

Another intriguing behavior of humpback whales is singing, which is done only by males. Several research projects have studied the relationship between singing and the whales’ social interactions. Log on to hear some of the mysterious songs and learn more about the research.

At the Hawaiian Islands Humpback Whale National Marine Sanctuary, much research has been done on humpback whales; however, many unanswered questions remain. More information about the whales’ habitat requirements, population dynamics, social behaviors, and vital life rates (e.g., age at sexual maturity, pregnancy rates, variability in reproductive success, calving intervals, and longevity) is necessary to formulate effective management strategies.

An important database of information on humpback whale populations and distribution patterns around the Hawaiian Islands is being collected during an annual event called the Ocean Count. During this one-day event, volunteers are stationed at shore sites around various islands for a three-hour period, with the job of recording the number of humpback whales sighted and the behaviors observed. In 2001, the Ocean Count took place on February 24 with volunteers covering a total of 80 sites on the islands of Kaua`i, Oahu, and Hawai`i.

Data Activity
We will focus on the data from Kaua`i, but first a note about Oahu. Some high-tech observations were conducted from the air on the north shore of Oahu using an instrument called the Advanced Airborne Hyperspectral Imaging System (AAHIS). This instrument can be mounted on the underside of a light twin aircraft and collects data in the visible to near-infrared wavelength range. Optimized for coastal applications, AAHIS has performed in various field conditions to accomplish environmental monitoring, vegetation discrimination, and effluent detection as well as military target recognition on land and underwater. Other surveys are conducted from shore or from vessels.

The area covered by the plane encompassed the ocean area being monitored by 8 of the Oahu Ocean Count sites. The shore sites reported 32 whale sightings and the plane reported 23 whale sightings. One possible explanation is that the shore sites were close together in some instances, which probably resulted in some whales being counted by more than one site as they moved along the coastline.

Take a look at the whale count data from Kaua`i’s shore sites.

1. Calculate the average number of whales counted per site over the entire 3-hour period.
2. Create a graph of the total number of whales counted over the entire 3-hour period at each site. Which site had the lowest whale count? Which site had the highest whale count? Using the following reports as resources (wave height & direction, bathymetry, volunteers’ whale count sheets), what factors do you think may have affected the variation in counts at different sites around the island?
3. What kinds of questions do the data elicit?
4. How would you modify next year’s approach to gain more information from next year’s data?

Coming soon!

Coming soon!