Historical and contemporary habitat use of sperm whales around the Galápagos Archipelago: Implications for conservation

The feeding success of sperm whales off the Galápagos Islands, Ecuador, was examined over 5 study years; 1985, 1987, 1988, 1989, and 1991. A total of 160 days were spent following sperm whales at sea. The defaecation rates of sperm whales were used as an indication of feeding success. The recorded acoustic click rates of sperm whales were used as an indication of aggregative and foraging behaviour. Significant variation in feeding success occurred temporally over periods of days, months, and years. Feeding success also varied spatially with geographic area. Feeding success was inversely related to sea surface temperature (SST). The foraging and associative behaviour of sperm whales also varied with feeding success, SST, and by year. Variations in the feeding success and behaviour of Galápagos sperm whales can likely be attributed to changing oceanographic conditions in the waters surrounding the Galápagos archipelago.

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Correcting Positional Errors in Shore-Based Theodolite Measurements of Animals at Sea

Journal of Marine Biology ◽

10.1155/2014/267917 ◽

2014 ◽

Vol 2014 ◽

pp. 1-8 ◽

Cited By ~ 3

Author(s):

Ophélie Sagnol ◽

Femke Reitsma ◽

Christoph Richter ◽

Laurence H. Field

Keyword(s):

New Zealand ◽

Habitat Use ◽

Marine Mammal ◽

Positional Information ◽

Physeter Macrocephalus ◽

Sperm Whales ◽

Vertical Angle ◽

Position Accuracy ◽

Wide Range ◽

The Difference

Determining the position of animals at sea can be particularly difficult and yet, accurate range and position of animals at sea are essential to answer a wide range of biological questions. Shore-based theodolite techniques have been used in a number of studies to examine marine mammal movement patterns and habitat use, offering reliable position measurements. In this study we explored the accuracy of theodolite measurements by comparing positional information of the same objects using two independent techniques: a shore-based theodolite station and an onboard GPS over a range of 25 km from the shore-based station. The technique was developed to study the habitat use of sperm whales (Physeter macrocephalus) off Kaikoura, New Zealand. We observed that the position accuracy fell rapidly with an increase in range from the shore-based station. Results showed that the horizontal angle was accurately determined, but this was not the case for the vertical angle. We calibrated the position of objects at sea with a regression-based correction to fit the difference in distance between simultaneously recorded theodolite fixes and GPS positions. This approach revealed the necessity to calibrate theodolite measurements with objects at sea of known position.

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