Field Surveys Will Improve Models of Stressors Affecting Gulf of Mexico Sperm Whale Populations

Sperm whale with an advanced dive behavior tag. (Photo: NOAA, under research permit 779-1633)

Whales and dolphins (cetaceans) living in the Northern Gulf of Mexico are often exposed to multiple stressors. Quantifying the cumulative impact of these stressors is essential for effectively implementing and managing restoration efforts. The Open Ocean Trustees have approved Phase 2 (PDF, 16 pages) of the Monitoring and Adaptive Management (MAM) Activity, Evaluating the Cumulative Impacts of Multiple Stressors on Cetaceans (PDF, 16 pages).  

During Phase 1 of the project, a population dynamics model for Gulf of Mexico sperm whales was developed based on the Population Consequences of Multiple Stressors (PCoMS) framework. This model was designed to evaluate the effects of various stressors (oil spills, vessel strikes, exposure to noise) on animal survival, reproduction, and population growth. Analyses performed during Phase 1 revealed that Field Metabolic Rate (FMR)–or the energy an animal uses during its daily activities–is a key data point in determining the impact of stressors on feeding habits. Because FMR ranges were originally inferred from studies of orca (killer) whales, a primary objective of Phase 2 is to gather more accurate, species-specific FMR values for Gulf of Mexico sperm whales.

In order to capture the unique aspects of the biology of sperm whales in the northern Gulf of Mexico, Phase 2 will utilize the deployment of telemetry tags. These tags will provide researchers with accurate FMR values and daily activity budgets – a tool used to quantify the behavior of animals over time and across populations. Additionally, Phase 2 field studies will include observations of body size and mass of encountered sperm whales, evaluation of reproductive status based on hormones measured, and additional information collected through the analysis of blubber samples.

NOAA will conduct these field studies from one of its large research vessels. Smaller boats will be deployed from the research vessel to allow close approaches to sperm whales for the collection of photographs and samples, and to attach telemetry tags. The survey will include approximately 60 days at sea, which will allow sufficient opportunities to locate sperm whales and collect the required data. The survey will focus on areas where large numbers of sperm whales typically reside to ensure relatively high encounter rates. If time allows, the survey will include secondary areas in the southeastern and western Gulf of Mexico to allow regional comparisons among sperm whale groups. These field studies will be performed under a permit to conduct scientific studies for protected species (number 21938-03), pending extension or replacement with a new permit.  

The data collected from this study will directly inform critical parameters in the sperm whale PCoMS model. 

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