The primary objectives of this exploratory study are to track the movements of sperm whales and obtain information about their diving and feeding behavior in the Gulf of California using satellite telemetry. This study will provide fundamental data to allow the PIs to address questions about seasonal movements, habitat-associations and vertical prey distribution. Despite their importance in marine trophic ecology and their cosmopolitan distribution, little is known about the daily and seasonal movements, behavior and habitat requirements of sperm whales because their sheer size and deep, long dives make them difficult to observe and track at sea. Much of what is known about their movements and behavior is based on historical catch rates and the recovery of static tags by the whaling industry. This study will be conducted in the Gulf of California in collaboration with the Centro Interdisciplinario de Ciencias Marinas, Instituto Politecnico Nacional, La Paz, Mexico which will provide an 8-meter research vessel for tagging. Satellite-linked depth recorders will be used to track the movements and monitor the diving behavior of up to five sperm whales. The Gulf of California is an ideal location to study the behavior and ecology of sperm whales for several reasons. The high density, year round occurrence and accessibility of sperm whales in the Gulf of California makes it easy to locate them for tagging. Earlier research by the PIs showed that sperm whales are consistently found in high densities within 20 nautical miles of the island of San Pedro Martir, which is near a port with marina and support facilities. The Gulf of California is also one of the only known areas where sperm whales feed on a commercially fished species of squid (the jumbo squid, Dosidicus gigas), and thus the PIs will be able to relate abundance, diving behavior and movements of sperm whales to estimated minimum jumbo squid biomass. Intellectual Merits of the Proposed Study. Sperm whales are the largest marine predator and range throughout all deep oceans. They are among the deepest diving marine mammals, and they are thought to feed at depths (ca. 500 m or deeper) that are beyond the diving ability of most other cetaceans with the exception of beaked whales. Hence, they are members of a small group of large marine predators that feed on large and medium size mesopelagic squid (thought to be the primary food source of sperm whales), placing them at the top of the food chain in this deep-sea ecosystem. Their importance in mesopelagic communities results from their large size and food requirements. Worldwide, sperm whales consume an estimated 320 x 106 tonnes of squid annually, 4.7-times more than the biomass of marine fish caught annually by commercial fisheries. Previous studies have relied primarily on tracking sperm whales acoustically from a boat and observing their behavior while at the surface. Satellite telemetry offers a more cost-effective means of tracking the long-term movements of sperm whales and provides detailed information on diving behavior. Analysis of the diving behavior and habitat associations of this species will open a new window to understanding the ecology of large marine predators. The results will produce a better understanding the role of sperm whales as apex predators in the marine ecosystem of the Gulf of California and in other parts of their range. In addition, this information will be useful for creating meaningful management strategies for these endangered animals. Broader impacts resulting from the proposed activity. This project will provide an opportunity for Mexican graduate students to learn about satellite telemetry, marine mammal tagging techniques, and sperm whale biology. This research will develop and improve satellite telemetry techniques for sperm whales and will create a foundation for similar research in other parts of their range where they are more difficult to study. Outreach activities will include interviews, public lectures and written material and photographs to popular magazines in both English and Spanish. Previous research by the PIs has been the focus of several documentary films on cetaceans in the Gulf of California that excite the imagination and help instill an interest in science and wildlife conservation in children and adults.
