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- Adapted to change: Low energy requirements in a low and unpredictable productivity environment, the case of the Galapagos sea lion
- Villegas-Amtmann, McDonald, Páez-Rosas, Aurioles-Gamboa, Costa
- Cognitive control of heart rate in diving harbor porpoises
- Summary Marine mammals have adapted to forage while holding their breath in a suite of aquatic habitats from shallow rivers to deep oceans. The key to tolerate such extensive apnea is the dive response, which comprises bradycardia and peripheral vasoconstriction. Although initially considered an all-or-nothing reflex , numerous studies on freely diving marine mammals have revealed substantial dynamics of the dive response to meet the impending dive demands of depth, duration and exercise . Such adjustments are not only autonomic responses, but are under acute cognitive control in pinnipeds  living amphibiously on land and in water. The fully aquatic cetaceans would similarly benefit from cognitive cardiovascular control; however, even though they have exercise-modulated diving bradycardia  and full voluntary control of their respiratory system to such extent that even mild anesthesia often leads to asphyxiation , cognitive cardiovascular control has never been demonstrated for this large group of marine mammals. To address this, we tested the hypothesis that porpoises modulate bradycardia according to anticipated dive duration. Two harbor porpoises, instrumented with ECG recording tags, were trained to perform 20- and 80-second stationary dives, during which they adjusted bradycardia to the anticipated duration, demonstrating cognitive control of their dive response.
- Elmegaard, Johnson, Madsen, McDonald
- Why do satellite transmitters on emperor penguins stop transmitting?
- Investigation of early transmission failure from animal-borne, satellite transmitters should reveal vital information about the reliability of the technology, and the risk of application to the animal. Current technology available to the investigator does not provide firm evidence for causes of transmitter blackout. We address the five most likely causes of satellite transmitter failure on 20 adult (10 male and 10 female) emperor penguins tagged near Cape Colbeck, Antarctica, and one near the Drygalski Ice Tongue, Western Ross Sea, during late summer, 2013. They are: 1. Technical failure of the transmitter, 2. Instrument breakage, 3. Instrument loss because of attachment failure, 4. Predation, and 5. Icing of the salt water detection switch. The longest record of 323 days suggests that prior losses were not due to power failure. Various possibilities of transmission blackout are discussed, and we speculate about the most likely causes of termination of transmissions. A loss of transmission from six tags at similar locations early in the deployments suggests predation. Later losses at random times and locations may be because of antenna breakage or attachment failure. Definite conclusions cannot be made because of the indirect assessment of transmission loss. We suggest some changes in deployment procedures to improve our ability to determine cause of satellite transmission termination in the future. Understanding causes of blackout is important both scientifically and ethically in terms of accurate data interpretation and balancing the benefits of scientific gain with the costs of animal disturbance.
- Kooyman, McDonald, Goetz