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Browsing Biology Data Sets by Subject "Diel patterns"
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DatasetSeasonal trends and diel patterns of downsweep and SEP calls in Chilean blue whales (Balaenoptera musculus)(Woods Hole Oceanographic Institution, 2022-01-13) Redaelli, Laura ; Mangia Woods, Sari ; Landea Briones, Rafaela ; Sayigh, Laela S.To learn more about occurrence and behavior of a recently discovered population of blue whales, passive acoustic data were collected for 15 consecutive months (January 2012 – April 2013) in the Chiloense ecoregion of southern Chile. Automatic detectors and manual auditing were used to detect blue whale songs (SEP calls) and D calls, which were then analyzed to gain insights into temporal calling patterns. We found a year-round acoustic presence of D calls, with the majority occurring during austral summer (December to April), with several sub-monthly peaks. On the other hand, no SEP calls were found during austral winter. Thus, our results support previous studies documenting austral summer residency of blue whales in the Chiloense ecoregion, although they suggest that some individuals remain in the area year-round, highlighting the importance of the Chiloense ecoregion as blue whale habitat. We also investigated daily occurrence of each call type and found that D calls occurred more frequently during dusk and night hours compared to dawn and day periods, whereas SEP calls did not show any significant diel differences. Overall, these findings contribute to a better understanding of occurrence and behavior of endangered Chilean blue whales, which can enhance our ability to develop conservation strategies in this important southern hemisphere habitat.
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DatasetTemporal trends and effects of noise on upsweep calls of Eastern South Pacific southern right whales(Woods Hole Oceanographic Institution, 2022-03-30) Jacobs, Ellen ; Landea Briones, Rafaela ; Sayigh, Laela S.Eastern South Pacific southern right whales (ESPSRW) are a subpopulation of southern right whales (Eubalaena australis) off the coasts of Peru and Chile recognized by the International Union for the Conservation of Nature (IUCN) as critically endangered as a result of heavy whaling efforts in the late 18th to 20th centuries. Most recent population estimates put their numbers around 50 individuals. To test for the efficacy of passive acoustic monitoring of this population, we recorded five months of continuous acoustic data (January 2012-June 2012) off the southwestern tip of Isla de Chiloé. To test for trends in occurrence, we identified a total of 11,313 individual ESPSRW upsweep calls, which have been associated with maintaining contact with conspecifics. Calls increased over the course of the deployment and peaked between April and June, indicating an increase in use of the habitat consistent with the concurrent blue whale migration in the area. A clear diel pattern in which upsweep calls were predominately detected during dusk and night hours was identified, indicating that ESPSRW are likely foraging during daylight hours, as upsweep calls are known to be inversely related to foraging behavior. We also quantified noise levels in the frequency range of their communication (100 Hz third octave) to understand the change in active space whales may be experiencing. We measured noise levels from 90 dB re 1 µPa to 111 dB re 1 µPa (5th and 95th percentile), a 21 dB fluctuation that results in an order-of-magnitude decrease in active space area. We identified sources of high noise at or above the 75th percentile as predominately blue and humpback whale calls (occurring in 71.6% of total sampled minutes) and ship noise (occurring in 69.4% of total sampled minutes). Ship noise was responsible for outliers in excess of 140 dB re 1 µPa. In a population as diminished as ESPSRW, such disruptions of their communication range could result in significant barriers to maintaining contact with conspecifics. Passive acoustic monitoring is a powerful tool for monitoring populations as rarely sighted as ESPSRW. Understanding trends in presence and behavior as well as potential sources of disruption of their calling behavior is vital to determining conservation measures that will be most effective toward helping this critically endangered population.