Shifting phenology of an apex/specialist predator tracks changes in its favored prey
Phenology, or the timing of biological activities such as migration, growth, and reproduction, can have dramatic implications for fitness; consumer phenology that is out of step with its resource phenology can cause increased mortality or reduced reproductive success. The timing of southern resident...
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| Format: | Text |
| Language: | English |
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Western CEDAR
2020
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| Online Access: | https://cedar.wwu.edu/ssec/2020ssec/allsessions/80 https://cedar.wwu.edu/cgi/viewcontent.cgi?article=3138&context=ssec |
| Summary: | Phenology, or the timing of biological activities such as migration, growth, and reproduction, can have dramatic implications for fitness; consumer phenology that is out of step with its resource phenology can cause increased mortality or reduced reproductive success. The timing of southern resident killer whale (SRKW, Orcinus orca) movements in the Salish Sea is thought to be related to seasonal migrations of their prey. In recent decades, the abundance and phenology of the favored prey of SRKWs, salmon, has shifted in many locations across the western United States. Here, we use the OrcaMaster Database to quantify seasonal variation in SRKW activity in the Salish Sea, the extent to which these seasonal patterns have shifted in recent decades, and how potential shifts compare to shifts in their prey. Since 1994, we find that SRKWs are arriving later, leaving earlier, and spending fewer days at one well-monitored location adjacent to San Juan Island, and that the timing of SRKW activity corresponds to the timing and abundance of Fraser River Chinook salmon. Across the broader Central Salish Sea region, we find that shifts in SRKW phenology vary by pod. Phenology of J pod has shifted later in the Central Salish Sea, with estimates of peak probability of occupancy delaying at a rate of 5.5 days per year since 2001. Our estimates of phenology of K and L pods, on the other hand, have not shifted dramatically across the dataset. To better understand the extent to which prey availability controls the timing of SRKW activity in inland waters, there is a need for quantification of seasonal variation in salmon abundance throughout the Salish Sea. |
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