Presentation Abstract
Vessel traffic is a global threat to many marine mammals. Vessels can strike individuals, introduce pollutants, disrupt behavior, and generate noise. Moreover, marine mammals face other threats such as altered prey fields due to anthropogenic factors (e.g. habitat, fisheries, climate change). However, there is often uncertainty regarding what aspects of these threats create the greatest risks given difficulties of studying marine mammal behavior. Here, we use high-resolution animal-borne Dtags to study the behavioral ecology of endangered Southern Resident killer whales (SRKW) that rely on biosonar to hunt Pacific salmon and investigate how proximate vessels affect foraging behavior and outcomes. We used tag data to identify subsurface behavior, including foraging and prey capture events, and test several predictor variables related to SRKW vessel/noise and prey risk factors on (1) behavioral state occurrence, (2) time spent within each state, (3) transition probabilities among states, (4) the probability of prey capture, and (5) multiple parameters of prey capture dives. Whales made fewer dives and spent less time in prey capture dives, with females more likely to transition to a non-foraging state, when vessels were close (average distance < 400 yd/366 m). Additionally, lower abundance of preferred prey and higher vessel speed reduced the probability of prey capture, empirically confirming the interplay between prey availability and vessel disturbance. Finally, whales descended to depth more slowly while increasing the duration of prey capture dives when vessel emitted navigational sonar but descended to depth more quickly when foraging with higher broadband noise and closer vessels. We also highlight current efforts to collect additional tag data to better understand foraging behavior and noise exposure over the diel cycle. Findings advance awareness of the negative consequences of vessels, reveal a sex effect on foraging, demonstrate an effect of echosounders on foraging behavior, and inform management of endangered species.
Session Title
Southern Resident Killer Whales Vessel Impacts & Foraging Success
Conference Track
SSE5: Southern Resident Killer Whales and Vessel Impacts
Conference Name
Salish Sea Ecosystem Conference (2022 : Online)
Document Type
Event
SSEC Identifier
SSE-traditionals-375
Start Date
27-4-2022 11:30 AM
End Date
27-4-2022 1:00 PM
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Type
Text
Language
English
Interactive threats reduce foraging and prey capture effort by endangered killer whales
Vessel traffic is a global threat to many marine mammals. Vessels can strike individuals, introduce pollutants, disrupt behavior, and generate noise. Moreover, marine mammals face other threats such as altered prey fields due to anthropogenic factors (e.g. habitat, fisheries, climate change). However, there is often uncertainty regarding what aspects of these threats create the greatest risks given difficulties of studying marine mammal behavior. Here, we use high-resolution animal-borne Dtags to study the behavioral ecology of endangered Southern Resident killer whales (SRKW) that rely on biosonar to hunt Pacific salmon and investigate how proximate vessels affect foraging behavior and outcomes. We used tag data to identify subsurface behavior, including foraging and prey capture events, and test several predictor variables related to SRKW vessel/noise and prey risk factors on (1) behavioral state occurrence, (2) time spent within each state, (3) transition probabilities among states, (4) the probability of prey capture, and (5) multiple parameters of prey capture dives. Whales made fewer dives and spent less time in prey capture dives, with females more likely to transition to a non-foraging state, when vessels were close (average distance < 400 yd/366 m). Additionally, lower abundance of preferred prey and higher vessel speed reduced the probability of prey capture, empirically confirming the interplay between prey availability and vessel disturbance. Finally, whales descended to depth more slowly while increasing the duration of prey capture dives when vessel emitted navigational sonar but descended to depth more quickly when foraging with higher broadband noise and closer vessels. We also highlight current efforts to collect additional tag data to better understand foraging behavior and noise exposure over the diel cycle. Findings advance awareness of the negative consequences of vessels, reveal a sex effect on foraging, demonstrate an effect of echosounders on foraging behavior, and inform management of endangered species.
