Development of an animal-borne “sonar tag” for quantifying prey availability: test deployments on northern elephant seals

Lawson, Gareth L.; Hückstädt, Luis A.; Lavery, Andone C.; Jaffré, Frederic; Wiebe, Peter H.; Fincke, Jonathan R.; Crocker, Daniel E.; Costa, Daniel P.

doi:10.1186/s40317-015-0054-7

Cited by 22 publications

(26 citation statements)

References 55 publications

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“…This makes it difficult to assess the deeper limit of the prey patch on which the SES feed at the bottom of their dives or to test predictions about their foraging behaviour. The development of video camera [34,91,95] and miniaturized sonar loggers [96] may help to overcome these difficulties by providing information about the prey quality and extend our perception range of environment surrounding the SES.…”

Section: Discussionmentioning

confidence: 99%

How Elephant Seals (Mirounga leonina) Adjust Their Fine Scale Horizontal Movement and Diving Behaviour in Relation to Prey Encounter Rate

et al. 2016

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Understanding the diving behaviour of diving predators in relation to concomitant prey distribution could have major practical applications in conservation biology by allowing the assessment of how changes in fine scale prey distribution impact foraging efficiency and ultimately population dynamics. The southern elephant seal (Mirounga leonina, hereafter SES), the largest phocid, is a major predator of the southern ocean feeding on myctophids and cephalopods. Because of its large size it can carry bio-loggers with minimal disturbance. Moreover, it has great diving abilities and a wide foraging habitat. Thus, the SES is a well suited model species to study predator diving behaviour and the distribution of ecologically important prey species in the Southern Ocean. In this study, we examined how SESs adjust their diving behaviour and horizontal movements in response to fine scale prey encounter densities using high resolution accelerometers, magnetometers, pressure sensors and GPS loggers. When high prey encounter rates were encountered, animals responded by (1) diving and returning to the surface with steeper angles, reducing the duration of transit dive phases (thus improving dive efficiency), and (2) exhibiting more horizontally and vertically sinuous bottom phases. In these cases, the distance travelled horizontally at the surface was reduced. This behaviour is likely to counteract horizontal displacement from water currents, as they try to remain within favourable prey patches. The prey encounter rate at the bottom of dives decreased with increasing diving depth, suggesting a combined effect of decreased accessibility and prey density with increasing depth. Prey encounter rate also decreased when the bottom phases of dives were spread across larger vertical extents of the water column. This result suggests that the vertical aggregation of prey can regulate prey density, and as a consequence impact the foraging success of SESs. To our knowledge, this is one of only a handful of studies showing how the vertical distributions and structure of prey fields influence the prey encounter rates of a diving predator.

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Section: Discussionmentioning

confidence: 99%

How Elephant Seals (Mirounga leonina) Adjust Their Fine Scale Horizontal Movement and Diving Behaviour in Relation to Prey Encounter Rate

et al. 2016

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“…Responses observed are similar to hypothesized elephant seal behavior to escape predators by diving deeper [37], and responses to anthropogenic sound sources are not unexpected [13,44]. Responses elicited during CEEs Table 4 Mean change in depth for non-exposure and exposure dive inversions Dive inversions are defined by a change from ascending to descending >3 m over 4 s, for all dives deeper than 100 m. Standard deviation is given in parentheses, and n is given for each.…”

Section: Animal Response To Disturbancementioning

confidence: 67%

“…This is the first dedicated BRS conducted on any marine mammal using an animal-borne sound source (see [44] for incidental BRS with an active sonar tag). This approach has the potential to expand and complement current CEE methodologies.…”

Section: Discussionmentioning

confidence: 99%

An animal-borne active acoustic tag for minimally invasive behavioral response studies on marine mammals

et al. 2016

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Background:There is a variety of evidence that increased anthropogenic noise (e.g., shipping, explosions, sonar) has a measureable effect on marine mammal species. Observed impacts range in severity from brief interruptions of basic life functions to physiological changes, acute injury, and even death. New research tools are needed to better measure and understand the potential effects of anthropogenic noise on marine mammals. Current behavioral response studies typically utilize ship-based sound sources to study potential acute behavioral responses in tagged animals experimentally exposed to noise. Integrating the sound source within animal-mounted passive acoustic and motionsensing tags provides a novel tool for conducting additional highly controlled response studies. Results:We developed and conducted pilot field trials of a prototype tag on five juvenile northern elephant seals, Mirounga angustirostris, using experimental exposures to both natural and anthropogenic noise stimuli. Results indicate behavioral responses were elicited in tagged individuals. However, no pattern was found in the occurrence and types of response compared to stimulus type. Responses during the ascending dive phase consisted of a dive inversion, or sustained reversal from ascending to descending (8 of 9 exposures). Dive inversions following exposure were 4-11 times larger than non-exposure inversions. Exposures received during the descending dive phase resulted in increased descent rates in 9 of 10 exposures. All 8 exposures during dives in which maximum dive depth was limited by bathymetry were characterized by increased flow noise in the audio recordings following exposure, indicating increased swim speed. Conclusions:Results of this study demonstrate the ability of an animal-mounted sound source to elicit behavioral responses in free-ranging individuals. Behavioral responses varied by seal, dive state at time of exposure, and bathymetry, but followed an overall trend of diving deeper and steeper and swimming faster. Responses did not consistently differ based on stimulus type, which may be attributable to the unique exposure context of the very close proximity of the sound source. Further technological development and focused field efforts are needed to advance and apply these tools and methods in subsequent behavioral response studies to address specific questions.

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“…Even the normal operation of tags may have unintended negative effects, as demonstrated by changes in behavior of juvenile northern elephant seals deployed with a pinging “sonar tag” (Lawson et al . ).…”

Section: Discussionmentioning

confidence: 97%

Telemetry tags increase the costs of swimming in northern fur seals, Callorhinus ursinus

Rosen

Gerlinsky

Trites

2017

Marine Mammal Science

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Animal‐borne instruments have become a standard tool for collecting important data from marine mammals. However, few studies have examined whether placement of these data loggers affects the behavior and energetics of individual animals, potentially leading to biasing data. We measured the effect of two types of relatively small data loggers (<1% of animals’ mass and front profile) on the swimming speeds and energy expenditure of four female northern fur seals (Callorhinus ursinus) while swimming at depth. Swim speeds and rates of oxygen consumption were measured as the trained fur seals repeatedly swam an underwater circuit, with or without the tags. We found the placement of either tested tag significantly affected both the behavior and energetics of the fur seals in our study. Diving metabolic rate increased an average of 8.1%–12.3% (depending on tag type) and swim speed decreased an average of 3.0%–6.0% when wearing the tags. The combined changes in velocities and metabolic rates resulted in a 12.0%–19.0% increase in the total energy required by the fur seals to swim a set distance. The demonstrated effects of tags on behavior and energy expenditure may bias data sets from wild animals and potentially incur longer‐term impacts on the studied animals.

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Development of an animal-borne “sonar tag” for quantifying prey availability: test deployments on northern elephant seals

Cited by 22 publications

References 55 publications

How Elephant Seals (Mirounga leonina) Adjust Their Fine Scale Horizontal Movement and Diving Behaviour in Relation to Prey Encounter Rate

How Elephant Seals (Mirounga leonina) Adjust Their Fine Scale Horizontal Movement and Diving Behaviour in Relation to Prey Encounter Rate

An animal-borne active acoustic tag for minimally invasive behavioral response studies on marine mammals

Telemetry tags increase the costs of swimming in northern fur seals, Callorhinus ursinus

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