scholarly journals Daily and seasonal movements of Cape Cod gray seals vary with predation risk

2020 ◽  
Vol 644 ◽  
pp. 215-228 ◽  
Author(s):  
JH Moxley ◽  
G Skomal ◽  
J Chisholm ◽  
P Halpin ◽  
DW Johnston
Keyword(s):  
Predation Risk ◽  
White Shark ◽  
Halichoerus Grypus ◽  
Cape Cod ◽  
Gray Seal ◽  
Predator Prey ◽  
Seasonal Movements ◽  
Nocturnal Foraging ◽  
And Behavior ◽  
Gray Seals

White sharks Carcharodon carcharias and gray seals Halichoerus grypus are re-establishing their ecological roles within the Northwestern Atlantic Ocean, presenting an opportunity to understand gray seal movement and at-sea behavior under predation risk. As with other shark-seal hotspots, movements to and from terrestrial haul outs can be risky for gray seals, thereby eliciting antipredator strategies. We investigated the movement and coastal behavior of gray seals on Cape Cod (USA) in relation to seasonal and diel changes in white shark activity. Analyzing 412 trips to sea by 8 seals and more than 25000 acoustic detections from 23 individual white sharks, we observed seasonally homogeneous movements in seal behavior during months with greater shark presence. During riskier months, seal behavior manifested in near-exclusive nocturnal foraging, reduced offshore ranging, and limited at-sea activity. On these nocturnal trips to sea, seals returning to haul outs tended to avoid daybreak and traversed during diel minima in shark activity. However, seals tended to depart haul outs at dusk when shark presence was maximal. As conservation efforts succeed in rebuilding depleted populations of coastal predators, studying re-emerging predator-prey interactions can enhance our understanding about the drivers of movement and behavior.

Flatfish may be underestimated in the diet of gray seals (Halichoerus grypus)

2021 ◽  
pp. 1-8
Author(s):  
Michelle N. Dufault ◽  
Zachary H. Olson ◽  
Dominique M. Mellone ◽  
Kelly R. Flanders ◽  
Kathryn A. Ono
Keyword(s):  
New England ◽  
Ecological Impact ◽  
The United States ◽  
Diet Analysis ◽  
Halichoerus Grypus ◽  
Cape Cod ◽  
Gray Seal ◽  
Study Objective ◽  
Species Specific ◽  
Gray Seals

The United States east coast population of the gray seal (Halichoerus grypus (Fabricius, 1791)) was once hunted to near extirpation, but the population has since rebounded due to protection by the Marine Mammal Protection Act of 1972. Although this population growth is seen as a success by conservationists, others are concerned about the economic and ecological impact of gray seals on New England fisheries. The study objective was to quantify flatfish presence in the diet of gray seals using an analysis of prey DNA in seal scat (molecular scatology). This may reduce a potential bias in other diet analysis methods since flatfish may not be swallowed whole, and therefore, their identifying otoliths may not be present. Scats were collected from Muskeget and Monomoy islands off Cape Cod, Massachusetts, USA, in 2016, 2017, and 2018 and analyzed for flatfish presence using species-specific polymerase chain reaction (PCR) assays and a hard parts analysis using otoliths. Frequency of occurrence for flatfish species from DNA was higher than estimated in previous literature on gray seal diet and a concurrent otolith analysis of the same samples, suggesting that previous analyses may have potentially underestimated the importance of flatfish in the diet.

scholarly journals Dynamics of the formation of a differentiation track conditioned reflex to sound stimuli of a certain duration in the gray seal Halichoerus grypus Fabricius, 1791 by the methods of operant conditioning.

2021 ◽  
Vol 12 (3-2021) ◽  
pp. 7-13
Author(s):  
A.F. Berdnik ◽  
Keyword(s):  
Reaction Time ◽  
Operant Conditioning ◽  
Conditioned Reflex ◽  
Audio Signal ◽  
Halichoerus Grypus ◽  
Audio Signals ◽  
Gray Seal ◽  
And Behavior ◽  
Sound Duration

In the course of the study, a 15-year-old female gray seal was trained to press a button after displaying an audio signal for 5 seconds and ignore similar audio signals of longer or shorter duration. The conducted research has demonstrated the ability of the experimental seal to reliably differentiate sound signals with a difference in sound duration of 3 seconds. Changes in the reaction time and behavior of the seal during the demonstration of sound stimuli with distinguishable and indistinguishable time ranges are described.

Seasonal variability and individual consistency in gray seal (Halichoerus grypus) isotopic niches

2019 ◽  
Vol 97 (11) ◽  
pp. 1071-1077
Author(s):  
K.M. Hernandez ◽  
A.L. Bogomolni ◽  
J.H. Moxley ◽  
G.T. Waring ◽  
R.A. DiGiovanni ◽  
...  
Keyword(s):  
United States ◽  
Seasonal Variability ◽  
Foraging Ecology ◽  
Population Level ◽  
The United States ◽  
Halichoerus Grypus ◽  
Dietary Specialization ◽  
Gray Seal ◽  
Individual Consistency ◽  
Gray Seals

Although it is often assumed that individuals in generalist populations are equivalent, recent research indicates that individual dietary specialization can be common in marine predators. Gray seals (Halichoerus grypus (Fabricius, 1791)) were considered locally extinct in United States waters by 1958 but have since recolonized the region. Although considered generalists, less is known about gray seal foraging ecology in the United States. To address this, we used carbon and nitrogen stable isotope analyses to investigate the foraging niches of adult gray seals in Massachusetts, USA. We examined skin, fur, and blood components to investigate seasonal variability and individual consistency in foraging niches, and serially sampled vibrissae to quantify the degree of individual foraging specialization in this population. Our results suggest that seals shift from coastal foraging habitats before molt to offshore habitats after molt, with a coincident shift from higher to lower trophic-level prey. Adult gray seals also exhibited individual consistency in foraging niches independent of population-level shifts and reflect a generalist population composed of individual foraging specialists. These findings serve as a baseline for subsequent research on gray seals in United States waters that could help to determine the mechanisms which promote individual specialization in this population.

Gray Seal Behavior in a Fish Weir Observed Using Dual-Frequency Identification Sonar

2014 ◽  
Vol 48 (4) ◽  
pp. 72-78 ◽  
Author(s):  
Owen C. Nichols ◽  
Ernie Eldredge ◽  
Steven X. Cadrin
Keyword(s):  
Halichoerus Grypus ◽  
Fishing Gear ◽  
Dual Frequency ◽  
Pomatomus Saltatrix ◽  
Negative Effects ◽  
Behavioral Observations ◽  
Frequency Identification ◽  
And Behavior ◽  
Fish Weir ◽  
Gray Seals

AbstractMarine mammal depredation can have significant negative effects on the performance of fixed fishing gears. Gray seals (Halichoerus grypus grypus) have been observed feeding on fish weir catches in Nantucket Sound, and remnants of longfin inshore squid (Doryteuthis pealeii) and finfish in the nets are attributable to seal depredation. A dual-frequency identification sonar (DIDSON) deployed in a weir to monitor squid and fish occurrence captured observations of seal presence and behavior. Continuous recordings of 24+ h were subsampled at multiple intervals to optimize the likelihood of seal detection while minimizing processing time. Targets detected and identified to species included squid, bluefish (Pomatomus saltatrix), and gray seals. Seal occurrence in the weir was observed primarily at night. The presence and behavior of seals may negatively affect the efficiency of the weir due to disruption of the passage of schooling squid and finfish into the catch chamber. Behavioral observations collected using DIDSON can aid in the design of fishing gear modifications to reduce seal depredation.

scholarly journals Pre- and Postnatal Predator Cues Shape Offspring Anti-predatory Behavior Similarly in the Bank Vole

2021 ◽  
Vol 9 ◽  
Author(s):  
Thorbjörn Sievert ◽  
Kerstin Bouma ◽  
Marko Haapakoski ◽  
Kevin D. Matson ◽  
Hannu Ylönen
Keyword(s):  
Predation Risk ◽  
Predatory Behavior ◽  
Behavioral Changes ◽  
Offspring Performance ◽  
Predator Prey ◽  
Maternal Treatment ◽  
Offspring Growth ◽  
Pup Growth ◽  
And Behavior ◽  
Timing Of Exposure

Prey animals can assess the risks predators present in different ways. For example, direct cues produced by predators can be used, but also signals produced by prey conspecifics that have engaged in non-lethal predator-prey interactions. These non-lethal interactions can thereby affect the physiology, behavior, and survival of prey individuals, and may affect offspring performance through maternal effects. We investigated how timing of exposure to predation-related cues during early development affects offspring behavior after weaning. Females in the laboratory were exposed during pregnancy or lactation to one of three odor treatments: (1) predator odor (PO) originating from their most common predator, the least weasel, (2) odor produced by predator-exposed conspecifics, which we call conspecific alarm cue (CAC), or (3) control odor (C). We monitored postnatal pup growth, and we quantified foraging and exploratory behaviors of 4-week-old pups following exposure of their mothers to each of the three odour treatments. Exposure to odors associated with predation risk during development affected the offspring behavior, but the timing of exposure, i.e., pre- vs. postnatally, had only a weak effect. The two non-control odors led to different behavioral changes: an attraction to CAC and an avoidance of PO. Additionally, pup growth was affected by an interaction between litter size and maternal treatment, again regardless of timing. Pups from the CAC maternal treatment grew faster in larger litters; pups from the PO maternal treatment tended to grow faster in smaller litters. Thus, in rodents, offspring growth and behavior are seemingly influenced differently by the type of predation risk perceived by their mothers.

scholarly journals Assessing the disturbance potential of small unoccupied aircraft systems (UAS) on gray seals (Halichoerus grypus) at breeding colonies in Nova Scotia, Canada

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4467 ◽  
Author(s):  
Lauren Arona ◽  
Julian Dale ◽  
Susan G. Heaslip ◽  
Michael O. Hammill ◽  
David W. Johnston
Keyword(s):  
Image Analysis ◽  
Nova Scotia ◽  
Acoustic Properties ◽  
Matched Pair ◽  
Short Term ◽  
Gray Seal ◽  
Aircraft Systems ◽  
Sequential Image ◽  
Young Of The Year ◽  
Gray Seals

The use of small unoccupied aircraft systems (UAS) for ecological studies and wildlife population assessments is increasing. These methods can provide significant benefits in terms of costs and reductions in human risk, but little is known if UAS-based approaches cause disturbance of animals during operations. To address this knowledge gap, we conducted a series of UAS flights at gray seal breeding colonies on Hay and Saddle Islands in Nova Scotia, Canada. Using a small fixed-wing UAS, we assessed both immediate and short-term effects of surveys using sequential image analysis and between-flight seal counts in ten, 50 m2 random quadrats at each colony. Counts of adult gray seals and young-of-the-year animals between first and second flights revealed no changes in abundance in quadrats (matched pair t-test p > 0.69) and slopes approaching 1 for linear regression comparisons (r2 > 0.80). Sequential image analysis revealed no changes in orientation or posture of imaged animals. We also assessed the acoustic properties of the small UAS in relation to low ambient noise conditions using sound equivalent level (Leq) measurements with a calibrated U-MIK 1 and a 1/3 octave band soundscape approach. The results of Leq measurements indicate that small fixed-wing UAS are quiet, with most energy above 160 Hz, and that levels across 1/3 octave bands do not greatly exceed ambient acoustic measurements in a quiet field during operations at standard survey altitudes. As such, this platform is unlikely to acoustically disturb gray seals at breeding colonies during population surveys. The results of the present study indicate that the effects of small fixed-wing UAS on gray seals at breeding colonies are negligible, and that fixed-wing UAS-based approaches should be considered amongst best practices for assessing gray seal colonies.

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