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Kastelein R.A.,Sea Mammal Research Company SEAMARCO | Helder-Hoek L.,Sea Mammal Research Company SEAMARCO | Gransier R.,Sea Mammal Research Company SEAMARCO | Gransier R.,Catholic University of Leuven | And 3 more authors.
Hydrobiologia | Year: 2015

Acoustic mitigation devices (AMDs) are used to deter marine mammals from construction sites to prevent hearing injury by offshore pile-driving noise. In order to quantify the distance at which AMDs designed as ‘seal scarers’ are detected by seals, the 50% hearing thresholds for playbacks of their sounds were determined. The broadband hearing threshold sound pressure levels (SPLs) of two harbor seals for signals from two AMDs were similar (63–69 dB re 1 μPa, rms). Effects of the AMDs on the seals’ behavior were quantified at three SPLs: one which just did not cause behavioral changes, one which caused one of the seals to haul out occasionally, and one which caused one of the seals to haul out more than 10% of the time. The corresponding mean received SPLs were, respectively, Ace Aquatec: 109, 124, and 134 dB re 1 μPa, rms; Lofitech: 128, 133, and 138 dB re 1 μPa, rms. Thus at similar received levels, the Ace Aquatec seems more effective than the Lofitech in deterring harbor seals. Detection and behavioral response distances of the AMD sounds for harbor seals at sea can be estimated by combining the results from the present study with data on AMD source levels, propagation conditions, and background noise levels near construction sites. © 2014, Springer International Publishing Switzerland. Source


Kastelein R.A.,Sea Mammal Research Company SEAMARCO | Hoek L.,Sea Mammal Research Company SEAMARCO | Gransier R.,Sea Mammal Research Company SEAMARCO | Gransier R.,Catholic University of Leuven | And 3 more authors.
Hydrobiologia | Year: 2015

Acoustic Mitigation Devices (AMDs) are used to deter marine mammals from construction sites, in order to prevent hearing injury by offshore pile driving noise. To estimate the distance at which two AMDs designed as ‘seal scarers’ (Ace Aquatec and Lofitech) are detected by harbor porpoises, the 50% hearing detection thresholds for playbacks of recordings of the AMD sounds were assessed. Both became audible at a received broadband sound pressure level (SPL) of 55 dB re 1 μPa. The effect of the AMDs on porpoise behavior was quantified at three SPLs determined during a pre-test: one which just did not cause a behavioral change, one which caused a small change in surfacing and swimming pattern, and one which caused the harbor porpoise to swim away from the transducers. The corresponding mean received SPLs in the pool were respectively: Ace Aquatec: 77, 117, and 139 dB re 1 μPa; and: Lofitech: 91, 121, and 151 dB re 1 μPa. As the mean received SPL increased, greater displacement occurred, and higher numbers of surfacings and increased swimming speed occurred in test periods than in associated baseline periods. By combining these results with the source level, the current local propagation conditions and the background noise, the deterring distance at sea for the AMDs can be calculated. © 2014, Springer International Publishing Switzerland. Source


Kastelein R.A.,Sea Mammal Research Company SEAMARCO | Hoek L.,Sea Mammal Research Company SEAMARCO | Gransier R.,Sea Mammal Research Company SEAMARCO | Jennings N.,Dotmoth
Journal of the Acoustical Society of America | Year: 2013

Pile driving, which creates high amplitude sounds with potentially negative impacts on the marine environment, is used to attach wind turbines to the sea bed. To quantify the distance at which pile driving sounds can be detected by harbor seals, unmasked hearing thresholds were obtained for series of five pile driving sounds recorded at 100 and 800 m from a pile driving location. The played back spectra resembled the spectra of sounds recorded under certain conditions 10-50 km from an offshore pile driving site. The lower the received level, the later within the series of sounds the harbor seals responded. The mean 50% detection threshold sound exposure levels for any sound in the series were: 40 (seal 01, 100 m), 39 (seal 01, 800 m), 43 (seal 02, 100 m), and 43 (seal 02, 800 m) dB re 1 μPa2s (add 9 dB for sound pressure level, dB re 1 μPa). The mean 50% detection thresholds based on detection of only the first sound of the series were ca. 5 dB higher. Detection at sea depends on the actual propagation conditions and on the degree of masking of the sounds by ambient noise, but the present study suggests that pile driving sounds are audible to harbor seals up to hundreds of kilometers from pile driving sites. © 2013 Acoustical Society of America. Source


Kastelein R.A.,Sea Mammal Research Company SEAMARCO | Triesscheijn R.J.V.,Sea Mammal Research Company SEAMARCO | Jennings N.,Dotmoth
Aquatic Mammals | Year: 2016

The dorsal fin of odontocetes has, among other roles, hydrodynamic and thermoregulatory functions. In captivity, the dorsal fin sometimes bends laterally. Bending of the dorsal fin was described in 13 captive harbor porpoises and one captive striped dolphin. All had stranded and been given veterinary care in a small indoor treatment pool. After recovery, most of the animals were moved to a large outdoor floating pen for rehabilitation before being released at sea. The degree of bending of the dorsal fins was related to one, or several, of the following situations: (1) sickness, (2) recovery, (3) addition of pool-mates, (4) change in the direction of current in the pool, and (5) the move to the floating pen. In general, fins began to bend soon after stranding when the animals were ill, floating at the water surface and hardly moving in the small pool. Later in the recovery phase, when the animals could dive and had stereotypical swimming patterns, the fin bent even more. The fin often straightened when the social situation changed due to the introduction of pool-mates; the increase in social interactions usually led to irregular swimming patterns. When the direction of the current in the pool was changed, animals often changed their swimming direction. This often coincided with a change in the angles of their dorsal fins. When recovered, healthy animals were moved to the large floating pen to allow them to become fit enough for release. In the pen, their dorsal fins generally straightened. In order to avoid dorsal fin bending in captive cetaceans, we recommend that the direction of the current in pools should be changed often and that environments should be made as stimulating as possible. Bent dorsal fins of captive harbor porpoises can straighten to some degree. Rehabilitated stranded animals should spend some time in a large pool or pen, preferably with conspecific pool-mates, prior to being released. Source


Kastelein R.A.,Sea Mammal Research Company SEAMARCO | van den Belt I.,Sea Mammal Research Company SEAMARCO | Jennings N.,Dotmoth | de Kruijf R.,Meester van Ekartstraat 22
Zoo Biology | Year: 2014

The behavior of a 13-year-old female Pacific walrus and her first calf is described during the first 7 months of the 19-month suckling period. The calf vocalized before 62% of suckling sessions. The mother immediately responded after 84% of vocalizations; after 44% she allowed a suckling session. The number of suckling sessions per 24-h period decreased from on average nine in the second week after birth to two by the thirteenth week. Thereafter, the number of suckling sessions fluctuated between 3 and 5/day. The average suckling session duration increased from 4min/day to around 17min/day. The average effective suckling time per session increased from on average 2 to 10min. The number of breaks decreased during the study period from around 40 to 20 per session. The mother spent on average 47% of her time resting, the calf 44%. The remaining time was spent in locomotion, and suckling, playing, investigating, and looking. Mother and calf spent on average 51% of time indoors. The mother spent 43% of her time in the water, the calf 39%. The calf's body mass at birth was 55kg; it increased to 178kg at 27 weeks. The mother did not eat for the first 5 days after delivery, and she ate less than usual during the next 6 days. The mother's mass eventually stabilized at 1024kg (>before gestation). The calf was not given formula and was weaned onto fish. This is the first detailed description of a captive Pacific walrus's suckling period. It could benefit the husbandry of future captive-born walruses, and may elucidate the behavior of wild walruses during suckling. Zoo Biol. 34:9-19, 2015. © 2014 Wiley Periodicals, Inc. Source

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