Witteveen, B.H., Worthy, G.A.J., Wynne, K.M., Hirons, A.C., Andrews III, A.G., Markel, R.W. 2011. Trophic Levels of North Pacific Humpback Whales (Megaptera novaeangliae) Through Analysis of Stable Isotopes: Implications on Prey and Resource Quality. Aquatic Mammals 37(2), 101-110, DOI 10.1578/AM.37.2.2011.101

Trophic levels of 1,105 humpback whales from six geographically and isotopically distinct North Pacific feeding groups were calculated using δ15N of humpback whales and regional primary consumers. The overall mean trophic level for North Pacific humpback whales was 3.6 ± 0.02, indicating a diet of both fish and zooplankton, and, thus, supporting assumptions of humpback whales as generalist predators. The highest mean trophic level was calculated for the north Gulf of Alaska group (4.0 ± 0.03), while the lowest was found for the Russian and the western Aleutian Islands group (3.3 ± 0.08). Differences in mean trophic levels suggest that feeding groups differ in the proportion of fish and zooplankton in their diets.

Dwyer, S.L., Visser, I.N. 2011. Cookie Cutter Shark (Isistius sp.) Bites on Cetaceans, with Particular Reference to Killer Whales (Orca) (Orcinus orca). Aquatic Mammals 37(2), 111-138, DOI 10.1578/AM.37.2.2011.111

Forty-nine species of cetaceans have been recorded in the literature with cookie cutter shark (Isistius sp.) bites. The first record of a cookie cutter shark bite mark on orca (Orcinus orca) was from New Zealand waters in 1955. We present 37 unpublished records of cookie cutter shark bite marks on orca in tropical to cold waters; a further six published records were collated, and additionally 35 individuals with bite marks were noted in photo-identification catalogues. A total of 120 individuals and 198 bite marks were recorded, with the northernmost at 70° 44' N and the southernmost at 77° 14' S. We provide the first healing rate of a cookie cutter shark bite mark on an orca in New Zealand waters, with a maximum of 150 d between open wound and healed scar. Longevity of scars is considered, with one particular bite mark still visible as a dark grey oval/elliptic mark 1,158 d post photographing the open wound. Open cookie cutter shark bite marks were not observed on orca photo-graphed in Antarctic waters, despite the majority of bite marks being recorded on Antarctic orca. This suggests a high level of movement outside the Antarctic cold water regions as the known distribution of cookie cutter sharks is in warm temperate to tropical waters. Supporting evidence for these movements is given by records of Antarctic orca in New Zealand waters with open cookie cutter shark bite marks.

Holst, M., Greene Jr., C.R., Richardson, W.J., McDonald, T.L., Bay, K., Schwartz, S.J., Smith, G. 2011. Responses of Pinnipeds to Navy Missile Launches at San Nicolas Island, California. Aquatic Mammals 37(2), 139-150, DOI 10.1578/AM.37.2.2011.139

To document the responses of pinnipeds to launches of missiles and similar aerial vehicles, three species of pinnipeds were observed during 77 launches from Navy-owned San Nicolas Island off California from August 2001 to October 2008. Pinniped behavior and flight sounds during each launch were recorded by unattended video cameras and acoustic recorders set up around the island’s periphery, usually in pairs, as vehicles flew over or near haul-out sites. Multiple logistic regression was used to assess dependence of pinniped responses on received sound, distance from flight path, type of vehicle, and natural factors. The majority of observed California sea lions (Zalophus californianus) startled and showed increased vigilance up to 2 min after each launch; responses often included movement on the beach or into the water and were significantly related to received sound level and distance from the vehicle’s closest point of approach. Most observed northern elephant seals (Mirounga angustirostris) showed little reaction to launches and merely raised their heads briefly. Nonetheless, their responses were also related to received sound level and distance from vehicle trajectory. The harbor seal (Phoca vitulina) was the most responsive species. During the majority of launches, most (average 68%; range 7 to 100%) observed harbor seals within ~4 km of the launch trajectory left their haul-out site by entering the water; harbor seals hauled out again at the same site several hours after a launch. Within the range of conditions studied, there was no clear correlation between harbor seal response and received sound level or distance from the closest point of approach of the vehicle. Despite these short-term behavioral reactions, the effects of launch operations are likely to have been minor and localized, with no consequences for local pinniped populations as pinniped population sizes on San Nicolas Island are stable or increasing.

Leeney, R.H., Carslake, D., Elwen, S.H. 2011. Using Static Acoustic Monitoring to Describe Echolocation Behaviour of Heaviside’s Dolphins (Cephalorhynchus heavisidii) in Namibia. Aquatic Mammals 37(2), 151-160, DOI 10.1578/AM.37.2.2011.151

Static acoustic monitoring is a cost-effective, low-effort means of gathering large datasets on echolocation click characteristics and habi­tat use by odontocetes. Heaviside’s dolphins (Cephalorhynchus heavisidii) were monitored using an acoustic monitoring unit, the T-POD, in July 2008 at a site of known high abundance for this species in Walvis Bay, Namibia. The T-POD successfully detected clicks from Heaviside’s dol­phins, and these clicks were detected in the 120 to 140 kHz frequency range. A distinct diel pattern to the hourly mean inter-click interval was observed, with higher values during daylight hours than at night, suggesting that click trains are produced at faster rates at night time. There was no apparent diel pattern in the proportion of buzz trains produced, however. A diel pattern in click activity was observed, with many more detection-positive minutes per hour recorded between dusk and dawn, and vocalization activity dropping to low levels in the middle of the day. This corresponded with visual observations made on abundance of dolphins in the study area. These results suggest that Heaviside’s dolphins use this site primarily during the night. Static acoustic monitoring proved to be an effective technique for monitoring patterns of habitat use by Heaviside’s dolphins.

Dennison, S.R., Boor, M., Fauquier, D., Van Bonn, W., Greig, D.J., Gulland, F.M.D. 2011. Foramen Ovale and Ductus Arteriosus Patency in Neonatal Harbor Seal (Phoca vitulina) Pups in Rehabilitation. Aquatic Mammals 37(2), 161-166, DOI 10.1578/AM.37.2.2011.161

Twenty neonatal harbor seal (Phoca vitulina) pups in rehabilitation following maternal separation underwent serial echocardiographic studies to assess patency and subsequent age of functional closure of the ductus arteriosus (d.a.). B-mode, color-flow Doppler, and pulse and continuous wave Doppler were utilized to identify the d.a. and determine patency and directionality of blood flow. Seals were also evaluated for evidence of foramen ovale (f.o.) patency. B-mode ultrasound was used to evaluate the inter-atrial septum for abnormal (aneurismal) motion, a sign of f.o. patency in other species. In one harbor seal, this motion was confirmed as being consistent with f.o. patency by contrast echocardiography. Closure of the f.o. was not confirmed in any harbor seal prior to release back into the free-ranging population. Data acquired indicate that there is patency of the f.o. and d.a. after birth for a longer period in phocids than in described terrestrial mammals. The f.o. may be patent up to 7 wks of age, and the d.a. may be patent up to 6 wks of age without evidence of clinical consequence. This difference in ontogeny between terrestrial mammals and harbor seals is presumptively a diving adaptation. Such an adaptation is counterintuitive given that humans with f.o. patency are at increased risk of stroke following the introduction or formation of intravascular gas bubbles and suggests that con-current protective mechanisms may be present.

Acevedo-Gutiérrez, A., Cendejas-Zarelli, S. 2011. Nocturnal Haul-Out Patterns of Harbor Seals (Phoca vitulina) Related to Airborne Noise Levels in Bellingham, Washington, USA. Aquatic Mammals 37(2), 167-174. DOI 10.1578/AM.37.2.2011.167

Given their distribution, harbor seals (Phoca vitulina) are likely to interact with human activities and potentially be disturbed. However, it is unclear how human development affects the haul-out behavior of harbor seals near urban areas. Because disturbance related to human development may increase noise levels in air, one might expect seals to haul-out at times when airborne noise levels are low. This study examined the number of harbor seals hauled-out relative to time of day, noise levels in air, and tide level at two haul-out sites in the city of Bellingham, Washington, USA. Harbor seals were observed from May 2008 to April 2009. Two surveys were conducted every 1 to 2 wks—one during the day and one at night. Harbor seal counts and in-air noise levels were recorded approximately 100 m from each haul-out site with binoculars and a sound level meter, respectively. Given the strong correlation between time of day and noise levels, one set of linear mixed effects models examined the interactive influence of time of day and tide level on harbor seal numbers. Another set of models examined the effect of noise level and tide level on harbor seal numbers. Despite fluctuations in harbor seal num­bers in relation to time of year and haul-out site, more harbor seals hauled-out during the night than during the day. The best model for the number of harbor seals hauled-out included an interaction between time of day and tide level, and an interac­tion between noise level and tide level. This study indicated that numbers of harbor seals hauling-out in Bellingham were correlated with time of day and in-air noise levels. However, it is unclear if the nocturnal haul-out behavior of harbor seals was a consequence of human development. It is still possible that an unknown factor associated with time of day was responsible for the observed results. To tease out the correlation between time of day and in-air noise levels, a future comparative study between nearby haul-out sites—one close to human activities and one away from them—is recommended.

Noke Durden, W., Stolen, E.D., Stolen, M.K. 2011. Abundance, Distribution, and Group Composition of Indian River Lagoon Bottlenose Dolphins (Tursiops truncatus). Aquatic Mammals 37(2), 175-186, DOI 10.1578/AM.37.2.2011.175

Information on the abundance and distribution of cetaceans is essential to management and conservation and necessary to assess mortality trends and anthropogenic impacts for stock assessment. Line-transect aerial surveys (n = 45) were conducted to assess bottlenose dolphin (Tursiops truncatus) abundance, distribution, and group composition in the Indian River Lagoon (IRL) estuary system, Florida, from 2002 to 2004. Calves composed 9.41% of all known age class animals sighted. Multiple covariate distance sampling was used to estimate abundance. Abundance estimates varied seasonally, ranging between 362 (95% CI = 192 to 622; summer 2003) and 1,316 dolphins (95% CI = 795 to 2,061; winter 2002-2003), with a mean abundance of 662 dolphins (95% CI = 544 to 842). Abundance estimates for the Mosquito Lagoon sub-basin exhibited the greatest seasonal variability. Seasonal differences in abundance within strata suggest seasonal movement patterns. This study provides the first abundance estimate for IRL dolphins in over 30 y. Further studies that investigate evidence of influx/efflux are needed to better under-stand the population biology of IRL dolphins.