[MARMAM] Abstracts - Aquatic Mammals, vol. 34, issue 4; 2008
dagmar_fertl at hotmail.com
Fri Feb 6 19:54:20 PST 2009
Dear Marmam and ECS-mailbase subscribers,
Apologies to those of you who will get duplicate emails due to cross-posting. The following are abstracts from the most recent issue of Aquatic Mammals, the scientific peer-reviewed journal of the European Association for Aquatic Mammals (EAAM). Abstracts are presented as a courtesy to the EAAM and the journal editors – Drs. Jeanette Thomas (managing editor; aquaticmammals at gmail.com) and Kathleen Dudzinski (co-editor; kdudzinski at dolphincommunicationproject.org). The journal publishes papers dealing with all aspects of the care, conservation, medicine and science of aquatic mammals. The journal receives support of the Alliance of Marine Mammal Parks and Aquariums and the International Marine Animal Trainers' Association (IMATA). For more information on the journal, please go to: http://www.aquaticmammalsjournal.org/. Contact information is provided for the corresponding author for each article. Please do not contact the listserve editors or me for pdfs or copies of the articles.
Thank you for your continued interest in the journal and these postings.
dfertl at gmail.com
Walker, K.A.*, J.W. Davis, and D.A. Duffield. 2008. Activity budgets and prey consumption of sea otters (Enhydra lutris kenyoni) in Washington. Aquatic Mammals 34(4):393-401.
*email: walkerkr at interchange.ubc.ca
Northern sea otters (Enhydra lutris kenyoni) were extirpated from the Washington coast in the early 1900s. Reintroductions of sea otters from Amchitka Island, Alaska, occurred in 1969 and 1970. By 2005, 814 sea otters occupied a range from Destruction Island north to Makah Bay. The focus of this study was to investigate diurnal activity budgets and variability in prey consumption at four locations in the current Washington sea otter range to test hypotheses concerning population growth potential and local impact of sea otters on prey availability. Overall, sea otters primarily spent their daylight hours resting (62.3%), grooming (19.7%), and feeding (7.6%). These activities varied by location. Diet consisted predominantly of crabs, clams, and sea stars. In each study area, one main prey item comprised 33.4 to 64.4% of the total prey consumed; however, the main prey item differed among locations. Of the foraging dives observed, 81.4% were successful. Average dive duration was 35.6 s; however, this varied among locations as well. The study locations were utilized differently—some as resting sites and others as feeding sites. The low diurnal feeding activity found in this study indicates that food availability was high, suggesting that this Washington population of sea otters is currently below equilibrium density.
Timmel, G.*, S. Courbis, H. Sargeant-Green, and H. Markowitz. 2008. Effects of human traffic on the movement patterns of Hawaiian spinner dolphins (Stenella longirostris) in Kealakekua Bay, Hawaii. Aquatic Mammals 34(4):402-411.
*email: gtimmel at berkeley.edu
Kealakekua Bay is an important resting site for Hawaiian spinner dolphins (Stenella longirostris) and is popular with both local residents and tourists. Human activities occurring here include swimming, snorkeling, kayaking, and motor-boating. The objectives of this study were to document movement patterns of dolphin groups in Kealakekua Bay, to determine if different types and levels of human activity within the bay result in quantifiable changes in dolphin group movement patterns, and to provide baseline data for future studies. Theodolite tracking was used to assess responses of dolphin groups to human traffic. Variables examined included group mean leg speed (leg speed: the distance between two consecutive theodolite fixes of a dolphin group divided by time; mean leg speed: the average of all leg speeds comprising a track) and group reorientation rate. Swimmers and/or vessels were present within 100 m of all dolphin groups tracked during all surveys. Regression analyses were used to examine potential relationships between dolphin group related variables (e.g., reorientation rate, mean leg speed) and variables related to human activities (e.g., swimming, kayaking, motor-boating). Increasing levels of human activity had a limited but measurable effect on the movement patterns of Hawaiian spinner dolphin groups at this site.
Halvorsen, K.M.*, and E.O. Keith. 2008. Immunosuppression cascade in the Florida manatee (Trichechus manatus latirostris). Aquatic Mammals 34(4):412-419.
*email: Katherinemarina at gmail.com
The Florida manatee (Trichechus manatus latirostris) is a federally endangered marine mammal that resides on both coasts of the Florida peninsula. The species faces many anthropogenic and natural threats, including boat strikes, exposure to harmful algal blooms, and cold water temperatures. We have developed a conceptual model that depicts how changes in the environment, such as reduced water temperature, can trigger an immunosuppressive cascade of interrelated diseases and pathological conditions ultimately leading to the death of the animal. Although the Florida manatee has a relatively robust immune system, rendering it resistant to several diseases, the onset of unfavorable environmental conditions has been shown to compromise the immune system, often leading to infections that make an animal more susceptible to opportunistic pathogens. In this paper, we review several common diseases of the Florida manatee and compare and contrast their symptoms. We then interrelate these diseases and generate a conceptual model of a cascade of immunosuppressive conditions originally triggered by adverse environmental conditions or one of the diseases. The end result of the cascade is the death of the animal.
Kastelein, R.A.*, and P.J. Wensveen. 2008. Effect of two levels of masking noise on the hearing threshold of a harbor porpoise (Phocoena phocoena) for a 4.0 kHz signal. Aquatic Mammals 34(4):420-425.
*email: researchteam at zonnet.nl
The 50% detection hearing thresholds of a harbor porpoise for a 4.0 kHz narrow-band FM signal, presented at the background noise level in a pool and with two masking noise levels, were measured using a go/no-go response paradigm and an up-down staircase psychometric method. The masker consisted of a ⅙-octave noise band with a center frequency of 4.25 kHz. Its amplitude declined at 24 dB/octave on both sides of the spectral plateau. The absolute hearing threshold of the porpoise, found previously, was confirmed. The animal's auditory system responded in a linear fashion to the increase in masking noise. Since the narrow-band noise was off-center of the test frequency, the critical ratio of a harbor porpoise for 4.0 kHz tonal signals in white noise can at present only be estimated to be between 18 and 21 dB re: 1 μPa.
Pereira, J.N.D.S.G. 2008. Field notes on Risso's dolphin (Grampus griseus) distribution, social ecology, behaviour, and occcurrence in the Azores. Aquatic Mammals 34(4):426-435.
*email: jngpereira at oma.pt
This study reports new information on Grampus griseus (G. Cuvier, 1812) distribution with depth and slope, group size, general and interspecific behaviour, and calving intervals for the Azorean archipelago. Observations are in agreement with scarce previous work and most other regions in the North Atlantic and Mediterranean. Data were collected on 107 sightings south of Pico Island that took place between 17 May and 29 August 2003 from opportunistic research platforms. Information on occurrence, provided by an observer with 50 y of land-based cetacean experience, was included for comparison. Risso's dolphins preferred areas between 497 and 1,233 m depth (modal class 600 to 650 m; N = 69), with slopes between 27 and 35%, although these data require validation. The majority of groups were composed of up to 20 individuals (modal 6 to 10), averaging 12.3 (1 to 55; N = 74). Large socializing aggregations observed during July and August (55 to ∼175 individuals) were similar to land-based observations between 1992 and 2005.G. griseus's diurnal activities in this study were mostly traveling (77%) and socializing (13%), with feeding (5%) and resting (3.7%) occurring less frequently. The first newborn calves are reported. Two-species groups and interactions with six cetacean species are described. Harassment behaviours with Globicephala spp. and Physeter macrocephalus suggest competitive interference. Year-round observations between 1992 and 2005 near Pico Island, together with birth reports and recent data on site fidelity, suggest population residency.
Weir, C.R.*, S. Canning, K. Hepworth, I. Sim, and K.A. Stockin. 2008. A long-term opportunistic photo-identification study of bottlenose dolphins (Tursiops truncatus) off Aberdeen, United Kingdom: Conservation value and limitations. Aquatic Mammals 34(4):436-447.
*email: c.r.weir at abdn.ac.uk
The waters of the Inner Moray Firth were designated a Special Area of Conservation (SAC) in 2005 for the conservation of the bottlenose dolphin (Tursiops truncatus) in northeast Scotland. However, the long-term conservation of this population requires monitoring throughout its entire known range. Opportunistic photo-identification of bottlenose dolphins occurred during 65 cetacean surveys conducted between 1999 and 2008 in the coastal waters of Aberdeenshire. A total of 88 bottlenose dolphin photo-identification encounters resulted in one to 45 animals identified per survey. The minimum annual total population size based on marked animals alone was 62 individuals, and the discovery curve indicated that the population has not yet been adequately sampled. Of 40 highly distinctive adult animals, the annual sighting rate ranged from 0.167 (seen in one year only) to 1.000 (seen every year). The cumulative monthly sighting rate varied from 0.091 (photographed in one month only) to 0.636 (photographed during seven of the 11 combined survey months in the 2001 to 2008 study period). The overall seasonal occurrence of dolphins off Aberdeenshire peaked during May and June, when 65% of distinctively marked animals were recorded per month (combined data for 2001 to 2008). Eighty-four percent of distinctively marked dolphins were matched with those photographed in the Inner Moray Firth, while 93% were matched with those photographed in the southern Outer Moray Firth. Despite its opportunistic nature, the photo-identification study provided valuable information on a population of bottlenose dolphins in a poorly studied part of their range. The high percentage of matches with dolphins from the Moray Firth SAC indicates that over half of the known northeast Scotland population uses the Aberdeenshire region, and some individuals do so regularly. The frequent occurrence off Aberdeen of bottlenose dolphins from a protected SAC has repercussions for the conservation and management of the population and for the effectiveness of the SAC for their long-term protection.
Richlen, M.F.*, and J.A. Thomas. 2008. Acoustic behavior of Antarctic killer whales (Orcinus orca) recorded near the ice edge of McMurdo Sound, Antarctica. Aquatic Mammals 34(4):448-457.
*email: richlen at hawaii.edu
Underwater acoustic recordings of a group of seven to nine killer whales (Orcinus orca) were made opportunistically along a lead within the fast-ice in McMurdo Sound, Ross Sea, Antarctica in early December 1979. At the time of the recordings, the killer whale group was chasing Adélie penguins (Pygoscelis adeliae); however, no predation events were observed. A total of 87 min and 39 s were recorded and examined, with 506 sounds analyzed. The animals produced echolocation clicks, buzz sequences, pulsed signals, and whistles. Seven previously undocumented call types were described from these killer whales based on consistent aural and spectrographic analysis of signals. Acoustic measurements were made in the frequency and time domains using spectrographic and power spectrum analysis. This preliminary study is the first quantitative report on the acoustic features of underwater sounds produced by a specific group of killer whales in Antarctic waters. The acoustic characteristics are similar to sounds described from killer whale populations throughout the world, and the consistent repetition of call types suggests a pod-specific repertoire. Three different ecotypes of killer whales have been described in Antarctic waters based on their color pattern, habitat use, and prey preference. The group of animals recorded in this study is believed to be Type C killer whales based on photographs as well as behavioral observations at the surface. In order to compare vocal repertoires and acoustic behavior with analogous sympatric ecotypes from, for example, the Northeast Pacific, it will be necessary to analyze calls made from the other known Antarctic ecotypes. Acoustic analyses could very likely be a reliable diagnostic tool for identifying sympatric ecotypes in Antarctic waters.
Oviedo, L.*, H.M. Guzman, L. Flórez-González, J.C. Alzueta, and J.M. Mair. 2008. The song of the southeast Pacific humpback whale (Megaptera novaeangliae) off Las Perlas Archipelago, Panama: Preliminary characterization. Aquatic Mammals 34(4):458-463.
*email: leninovi1 at gmail.com
Humpback whales (Megaptera novaeangliae) aggregate in winter breeding and calving grounds in tropical waters. Acoustic features of song produced by males in breeding wintering areas remain unknown for many breeding sites such as those located in Central America. In other areas, recordings of humpback whale songs in wintering grounds have been used to establish geographical differences among populations. Previous investigations have revealed that geographically isolated populations produce distinctive songs. This study represents the first efforts to record and analyze songs from the Southeastern Pacific stock of M. novaeangliae in the tropical wintering grounds off Central America. The aim of this study was to characterize underwater sounds of whales recorded in Las Perlas Archipelago, Panama. The acoustical structure of the themes for years 2006 and 2007 was typical of songs recorded in other wintering areas. As a result of this analysis, Las Perlas Archipelago should be identified as a critical area for breeding humpback whales.
Simard, P.*, D.A. Mann, and S. Gowans. 2008. Burst-pulse sounds recorded from white-beaked dolphins (Lagenorhynchus albirostris). Aquatic Mammals 34(4):464-470.
*email: psimard at mail.usf.edu
Dolphin sounds are generally categorized as tonal whistles or pulsed clicks. Pulsed signals in dolphins are usually associated with echolocation; however, an increasing number of species have been found to produce burst-pulse signals, which may be used for communication. Groups of white-beaked dolphins (Lagenorhynchus albirostris) were recorded near Halifax, Nova Scotia, Canada, with a hydrophone towed 25 m behind the boat at a depth of approximately 5 m and an M-Audio 24/96 digital recorder (16 bit, 96 kHz). During one 50-min encounter, 10 burst-pulse segments were recorded. Mean burst-pulse duration was 0.33 s (SD 0.17 s, range 0 3 to 0.60 s). Peaks from burst-pulses were accurately identified with a MATLAB software-based signal detection and analysis program in nine segments of the recordings, totaling 521 individual peaks. Mean pulse rate was 719 Hz (SD 207 Hz, range 423 to 1,103 Hz), while the mean pulse period was 1.39 ms (SD 0.41 ms, range 0.91 to 2.36 ms). Mean peak frequency was 35.3 kHz (SD 11 kHz, range 1.5 to 46.5 kHz), and mean 3-dB bandwidth was 5.1 kHz (SD 1.4 kHz, range 3 to 10.5 kHz). Maximum received level was 159 dB re 1 μPa. The observed pulse rates were likely too rapid to be of use for echolocation. These sounds were made immediately before the group began actively swimming away from the boat at high speed, suggesting that they were used for communication as has been proposed for other species of dolphins. This is the first time burst-pulses have been quantitatively analyzed for this genus of dolphin.
Ridgway, S.H. 2008. History of veterinary medicine and marine mammals: A personal perspective. Aquatic Mammals 34(4):471-513.
*no email address provided. Contact information: U.S. Navy Marine Mammal Program, 53560 Hull Street, San Diego, CA 92152, USA and Department of Pathology, School of Medicine, University of California at San Diego, La Jolla, CA 92093, USA
Dr. Ridgway is one of the founding fathers of marine mammal medicine, having completed the lion's share of the seminal work in marine mammal medicine, while continuing to this day to promote both applied and basic research in the field of marine mammalogy. He has published over 250 papers, book chapters and books, including one of the most definitive works on marine mammals, Mammals of the Sea, published in 1972. He has spent his entire career working for the US Navy Marine Mammal Program.
Di Guardo, G. 2008. Dolphin morbillivirus in the Mediterranean Sea. Aquatic Mammals 34(4):514-515.
*email: gdiguardo at unite.it
No abstract provided. This is a letter to the editor.
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