Age-specific survival, abundance, and immigration rates of a Weddell seal (Leptonychotes weddellii) population in McMurdo Sound, Antarctica

2004 ◽  
Vol 82 (4) ◽  
pp. 601-615 ◽  
Author(s):  
Michael F Cameron ◽  
Donald B Siniff
Keyword(s):  
Information Criterion ◽  
Weddell Seal ◽  
Adult Survival ◽  
Sea Ice Extent ◽  
Leptonychotes Weddellii ◽  
Mcmurdo Sound ◽  
Weddell Seals ◽  
Abundance Estimates ◽  
Fast Ice ◽  
The 1960S

Since the 1960s, Weddell seals (Leptonychotes weddellii (Lesson, 1826)) have been tagged and surveyed annually in McMurdo Sound, Antarctica. Mark–recapture analyses and model selection trials using Akaike's Information Criterion indicate that sex, cohort, and year affect juvenile (ages 1 and 2) survival. In contrast, year and perhaps sex and cohort are less important factors for adult survival. Average annual survival is higher among adults (0.93) than juveniles (0.55–0.59) and there is little evidence for senescence to at least age 17. The oldest known-aged female and male in the study were 27 and 24 years old, respectively. Data suggest that the abundance of a resident population of Weddell seals remains relatively stable over time despite annual fluctuations in Jolly–Seber abundance estimates for the entire population. We argue that this annual variability is likely the result of temporary immigration of animals born outside the study area; mean rates are estimated from a simulation model and tagging data to be between 16.8% and 39.7% for females and between –13.1% and 31.6% for males. Sea ice extent appears to affect immigration where, during times of reduced fast-ice, immigrants are forced, or allowed easier access, into the ice-covered areas of Erebus Bay from surrounding locations. Our findings contradict previous studies reporting lower survival and higher immigration. Model choice is shown to be the most likely cause of these discrepancies and we provide evidence that our models are more appropriate than those used elsewhere.

Preweaning mortality of Weddell seal pups

1996 ◽  
Vol 74 (9) ◽  
pp. 1775-1778 ◽  
Author(s):  
Jason F. Schreer ◽  
Kelly K. Hastings ◽  
J. Ward Testa
Keyword(s):  
Mortality Rates ◽  
Weddell Seal ◽  
Leptonychotes Weddellii ◽  
Mark Recapture ◽  
Mcmurdo Sound ◽  
Weddell Seals ◽  
Ice Surface ◽  
Open Populations ◽  
Significant Mortality

We examined mortality prior to weaning of Weddell seal pups (Leptonychotes weddellii), using resighting data collected from 1984 to 1993 on the annual ice of McMurdo Sound, Antarctica. Mortality rates were estimated using counts of dead pups found on the surface and mark–recapture techniques. The standard Jolly–Seber model for open populations fit the recapture data best and corresponded well to the known biology of these animals. Yearly mortality rates estimated by mark–recapture techniques ranged from 6 to 22%, with a mean across years of 13%. These values are twice as high as those previously reported for Weddell seals and those calculated from counts of dead pups in this study. This suggests that there is significant unseen mortality due either to undiscovered fatalities on the ice surface or to significant mortality occurring in the water.

Juvenile survival and recruitment in a population of Weddell seals (Leptonychotes weddellii) in McMurdo Sound, Antarctica

1987 ◽  
Vol 65 (12) ◽  
pp. 2993-2997 ◽  
Author(s):  
J. Ward Testa
Keyword(s):  
Census Data ◽  
Survival Rates ◽  
Breeding Population ◽  
Weddell Seal ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Apparent Survival ◽  
Mcmurdo Sound ◽  
Juvenile Dispersal ◽  
Weddell Seals

Survival and recruitment of Weddell seal pups were studied in eastern McMurdo Sound, Antarctica. Pups were marked and their apparent survival estimated by mark–recapture methods. The resulting estimates were used together with published estimates of adult survival, yearly sighting probabilities, and direct counts of pup production to simulate the dynamics of the population and evaluate the assumption that it is closed to immigration. Estimates derived from census data in 1982 and 1983 were over five times larger than those simulated. This discrepancy was due to the extremely low juvenile survival rates calculated from marked seals. Since few animals born in Erebus Bay return to breed, the large adult breeding population must be the result of substantial immigration, indicating an important role for juvenile dispersal in the population dynamics of Weddell seals.

Over-winter movements and diving behavior of female Weddell seals (Leptonychotes weddellii) in the southwestern Ross Sea, Antarctica

1994 ◽  
Vol 72 (10) ◽  
pp. 1700-1710 ◽  
Author(s):  
J. Ward Testa
Keyword(s):  
Ross Sea ◽  
Diving Behavior ◽  
Winter Period ◽  
Pleuragramma Antarcticum ◽  
Long Distance ◽  
Leptonychotes Weddellii ◽  
Mcmurdo Sound ◽  
Weddell Seals ◽  
Pack Ice ◽  
Fast Ice

The movements and diving behavior of 18 adult female Weddell seals (Leptonychotes weddellii) were determined by satellite telemetry during the over-winter period in 1990 and 1991. Nine seals provided diving and movement data for 8 – 9 months. Seals that normally bred in the eastern part of McMurdo Sound spent most of the winter in the middle and northern parts of McMurdo Sound before the annual shore-fast ice had formed in those areas, or in the pack ice 0–50 km north of the sound and Ross Island. This is a greater use of pack ice, as opposed to shore-fast ice, in winter than was previously believed. Some long-distance movements (one over 1500 km in total) to the middle and northwestern parts of the Ross Sea also occurred. Although highly variable within and between individuals, dives indicative of foraging were primarily to mid-water regions (100 – 350 m) in both years, and were similar to those that have been observed in spring and summer, when Pleuragramma antarcticum is the primary prey of Weddell seals in McMurdo Sound.

The behavioural response of lactating Weddell seals (Leptonychotes weddellii) to over-snow vehicles: a case study

2007 ◽  
Vol 85 (4) ◽  
pp. 488-496 ◽  
Author(s):  
T.D. van Polanen Petel ◽  
M.A. Giese ◽  
S. Wotherspoon ◽  
M.A. Hindell
Keyword(s):  
Adult Female ◽  
Scientific Research ◽  
Weddell Seal ◽  
Behavioural Response ◽  
Leptonychotes Weddellii ◽  
Weddell Seals ◽  
Fast Ice ◽  
Vehicle Activity

Over-snow vehicles are used extensively at Antarctic scientific research stations. Adult female Weddell seals ( Leptonychotes weddellii (Lesson, 1826)) also utilise the fast-ice and are therefore often exposed to vehicular activity, with the potential of affecting their behaviour. Guidelines for vehicular travel have been developed to minimise disturbance to Antarctic wildlife; however, these guidelines have not yet been scientifically tested. To examine the efficiency and sensitivity of existing guidelines used within the Australian Antarctic Territory (AAT), we conducted drive-by experiments of two types of over-snow vehicles. The results of these experiments showed that the probability of a lactating Weddell seal looking at the vehicles and the duration of the seals’ looking at the vehicles were dependent on the distance between vehicles and seals, the position of the pups in relation to its mother, and the distance the adult female was from the water. Although the seals apparently perceived the vehicles to be a threat, no seals fled in response to vehicle activity. We propose that the existing guidelines used in the AAT could be amended to increase separation distances between vehicles and breeding Weddell seals if the goal of management is to ensure that Weddell seal behaviour is unaffected by vehicle travel.

Possible food caching and defence in the Weddell seal: observations from McMurdo Sound, Antarctica

2005 ◽  
Vol 17 (1) ◽  
pp. 71-72 ◽  
Author(s):  
S.L. KIM ◽  
K. CONLAN ◽  
D.P. MALONE ◽  
C.V. LEWIS
Keyword(s):  
Shallow Water ◽  
Benthic Communities ◽  
Weddell Seal ◽  
Leptonychotes Weddellii ◽  
Mcmurdo Sound ◽  
Weddell Seals ◽  
Food Caching ◽  
The Common ◽  
Made In

On the basis of observations of Weddell seals (Leptonychotes weddellii Lesson) made in the course of studying shallow-water benthic communities in McMurdo Sound, Antarctica, we suggest that caching and/or defence of uneaten food may be a strategy practiced by this animal. Such a phenomenon is uncommon but taxonomically widespread among vertebrates. Depending on circumstances, it is termed hoarding, caching, or storage and may be short- or long-term, include defence of the resource, or have other variable expressions, with the common threads being deferred consumption and deterrence of consumption by others (Vanderwall 1990). Many vertebrate taxa exhibit hoarding behaviour, including rodents (e.g. Sciuridae), carnivores (e.g. Canidae, Felinidae) and birds (e.g. Corvidae, Picidae). No form of food caching, to our knowledge, has ever been reported in a wild pinniped.

Animal-Borne Instrumentation Systems and the Animals that Bear Them: Then (1939) and Now (2007)

2007 ◽  
Vol 41 (4) ◽  
pp. 6-8 ◽  
Author(s):  
Gerald Kooyman
Keyword(s):  
Loggerhead Turtle ◽  
Video Camera ◽  
Weddell Seal ◽  
Gps Tracking ◽  
Major Step ◽  
Mcmurdo Sound ◽  
Weddell Seals ◽  
History Of ◽  
Archival Systems ◽  
Microprocessor Technology

The history of animal-borne instrumentation is reviewed from the first basic depth gauge invented in the late 1800s, to the complex animal-borne imagery and archival systems of the present day. A major breakthrough occurred in 1964 when the first time-depth recorder was deployed on a Weddell Seal in McMurdo Sound, Antarctica. The next phase in the study of animals at sea was the use of microprocessors as archival recorders in the mid-1980s. These also were first attached to Weddell seals in McMurdo Sound. Microprocessor technology made possible the next major step of attaching a video camera housed in a submersible case (Crittercam) to a loggerhead turtle. Since the 1990s the field of “Biologging” has flourished, with new additions of satellite and GPS tracking, and resulted in three major international symposiums in the past four years (2003-2007).

Calling depth and time and frequency attributes of harp (Pagophilus groenlandicus) and Weddell (Leptonychotes weddellii) seal underwater vocalizations

2005 ◽  
Vol 83 (11) ◽  
pp. 1438-1452 ◽  
Author(s):  
Hilary B Moors ◽  
John M Terhune
Keyword(s):  
Light Condition ◽  
Weddell Seal ◽  
Harp Seal ◽  
Vertical Array ◽  
Vocal Cords ◽  
Leptonychotes Weddellii ◽  
Call Duration ◽  
Weddell Seals ◽  
Pagophilus Groenlandicus ◽  
Breeding Seasons

Harp seal (Pagophilus groenlandicus (Erxleben, 1777)) daytime calling depth during the breeding season and Weddell seal (Leptonychotes weddellii (Lesson, 1826)) daytime and nighttime calling depth during the winter and breeding seasons were investigated using a small vertical array with hydrophones placed at depths of 10 and 60 m. Rough calling depth estimates (<35 m, ~35 m, >35 m) and more accurate point depth estimates (±5–10 m in most cases) were obtained. Significantly more calls were produced at depths ≤35 m for both species. The point depth estimates indicated that the calls occurred most frequently at depths >10 m; 60% of harp seal calls and 71% of Weddell seal calls occurred at depths between 10 and 35 m. The seals called predominately within areas of the water column where light would likely penetrate, but still avoided sea-ice interference to some extent. The vocalizations did not change over depth with respect to call type, the number of elements within a call, or total call duration, or with respect to season and light condition for Weddell seals. Frequency (kHz) of calls also did not change with depth, suggesting that harp and Weddell seals control the pitch of their vocalizations with the vocal cords of the larynx.

Geographic variation in the underwater vocalizations of Weddell seals (Leptonychotes weddelli) from Palmer Peninsula and McMurdo Sound, Antarctica

1983 ◽  
Vol 61 (10) ◽  
pp. 2203-2212 ◽  
Author(s):  
Jeànette A. Thomas ◽  
Ian Stirling
Keyword(s):  
Mating System ◽  
Weddell Seal ◽  
Mirror Image ◽  
The Other ◽  
Mcmurdo Sound ◽  
Breeding Sites ◽  
Weddell Seals ◽  
Antarctic Seals ◽  
Geographic Differences ◽  
Polygynous Mating System

The Weddell seal (Leptonychotes weddelli) is one of the most vocal pinnipeds. The repertoires of subice vocalizations of Weddell seals recorded at Palmer Peninsula and at McMurdo Sound, Antarctica, are different. Although seals at both sites give some of the same vocalizations, there are subtle spectral and temporal differences. In addition each population has unique vocalizations which are not heard at the other site. At Palmer Peninsula, there are several usage characteristics not exhibited at McMurdo Sound, such as mirror-image vocalization pairs and vocalization trios. Weddell seals in McMurdo Sound make extensive use of nine auxiliary sounds, while the Peninsula repertoire has none. Factors which appear to have been important in the development of these geographic differences appear to include strong fidelity to breeding sites, a polygynous mating system, and learning. Geographically different vocal repertoires have potential for identifying discrete breeding stocks of Antarctic seals.

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