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.

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.

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).

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.

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.

The fall and rise of bison populations in Wood Buffalo National Park: 1971 to 2003

2005 ◽  
Vol 83 (9) ◽  
pp. 1195-1205 ◽  
Author(s):  
Mark Bradley ◽  
John Wilmshurst
Keyword(s):  
National Park ◽  
Census Data ◽  
Disease Incidence ◽  
Population Decline ◽  
Survival Rates ◽  
Bison Bison ◽  
Adult Survival ◽  
Risk Of Predation ◽  
Increased Risk ◽  
Wood Buffalo National Park

Two hypotheses have been proposed to explain the decline of bison (Bison bison (L., 1758)) abundance in Wood Buffalo National Park (WBNP). The "disease–predation" hypothesis proposes that tuberculosis (Mycobacterium bovis (Karlson and Lessel 1970)) and brucellosis (Brucella abortus (Schmidt 1901)) reduce bison survival and reproduction, resulting in a low-density, predator-regulated equilibrium. The "habitat dispersion hypothesis" proposes that bison in one area of WBNP, the Peace–Athabasca Delta (Delta), have an increased risk of predation because they are concentrated in large meadows with high temporal and spatial predictability. We incorporate bison census data, calf and yearling segregation counts, reproductive rates, adult survival rates, and adult disease incidence in a stochastic population model to show that the historical decline of bison in WBNP would have occurred regardless of disease prevalence. Our model shows that survival of juveniles, the age class that is least susceptible to disease effects, was likely an important determinant of historical changes in population size. We also demonstrate that the population decline was most pronounced in the Delta and that juvenile survival was lower in the Delta, despite evidence that disease incidence was lower in the Delta than in the rest of WBNP. Lastly, the current population trend in WBNP is one of rapid increase, even in the presence of disease.

scholarly journals Cyclic dynamics of snowshoe hares on a small island in the Yukon

2002 ◽  
Vol 80 (8) ◽  
pp. 1442-1450 ◽  
Author(s):  
Charles J Krebs ◽  
Todd N Zimmerling ◽  
Claire Jardine ◽  
Kim A Trostel ◽  
Alice J Kenney ◽  
...  
Keyword(s):  
Population Decline ◽  
Survival Rates ◽  
Ground Squirrels ◽  
Adult Survival ◽  
Small Island ◽  
Juvenile Survival ◽  
Lower Amplitude ◽  
Arctic Ground Squirrels ◽  
Reproductive Rates ◽  
Survival Differences

Snowshoe hare (Lepus americanus) populations were monitored from 1977 to 2001 on Jacquot Island (5 km2) in Kluane Lake, southwestern Yukon, and on nearby mainland sites. Jacquot Island hares averaged twice the density of mainland control populations and, although they show 10-year cycles, fluctuate with much lower amplitude than mainland populations. Three separate intensive studies over 6 years attempted to determine what caused these differences. We tested two hypotheses to explain the dynamics. Reproductive rates of hares were similar on Jacquot Island and the mainland. Adult survival rates were higher on the island in most years, with the exception of years of population decline. Juvenile survival rates from 0 to 30 days of life were much higher on the island than on the mainland except for decline summers. The adult- and juvenile-survival differences between the island and the mainland were explained most consistently by predation. Improved survival on the island is correlated with a reduction in the numbers and types of predators found on Jacquot Island compared with the mainland. In particular, red squirrels were rare on Jacquot Island, arctic ground squirrels were absent, and the larger predators, like lynx and great-horned owls, were sporadic in occurrence on this small island.

scholarly journals Age-specific survival in an English Twite population.

2021 ◽  
Author(s):  
Ismini Gkourtsouli-Antoniadou ◽  
Steven R. Ewing ◽  
George Hudson ◽  
Michael A. Pearson ◽  
Julia Schroeder ◽  
...  
Keyword(s):  
Habitat Degradation ◽  
Survival Rates ◽  
Bird Species ◽  
Small Population ◽  
Juvenile Survival ◽  
Apparent Survival ◽  
Mark Recapture ◽  
The Uk ◽  
Rule Out

Like many bird species associated with agricultural habitats in the UK, the Twite Linaria flavirostris has undergone severe declines over recent decades due to habitat degradation, with populations in England, Wales and Ireland now restricted to a few small pockets. However, the demographic drivers of these declines are still largely unresolved. We estimated the survival of Twite from a small population at the southernmost edge of the English range in Derbyshire using capture-mark-recapture data from 2016–2019. Annual apparent survival for juveniles (0.14–0.34) was lower than for adults (0.29–0.56) and less than that of other Cardueline finches. Our results suggest that low juvenile survival may be one demographic driver underpinning the recent decline of the Derbyshire Twite population, although we also cannot rule out the possibility that differences in emigration of juveniles and adults from the population also contribute to the observed age-specific apparent survival rates.

Movements of the weddell seals in McMurdo Sound, Antarctica

1974 ◽  
Vol 22 (1) ◽  
pp. 39 ◽  
Author(s):  
I Stirling
Keyword(s):  
Weddell Seal ◽  
Behavioural Plasticity ◽  
Mcmurdo Sound ◽  
Weddell Seals ◽  
Adult Females ◽  
Ice Conditions ◽  
High Degree

Weddell seal populations are sedentary and discrete in stable ice areas. Adult females showed a high degree of fidelity to specific pupping colonies but retained the behavioural plasticity to accept adjacent colonies in unfavourable ice conditions. The movements of non-parturient females during the pupping season were not related to the colony at which they preferred to give birth.

Observations on a stabilizing population of weddell seals

1972 ◽  
Vol 20 (1) ◽  
pp. 23 ◽  
Author(s):  
I Stirling ◽  
DJ Greenwood
Keyword(s):  
Weddell Seal ◽  
Mcmurdo Sound ◽  
Weddell Seals ◽  
Seal Population

The Weddell seal population of eastern McMurdo Sound, after a period of increase and subsequent decline, is now stabilizing in terms of total numbers and pup production. Increased intrasexual strife resulting mainly from competition for access to the best pupping and breeding colonies appears to be the major factor causing stabilization.

Cow-Pup Behaviour of the Weddell Seal, Leptonychotes Weddelli (Pinnipedia), in Mcmurdo Sound, Antarctica.

1979 ◽  
Vol 6 (1) ◽  
pp. 19 ◽  
Author(s):  
RA Tedman ◽  
MM Bryden
Keyword(s):  
Weddell Seal ◽  
Diurnal Pattern ◽  
Mcmurdo Sound ◽  
Weddell Seals

Study was of the behaviour of 9 marked female Weddell seals, Leptonychotes weddelli, and their young in a colony of 35 to 40 such pairs at Turtle Rock, McMurdo Sound, off Ross Island, Antarctica. The young sucked first about 80 min after birth. Sucking was usually initiated by the young seal, which had to raise its head to reach either of the 2 nipples. After sucking for 10 to 20 sec the young seal dropped down to the ice and waited for 1 to 2 min before sucking again. It was not clear whether the young seal had to rest after supporting itself or whether it had cleared the milk from the gland cistern and had to wait while milk from alveoli and ducts refilled the cistern. For young more than 1 week old there was a diurnal pattern of sucking with peaks between 1200 and 2359 h and least between 0300 and 0600 h. When the young began to swim they used more energy, stored less fat and sucked less. Early swimming, resulting in lower bodyweight at weaning, could affect survival during the following winter. Published values for bodyweight increments of growing seals are given. Young Weddell seals accumulate less fat than some species but learn to catch food before they are weaned.

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