scholarly journals Earlier pupping in harbour seals, Phoca vitulina

2010 ◽  
Vol 6 (6) ◽  
pp. 854-857 ◽  
Author(s):  
Peter J. H. Reijnders ◽  
Sophie M. J. M. Brasseur ◽  
Erik H. W. G. Meesters
Keyword(s):  
Life History Traits ◽  
Annual Variation ◽  
Wadden Sea ◽  
Phoca Vitulina ◽  
Birth Date ◽  
Embryonic Diapause ◽  
Potential Mechanism ◽  
Annual Reproductive Cycle ◽  
Harbour Seals ◽  
Large Predator

The annual reproductive cycle of most seal species is characterized by a tight synchrony of births. Typically, timing of birth shows little inter-annual variation. Here, however we show that harbour seals Phoca vitulina from the Wadden Sea (southeast North Sea) have shortened their yearly cycle, moving parturition to earlier dates since the early 1970s. Between 1974 and 2009, the birth date of harbour seals shifted on average by −0.71 d yr −1 , three and a half weeks (25 days) earlier, in the Dutch part of the Wadden Sea. Pup counts available for other parts of the Wadden Sea were analysed, showing a similar shift. To elucidate potential mechanism(s) for this shift in pupping phenology, possible changes in population demography, changes in maternal life-history traits and variations in environmental conditions were examined. It was deduced that the most likely mechanism was a shortening of embryonic diapause. We hypothesize that this could have been facilitated by an improved forage base, e.g. increase of small fishes, attributable to overfishing of large predator fishes and size-selective fisheries.

scholarly journals Options for modulating intra-specific competition in colonial pinnipeds: the case of harbour seals (Phoca vitulina) in the Wadden Sea

PeerJ ◽  
2015 ◽  
Vol 3 ◽  
pp. e957 ◽  
Author(s):  
Rory P. Wilson ◽  
Nikolai Liebsch ◽  
Agustina Gómez-Laich ◽  
William P. Kay ◽  
Andrew Bone ◽  
...  
Keyword(s):  
Wadden Sea ◽  
Phoca Vitulina ◽  
Harbour Seals

Population development of harbour seals Phoca vitulina in the Wadden Sea after the 1988 virus epizootic

1997 ◽  
Vol 38 (1-2) ◽  
pp. 161-168 ◽  
Author(s):  
Peter J.H. Reijnders ◽  
Edith H. Ries ◽  
Svend Tougaard ◽  
Niels Nørgaard ◽  
Günter Heidemann ◽  
...  
Keyword(s):  
Wadden Sea ◽  
Phoca Vitulina ◽  
Population Development ◽  
Harbour Seals

The importance of the North Sea for winter dispersal of harbour seals Phoca vitulina from the Wadden Sea

1997 ◽  
Vol 81 (1-2) ◽  
pp. 97-102 ◽  
Author(s):  
Mardik F. Leopold ◽  
Bert van der Werf ◽  
Edith H. Ries ◽  
Peter J.H. Reijnders
Keyword(s):  
North Sea ◽  
Wadden Sea ◽  
Phoca Vitulina ◽  
The North ◽  
Harbour Seals ◽  
The North Sea

Diving patterns of harbour seals (Phoca vitulina) in the Wadden Sea, the Netherlands and Germany, as indicated by VHF telemetry

1997 ◽  
Vol 75 (12) ◽  
pp. 2063-2068 ◽  
Author(s):  
Edith H. Ries ◽  
Petra Paffen ◽  
Ilona M. Traut ◽  
Paul W. Goedhart
Keyword(s):  
The Netherlands ◽  
Body Length ◽  
Air Temperature ◽  
Adult Male ◽  
Wadden Sea ◽  
Ambient Air ◽  
Phoca Vitulina ◽  
Late Autumn ◽  
Dive Behaviour ◽  
Harbour Seals

The diving behaviour of 25 harbour seals, Phoca vitulina (14 females and 11 males), of various body lengths was monitored by means of VHF telemetry at different locations in the Wadden Sea during late autumn in 1991 and 1992. Median dive durations for individual seals ranged from 46 s to 2.9 min. The maximum dive recorded was 31 min, performed by an adult male, which represents the longest dive reported for harbour seals. Dive endurance increased significantly in relation to body length. Female harbour seals tended to perform fewer short dives and had a more narrow distribution of dive times. We detected no diurnal differences in dive behaviour and only the ambient air temperature was found to influence the duration of surface periods, in that surface intervals tended to be shorter when temperatures were below 9 °C. The overall mean percentage of dive time was 85%, with individuals varying from 76 to 93%, and was in general higher in females.

The effect of maternal age and other factors on birth mass in the harbour seal

1994 ◽  
Vol 72 (1) ◽  
pp. 8-14 ◽  
Author(s):  
W. D. Bowen ◽  
O. T. Oftedal ◽  
D. J. Boness ◽  
S. J. Iverson
Keyword(s):  
Nova Scotia ◽  
Developmental Stage ◽  
Body Mass ◽  
Maternal Age ◽  
Phoca Vitulina ◽  
Harbour Seal ◽  
Birth Date ◽  
Young Mothers ◽  
Maternal Body ◽  
Harbour Seals

We studied the effects of maternal age, maternal body mass at parturition, year of birth, birth date, pup sex, and developmental stage (as indicated by the presence of a foetal pelage called lanugo) on the birth mass of harbour seals (Phoca vitulina) on Sable Island, Nova Scotia, Canada. Between 1987 and 1992, mass was obtained on 330 newborns and 259 of their mothers. Birth mass was significantly correlated with maternal mass (r = 0.42 for male pups; r = 0.32 for female pups). Among pups that had shed their lanugo, males were significantly heavier at birth (11.4 ± 0.09 kg, n = 107) than females (10.9 ± 0.09, n = 99). Birth mass increased significantly with maternal age (n = 71, range 4–12 years) even after the effects of maternal mass and pup sex were statistically removed. Mean birth mass varied significantly among years, from 10.5 to 11.5 kg. Newborns averaged 12.8% of maternal mass at parturition (84.8 ± 0.49 kg). Most (84%) pups had shed their lanugo before birth. Pups born with extensive lanugo were born earlier in the season and weighed about 20% less than pups born without lanugo. These data suggest that pups born with lanugo may be less developed than pups that had shed their foetal coat. Young mothers (4 and 5 years old) produced most of the underweight, lanugo-covered pups.

scholarly journals Variation in breeding phenology provides insights into drivers of long-term population change in harbour seals

2013 ◽  
Vol 280 (1764) ◽  
pp. 20130847 ◽  
Author(s):  
Line S. Cordes ◽  
Paul M. Thompson
Keyword(s):  
Annual Variation ◽  
Population Change ◽  
Negative Relationship ◽  
Population Level ◽  
Birth Date ◽  
Population Declines ◽  
Harbour Seals ◽  
Lactation Duration ◽  
Impacts Of Climate Change

Phenological trends provide important indicators of environmental change and population dynamics. However, the use of untested population-level measures can lead to incorrect conclusions about phenological trends, particularly when changes in population structure or density are ignored. We used individual-based estimates of birth date and lactation duration of harbour seals ( Phoca vitulina ) to investigate energetic consequences of changes in pupping phenology. Using generalized linear mixed models, we first demonstrate annual variation in pupping phenology. Second, we show a negative relationship between lactation duration and the timing of pupping, indicating that females who pup early nurse their pups longer, thereby highlighting lactation duration as a useful proxy of female condition and resource availability. Third, individual-based data were used to derive a population-level proxy that demonstrated an advance in pupping date over the last 25 years, co-incident with a reduction in population abundance that resulted from fisheries-related shootings. These findings demonstrate that phenological studies examining the impacts of climate change on mammal populations must carefully control for changes in population density and highlight how joint investigations of phenological and demographic change provide insights into the drivers of population declines.

scholarly journals Harbour seals (Phoca vitulina) and rehabilitation

2010 ◽  
Vol 8 ◽  
pp. 355 ◽  
Author(s):  
Nynke Osinga ◽  
Pieter ‘t Hart
Keyword(s):  
Social Support ◽  
Anthropogenic Impact ◽  
Wadden Sea ◽  
Quality Standards ◽  
Phoca Vitulina ◽  
The Past ◽  
Harbour Seals ◽  
Seal Population ◽  
One Year ◽  
Ecosystem Changes

Throughout the past few decades, rehabilitation of seals has become an activity that is anchored in the present day society of many countries. Seals are primarily rehabilitated to help individual animals in distress. At the same time, the release of seals which would have otherwise died can be considered as a contribution to the population. Most rehabilitated seals are animals under one year of age. They are mainly orphans, weaned seals with complications and seals with a parasiticbronchopneumonia. For the optimal handling of seals and their diseases, centralised operations with quality standards are essential. Rehabilitation provides an instrument to monitor the health of the seal population and its ecosystem. Changes in stranding trends or the appearance of new diseases can be monitored. Moreover, rehabilitation is important to show the general public thestate of the marine environment. In the Netherlands there is significant social support for the rehabilitation of seals. Experience obtained with seal care is of importance in countries where urgent help of threatened seal species is required. Here individual seals are also ambassadors to raise support for the protection of this species in general. Given that the anthropogenic impact on the seals and their environment is extensive in the Wadden Sea, rehabilitation centres can compensate the consequences of this impact on individual seals as well as the population as a whole.

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