Consequences of maternal size for reproductive expenditure and pupping success of grey seals at North Rona, Scotland

Pomeroy, P. P.; Fedak, Michael A.; Rothery, P.; Anderson, Sheila

doi:10.1046/j.1365-2656.1999.00281.x

Cited by 163 publications

(301 citation statements)

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“…However, they do show that the smallest, youngest females had the lowest pupping success rates. Smaller females (in terms of length and relative mass) breed later in the season (Fedak & Anderson 1982, Pomeroy et al 1999. Here, our data suggest an additional spatial difference, at least during the early season period, with many smaller females selecting (or being forced to select) less topographically suitable sites.…”

Section: Discussionmentioning

confidence: 61%

“…Longer females tend to be older, more experienced breeders and heavier females produce pups of greater mass at birth and at weaning although this relationship is complicated by interactions with body length (see Pomeroy et al 1999). Pomeroy et al (1999) suggest that reproductive senescence or greater metabolic overheads may account for the reduction in performance of the longest females in a long term study of known individuals at North Rona (Scotland). However, they do show that the smallest, youngest females had the lowest pupping success rates.…”

Section: Discussionmentioning

confidence: 99%

“…(1) year, (2) date during the breeding season, (3) female age class: (i) less than 19 years old, (ii) greater than or equal to 19 years old (a cut off at 19 years effectively divided the known age females into study females from recent (i) and previous (ii) marking efforts) and (iii) of unknown age, 12 (4) stage of the breeding season at which the mother gave birth, classified as (i) before 25% of births, (ii) between 25% and 75% of births, or (iii) after 75% of births in the study areas ( this classification was based upon the relative ages, sizes and success of individuals at the various stages of the season (see Pomeroy et al 1999)), (5): pup's location with respect to proximity to water bodies and maternal movements: each female-day was classified into five exclusive categories based on the distance from the pup's location to the nearest water bodies and on the 'commuting' behaviour of the mother on the day in question. These categories are intended to express the hypothesis that greater distances travelled increases potential costs to the female, not only in terms of distance, but also in terms of the likelihood of increased aggressive interactions on the way to the pool (a function of distance) and the number of individuals encountered and therefore interactions whilst in the pools (a function of pool size and usage).…”

Section: Behavioural Observationsmentioning

confidence: 99%

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Finescale topographical correlates of behavioural investment in offspring by female grey seals, Halichoerus grypus

Twiss¹,

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Pomeroy

et al. 2000

Animal Behaviour

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(2000) 'Finescale topographical correlates of behavioural investment in o spring by female grey seals, Halichoerus grypus.', Animal behaviour., 59 (2). pp. 327-338. Further information on publisher's website:http://dx.doi.org/10.1006/anbe.1999.1320 Publisher's copyright statement: This is the author's version of a work that was accepted for publication in Animal Behaviour. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be re ected in this document. Changes may have been made to this work since it was submitted for publication. A de nitive version was subsequently published in Animal Behaviour, 2000Behaviour, , 59, 2, 327 338, doi: 10.1006Behaviour, /anbe.1999Behaviour, .1320 Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTGrey seals breed colonially on substrates ranging from ice to rocky or sandy beaches. Clear differences in seal behaviour patterns exist among such broad classes of breeding habitat.However, finer scale topographic variation is likely to influence individual behaviour with consequences for pupping success. We examine topographic influences on breeding female grey seal behaviour by quantifying topography at a sub-seal size resolution. Using sub-metre resolution Digital Terrain Models of two sites within a rocky breeding colony we compare site topography in relation to observed differences in female behaviour at these sites. Females at both sites showed a preference for breeding close to water (standing pools or sea) and frequently commuted between their pups and water. Topographic models indicated that one site was more costly for seals in terms of their locations and movements within the site. This was due to a lack of low elevation land adjacent to the main access points from the sea and the reduced availability of pools. Females at this site showed reduced pup attendance and an increase in energetically costly behaviours, whilst females at the lower cost site spent more time interacting with their pups and resting. These topographically induced behavioural differences are likely to affect the quantity and quality of pup provisioning by mothers and influence individual pupping site selection. Less costly sites are likely to be colonised preferentially and by larger, older and more dominant females, potentially generating fine scale spatial heterogeneity in female quality within the breeding colony.Whilst it may be obvious that topography is likely to...

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Section: Discussionmentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Section: Behavioural Observationsmentioning

confidence: 99%

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Finescale topographical correlates of behavioural investment in offspring by female grey seals, Halichoerus grypus

Twiss¹,

Caudron

Pomeroy

et al. 2000

Animal Behaviour

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“…Each female produces a single pup which she attends and suckles over a period of approximately 18 days. Mothers remain ashore for an average of 20 days fasting, during which time they give birth, suckle their pups, mate and return to the sea (Pomeroy et al 1999). On NR it is uncommon for mothers to return to the sea during the breeding period.…”

Section: Datamentioning

confidence: 99%

Estimating demographic parameters for capture–recapture data in the presence of multiple mark types

2010

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In mark-recapture studies, various techniques can be used to uniquely identify individual animals, such as ringing, tagging or photo-identification using natural markings. In some long-term studies more than one type of marking procedure may be implemented during the study period. In these circumstances, ignoring the different mark types can produce biased survival estimates since the assumption that the different mark types are equally catchable (homogeneous capture probability across mark types) may be incorrect. We implement an integrated approach where we simultaneously analyse data obtained using three different marking techniques, assuming that animals can be cross-classified across the different mark types. We discriminate between competing models using the AIC statistic. This technique also allows us to estimate both relative mark-loss probabilities and relative recapture efficiency rates for the different marking methods. We initially perform a simulation study to explore the different biases that can be introduced if we assume a homogeneous recapture probability over mark type, before applying the method to a real dataset. We make use of data obtained from an intensive long-term observational study of UK female grey seals (Halichoerus grypus) at a single breeding colony, where three different methods are used to identify individuals within a single study: branding, tagging and photo-identification based on seal coat pattern or pelage.

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“…Females have at most 1 pup a year, and first parturition occurs at about 5.5 years of age (Table 2). It is also evident that not all adult females bear a pup each year (Table 4), especially not young females (Pomeroy et al 1999). An additional limitation for the population growth rate is given by the survival of adults.…”

Section: Long Term Maximum Growth Ratesmentioning

confidence: 99%

Status of Baltic grey seals: Population assessment and extinction risk

et al. 2007

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The grey seal (Halichoerus grypus) population in the Baltic Sea is recovering after a century of bounty hunting and 3 decades of low fertility rates caused by environmental pollution. A conservative estimate of the population size in 2003 was 19,400 animals, and available data suggest an annual rate of increase of 7.5% since 1990. The growing population has led to increased interactions with the fishery, and demands are being raised for the re-introduction of the hunt. We provide a demographic analysis and a risk assessment of the population, and make recommendations on how to decrease the risk of overexploitation. Although hunting increases the risk of quasi-extinction, the risk can be significantly reduced by the choice of a cautious hunting regime. The least hazardous regimes allow no hunting below a 'security level' in population size. Obviously, to implement such a hunting regime detailed knowledge of the population size and growth rate is required. It is not possible to estimate "true" risks for quasi-extinction, but we used an approach where the relative difference for different scenarios can be compared. With a security level at 5,000 females, the population quasi-extinction risk increases 50 fold at an annual hunt of 500 females compared with a scenario with no hunting. The risk of quasi-extinction is very sensitive to declines in the mean growth rate and to increased variance in growth rate. The variance in the population estimates over the last 14 years imply that it would take 9 years to detect a decline from 1.075 to 1.027 in the rate of population increase. We also show how the age composition of killed animals influences the impact of the hunt. The overall recommendation is that hunting should be kept to a minimum, carefully documented and accompanied by close population monitoring.Harding, K.C., Härkönen, T., Helander, B. and Karlsson, O. 2007. Status of Baltic grey seals: Population assessment and extinction risk. NAMMCO

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Consequences of maternal size for reproductive expenditure and pupping success of grey seals at North Rona, Scotland

Cited by 163 publications

References 58 publications

Finescale topographical correlates of behavioural investment in offspring by female grey seals, Halichoerus grypus

Finescale topographical correlates of behavioural investment in offspring by female grey seals, Halichoerus grypus

Estimating demographic parameters for capture–recapture data in the presence of multiple mark types

Status of Baltic grey seals: Population assessment and extinction risk

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