Colony‐specific differences in decadal longitudinal body composition of a capital‐breeding marine top predator

Abstract

1. Capital breeding animals such as true seals (Phocidae) rely on accumulated body reserves to rear offspring. A mother's body composition at the start of a breeding episode may depend on recent environmental conditions and sets the resources available for the reproductive episode.2. At two grey seal (Halichoerus grypus) breeding colonies with contrasting demographic characteristics, factors influencing individual variation and temporal trends in the body composition (expressed as the lipid-to-protein mass ratio) of females were examined.3. Maternal reproductive expenditure, and the consequences for mothers and their pups, were investigated. Individual variation in postpartum maternal body composition was considerable.Mean values of 27% (±5%) lipid and 18% (±1%) protein were estimated by hydrogen isotope dilution. No evidence of age effects was detected.5. Mothers with a high lipid-to-protein mass ratio expended a higher proportion of lipid resources, conserved protein and returned with more protein the following year.6. Average maternal postpartum body composition was similar between the two colonies, but temporal patterns differed at one colony where pup production was decreasing from another where pup production was increasing. Mothers at the declining colony consistently weaned larger pups than mothers at the increasing colony across the range of mother sizes, but measures of maternal body composition did not predict pup weaning masses.

Environment‐sensitive mass changes influence breeding frequency in a capital breeding marine top predator

“…However, even for capital breeders, body mass alone may not be a perfect metric of body reserves, because it masks the availability of all the nutrients required for a successful breeding episode. Often only lipid reserves are used to estimate ‘condition’ in capital breeders as they provide most of the energetic requirements of mother and offspring, but protein and other nutrients must also be available and in the extreme may be more limiting (Arnbom et al, ; Boyd, ; Hanson, Smout, Moss, & Pomeroy, ; Mellish, Iverson, & Bowen, ). Our modelling framework could be adapted to include more complex measures of body condition in future studies, including combining different measures, if such data are available.…”

“…The breeding decline at NR is present at other Hebridean grey seal colonies (Duck & Morris, ) and poor recruitment of seals tagged as pups to NR is a likely additional factor in explaining these trends (Pomeroy et al, ). Long term declines in measures of grey seal ‘condition’ at NR compared to IM suggests that colony‐level effects are reflected in individual phenotypic covariates and these are a local response to local conditions (Hanson et al, ) which likely explains lower fecundity at NR (Boyd, ). Longitudinal seabird surveys on NR have shown decadal declines in 9 of 15 species that use the island for breeding, in common with trends reported in such species elsewhere in the North Atlantic (Murray & Wilson, ).…”

Fitness correlates of blubber oxidative stress and cellular defences in grey seals (Halichoerus grypus): support for the life-history-oxidative stress theory from an animal model of simultaneous lactation and fasting

“…Grey seals are an ideal natural system in which to test the life-history-oxidative stress theory because they are typical mammalian capital breeders. Female grey seals increase in fat content from 12% after moulting to ~ 33% prior to parturition (Sparling et al 2006 ; Hanson et al 2019 ). Grey seal mothers fast during their ~ 18–21-day lactation, when they rely on blubber lipid for metabolic and milk production requirements and lose 40% of initial mass and 61–84% of fat reserves (Fedak and Anderson 1982 ; Pomeroy et al 1999 ).…”

Atlantic Grey Seal Milk Shows Continuous Changes in Key Metabolites and Indicators of Metabolic Transition in Pups From Birth to Weaning

“…Atlantic grey seals come ashore, give birth, nurse for about 15-20 days during which they do not feed, rarely if ever drink, then leave their pups abruptly and return to sea (Schulz and Bowen, 2004). The pups then stay on land for up to about 40 days before they have matured sufficiently to go to sea (Bennett et al, 2010;Hanson et al, 2019). So, not only must mothers provide for the dramatic weight gain of their pups, but must also supply them with sufficient resources to survive the post-weaning extra period of development without further nutritional intake.…”